merge with master

70 files changed, 1546 insertions, 1014 deletions

diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index 445a8b2..c3f29da 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -11,6 +11,7 @@ find_package(SDL2 REQUIRED)
 find_package(SDL2_image REQUIRED)
 find_package(SoLoud REQUIRED)
 find_package(GTest REQUIRED)
+find_package(whereami REQUIRED)
 find_library(BERKELEY_DB db)
 
 add_library(crepe SHARED)
@@ -25,6 +26,7 @@ target_link_libraries(crepe
 	PUBLIC SDL2
 	PUBLIC SDL2_image
 	PUBLIC ${BERKELEY_DB}
+	PUBLIC whereami
 )
 
 add_subdirectory(crepe)
diff --git a/src/crepe/Asset.cpp b/src/crepe/Asset.cpp
deleted file mode 100644
index 9c41ecb..0000000
--- a/src/crepe/Asset.cpp
+++ /dev/null
@@ -1,16 +0,0 @@
-#include <filesystem>
-
-#include "Asset.h"
-
-using namespace crepe;
-using namespace std;
-
-// FIXME: restore this
-// src(std::filesystem::canonical(src))
-Asset::Asset(const std::string & src) : src(src) {
-	this->file = std::ifstream(this->src, std::ios::in | std::ios::binary);
-}
-
-istream & Asset::get_stream() { return this->file; }
-
-const string & Asset::get_canonical() const { return this->src; }
diff --git a/src/crepe/Asset.h b/src/crepe/Asset.h
deleted file mode 100644
index 9051c5e..0000000
--- a/src/crepe/Asset.h
+++ /dev/null
@@ -1,41 +0,0 @@
-#pragma once
-
-#include <fstream>
-#include <iostream>
-#include <string>
-
-namespace crepe {
-
-/**
- * \brief Asset location helper
- *
- * This class is used to locate and canonicalize paths to game asset files, and should *always*
- * be used when retrieving files from disk.
- */
-class Asset {
-public:
-	/**
-	 * \param src  Unique identifier to asset
-	 */
-	Asset(const std::string & src);
-
-public:
-	/**
-	 * \brief Get an input stream to the contents of this asset
-	 * \return Input stream with file contents
-	 */
-	std::istream & get_stream();
-	/**
-	 * \brief Get the canonical path to this asset
-	 * \return Canonical path to this asset
-	 */
-	const std::string & get_canonical() const;
-
-private:
-	//! Canonical path to asset
-	const std::string src;
-	//! File handle (stream)
-	std::ifstream file;
-};
-
-} // namespace crepe
diff --git a/src/crepe/CMakeLists.txt b/src/crepe/CMakeLists.txt
index 3b05742..7e176e7 100644
--- a/src/crepe/CMakeLists.txt
+++ b/src/crepe/CMakeLists.txt
@@ -1,5 +1,4 @@
 target_sources(crepe PUBLIC
-	Asset.cpp
 	Particle.cpp
 	ComponentManager.cpp
 	Component.cpp
@@ -7,7 +6,6 @@ target_sources(crepe PUBLIC
 )
 
 target_sources(crepe PUBLIC FILE_SET HEADERS FILES
-	Asset.h
 	ComponentManager.h
 	ComponentManager.hpp
 	Component.h
diff --git a/src/crepe/Component.h b/src/crepe/Component.h
index 5279fb3..dc17721 100644
--- a/src/crepe/Component.h
+++ b/src/crepe/Component.h
@@ -27,6 +27,11 @@ protected:
 	//! Only the ComponentManager can create components
 	friend class ComponentManager;
 
+	Component(const Component &) = delete;
+	Component(Component &&) = delete;
+	virtual Component & operator=(const Component &) = delete;
+	virtual Component & operator=(Component &&) = delete;
+
 public:
 	virtual ~Component() = default;
 
diff --git a/src/crepe/ComponentManager.h b/src/crepe/ComponentManager.h
index 2107453..0956d1e 100644
--- a/src/crepe/ComponentManager.h
+++ b/src/crepe/ComponentManager.h
@@ -8,6 +8,7 @@
 #include "api/Vector2.h"
 
 #include "Component.h"
+#include "types.h"
 
 namespace crepe {
 
@@ -112,7 +113,7 @@ public:
 	 * \return A vector of all components of the specific type and id
 	 */
 	template <typename T>
-	std::vector<std::reference_wrapper<T>> get_components_by_id(game_object_id_t id) const;
+	RefVector<T> get_components_by_id(game_object_id_t id) const;
 	/**
 	 * \brief Get all components of a specific type
 	 * 
@@ -122,7 +123,7 @@ public:
 	 * \return A vector of all components of the specific type
 	 */
 	template <typename T>
-	std::vector<std::reference_wrapper<T>> get_components_by_type() const;
+	RefVector<T> get_components_by_type() const;
 
 private:
 	/**
diff --git a/src/crepe/ComponentManager.hpp b/src/crepe/ComponentManager.hpp
index be99cac..4d5eaf4 100644
--- a/src/crepe/ComponentManager.hpp
+++ b/src/crepe/ComponentManager.hpp
@@ -81,15 +81,14 @@ void ComponentManager::delete_components() {
 }
 
 template <typename T>
-std::vector<std::reference_wrapper<T>>
-ComponentManager::get_components_by_id(game_object_id_t id) const {
+RefVector<T> ComponentManager::get_components_by_id(game_object_id_t id) const {
 	using namespace std;
 
 	// Determine the type of T (this is used as the key of the unordered_map<>)
 	type_index type = typeid(T);
 
 	// Create an empty vector<>
-	vector<reference_wrapper<T>> component_vector;
+	RefVector<T> component_vector;
 
 	if (this->components.find(type) == this->components.end()) return component_vector;
 
@@ -114,14 +113,14 @@ ComponentManager::get_components_by_id(game_object_id_t id) const {
 }
 
 template <typename T>
-std::vector<std::reference_wrapper<T>> ComponentManager::get_components_by_type() const {
+RefVector<T> ComponentManager::get_components_by_type() const {
 	using namespace std;
 
 	// Determine the type of T (this is used as the key of the unordered_map<>)
 	type_index type = typeid(T);
 
 	// Create an empty vector<>
-	vector<reference_wrapper<T>> component_vector;
+	RefVector<T> component_vector;
 
 	// Find the type (in the unordered_map<>)
 	if (this->components.find(type) == this->components.end()) return component_vector;
diff --git a/src/crepe/api/Asset.cpp b/src/crepe/api/Asset.cpp
new file mode 100644
index 0000000..e148367
--- /dev/null
+++ b/src/crepe/api/Asset.cpp
@@ -0,0 +1,54 @@
+#include <filesystem>
+#include <stdexcept>
+#include <whereami.h>
+
+#include "api/Config.h"
+
+#include "Asset.h"
+
+using namespace crepe;
+using namespace std;
+
+Asset::Asset(const string & src) : src(find_asset(src)) {}
+Asset::Asset(const char * src) : src(find_asset(src)) {}
+
+const string & Asset::get_path() const noexcept { return this->src; }
+
+string Asset::find_asset(const string & src) const {
+	auto & cfg = Config::get_instance();
+	string & root_pattern = cfg.asset.root_pattern;
+
+	// if root_pattern is empty, find_asset must return all paths as-is
+	if (root_pattern.empty()) return src;
+
+	// absolute paths do not need to be resolved, only canonicalized
+	filesystem::path path = src;
+	if (path.is_absolute()) return filesystem::canonical(path);
+
+	// find directory matching root_pattern
+	filesystem::path root = this->whereami();
+	while (1) {
+		if (filesystem::exists(root / root_pattern)) break;
+		if (!root.has_parent_path())
+			throw runtime_error(format("Asset: Cannot find root pattern ({})", root_pattern));
+		root = root.parent_path();
+	}
+
+	// join path to root (base directory) and canonicalize
+	return filesystem::canonical(root / path);
+}
+
+string Asset::whereami() const noexcept {
+	string path;
+	size_t path_length = wai_getExecutablePath(NULL, 0, NULL);
+	path.resize(path_length + 1); // wai writes null byte
+	wai_getExecutablePath(path.data(), path_length, NULL);
+	path.resize(path_length);
+	return path;
+}
+
+bool Asset::operator==(const Asset & other) const noexcept { return this->src == other.src; }
+
+size_t std::hash<const Asset>::operator()(const Asset & asset) const noexcept {
+	return std::hash<string>{}(asset.get_path());
+};
diff --git a/src/crepe/api/Asset.h b/src/crepe/api/Asset.h
new file mode 100644
index 0000000..bfd0ac7
--- /dev/null
+++ b/src/crepe/api/Asset.h
@@ -0,0 +1,84 @@
+#pragma once
+
+#include <string>
+
+namespace crepe {
+
+/**
+ * \brief Asset location helper
+ *
+ * This class is used to locate game asset files, and should *always* be used
+ * instead of reading file paths directly.
+ */
+class Asset {
+public:
+	/**
+	 * \param src  Unique identifier to asset
+	 */
+	Asset(const std::string & src);
+	/**
+	 * \param src  Unique identifier to asset
+	 */
+	Asset(const char * src);
+
+public:
+	/**
+	 * \brief Get the path to this asset
+	 * \return path to this asset
+	 */
+	const std::string & get_path() const noexcept;
+
+	/**
+	 * \brief Comparison operator
+	 * \param other Possibly different instance of \c Asset to test equality against
+	 * \return True if \c this and \c other are equal
+	 */
+	bool operator==(const Asset & other) const noexcept;
+
+private:
+	//! path to asset
+	const std::string src;
+
+private:
+	/**
+	 * \brief Locate asset path, or throw exception if it cannot be found
+	 *
+	 * This function resolves asset locations relative to crepe::Config::root_pattern if it is
+	 * set and \p src is a relative path. If \p src is an absolute path, it is canonicalized.
+	 * This function only returns if the file can be found.
+	 *
+	 * \param src Arbitrary path to resource file
+	 *
+	 * \returns \p src if crepe::Config::root_pattern is empty
+	 * \returns Canonical path to \p src
+	 *
+	 * \throws std::runtime_error if root_pattern cannot be found
+	 * \throws std::filesystem::filesystem_error if the resolved path does not exist
+	 * \throws std::filesystem::filesystem_error if the path cannot be canonicalized
+	 */
+	std::string find_asset(const std::string & src) const;
+	/**
+	 * \returns The path to the current executable
+	 */
+	std::string whereami() const noexcept;
+};
+
+} // namespace crepe
+
+namespace std {
+
+//! Hash helper struct
+template <>
+struct hash<const crepe::Asset> {
+	/**
+	 * \brief Hash operator for crepe::Asset
+	 *
+	 * This function hashes a crepe::Asset instance, allowing it to be used as a key in an \c
+	 * std::unordered_map.
+	 *
+	 * \returns Hash value
+	 */
+	size_t operator()(const crepe::Asset & asset) const noexcept;
+};
+
+} // namespace std
diff --git a/src/crepe/api/CMakeLists.txt b/src/crepe/api/CMakeLists.txt
index 07b3a82..830f5bd 100644
--- a/src/crepe/api/CMakeLists.txt
+++ b/src/crepe/api/CMakeLists.txt
@@ -20,11 +20,12 @@ target_sources(crepe PUBLIC
 	BoxCollider.cpp
 	CircleCollider.cpp
 	EventManager.cpp
-	EventHandler.cpp
 	IKeyListener.cpp
 	IMouseListener.cpp
 	LoopManager.cpp
 	LoopTimer.cpp
+	Asset.cpp
+	EventHandler.cpp
 )
 
 target_sources(crepe PUBLIC FILE_SET HEADERS FILES
@@ -54,9 +55,11 @@ target_sources(crepe PUBLIC FILE_SET HEADERS FILES
 	EventManager.h
 	EventManager.hpp
 	EventHandler.h
+	EventHandler.hpp
 	Event.h
 	IKeyListener.h
 	IMouseListener.h
 	LoopManager.h
 	LoopTimer.h
+	Asset.h
 )
diff --git a/src/crepe/api/Config.h b/src/crepe/api/Config.h
index 3ab877a..13eabd1 100644
--- a/src/crepe/api/Config.h
+++ b/src/crepe/api/Config.h
@@ -62,6 +62,20 @@ public:
 		 */
 		double gravity = 1;
 	} physics;
+
+	//! Asset loading options
+	struct {
+		/**
+		 * \brief Pattern to match for Asset base directory
+		 *
+		 * All non-absolute paths resolved using \c Asset will be made relative to
+		 * the first parent directory relative to the calling executable where
+		 * appending this pattern results in a path that exists. If this string is
+		 * empty, path resolution is disabled, and Asset will return all paths
+		 * as-is.
+		 */
+		std::string root_pattern = ".crepe-root";
+	} asset;
 };
 
 } // namespace crepe
diff --git a/src/crepe/api/Event.h b/src/crepe/api/Event.h
index bd6a541..8a6b931 100644
--- a/src/crepe/api/Event.h
+++ b/src/crepe/api/Event.h
@@ -1,59 +1,115 @@
+// TODO discussing the location of these events
 #pragma once
-#include "KeyCodes.h"
-#include <iostream>
+
 #include <string>
-#include <typeindex>
+
 #include "system/CollisionSystem.h"
 
-class Event {
-public:
-};
+#include "KeyCodes.h"
 
+/**
+ * \brief Base class for all event types in the system.
+ */
+class Event {};
+
+/**
+ * \brief Event triggered when a key is pressed.
+ */
 class KeyPressEvent : public Event {
 public:
-	int repeat = 0;
+	//! false if first time press, true if key is repeated
+	bool repeat = false;
+
+	//! The key that was pressed.
 	Keycode key = Keycode::NONE;
 };
 
+/**
+ * \brief Event triggered when a key is released.
+ */
 class KeyReleaseEvent : public Event {
 public:
+	//! The key that was released.
 	Keycode key = Keycode::NONE;
 };
 
+/**
+ * \brief Event triggered when a mouse button is pressed.
+ */
 class MousePressEvent : public Event {
 public:
+	//! X-coordinate of the mouse position at the time of the event.
 	int mouse_x = 0;
+
+	//! Y-coordinate of the mouse position at the time of the event.
 	int mouse_y = 0;
+
+	//! The mouse button that was pressed.
 	MouseButton button = MouseButton::NONE;
 };
 
+/**
+ * \brief Event triggered when a mouse button is clicked (press and release).
+ */
 class MouseClickEvent : public Event {
 public:
+	//! X-coordinate of the mouse position at the time of the event.
 	int mouse_x = 0;
+
+	//! Y-coordinate of the mouse position at the time of the event.
 	int mouse_y = 0;
+
+	//! The mouse button that was clicked.
 	MouseButton button = MouseButton::NONE;
 };
+
+/**
+ * \brief Event triggered when a mouse button is released.
+ */
 class MouseReleaseEvent : public Event {
 public:
+	//! X-coordinate of the mouse position at the time of the event.
 	int mouse_x = 0;
+
+	//! Y-coordinate of the mouse position at the time of the event.
 	int mouse_y = 0;
+
+	//! The mouse button that was released.
 	MouseButton button = MouseButton::NONE;
 };
+
+/**
+ * \brief Event triggered when the mouse is moved.
+ */
 class MouseMoveEvent : public Event {
 public:
+	//! X-coordinate of the mouse position at the time of the event.
 	int mouse_x = 0;
+
+	//! Y-coordinate of the mouse position at the time of the event.
 	int mouse_y = 0;
 };
+
+/**
+ * \brief Event triggered during a collision between objects.
+ */
 class CollisionEvent : public Event {
 public:
 	crepe::CollisionSystem::CollisionInfo info;
 	CollisionEvent(const crepe::CollisionSystem::CollisionInfo& collisionInfo)
         : info(collisionInfo) {}
 };
+
+/**
+ * \brief Event triggered when text is submitted, e.g., from a text input.
+ */
 class TextSubmitEvent : public Event {
 public:
+	//! The submitted text.
 	std::string text = "";
 };
-class ShutDownEvent : public Event {
-public:
-};
+
+/**
+ * \brief Event triggered to indicate the application is shutting down.
+ */
+class ShutDownEvent : public Event {};
diff --git a/src/crepe/api/EventHandler.cpp b/src/crepe/api/EventHandler.cpp
index 93a116a..4dc232f 100644
--- a/src/crepe/api/EventHandler.cpp
+++ b/src/crepe/api/EventHandler.cpp
@@ -1,2 +1,5 @@
 #include "EventHandler.h"
-bool IEventHandlerWrapper::exec(const Event & e) { return call(e); }
+
+using namespace crepe;
+
+bool IEventHandlerWrapper::exec(const Event & e) { return this->call(e); }
diff --git a/src/crepe/api/EventHandler.h b/src/crepe/api/EventHandler.h
index 0ab90de..ef659fd 100644
--- a/src/crepe/api/EventHandler.h
+++ b/src/crepe/api/EventHandler.h
@@ -1,9 +1,11 @@
 #pragma once
-#include "Event.h"
+
 #include <functional>
-#include <iostream>
-#include <typeindex>
+#include <string>
 
+#include "Event.h"
+
+namespace crepe {
 /**
  * \brief A type alias for an event handler function.
  * 
@@ -11,8 +13,9 @@
  * indicating whether the event is handled.
  * 
  * \tparam EventType The type of event this handler will handle.
+ * 
+ * Returning \c false from an event handler results in the event being propogated to other listeners for the same event type, while returning \c true stops propogation altogether.
  */
-// TODO: typedef
 template <typename EventType>
 using EventHandler = std::function<bool(const EventType & e)>;
 
@@ -21,7 +24,7 @@ using EventHandler = std::function<bool(const EventType & e)>;
  * \brief An abstract base class for event handler wrappers.
  * 
  * This class provides the interface for handling events. Derived classes must implement the
- * `call()` method to process events and the `get_type()` method to return the handler's type.
+ * `call()` method to process events
  */
 class IEventHandlerWrapper {
 public:
@@ -40,15 +43,6 @@ public:
      */
 	bool exec(const Event & e);
 
-	/**
-     * \brief Get the type of the event handler.
-     * 
-     * This method returns the type of the event handler as a string.
-     * 
-     * \return A string representing the handler's type.
-     */
-	virtual std::string get_type() const = 0;
-
 private:
 	/**
      * \brief The method responsible for handling the event.
@@ -81,8 +75,7 @@ public:
      * 
      * \param handler The event handler function.
      */
-	explicit EventHandlerWrapper(const EventHandler<EventType> & handler)
-		: m_handler(handler), m_handler_type(m_handler.target_type().name()) {}
+	explicit EventHandlerWrapper(const EventHandler<EventType> & handler);
 
 private:
 	/**
@@ -93,20 +86,11 @@ private:
      * \param e The event to be handled.
      * \return A boolean value indicating whether the event is handled.
      */
-	bool call(const Event & e) override {
-		return m_handler(static_cast<const EventType &>(e));
-	}
-
-	/**
-     * \brief Returns the type of the handler.
-     * 
-     * This method returns a string representing the type of the event handler.
-     * 
-     * \return The handler type as a string.
-     */
-	std::string get_type() const override { return m_handler_type; }
+	bool call(const Event & e) override;
 	//! The event handler function.
-	EventHandler<EventType> m_handler;
-	//! The type name of the handler function.
-	const std::string m_handler_type;
+	EventHandler<EventType> handler;
 };
+
+} // namespace crepe
+
+#include "EventHandler.hpp"
diff --git a/src/crepe/api/EventHandler.hpp b/src/crepe/api/EventHandler.hpp
new file mode 100644
index 0000000..391dcca
--- /dev/null
+++ b/src/crepe/api/EventHandler.hpp
@@ -0,0 +1,18 @@
+#include <typeindex>
+
+#include "EventHandler.h"
+
+namespace crepe {
+
+// Implementation of EventHandlerWrapper constructor
+template <typename EventType>
+EventHandlerWrapper<EventType>::EventHandlerWrapper(const EventHandler<EventType> & handler)
+	: handler(handler) {}
+
+// Implementation of EventHandlerWrapper::call
+template <typename EventType>
+bool EventHandlerWrapper<EventType>::call(const Event & e) {
+	return this->handler(static_cast<const EventType &>(e));
+}
+
+} //namespace crepe
diff --git a/src/crepe/api/EventManager.cpp b/src/crepe/api/EventManager.cpp
index e881d49..20f0dd3 100644
--- a/src/crepe/api/EventManager.cpp
+++ b/src/crepe/api/EventManager.cpp
@@ -1,6 +1,7 @@
 #include "EventManager.h"
 
 using namespace crepe;
+using namespace std;
 
 EventManager & EventManager::get_instance() {
 	static EventManager instance;
@@ -8,74 +9,38 @@ EventManager & EventManager::get_instance() {
 }
 
 void EventManager::dispatch_events() {
-	for (std::vector<std::tuple<std::unique_ptr<Event>, int,
-								std::type_index>>::iterator event_it
-		 = this->events_queue.begin();
-		 event_it != this->events_queue.end();) {
-		std::unique_ptr<Event> & event = std::get<0>(*event_it);
-		int channel = std::get<1>(*event_it);
-		std::type_index event_type = std::get<2>(*event_it);
+	for (auto & event : this->events_queue) {
+		this->handle_event(event.type, event.channel, *event.event.get());
+	}
+	this->events_queue.clear();
+}
 
-		bool event_handled = false;
+void EventManager::handle_event(type_index type, event_channel_t channel, const Event & data) {
+	auto handlers_it = this->subscribers.find(type);
+	if (handlers_it == this->subscribers.end()) return;
 
-		if (channel) {
-			std::unordered_map<
-				std::type_index,
-				std::unordered_map<
-					int, std::vector<std::unique_ptr<IEventHandlerWrapper>>>>::
-				iterator handlers_it
-				= subscribers_by_event_id.find(event_type);
-			if (handlers_it != subscribers_by_event_id.end()) {
-				std::unordered_map<
-					int, std::vector<std::unique_ptr<IEventHandlerWrapper>>> &
-					handlers_map
-					= handlers_it->second;
-				std::unordered_map<
-					int, std::vector<std::unique_ptr<IEventHandlerWrapper>>>::
-					iterator handlers
-					= handlers_map.find(channel);
-				if (handlers != handlers_map.end()) {
-					std::vector<std::unique_ptr<IEventHandlerWrapper>> &
-						callbacks
-						= handlers->second;
-					for (std::vector<std::unique_ptr<IEventHandlerWrapper>>::
-							 iterator handler_it
-						 = callbacks.begin();
-						 handler_it != callbacks.end(); ++handler_it) {
-						if ((*handler_it)->exec(*event)) {
-							event_it = events_queue.erase(event_it);
-							event_handled = true;
-							break;
-						}
-					}
-				}
-			}
-		} else {
-			// Handle event for all channels
-			std::unordered_map<
-				std::type_index,
-				std::vector<std::unique_ptr<IEventHandlerWrapper>>>::iterator
-				handlers_it
-				= this->subscribers.find(event_type);
-			if (handlers_it != this->subscribers.end()) {
-				std::vector<std::unique_ptr<IEventHandlerWrapper>> & handlers
-					= handlers_it->second;
-				for (std::vector<std::unique_ptr<IEventHandlerWrapper>>::
-						 iterator handler_it
-					 = handlers.begin();
-					 handler_it != handlers.end(); ++handler_it) {
-					// remove event from queue since and continue when callback returns true
-					if ((*handler_it)->exec(*event)) {
-						event_it = this->events_queue.erase(event_it);
-						event_handled = true;
-						break;
-					}
-				}
-			}
-		}
+	vector<CallbackEntry> & handlers = handlers_it->second;
+	for (auto & handler : handlers) {
+		bool check_channel = handler.channel != CHANNEL_ALL || channel != CHANNEL_ALL;
+		if (check_channel && handler.channel != channel) continue;
+
+		bool handled = handler.callback->exec(data);
+		if (handled) return;
+	}
+}
+
+void EventManager::clear() {
+	this->subscribers.clear();
+	this->events_queue.clear();
+}
 
-		if (!event_handled) {
-			++event_it;
+void EventManager::unsubscribe(subscription_t id) {
+	for (auto & [event_type, handlers] : this->subscribers) {
+		for (auto it = handlers.begin(); it != handlers.end(); it++) {
+			// find listener with subscription id
+			if ((*it).id != id) continue;
+			it = handlers.erase(it);
+			return;
 		}
 	}
 }
diff --git a/src/crepe/api/EventManager.h b/src/crepe/api/EventManager.h
index 38d2e64..348a04d 100644
--- a/src/crepe/api/EventManager.h
+++ b/src/crepe/api/EventManager.h
@@ -1,8 +1,6 @@
 #pragma once
 
-#include <functional>
 #include <memory>
-#include <type_traits>
 #include <typeindex>
 #include <unordered_map>
 #include <vector>
@@ -10,113 +8,154 @@
 #include "Event.h"
 #include "EventHandler.h"
 
-
 namespace crepe {
+
+//! Event listener unique ID
+typedef size_t subscription_t;
+
+/**
+ * \brief Event channel
+ *
+ * Events can be sent to a specific channel, which prevents listeners on other channels from
+ * being called. The default channel is EventManager::CHANNEL_ALL, which calls all listeners.
+ */
+typedef size_t event_channel_t;
+
 /**
  * \class EventManager
- * \brief The EventManager class is responsible for managing the subscription, triggering, 
- * and queueing of events. It handles events and dispatches them to appropriate subscribers.
+ * \brief Manages event subscriptions, triggers, and queues, enabling decoupled event handling.
+ * 
+ * The `EventManager` acts as a centralized event system. It allows for registering callbacks
+ * for specific event types, triggering events synchronously, queueing events for later
+ * processing, and managing subscriptions via unique identifiers.
  */
 class EventManager {
 public:
-	/**
-     * \brief Deleted copy constructor to prevent copying of the EventManager instance.
-     */
-	EventManager(const EventManager &) = delete;
-
-	/**
-     * \brief Deleted copy assignment operator to prevent assignment of the EventManager instance.
-     */
-	const EventManager & operator=(const EventManager &) = delete;
+	static constexpr const event_channel_t CHANNEL_ALL = -1;
 
 	/**
-     * \brief Get the singleton instance of the EventManager.
-     * 
-     * This method returns the unique instance of the EventManager, creating it on the first call.
-     * 
-     * \return Reference to the EventManager instance.
-     */
+	 * \brief Get the singleton instance of the EventManager.
+	 * 
+	 * This method returns the unique instance of the EventManager, creating it if it
+	 * doesn't already exist. Ensures only one instance is active in the program.
+	 * 
+	 * \return Reference to the singleton instance of the EventManager.
+	 */
 	static EventManager & get_instance();
 
 	/**
-     * \brief Subscribe to an event.
-     * 
-     * This method allows the registration of a callback for a specific event type and channel.
-     * 
-     * \tparam EventType The type of the event to subscribe to.
-     * \param callback The callback function to invoke when the event is triggered.
-     * \param channel The channel number to subscribe to (default is 0).
-     */
+	 * \brief Subscribe to a specific event type.
+	 * 
+	 * Registers a callback for a given event type and optional channel. Each callback
+	 * is assigned a unique subscription ID that can be used for later unsubscription.
+	 * 
+	 * \tparam EventType The type of the event to subscribe to.
+	 * \param callback The callback function to be invoked when the event is triggered.
+	 * \param channel The channel number to subscribe to (default is CHANNEL_ALL, which listens to all channels).
+	 * \return A unique subscription ID associated with the registered callback.
+	 */
 	template <typename EventType>
-	void subscribe(EventHandler<EventType> && callback, int channel = 0);
+	subscription_t subscribe(const EventHandler<EventType> & callback,
+							 event_channel_t channel = CHANNEL_ALL);
 
 	/**
-     * \brief Unsubscribe from an event.
-     * 
-     * This method removes a previously registered callback from an event.
-     * 
-     * \tparam EventType The type of the event to unsubscribe from.
-     * \param callback The callback function to remove from the subscription list.
-     * \param channel The event ID to unsubscribe from.
-     */
-	template <typename EventType>
-	void unsubscribe(const EventHandler<EventType> &, int channel);
+	 * \brief Unsubscribe a previously registered callback.
+	 * 
+	 * Removes a callback from the subscription list based on its unique subscription ID.
+	 * 
+	 * \param event_id The unique subscription ID of the callback to remove.
+	 */
+	void unsubscribe(subscription_t event_id);
 
 	/**
-     * \brief Trigger an event.
-     * 
-     * This method invokes the appropriate callback(s) for the specified event.
-     * 
-     * \tparam EventType The type of the event to trigger.
-     * \param event The event data to pass to the callback.
-     * \param channel The channel from which to trigger the event (default is 0).
-     */
+	 * \brief Trigger an event immediately.
+	 * 
+	 * Synchronously invokes all registered callbacks for the given event type on the specified channel.
+	 * 
+	 * \tparam EventType The type of the event to trigger.
+	 * \param event The event instance to pass to the callbacks.
+	 * \param channel The channel to trigger the event on (default is CHANNEL_ALL, which triggers on all channels).
+	 */
 	template <typename EventType>
-	void trigger_event(const EventType & event, int channel);
+	void trigger_event(const EventType & event, event_channel_t channel = CHANNEL_ALL);
 
 	/**
-     * \brief Queue an event for later processing.
-     * 
-     * This method adds an event to the event queue, which will be processed in the 
-     * dispatch_events function.
-     * 
-     * \tparam EventType The type of the event to queue.
-     * \param event The event to queue.
-     * \param channel The channel number for the event (default is 0).
-     */
+	 * \brief Queue an event for later processing.
+	 * 
+	 * Adds an event to the event queue to be processed during the next call to `dispatch_events`.
+	 * 
+	 * \tparam EventType The type of the event to queue.
+	 * \param event The event instance to queue.
+	 * \param channel The channel to associate with the event (default is CHANNEL_ALL).
+	 */
 	template <typename EventType>
-	void queue_event(EventType && event, int channel);
+	void queue_event(const EventType & event, event_channel_t channel = CHANNEL_ALL);
 
 	/**
-     * \brief Dispatch all queued events.
-     * 
-     * This method processes all events in the event queue and triggers the corresponding 
-     * callbacks for each event.
-     */
+	 * \brief Process all queued events.
+	 * 
+	 * Iterates through the event queue and triggers callbacks for each queued event.
+	 * Events are removed from the queue once processed.
+	 */
 	void dispatch_events();
 
+	/**
+	 * \brief Clear all subscriptions.
+	 * 
+	 * Removes all registered event handlers and clears the subscription list.
+	 */
+	void clear();
+
 private:
 	/**
-     * \brief Default constructor for the EventManager.
-     * 
-     * This constructor is private to enforce the singleton pattern.
-     */
+	 * \brief Default constructor for the EventManager.
+	 * 
+	 * Constructor is private to enforce the singleton pattern.
+	 */
 	EventManager() = default;
 
-	//! The queue of events to be processed.
-	std::vector<std::tuple<std::unique_ptr<Event>, int, std::type_index>>
-		events_queue;
-	//! Registered event handlers.
-	std::unordered_map<std::type_index,
-					   std::vector<std::unique_ptr<IEventHandlerWrapper>>>
-		subscribers;
-	//! Event handlers indexed by event ID.
-	std::unordered_map<
-		std::type_index,
-		std::unordered_map<int,
-						   std::vector<std::unique_ptr<IEventHandlerWrapper>>>>
-		subscribers_by_event_id;
+	/**
+	 * \struct QueueEntry
+	 * \brief Represents an entry in the event queue.
+	 */
+	struct QueueEntry {
+		std::unique_ptr<Event> event; ///< The event instance.
+		event_channel_t channel = CHANNEL_ALL; ///< The channel associated with the event.
+		std::type_index type; ///< The type of the event.
+	};
+
+	/**
+	 * \brief Internal event handler
+	 *
+	 * This function processes a single event, and is used to process events both during
+	 * EventManager::dispatch_events and inside EventManager::trigger_event
+	 *
+	 * \param type \c typeid of concrete Event class
+	 * \param channel Event channel
+	 * \param data Event data
+	 */
+	void handle_event(std::type_index type, event_channel_t channel, const Event & data);
+
+	/**
+	 * \struct CallbackEntry
+	 * \brief Represents a registered event handler callback.
+	 */
+	struct CallbackEntry {
+		std::unique_ptr<IEventHandlerWrapper> callback; ///< The callback function wrapper.
+		event_channel_t channel = CHANNEL_ALL; ///< The channel this callback listens to.
+		subscription_t id = -1; ///< Unique subscription ID.
+	};
+
+	//! The queue of events to be processed during dispatch.
+	std::vector<QueueEntry> events_queue;
+
+	//! A map of event type to registered callbacks.
+	std::unordered_map<std::type_index, std::vector<CallbackEntry>> subscribers;
+
+	//! Counter to generate unique subscription IDs.
+	subscription_t subscription_counter = 0;
 };
 
 } // namespace crepe
+
 #include "EventManager.hpp"
diff --git a/src/crepe/api/EventManager.hpp b/src/crepe/api/EventManager.hpp
index b509097..a5f4556 100644
--- a/src/crepe/api/EventManager.hpp
+++ b/src/crepe/api/EventManager.hpp
@@ -1,140 +1,36 @@
+#pragma once
+
 #include "EventManager.h"
+
 namespace crepe {
 
 template <typename EventType>
-void EventManager::subscribe(EventHandler<EventType> && callback, int channel) {
+subscription_t EventManager::subscribe(const EventHandler<EventType> & callback,
+									   event_channel_t channel) {
+	subscription_counter++;
 	std::type_index event_type = typeid(EventType);
 	std::unique_ptr<EventHandlerWrapper<EventType>> handler
 		= std::make_unique<EventHandlerWrapper<EventType>>(callback);
-
-	if (channel) {
-		std::unordered_map<int,
-						   std::vector<std::unique_ptr<IEventHandlerWrapper>>> &
-			handlers_map
-			= this->subscribers_by_event_id[event_type];
-		std::unordered_map<
-			int, std::vector<std::unique_ptr<IEventHandlerWrapper>>>::iterator
-			handlers
-			= handlers_map.find(channel);
-		if (handlers != handlers_map.end()) {
-			handlers->second.emplace_back(std::move(handler));
-		} else {
-			handlers_map[channel].emplace_back(std::move(handler));
-		}
-	} else {
-		std::vector<std::unique_ptr<IEventHandlerWrapper>> & handlers
-			= this->subscribers[event_type];
-		handlers.emplace_back(std::move(handler));
-	}
-}
-
-template <typename EventType>
-void EventManager::queue_event(EventType && event, int channel) {
-	std::type_index event_type = std::type_index(typeid(EventType));
-
-	std::unique_ptr<EventType> event_ptr
-		= std::make_unique<EventType>(std::forward<EventType>(event));
-
-	std::tuple<std::unique_ptr<Event>, int, std::type_index> tuple(
-		std::move(event_ptr), channel, event_type);
-	this->events_queue.push_back(std::move(tuple));
+	std::vector<CallbackEntry> & handlers = this->subscribers[event_type];
+	handlers.emplace_back(CallbackEntry{
+		.callback = std::move(handler), .channel = channel, .id = subscription_counter});
+	return subscription_counter;
 }
 
 template <typename EventType>
-void EventManager::trigger_event(const EventType & event, int channel) {
-	std::type_index event_type = std::type_index(typeid(EventType));
-
-	if (channel > 0) {
-		std::unordered_map<int,
-						   std::vector<std::unique_ptr<IEventHandlerWrapper>>> &
-			handlers_map
-			= this->subscribers_by_event_id[event_type];
-		std::unordered_map<
-			int, std::vector<std::unique_ptr<IEventHandlerWrapper>>>::iterator
-			handlers_it
-			= handlers_map.find(channel);
-
-		if (handlers_it != handlers_map.end()) {
-			std::vector<std::unique_ptr<IEventHandlerWrapper>> & handlers
-				= handlers_it->second;
-			for (std::vector<std::unique_ptr<IEventHandlerWrapper>>::iterator it
-				 = handlers.begin();
-				 it != handlers.end();++it) {
-				// stops when callback returns true
-				if((*it)->exec(event)){
-					break;
-				}
-			}
-		}
-	} else {
-		std::vector<std::unique_ptr<IEventHandlerWrapper>> & handlers
-			= this->subscribers[event_type];
-		for (std::vector<std::unique_ptr<IEventHandlerWrapper>>::iterator it
-			 = handlers.begin();
-			 it != handlers.end();++it) {
-			// stops when callback returns true
-			if((*it)->exec(event)){
-					break;
-				}
-		}
-	}
+void EventManager::queue_event(const EventType & event, event_channel_t channel) {
+	static_assert(std::is_base_of<Event, EventType>::value,
+				  "EventType must derive from Event");
+	this->events_queue.push_back(QueueEntry{
+		.event = std::make_unique<EventType>(event),
+		.channel = channel,
+		.type = typeid(EventType),
+	});
 }
 
 template <typename EventType>
-void EventManager::unsubscribe(const EventHandler<EventType> & callback,
-							   int channel) {
-	std::type_index event_type(typeid(EventType));
-	std::string handler_name = callback.target_type().name();
-
-	if (channel) {
-		std::unordered_map<
-			std::type_index,
-			std::unordered_map<
-				int, std::vector<std::unique_ptr<IEventHandlerWrapper>>>>::
-			iterator subscriber_list
-			= this->subscribers_by_event_id.find(event_type);
-		if (subscriber_list != this->subscribers_by_event_id.end()) {
-			std::unordered_map<
-				int, std::vector<std::unique_ptr<IEventHandlerWrapper>>> &
-				handlers_map
-				= subscriber_list->second;
-			std::unordered_map<
-				int,
-				std::vector<std::unique_ptr<IEventHandlerWrapper>>>::iterator
-				handlers
-				= handlers_map.find(channel);
-			if (handlers != handlers_map.end()) {
-				std::vector<std::unique_ptr<IEventHandlerWrapper>> & callbacks
-					= handlers->second;
-				for (std::vector<
-						 std::unique_ptr<IEventHandlerWrapper>>::iterator it
-					 = callbacks.begin();
-					 it != callbacks.end(); ++it) {
-					if ((*it)->get_type() == handler_name) {
-						it = callbacks.erase(it);
-						return;
-					}
-				}
-			}
-		}
-	} else {
-		std::unordered_map<std::type_index,
-						   std::vector<std::unique_ptr<IEventHandlerWrapper>>>::
-			iterator handlers_it
-			= this->subscribers.find(event_type);
-		if (handlers_it != this->subscribers.end()) {
-			std::vector<std::unique_ptr<IEventHandlerWrapper>> & handlers
-				= handlers_it->second;
-			for (std::vector<std::unique_ptr<IEventHandlerWrapper>>::iterator it
-				 = handlers.begin();
-				 it != handlers.end(); ++it) {
-				if ((*it)->get_type() == handler_name) {
-					it = handlers.erase(it);
-					return;
-				}
-			}
-		}
-	}
+void EventManager::trigger_event(const EventType & event, event_channel_t channel) {
+	this->handle_event(typeid(EventType), channel, event);
 }
 
-}
+} // namespace crepe
diff --git a/src/crepe/api/GameObject.cpp b/src/crepe/api/GameObject.cpp
index 287e81d..4874426 100644
--- a/src/crepe/api/GameObject.cpp
+++ b/src/crepe/api/GameObject.cpp
@@ -23,12 +23,10 @@ void GameObject::set_parent(const GameObject & parent) {
 	ComponentManager & mgr = this->component_manager;
 
 	// Set parent on own Metadata component
-	vector<reference_wrapper<Metadata>> this_metadata
-		= mgr.get_components_by_id<Metadata>(this->id);
+	RefVector<Metadata> this_metadata = mgr.get_components_by_id<Metadata>(this->id);
 	this_metadata.at(0).get().parent = parent.id;
 
 	// Add own id to children list of parent's Metadata component
-	vector<reference_wrapper<Metadata>> parent_metadata
-		= mgr.get_components_by_id<Metadata>(parent.id);
+	RefVector<Metadata> parent_metadata = mgr.get_components_by_id<Metadata>(parent.id);
 	parent_metadata.at(0).get().children.push_back(this->id);
 }
diff --git a/src/crepe/api/IKeyListener.cpp b/src/crepe/api/IKeyListener.cpp
index 4fd9855..8642655 100644
--- a/src/crepe/api/IKeyListener.cpp
+++ b/src/crepe/api/IKeyListener.cpp
@@ -2,50 +2,18 @@
 
 using namespace crepe;
 
-IKeyListener::IKeyListener() {
-	this->channel = channel;
-	this->subscribe_events();
-}
-IKeyListener::IKeyListener(int channel) {
-	this->channel = channel;
-	this->subscribe_events();
-}
-IKeyListener::~IKeyListener() { this->unsubscribe_events(); }
-
-void IKeyListener::subscribe_events() {
-	key_pressed_handler = [this](const KeyPressEvent & event) {
-		return this->on_key_pressed(event);
-	};
-	key_released_handler = [this](const KeyReleaseEvent & event) {
-		return this->on_key_released(event);
-	};
-	EventManager::get_instance().subscribe<KeyPressEvent>(
-		std::move(this->key_pressed_handler), this->channel);
-	EventManager::get_instance().subscribe<KeyReleaseEvent>(
-		std::move(this->key_released_handler), this->channel);
+// Constructor with specified channel
+IKeyListener::IKeyListener(event_channel_t channel)
+	: event_manager(EventManager::get_instance()) {
+	this->press_id = event_manager.subscribe<KeyPressEvent>(
+		[this](const KeyPressEvent & event) { return this->on_key_pressed(event); }, channel);
+	this->release_id = event_manager.subscribe<KeyReleaseEvent>(
+		[this](const KeyReleaseEvent & event) { return this->on_key_released(event); },
+		channel);
 }
 
-void IKeyListener::unsubscribe_events() {
-	EventManager::get_instance().unsubscribe<KeyPressEvent>(
-		this->key_pressed_handler, channel);
-	EventManager::get_instance().unsubscribe<KeyReleaseEvent>(
-		this->key_released_handler, channel);
-	std::cout << std::endl;
-}
-void IKeyListener::activate_keys() {
-	if (this->active) {
-		return;
-	}
-	this->subscribe_events();
-}
-void IKeyListener::deactivate_keys() {
-	if (!this->active) {
-		return;
-	}
-	this->unsubscribe_events();
-}
-void IKeyListener::set_channel(int channel) {
-	this->unsubscribe_events();
-	this->channel = channel;
-	this->subscribe_events();
+// Destructor, unsubscribe events
+IKeyListener::~IKeyListener() {
+	event_manager.unsubscribe(this->press_id);
+	event_manager.unsubscribe(this->release_id);
 }
diff --git a/src/crepe/api/IKeyListener.h b/src/crepe/api/IKeyListener.h
index 839acbf..328a4c2 100644
--- a/src/crepe/api/IKeyListener.h
+++ b/src/crepe/api/IKeyListener.h
@@ -1,8 +1,11 @@
 #pragma once
+
 #include "Event.h"
 #include "EventHandler.h"
 #include "EventManager.h"
 
+namespace crepe {
+
 /**
  * \class IKeyListener
  * \brief Interface for keyboard event handling in the application.
@@ -13,17 +16,12 @@ public:
      * \brief Constructs an IKeyListener with a specified channel.
      * \param channel The channel ID for event handling.
      */
-	IKeyListener(int channel);
-
-	/**
-     * \brief Default constructor for IKeyListener.
-     */
-	IKeyListener();
-
-	/**
-     * \brief Destructor.
-     */
+	IKeyListener(event_channel_t channel = EventManager::CHANNEL_ALL);
 	virtual ~IKeyListener();
+	IKeyListener(const IKeyListener &) = delete;
+	IKeyListener & operator=(const IKeyListener &) = delete;
+	IKeyListener & operator=(IKeyListener &&) = delete;
+	IKeyListener(IKeyListener &&) = delete;
 
 	/**
      * \brief Pure virtual function to handle key press events.
@@ -39,40 +37,13 @@ public:
      */
 	virtual bool on_key_released(const KeyReleaseEvent & event) = 0;
 
-	/**
-     * \brief Activates key listening.
-     */
-	void activate_keys();
-
-	/**
-     * \brief Deactivates key listening.
-     */
-	void deactivate_keys();
-
-	/**
-     * \brief Sets the channel ID for event handling.
-     * \param channel The channel ID to set.
-     */
-	void set_channel(int channel);
-
-protected:
-	/**
-     * \brief Subscribes to key events.
-     */
-	void subscribe_events();
-
-	/**
-     * \brief Unsubscribes from key events.
-     */
-	void unsubscribe_events();
-
 private:
-	//! Indicates whether key listening is active.
-	bool active = true;
-	//! Channel ID for event handling.
-	int channel = 0;
-	//! Key press event handler.
-	EventHandler<KeyPressEvent> key_pressed_handler;
-	//!< Key release event handler.
-	EventHandler<KeyReleaseEvent> key_released_handler;
+	//! Key press event id
+	subscription_t press_id = -1;
+	//! Key release event id
+	subscription_t release_id = -1;
+	//! EventManager reference
+	EventManager & event_manager;
 };
+
+} // namespace crepe
diff --git a/src/crepe/api/IMouseListener.cpp b/src/crepe/api/IMouseListener.cpp
index 489e55b..989aeb3 100644
--- a/src/crepe/api/IMouseListener.cpp
+++ b/src/crepe/api/IMouseListener.cpp
@@ -2,63 +2,28 @@
 
 using namespace crepe;
 
-IMouseListener::IMouseListener(int channel) { this->channel = channel; }
-
-IMouseListener::IMouseListener() { this->subscribe_events(); }
-
-IMouseListener::~IMouseListener() { this->unsubscribe_events(); }
-
-void IMouseListener::subscribe_events() {
-	// Define handler lambdas and subscribe them
-	mouse_click_handler = [this](const MouseClickEvent & event) {
-		return this->on_mouse_clicked(event);
-	};
-	mouse_press_handler = [this](const MousePressEvent & event) {
-		return this->on_mouse_pressed(event);
-	};
-	mouse_release_handler = [this](const MouseReleaseEvent & event) {
-		return this->on_mouse_released(event);
-	};
-	mouse_move_handler = [this](const MouseMoveEvent & event) {
-		return this->on_mouse_moved(event);
-	};
-	EventManager::get_instance().subscribe<MouseClickEvent>(
-		std::move(this->mouse_click_handler), this->channel);
-	EventManager::get_instance().subscribe<MousePressEvent>(
-		std::move(this->mouse_press_handler), this->channel);
-	EventManager::get_instance().subscribe<MouseReleaseEvent>(
-		std::move(this->mouse_release_handler), this->channel);
-	EventManager::get_instance().subscribe<MouseMoveEvent>(
-		std::move(this->mouse_move_handler), this->channel);
-}
-// TODO: reference voor singleton
-void IMouseListener::unsubscribe_events() {
-	EventManager::get_instance().unsubscribe<MouseClickEvent>(
-		this->mouse_click_handler, this->channel);
-	EventManager::get_instance().unsubscribe<MousePressEvent>(
-		this->mouse_press_handler, this->channel);
-	EventManager::get_instance().unsubscribe<MouseReleaseEvent>(
-		this->mouse_release_handler, this->channel);
-	EventManager::get_instance().unsubscribe<MouseMoveEvent>(
-		this->mouse_move_handler, this->channel);
-}
-
-void IMouseListener::activate_mouse() {
-	if (this->active) {
-		return;
-	}
-	this->subscribe_events();
-}
-
-void IMouseListener::deactivate_mouse() {
-	if (!this->active) {
-		return;
-	}
-	this->unsubscribe_events();
+IMouseListener::IMouseListener(event_channel_t channel)
+	: event_manager(EventManager::get_instance()) {
+	this->click_id = event_manager.subscribe<MouseClickEvent>(
+		[this](const MouseClickEvent & event) { return this->on_mouse_clicked(event); },
+		channel);
+
+	this->press_id = event_manager.subscribe<MousePressEvent>(
+		[this](const MousePressEvent & event) { return this->on_mouse_pressed(event); },
+		channel);
+
+	this->release_id = event_manager.subscribe<MouseReleaseEvent>(
+		[this](const MouseReleaseEvent & event) { return this->on_mouse_released(event); },
+		channel);
+
+	this->move_id = event_manager.subscribe<MouseMoveEvent>(
+		[this](const MouseMoveEvent & event) { return this->on_mouse_moved(event); }, channel);
 }
 
-void IMouseListener::set_channel(int channel) {
-	this->unsubscribe_events();
-	this->channel = channel;
-	this->subscribe_events();
+IMouseListener::~IMouseListener() {
+	// Unsubscribe event handlers
+	event_manager.unsubscribe(this->click_id);
+	event_manager.unsubscribe(this->press_id);
+	event_manager.unsubscribe(this->release_id);
+	event_manager.unsubscribe(this->move_id);
 }
diff --git a/src/crepe/api/IMouseListener.h b/src/crepe/api/IMouseListener.h
index 7e92956..15e1619 100644
--- a/src/crepe/api/IMouseListener.h
+++ b/src/crepe/api/IMouseListener.h
@@ -4,6 +4,8 @@
 #include "EventHandler.h"
 #include "EventManager.h"
 
+namespace crepe {
+
 /**
  * \class IMouseListener
  * \brief Interface for mouse event handling in the application.
@@ -11,34 +13,14 @@
 class IMouseListener {
 public:
 	/**
-     * \brief Default constructor.
-     */
-	IMouseListener();
-
-	/**
      * \brief Constructs an IMouseListener with a specified channel.
      * \param channel The channel ID for event handling.
      */
-	IMouseListener(int channel);
-
-	/**
-     * \brief Destructor.
-     */
+	IMouseListener(event_channel_t channel = EventManager::CHANNEL_ALL);
 	virtual ~IMouseListener();
-
-	/**
-     * \brief Copy constructor (deleted).
-     */
-	IMouseListener(const IMouseListener &) = delete;
-
-	/**
-     * \brief Copy assignment operator (deleted).
-     */
 	IMouseListener & operator=(const IMouseListener &) = delete;
-
-	/**
-     * \brief Move constructor (deleted).
-     */
+	IMouseListener(const IMouseListener &) = delete;
+	IMouseListener & operator=(const IMouseListener &&) = delete;
 	IMouseListener(IMouseListener &&) = delete;
 
 	/**
@@ -74,44 +56,17 @@ public:
      */
 	virtual bool on_mouse_moved(const MouseMoveEvent & event) = 0;
 
-	/**
-     * \brief Activates mouse listening.
-     */
-	void activate_mouse();
-
-	/**
-     * \brief Deactivates mouse listening.
-     */
-	void deactivate_mouse();
-
-	/**
-     * \brief Sets the channel ID for event handling.
-     * \param channel The channel ID to set.
-     */
-	void set_channel(int channel);
-
-protected:
-	/**
-     * \brief Subscribes to mouse events on the specified channel.
-     */
-	void subscribe_events();
-
-	/**
-     * \brief Unsubscribes from mouse events on the specified channel.
-     */
-	void unsubscribe_events();
-
 private:
-	//! Indicates whether mouse listening is active.
-	bool active = true;
-	//! Channel ID for event handling.
-	int channel = 0;
-	//! Mouse click event handler.
-	EventHandler<MouseClickEvent> mouse_click_handler;
-	//! Mouse press event handler.
-	EventHandler<MousePressEvent> mouse_press_handler;
-	//! Mouse release event handler.
-	EventHandler<MouseReleaseEvent> mouse_release_handler;
-	//! Mouse move event handler.
-	EventHandler<MouseMoveEvent> mouse_move_handler;
+	//! Mouse click event id
+	subscription_t click_id = -1;
+	//! Mouse press event id
+	subscription_t press_id = -1;
+	//! Mouse release event id
+	subscription_t release_id = -1;
+	//! Mouse move event id
+	subscription_t move_id = -1;
+	//! EventManager reference
+	EventManager & event_manager;
 };
+
+} //namespace crepe
diff --git a/src/crepe/api/KeyCodes.h b/src/crepe/api/KeyCodes.h
index e5a91fc..9e173e0 100644
--- a/src/crepe/api/KeyCodes.h
+++ b/src/crepe/api/KeyCodes.h
@@ -1,94 +1,93 @@
 #pragma once
 
+//! Enumeration for mouse button inputs, including standard and extended buttons.
 enum class MouseButton {
-	NONE = 0,
-	LEFT_MOUSE = 1,
-	RIGHT_MOUSE = 2,
-	MIDDLE_MOUSE = 3,
-	X1_MOUSE = 4,
-	X2_MOUSE = 5,
-	SCROLL_UP = 6,
-	SCROLL_DOWN = 7,
+	NONE = 0, //!< No mouse button input.
+	LEFT_MOUSE = 1, //!< Left mouse button.
+	RIGHT_MOUSE = 2, //!< Right mouse button.
+	MIDDLE_MOUSE = 3, //!< Middle mouse button (scroll wheel press).
+	X1_MOUSE = 4, //!< First extended mouse button.
+	X2_MOUSE = 5, //!< Second extended mouse button.
+	SCROLL_UP = 6, //!< Scroll wheel upward movement.
+	SCROLL_DOWN = 7, //!< Scroll wheel downward movement.
 };
 
-enum class Keycode : int {
-	NONE = 0,
-	SPACE = 32,
-	APOSTROPHE = 39, /* ' */
-	COMMA = 44, /* , */
-	MINUS = 45, /* - */
-	PERIOD = 46, /* . */
-	SLASH = 47, /* / */
-
-	D0 = 48, /* 0 */
-	D1 = 49, /* 1 */
-	D2 = 50, /* 2 */
-	D3 = 51, /* 3 */
-	D4 = 52, /* 4 */
-	D5 = 53, /* 5 */
-	D6 = 54, /* 6 */
-	D7 = 55, /* 7 */
-	D8 = 56, /* 8 */
-	D9 = 57, /* 9 */
-
-	SEMICOLON = 59, /* ; */
-	EQUAL = 61, /* = */
-
-	A = 65,
-	B = 66,
-	C = 67,
-	D = 68,
-	E = 69,
-	F = 70,
-	G = 71,
-	H = 72,
-	I = 73,
-	J = 74,
-	K = 75,
-	L = 76,
-	M = 77,
-	N = 78,
-	O = 79,
-	P = 80,
-	Q = 81,
-	R = 82,
-	S = 83,
-	T = 84,
-	U = 85,
-	V = 86,
-	W = 87,
-	X = 88,
-	Y = 89,
-	Z = 90,
-
-	LEFT_BRACKET = 91, /* [ */
-	BACKSLASH = 92, /* \ */
-	RIGHT_BRACKET = 93, /* ] */
-	GRAVE_ACCENT = 96, /* ` */
-
-	WORLD1 = 161, /* non-US #1 */
-	WORLD2 = 162, /* non-US #2 */
-
-	/* Function keys */
-	ESCAPE = 256,
-	ENTER = 257,
-	TAB = 258,
-	BACKSPACE = 259,
-	INSERT = 260,
-	DELETE = 261,
-	RIGHT = 262,
-	LEFT = 263,
-	DOWN = 264,
-	UP = 265,
-	PAGE_UP = 266,
-	PAGE_DOWN = 267,
-	HOME = 268,
-	END = 269,
-	CAPS_LOCK = 280,
-	SCROLL_LOCK = 281,
-	NUM_LOCK = 282,
-	PRINT_SCREEN = 283,
-	PAUSE = 284,
+//! Enumeration for keyboard key inputs, including printable characters, function keys, and keypad keys.
+enum class Keycode {
+	NONE = 0, //!< No key input.
+	SPACE = 32, //!< Spacebar.
+	APOSTROPHE = 39, //!< Apostrophe (').
+	COMMA = 44, //!< Comma (,).
+	MINUS = 45, //!< Minus (-).
+	PERIOD = 46, //!< Period (.).
+	SLASH = 47, //!< Slash (/).
+	D0 = 48, //!< Digit 0.
+	D1 = 49, //!< Digit 1.
+	D2 = 50, //!< Digit 2.
+	D3 = 51, //!< Digit 3.
+	D4 = 52, //!< Digit 4.
+	D5 = 53, //!< Digit 5.
+	D6 = 54, //!< Digit 6.
+	D7 = 55, //!< Digit 7.
+	D8 = 56, //!< Digit 8.
+	D9 = 57, //!< Digit 9.
+	SEMICOLON = 59, //!< Semicolon (;).
+	EQUAL = 61, //!< Equal sign (=).
+	A = 65, //!< Key 'A'.
+	B = 66, //!< Key 'B'.
+	C = 67, //!< Key 'C'.
+	D = 68, //!< Key 'D'.
+	E = 69, //!< Key 'E'.
+	F = 70, //!< Key 'F'.
+	G = 71, //!< Key 'G'.
+	H = 72, //!< Key 'H'.
+	I = 73, //!< Key 'I'.
+	J = 74, //!< Key 'J'.
+	K = 75, //!< Key 'K'.
+	L = 76, //!< Key 'L'.
+	M = 77, //!< Key 'M'.
+	N = 78, //!< Key 'N'.
+	O = 79, //!< Key 'O'.
+	P = 80, //!< Key 'P'.
+	Q = 81, //!< Key 'Q'.
+	R = 82, //!< Key 'R'.
+	S = 83, //!< Key 'S'.
+	T = 84, //!< Key 'T'.
+	U = 85, //!< Key 'U'.
+	V = 86, //!< Key 'V'.
+	W = 87, //!< Key 'W'.
+	X = 88, //!< Key 'X'.
+	Y = 89, //!< Key 'Y'.
+	Z = 90, //!< Key 'Z'.
+	LEFT_BRACKET = 91, //!< Left bracket ([).
+	BACKSLASH = 92, //!< Backslash (\).
+	RIGHT_BRACKET = 93, //!< Right bracket (]).
+	GRAVE_ACCENT = 96, //!< Grave accent (`).
+	WORLD1 = 161, //!< Non-US key #1.
+	WORLD2 = 162, //!< Non-US key #2.
+	ESCAPE = 256, //!< Escape key.
+	ENTER = 257, //!< Enter key.
+	TAB = 258, //!< Tab key.
+	BACKSPACE = 259, //!< Backspace key.
+	INSERT = 260, //!< Insert key.
+	DELETE = 261, //!< Delete key.
+	RIGHT = 262, //!< Right arrow key.
+	LEFT = 263, //!< Left arrow key.
+	DOWN = 264, //!< Down arrow key.
+	UP = 265, //!< Up arrow key.
+	PAGE_UP = 266, //!< Page Up key.
+	PAGE_DOWN = 267, //!< Page Down key.
+	HOME = 268, //!< Home key.
+	END = 269, //!< End key.
+	CAPS_LOCK = 280, //!< Caps Lock key.
+	SCROLL_LOCK = 281, //!< Scroll Lock key.
+	NUM_LOCK = 282, //!< Num Lock key.
+	PRINT_SCREEN = 283, //!< Print Screen key.
+	PAUSE = 284, //!< Pause key.
+	/**
+	 * \name Function keys (F1-F25).
+	 * \{
+	 */
 	F1 = 290,
 	F2 = 291,
 	F3 = 292,
@@ -114,8 +113,11 @@ enum class Keycode : int {
 	F23 = 312,
 	F24 = 313,
 	F25 = 314,
-
-	/* Keypad */
+	/// \}
+	/**
+	 * \name Keypad digits and operators.
+	 * \{
+	 */
 	KP0 = 320,
 	KP1 = 321,
 	KP2 = 322,
@@ -133,7 +135,11 @@ enum class Keycode : int {
 	KP_ADD = 334,
 	KP_ENTER = 335,
 	KP_EQUAL = 336,
-
+	/// \}
+	/**
+	 * \name Modifier keys.
+	 * \{
+	 */
 	LEFT_SHIFT = 340,
 	LEFT_CONTROL = 341,
 	LEFT_ALT = 342,
@@ -142,5 +148,6 @@ enum class Keycode : int {
 	RIGHT_CONTROL = 345,
 	RIGHT_ALT = 346,
 	RIGHT_SUPER = 347,
-	MENU = 348
+	/// \}
+	MENU = 348, //!< Menu key.
 };
diff --git a/src/crepe/api/LoopManager.h b/src/crepe/api/LoopManager.h
index 37f13ac..13e6dac 100644
--- a/src/crepe/api/LoopManager.h
+++ b/src/crepe/api/LoopManager.h
@@ -8,11 +8,24 @@
 
 namespace crepe {
 
+/**
+ * \brief Main game loop manager
+ *
+ * This class is responsible for managing the game loop, including initialization and updating.
+ */
 class LoopManager {
 public:
 	void start();
 	LoopManager();
 
+	/**
+	 * \brief Add a new concrete scene to the scene manager
+	 *
+	 * \tparam T  Type of concrete scene
+	 */
+	template <typename T>
+	void add_scene();
+
 private:
 	/**
 	 * \brief Setup function for one-time initialization.
@@ -54,12 +67,14 @@ private:
 	 * This function updates physics and game logic based on LoopTimer's fixed_delta_time.
 	 */
 	void fixed_update();
+
 	/**
 	 * \brief Set game running variable
 	 *
 	 * \param running running (false = game shutdown, true = game running)
 	 */
 	void set_running(bool running);
+
 	/**
 	 * \brief Function for executing render-related systems.
 	 *
@@ -72,9 +87,9 @@ private:
 private:
 	//! Component manager instance
 	ComponentManager component_manager{};
-public:
 	//! Scene manager instance
 	SceneManager scene_manager{component_manager};
+
 private:
 	/**
 	 * \brief Collection of System instances
diff --git a/src/crepe/api/LoopManager.hpp b/src/crepe/api/LoopManager.hpp
index 0b14fdb..9cf470b 100644
--- a/src/crepe/api/LoopManager.hpp
+++ b/src/crepe/api/LoopManager.hpp
@@ -11,6 +11,11 @@
 namespace crepe {
 
 template <class T>
+void LoopManager::add_scene() {
+	this->scene_manager.add_scene<T>();
+}
+
+template <class T>
 T & LoopManager::get_system() {
 	using namespace std;
 	static_assert(is_base_of<System, T>::value,
diff --git a/src/crepe/api/Scene.cpp b/src/crepe/api/Scene.cpp
index 88aa82d..849945e 100644
--- a/src/crepe/api/Scene.cpp
+++ b/src/crepe/api/Scene.cpp
@@ -2,6 +2,4 @@
 
 using namespace crepe;
 
-Scene::Scene(ComponentManager & mgr, const std::string & name)
-	: component_manager(mgr),
-	  name(name) {}
+Scene::Scene(ComponentManager & mgr) : component_manager(mgr) {}
diff --git a/src/crepe/api/Scene.h b/src/crepe/api/Scene.h
index 0e516b6..869bf6f 100644
--- a/src/crepe/api/Scene.h
+++ b/src/crepe/api/Scene.h
@@ -7,19 +7,36 @@ namespace crepe {
 class SceneManager;
 class ComponentManager;
 
+/**
+ * \brief Represents a Scene
+ * 
+ * This class represents a Scene. The Scene class is only used as an interface for the game
+ * programmer.
+ */
 class Scene {
 protected:
-	Scene(ComponentManager & mgr, const std::string & name);
+	//TODO: Use Loek's custom reference class to set ComponentManger via SceneManager instead of via constructor
+	/**
+	 * \param mgr  Reference to the ComponentManager
+	 */
+	Scene(ComponentManager & mgr);
+	//! SceneManager instances Scene
 	friend class SceneManager;
 
 public:
 	virtual ~Scene() = default;
 
 public:
+	//! Load the scene
 	virtual void load_scene() = 0;
-	const std::string name;
+	/**
+	 * \brief Get the scene's name
+	 * \return The scene's name
+	 */
+	virtual std::string get_name() const = 0;
 
 protected:
+	//! Reference to the ComponentManager
 	ComponentManager & component_manager;
 };
 
diff --git a/src/crepe/api/SceneManager.cpp b/src/crepe/api/SceneManager.cpp
index 7fb5cb0..1f783ad 100644
--- a/src/crepe/api/SceneManager.cpp
+++ b/src/crepe/api/SceneManager.cpp
@@ -18,7 +18,7 @@ void SceneManager::load_next_scene() {
 
 	auto it = find_if(this->scenes.begin(), this->scenes.end(),
 					  [&next_scene = this->next_scene](unique_ptr<Scene> & scene) {
-						  return scene->name == next_scene;
+						  return scene.get()->get_name() == next_scene;
 					  });
 
 	// next scene not found
diff --git a/src/crepe/api/SceneManager.h b/src/crepe/api/SceneManager.h
index e854794..45ba668 100644
--- a/src/crepe/api/SceneManager.h
+++ b/src/crepe/api/SceneManager.h
@@ -1,7 +1,6 @@
 #pragma once
 
 #include <memory>
-#include <queue>
 #include <vector>
 
 #include "Scene.h"
@@ -10,8 +9,15 @@ namespace crepe {
 
 class ComponentManager;
 
+/**
+ * \brief Manages scenes
+ *
+ * This class manages scenes. It can add new scenes and load them. It also manages the current scene
+ * and the next scene.
+ */
 class SceneManager {
 public:
+	//! \param mgr  Reference to the ComponentManager
 	SceneManager(ComponentManager & mgr);
 
 public:
@@ -19,10 +25,9 @@ public:
 	 * \brief Add a new concrete scene to the scene manager
 	 *
 	 * \tparam T  Type of concrete scene
-	 * \param name  Name of new scene
 	 */
 	template <typename T>
-	void add_scene(const std::string & name);
+	void add_scene();
 	/**
 	 * \brief Set the next scene
 	 *
@@ -35,8 +40,11 @@ public:
 	void load_next_scene();
 
 private:
+	//! Vector of concrete scenes (added by add_scene())
 	std::vector<std::unique_ptr<Scene>> scenes;
+	//! Next scene to load
 	std::string next_scene;
+	//! Reference to the ComponentManager
 	ComponentManager & component_manager;
 };
 
diff --git a/src/crepe/api/SceneManager.hpp b/src/crepe/api/SceneManager.hpp
index 714f690..94e5946 100644
--- a/src/crepe/api/SceneManager.hpp
+++ b/src/crepe/api/SceneManager.hpp
@@ -5,16 +5,16 @@
 namespace crepe {
 
 template <typename T>
-void SceneManager::add_scene(const std::string & name) {
+void SceneManager::add_scene() {
 	using namespace std;
 	static_assert(is_base_of<Scene, T>::value, "T must be derived from Scene");
 
-	Scene * scene = new T(this->component_manager, name);
+	Scene * scene = new T(this->component_manager);
 	this->scenes.emplace_back(unique_ptr<Scene>(scene));
 
 	// The first scene added, is the one that will be loaded at the beginning
 	if (next_scene.empty()) {
-		next_scene = name;
+		next_scene = scene->get_name();
 	}
 }
 
diff --git a/src/crepe/api/Script.h b/src/crepe/api/Script.h
index 939d142..0702e36 100644
--- a/src/crepe/api/Script.h
+++ b/src/crepe/api/Script.h
@@ -62,15 +62,15 @@ protected:
 	 * \returns List of component references
 	 */
 	template <typename T>
-	std::vector<std::reference_wrapper<T>> get_components() const;
-	
+	RefVector<T> get_components() const;
+
 	/**
 	 * \brief Gets game object id this script is attached to
 	 *
 	 * \returns game object id
 	 */
 	game_object_id_t get_game_object_id() const {return this->game_object_id;};
-	
+
 protected:
 	// NOTE: Script must have a constructor without arguments so the game programmer doesn't need
 	// to manually add `using Script::Script` to their concrete script class.
diff --git a/src/crepe/api/Script.hpp b/src/crepe/api/Script.hpp
index a064a90..a85d814 100644
--- a/src/crepe/api/Script.hpp
+++ b/src/crepe/api/Script.hpp
@@ -10,7 +10,7 @@ namespace crepe {
 template <typename T>
 T & Script::get_component() const {
 	using namespace std;
-	vector<reference_wrapper<T>> all_components = this->get_components<T>();
+	RefVector<T> all_components = this->get_components<T>();
 	if (all_components.size() < 1)
 		throw runtime_error(
 			format("Script: no component found with type = {}", typeid(T).name()));
@@ -19,9 +19,8 @@ T & Script::get_component() const {
 }
 
 template <typename T>
-std::vector<std::reference_wrapper<T>> Script::get_components() const {
+RefVector<T> Script::get_components() const {
 	auto & mgr = *this->component_manager_ref;
-
 	return mgr.get_components_by_id<T>(this->game_object_id);
 }
 
diff --git a/src/crepe/api/Texture.cpp b/src/crepe/api/Texture.cpp
index de0d0ea..9be9421 100644
--- a/src/crepe/api/Texture.cpp
+++ b/src/crepe/api/Texture.cpp
@@ -26,7 +26,7 @@ Texture::~Texture() {
 
 void Texture::load(unique_ptr<Asset> res) {
 	SDLContext & ctx = SDLContext::get_instance();
-	this->texture = std::move(ctx.texture_from_path(res->get_canonical()));
+	this->texture = std::move(ctx.texture_from_path(res->get_path()));
 }
 
 int Texture::get_width() const {
@@ -35,5 +35,5 @@ int Texture::get_width() const {
 }
 int Texture::get_height() const {
 	if (this->texture == nullptr) return 0;
-	return SDLContext::get_instance().get_width(*this);
+	return SDLContext::get_instance().get_height(*this);
 }
diff --git a/src/crepe/facade/DB.cpp b/src/crepe/facade/DB.cpp
index d5d19dc..95cf606 100644
--- a/src/crepe/facade/DB.cpp
+++ b/src/crepe/facade/DB.cpp
@@ -18,8 +18,8 @@ DB::DB(const string & path) {
 	this->db = {db, [](libdb::DB * db) { db->close(db, 0); }};
 
 	// load or create database file
-	ret = this->db->open(this->db.get(), NULL, path.c_str(), NULL, libdb::DB_BTREE, DB_CREATE,
-						 0);
+	const char * file = path.empty() ? NULL : path.c_str();
+	ret = this->db->open(this->db.get(), NULL, file, NULL, libdb::DB_BTREE, DB_CREATE, 0);
 	if (ret != 0) throw runtime_error(format("db->open: {}", libdb::db_strerror(ret)));
 
 	// create cursor
diff --git a/src/crepe/facade/DB.h b/src/crepe/facade/DB.h
index 629b0eb..115c0f1 100644
--- a/src/crepe/facade/DB.h
+++ b/src/crepe/facade/DB.h
@@ -22,8 +22,10 @@ class DB {
 public:
 	/**
 	 * \param path  The path of the database (created if nonexistant)
+	 *
+	 * \note If \p path is empty, the database is entirely in-memory
 	 */
-	DB(const std::string & path);
+	DB(const std::string & path = "");
 	virtual ~DB() = default;
 
 public:
diff --git a/src/crepe/facade/SDLContext.cpp b/src/crepe/facade/SDLContext.cpp
index 803516e..00523a6 100644
--- a/src/crepe/facade/SDLContext.cpp
+++ b/src/crepe/facade/SDLContext.cpp
@@ -1,5 +1,6 @@
 #include <SDL2/SDL.h>
 #include <SDL2/SDL_image.h>
+#include <SDL2/SDL_keycode.h>
 #include <SDL2/SDL_rect.h>
 #include <SDL2/SDL_render.h>
 #include <SDL2/SDL_surface.h>
@@ -7,13 +8,15 @@
 #include <cmath>
 #include <cstddef>
 #include <functional>
-#include <iostream>
 #include <memory>
+#include <stdexcept>
 #include <string>
 
+#include "../api/Camera.h"
 #include "../api/Sprite.h"
 #include "../api/Texture.h"
 #include "../api/Transform.h"
+#include "../api/Vector2.h"
 #include "../util/Log.h"
 
 #include "SDLContext.h"
@@ -30,29 +33,22 @@ SDLContext::SDLContext() {
 	dbg_trace();
 	// FIXME: read window defaults from config manager
 
-	if (SDL_Init(SDL_INIT_VIDEO) < 0) {
-		// FIXME: throw exception
-		std::cerr << "SDL could not initialize! SDL_Error: " << SDL_GetError() << std::endl;
-		return;
+	if (SDL_Init(SDL_INIT_VIDEO) != 0) {
+		throw runtime_error(format("SDLContext: SDL_Init error: {}", SDL_GetError()));
 	}
 	SDL_Window * tmp_window
 		= SDL_CreateWindow("Crepe Game Engine", SDL_WINDOWPOS_CENTERED, SDL_WINDOWPOS_CENTERED,
 						   this->viewport.w, this->viewport.h, 0);
 	if (!tmp_window) {
-		// FIXME: throw exception
-		std::cerr << "Window could not be created! SDL_Error: " << SDL_GetError() << std::endl;
-		return;
+		throw runtime_error(format("SDLContext: SDL_Window error: {}", SDL_GetError()));
 	}
 	this->game_window = {tmp_window, [](SDL_Window * window) { SDL_DestroyWindow(window); }};
 
 	SDL_Renderer * tmp_renderer
 		= SDL_CreateRenderer(this->game_window.get(), -1, SDL_RENDERER_ACCELERATED);
 	if (!tmp_renderer) {
-		// FIXME: throw exception
-		std::cerr << "Renderer could not be created! SDL_Error: " << SDL_GetError()
-				  << std::endl;
-		SDL_DestroyWindow(this->game_window.get());
-		return;
+		throw runtime_error(
+			format("SDLContext: SDL_CreateRenderer error: {}", SDL_GetError()));
 	}
 
 	this->game_renderer
@@ -60,9 +56,7 @@ SDLContext::SDLContext() {
 
 	int img_flags = IMG_INIT_PNG;
 	if (!(IMG_Init(img_flags) & img_flags)) {
-		// FIXME: throw exception
-		std::cout << "SDL_image could not initialize! SDL_image Error: " << IMG_GetError()
-				  << std::endl;
+		throw runtime_error("SDLContext: SDL_image could not initialize!");
 	}
 }
 
@@ -78,7 +72,6 @@ SDLContext::~SDLContext() {
 	IMG_Quit();
 	SDL_Quit();
 }
-
 void SDLContext::handle_events(bool & running) {
 	//TODO: wouter i need events
 	/*
@@ -103,40 +96,63 @@ void SDLContext::handle_events(bool & running) {
 void SDLContext::clear_screen() { SDL_RenderClear(this->game_renderer.get()); }
 void SDLContext::present_screen() { SDL_RenderPresent(this->game_renderer.get()); }
 
-void SDLContext::draw(const Sprite & sprite, const Transform & transform, const Camera & cam) {
-
-	SDL_RendererFlip render_flip
-		= (SDL_RendererFlip) ((SDL_FLIP_HORIZONTAL * sprite.flip.flip_x)
-							  | (SDL_FLIP_VERTICAL * sprite.flip.flip_y));
-
-	double adjusted_x = (transform.position.x - cam.x -(sprite.sprite_rect.w/2)) * cam.zoom;
-	double adjusted_y = (transform.position.y - cam.y -(sprite.sprite_rect.h/2)) * cam.zoom;
-	double adjusted_w = sprite.sprite_rect.w * transform.scale * cam.zoom;
-	double adjusted_h = sprite.sprite_rect.h * transform.scale * cam.zoom;
-
-	SDL_Rect srcrect = {
+SDL_Rect SDLContext::get_src_rect(const Sprite & sprite) const {
+	return SDL_Rect{
 		.x = sprite.sprite_rect.x,
 		.y = sprite.sprite_rect.y,
 		.w = sprite.sprite_rect.w,
 		.h = sprite.sprite_rect.h,
 	};
+}
+SDL_Rect SDLContext::get_dst_rect(const Sprite & sprite, const Vector2 & pos,
+								  const double & scale, const Camera & cam) const {
 
-	SDL_Rect dstrect = {
+	double adjusted_x = (pos.x - cam.x) * cam.zoom;
+	double adjusted_y = (pos.y - cam.y) * cam.zoom;
+	double adjusted_w = sprite.sprite_rect.w * scale * cam.zoom;
+	double adjusted_h = sprite.sprite_rect.h * scale * cam.zoom;
+
+	return SDL_Rect{
 		.x = static_cast<int>(adjusted_x),
 		.y = static_cast<int>(adjusted_y),
 		.w = static_cast<int>(adjusted_w),
 		.h = static_cast<int>(adjusted_h),
 	};
+}
+
+void SDLContext::draw_particle(const Sprite & sprite, const Vector2 & pos,
+							   const double & angle, const double & scale,
+							   const Camera & camera) {
+
+	SDL_RendererFlip render_flip
+		= (SDL_RendererFlip) ((SDL_FLIP_HORIZONTAL * sprite.flip.flip_x)
+							  | (SDL_FLIP_VERTICAL * sprite.flip.flip_y));
+
+	SDL_Rect srcrect = this->get_src_rect(sprite);
+	SDL_Rect dstrect = this->get_dst_rect(sprite, pos, scale, camera);
+
+	SDL_RenderCopyEx(this->game_renderer.get(), sprite.sprite_image->texture.get(), &srcrect,
+					 &dstrect, angle, NULL, render_flip);
+}
+
+void SDLContext::draw(const Sprite & sprite, const Transform & transform, const Camera & cam) {
+
+	SDL_RendererFlip render_flip
+		= (SDL_RendererFlip) ((SDL_FLIP_HORIZONTAL * sprite.flip.flip_x)
+							  | (SDL_FLIP_VERTICAL * sprite.flip.flip_y));
+
+	SDL_Rect srcrect = this->get_src_rect(sprite);
+	SDL_Rect dstrect = this->get_dst_rect(sprite, transform.position, transform.scale, cam);
 
 	SDL_RenderCopyEx(this->game_renderer.get(), sprite.sprite_image->texture.get(), &srcrect,
 					 &dstrect, transform.rotation, NULL, render_flip);
 }
 
-void SDLContext::camera(const Camera & cam) {
+void SDLContext::set_camera(const Camera & cam) {
 	this->viewport.w = static_cast<int>(cam.aspect_width);
 	this->viewport.h = static_cast<int>(cam.aspect_height);
-	this->viewport.x = static_cast<int>(cam.x) - (SCREEN_WIDTH / 2);
-	this->viewport.y = static_cast<int>(cam.y) - (SCREEN_HEIGHT / 2);
+	this->viewport.x = static_cast<int>(cam.x) - (this->viewport.w / 2);
+	this->viewport.y = static_cast<int>(cam.y) - (this->viewport.h / 2);
 
 	SDL_SetRenderDrawColor(this->game_renderer.get(), cam.bg_color.r, cam.bg_color.g,
 						   cam.bg_color.b, cam.bg_color.a);
@@ -148,9 +164,8 @@ std::unique_ptr<SDL_Texture, std::function<void(SDL_Texture *)>>
 SDLContext::texture_from_path(const std::string & path) {
 
 	SDL_Surface * tmp = IMG_Load(path.c_str());
-	if (tmp == nullptr) {
-		tmp = IMG_Load("../asset/texture/ERROR.png");
-	}
+	if (tmp == nullptr)
+		throw runtime_error(format("SDLContext: IMG_Load error: {}", SDL_GetError()));
 
 	std::unique_ptr<SDL_Surface, std::function<void(SDL_Surface *)>> img_surface;
 	img_surface = {tmp, [](SDL_Surface * surface) { SDL_FreeSurface(surface); }};
@@ -159,7 +174,7 @@ SDLContext::texture_from_path(const std::string & path) {
 		= SDL_CreateTextureFromSurface(this->game_renderer.get(), img_surface.get());
 
 	if (tmp_texture == nullptr) {
-		throw runtime_error(format("Texture cannot be load from {}", path));
+		throw runtime_error(format("SDLContext: Texture cannot be load from {}", path));
 	}
 
 	std::unique_ptr<SDL_Texture, std::function<void(SDL_Texture *)>> img_texture;
diff --git a/src/crepe/facade/SDLContext.h b/src/crepe/facade/SDLContext.h
index 652a83e..841ffc9 100644
--- a/src/crepe/facade/SDLContext.h
+++ b/src/crepe/facade/SDLContext.h
@@ -1,8 +1,10 @@
 #pragma once
 
 #include <SDL2/SDL_keycode.h>
+#include <SDL2/SDL_rect.h>
 #include <SDL2/SDL_render.h>
 #include <SDL2/SDL_video.h>
+#include <cmath>
 #include <functional>
 #include <memory>
 #include <string>
@@ -10,10 +12,7 @@
 #include "../api/Sprite.h"
 #include "../api/Transform.h"
 #include "api/Camera.h"
-
-// FIXME: this needs to be removed
-const int SCREEN_WIDTH = 640;
-const int SCREEN_HEIGHT = 480;
+#include "api/Vector2.h"
 
 namespace crepe {
 
@@ -121,6 +120,9 @@ private:
 	 */
 	void draw(const Sprite & sprite, const Transform & transform, const Camera & camera);
 
+	void draw_particle(const Sprite & sprite, const Vector2 & pos, const double & angle,
+					   const double & scale, const Camera & camera);
+
 	//! Clears the screen, preparing for a new frame.
 	void clear_screen();
 
@@ -128,10 +130,31 @@ private:
 	void present_screen();
 
 	/**
-	 * \brief Sets the current camera for rendering.
+	 * \brief sets the background of the camera (will be adjusted in future PR)
 	 * \param camera Reference to the Camera object.
 	 */
-	void camera(const Camera & camera);
+	void set_camera(const Camera & camera);
+
+private:
+	/**
+	 * \brief calculates the sqaure size of the image
+	 *
+	 * \param sprite Reference to the sprite to calculate the rectangle
+	 * \return sdl rectangle to draw a src image
+	 */
+	SDL_Rect get_src_rect(const Sprite & sprite) const;
+	/**
+	 * \brief calculates the sqaure size of the image for an destination
+	 *
+	 * \param sprite Reference to the sprite to calculate the rectangle
+	 * \param pos the pos in pixel positions
+	 * \param scale the multiplier to increase of decrease for the specified sprite 
+	 * \param cam Reference to the current camera in the scene to calculate the position based
+	 * on the camera 
+	 * \return sdl rectangle to draw a dst image to draw on the screen
+	 */
+	SDL_Rect get_dst_rect(const Sprite & sprite, const Vector2 & pos, const double & scale,
+						  const Camera & cam) const;
 
 private:
 	//! sdl Window
diff --git a/src/crepe/facade/Sound.cpp b/src/crepe/facade/Sound.cpp
index 7aa89a9..4d3abf5 100644
--- a/src/crepe/facade/Sound.cpp
+++ b/src/crepe/facade/Sound.cpp
@@ -16,7 +16,7 @@ Sound::Sound(const char * src) {
 	this->load(make_unique<Asset>(src));
 }
 
-void Sound::load(unique_ptr<Asset> res) { this->sample.load(res->get_canonical().c_str()); }
+void Sound::load(unique_ptr<Asset> res) { this->sample.load(res->get_path().c_str()); }
 
 void Sound::play() {
 	SoundContext & ctx = SoundContext::get_instance();
diff --git a/src/crepe/facade/Sound.h b/src/crepe/facade/Sound.h
index 32b6478..4c68f32 100644
--- a/src/crepe/facade/Sound.h
+++ b/src/crepe/facade/Sound.h
@@ -4,7 +4,7 @@
 #include <soloud/soloud.h>
 #include <soloud/soloud_wav.h>
 
-#include "../Asset.h"
+#include "../api/Asset.h"
 
 namespace crepe {
 
diff --git a/src/crepe/system/AnimatorSystem.cpp b/src/crepe/system/AnimatorSystem.cpp
index 9d18873..676e485 100644
--- a/src/crepe/system/AnimatorSystem.cpp
+++ b/src/crepe/system/AnimatorSystem.cpp
@@ -1,6 +1,4 @@
 #include <cstdint>
-#include <functional>
-#include <vector>
 
 #include "api/Animator.h"
 #include "facade/SDLContext.h"
@@ -13,8 +11,7 @@ using namespace crepe;
 void AnimatorSystem::update() {
 	ComponentManager & mgr = this->component_manager;
 
-	std::vector<std::reference_wrapper<Animator>> animations
-		= mgr.get_components_by_type<Animator>();
+	RefVector<Animator> animations = mgr.get_components_by_type<Animator>();
 
 	uint64_t tick = SDLContext::get_instance().get_ticks();
 	for (Animator & a : animations) {
diff --git a/src/crepe/system/ParticleSystem.cpp b/src/crepe/system/ParticleSystem.cpp
index 7316309..fcf7522 100644
--- a/src/crepe/system/ParticleSystem.cpp
+++ b/src/crepe/system/ParticleSystem.cpp
@@ -14,8 +14,7 @@ using namespace crepe;
 void ParticleSystem::update() {
 	// Get all emitters
 	ComponentManager & mgr = this->component_manager;
-	std::vector<std::reference_wrapper<ParticleEmitter>> emitters
-		= mgr.get_components_by_type<ParticleEmitter>();
+	RefVector<ParticleEmitter> emitters = mgr.get_components_by_type<ParticleEmitter>();
 
 	for (ParticleEmitter & emitter : emitters) {
 		// Get transform linked to emitter
diff --git a/src/crepe/system/PhysicsSystem.cpp b/src/crepe/system/PhysicsSystem.cpp
index 4a7dbfb..bcde431 100644
--- a/src/crepe/system/PhysicsSystem.cpp
+++ b/src/crepe/system/PhysicsSystem.cpp
@@ -12,10 +12,8 @@ using namespace crepe;
 
 void PhysicsSystem::update() {
 	ComponentManager & mgr = this->component_manager;
-	std::vector<std::reference_wrapper<Rigidbody>> rigidbodies
-		= mgr.get_components_by_type<Rigidbody>();
-	std::vector<std::reference_wrapper<Transform>> transforms
-		= mgr.get_components_by_type<Transform>();
+	RefVector<Rigidbody> rigidbodies = mgr.get_components_by_type<Rigidbody>();
+	RefVector<Transform> transforms = mgr.get_components_by_type<Transform>();
 
 	double gravity = Config::get_instance().physics.gravity;
 	for (Rigidbody & rigidbody : rigidbodies) {
diff --git a/src/crepe/system/RenderSystem.cpp b/src/crepe/system/RenderSystem.cpp
index 96c5f27..8f9467e 100644
--- a/src/crepe/system/RenderSystem.cpp
+++ b/src/crepe/system/RenderSystem.cpp
@@ -1,12 +1,16 @@
 #include <algorithm>
 #include <cassert>
+#include <cmath>
 #include <functional>
+#include <iostream>
 #include <stdexcept>
 #include <vector>
 
 #include "../ComponentManager.h"
+#include "../api/ParticleEmitter.h"
 #include "../api/Sprite.h"
 #include "../api/Transform.h"
+#include "../api/Vector2.h"
 #include "../facade/SDLContext.h"
 
 #include "RenderSystem.h"
@@ -20,12 +24,15 @@ void RenderSystem::present_screen() { this->context.present_screen(); }
 void RenderSystem::update_camera() {
 	ComponentManager & mgr = this->component_manager;
 
-	std::vector<std::reference_wrapper<Camera>> cameras = mgr.get_components_by_type<Camera>();
+	RefVector<Camera> cameras = mgr.get_components_by_type<Camera>();
+
+	if (cameras.size() == 0) throw std::runtime_error("No cameras in current scene");
 
 	if (cameras.size() == 0) throw std::runtime_error("No cameras in current scene");
 
 	for (Camera & cam : cameras) {
-		this->context.camera(cam);
+		if (!cam.active) continue;
+		this->context.set_camera(cam);
 		this->curr_cam_ref = &cam;
 	}
 }
@@ -37,29 +44,61 @@ bool sorting_comparison(const Sprite & a, const Sprite & b) {
 	return false;
 }
 
-std::vector<std::reference_wrapper<Sprite>>
-RenderSystem::sort(std::vector<std::reference_wrapper<Sprite>> & objs) {
-
-	std::vector<std::reference_wrapper<Sprite>> sorted_objs(objs);
+RefVector<Sprite> RenderSystem::sort(RefVector<Sprite> & objs) const {
+	RefVector<Sprite> sorted_objs(objs);
 	std::sort(sorted_objs.begin(), sorted_objs.end(), sorting_comparison);
 
 	return sorted_objs;
 }
 
-void RenderSystem::render_sprites() {
+void RenderSystem::update() {
+	this->clear_screen();
+	this->update_camera();
+	this->render();
+	this->present_screen();
+}
+
+bool RenderSystem::render_particle(const Sprite & sprite, const double & scale) {
+
 	ComponentManager & mgr = this->component_manager;
-	vector<reference_wrapper<Sprite>> sprites = mgr.get_components_by_type<Sprite>();
-	vector<reference_wrapper<Sprite>> sorted_sprites = this->sort(sprites);
 
-	for (const Sprite & sprite : sorted_sprites) {
-		auto transforms = mgr.get_components_by_id<Transform>(sprite.game_object_id);
-		this->context.draw(sprite, transforms[0], *this->curr_cam_ref);
+	vector<reference_wrapper<ParticleEmitter>> emitters
+		= mgr.get_components_by_id<ParticleEmitter>(sprite.game_object_id);
+
+	bool rendering_particles = false;
+
+	for (const ParticleEmitter & em : emitters) {
+		if (!(&em.data.sprite == &sprite)) continue;
+		rendering_particles = true;
+		if (!em.active) continue;
+
+		for (const Particle & p : em.data.particles) {
+			if (!p.active) continue;
+			this->context.draw_particle(sprite, p.position, p.angle, scale,
+										*this->curr_cam_ref);
+		}
 	}
+	return rendering_particles;
+}
+void RenderSystem::render_normal(const Sprite & sprite, const Transform & tm) {
+	this->context.draw(sprite, tm, *this->curr_cam_ref);
 }
 
-void RenderSystem::update() {
-	this->clear_screen();
-	this->update_camera();
-	this->render_sprites();
-	this->present_screen();
+void RenderSystem::render() {
+
+	ComponentManager & mgr = this->component_manager;
+	RefVector<Sprite> sprites = mgr.get_components_by_type<Sprite>();
+	RefVector<Sprite> sorted_sprites = this->sort(sprites);
+
+	for (const Sprite & sprite : sorted_sprites) {
+		if (!sprite.active) continue;
+		const Transform & transform
+			= mgr.get_components_by_id<Transform>(sprite.game_object_id).front().get();
+
+		bool rendered_particles = this->render_particle(sprite, transform.scale);
+
+		if (rendered_particles) continue;
+
+		this->render_normal(sprite, transform);
+	}
 }
diff --git a/src/crepe/system/RenderSystem.h b/src/crepe/system/RenderSystem.h
index 57b9c73..30b41cf 100644
--- a/src/crepe/system/RenderSystem.h
+++ b/src/crepe/system/RenderSystem.h
@@ -6,6 +6,7 @@
 #include "facade/SDLContext.h"
 
 #include "System.h"
+#include <cmath>
 
 namespace crepe {
 
@@ -38,8 +39,25 @@ private:
 	//! Updates the active camera used for rendering.
 	void update_camera();
 
-	//! Renders all active sprites to the screen.
-	void render_sprites();
+	//! Renders the whole screen
+	void render();
+
+	/**
+	 * \brief Renders all the particles on the screen from a given sprite.
+	 *
+	 * \param sprite renders the particles with given texture
+	 * \param tm the Transform component for scale
+	 * \return true if particles have been rendered
+	 */
+	bool render_particle(const Sprite & sprite, const double & scale);
+
+	/**
+	 * \brief renders a sprite with a Transform component on the screen 
+	 *
+	 * \param sprite  the sprite component that holds all the data
+	 * \param tm the Transform component that holds the position,rotation and scale 
+	 */
+	void render_normal(const Sprite & sprite, const Transform & tm);
 
 	/**
 	 * \brief sort a vector sprite objects with
@@ -47,12 +65,10 @@ private:
 	 * \param objs the vector that will do a sorting algorithm on 
 	 * \return returns a sorted reference vector
 	 */
-	std::vector<std::reference_wrapper<Sprite>>
-	sort(std::vector<std::reference_wrapper<Sprite>> & objs);
+	RefVector<Sprite> sort(RefVector<Sprite> & objs) const;
 
 	/**
 	 * \todo Include color handling for sprites.
-	 * \todo Implement particle emitter rendering with sprites.
 	 * \todo Add text rendering using SDL_ttf for text components.
 	 * \todo Implement a text component and a button component.
 	 * \todo Ensure each sprite is checked for active status before rendering.
diff --git a/src/crepe/system/ScriptSystem.cpp b/src/crepe/system/ScriptSystem.cpp
index c4d724c..c33309c 100644
--- a/src/crepe/system/ScriptSystem.cpp
+++ b/src/crepe/system/ScriptSystem.cpp
@@ -1,6 +1,4 @@
-#include <forward_list>
 #include <functional>
-#include <vector>
 
 #include "../ComponentManager.h"
 #include "../api/BehaviorScript.h"
@@ -14,7 +12,7 @@ using namespace crepe;
 void ScriptSystem::update() {
 	dbg_trace();
 
-	forward_list<reference_wrapper<Script>> scripts = this->get_scripts();
+	RefVector<Script> scripts = this->get_scripts();
 
 	for (auto & script_ref : scripts) {
 		Script & script = script_ref.get();
@@ -26,18 +24,17 @@ void ScriptSystem::update() {
 	}
 }
 
-forward_list<reference_wrapper<Script>> ScriptSystem::get_scripts() const {
-	forward_list<reference_wrapper<Script>> scripts = {};
+RefVector<Script> ScriptSystem::get_scripts() const {
+	RefVector<Script> scripts = {};
 	ComponentManager & mgr = this->component_manager;
-	vector<reference_wrapper<BehaviorScript>> behavior_scripts
-		= mgr.get_components_by_type<BehaviorScript>();
+	RefVector<BehaviorScript> behavior_scripts = mgr.get_components_by_type<BehaviorScript>();
 
 	for (auto behavior_script_ref : behavior_scripts) {
 		BehaviorScript & behavior_script = behavior_script_ref.get();
 		if (!behavior_script.active) continue;
 		Script * script = behavior_script.script.get();
 		if (script == nullptr) continue;
-		scripts.push_front(*script);
+		scripts.push_back(*script);
 	}
 
 	return scripts;
diff --git a/src/crepe/system/ScriptSystem.h b/src/crepe/system/ScriptSystem.h
index deb89cb..32e1fcd 100644
--- a/src/crepe/system/ScriptSystem.h
+++ b/src/crepe/system/ScriptSystem.h
@@ -1,9 +1,9 @@
 #pragma once
 
-#include <forward_list>
-
 #include "System.h"
 
+#include "../types.h"
+
 namespace crepe {
 
 class Script;
@@ -33,7 +33,7 @@ private:
 	 *
 	 * \returns List of active \c Script instances
 	 */
-	std::forward_list<std::reference_wrapper<Script>> get_scripts() const;
+	RefVector<Script> get_scripts() const;
 };
 
 } // namespace crepe
diff --git a/src/crepe/types.h b/src/crepe/types.h
index 0d459e8..914c76c 100644
--- a/src/crepe/types.h
+++ b/src/crepe/types.h
@@ -1,9 +1,16 @@
 #pragma once
 
 #include <cstdint>
+#include <functional>
+#include <vector>
 
 namespace crepe {
 
+//! GameObject ID
 typedef uint32_t game_object_id_t;
 
-}
+//! vector of reference_wrapper
+template <typename T>
+using RefVector = std::vector<std::reference_wrapper<T>>;
+
+} // namespace crepe
diff --git a/src/crepe/util/CMakeLists.txt b/src/crepe/util/CMakeLists.txt
index 4be738a..94ed906 100644
--- a/src/crepe/util/CMakeLists.txt
+++ b/src/crepe/util/CMakeLists.txt
@@ -9,5 +9,7 @@ target_sources(crepe PUBLIC FILE_SET HEADERS FILES
 	Log.hpp
 	Proxy.h
 	Proxy.hpp
+	OptionalRef.h
+	OptionalRef.hpp
 )
 
diff --git a/src/crepe/util/OptionalRef.h b/src/crepe/util/OptionalRef.h
new file mode 100644
index 0000000..3201667
--- /dev/null
+++ b/src/crepe/util/OptionalRef.h
@@ -0,0 +1,58 @@
+#pragma once
+
+namespace crepe {
+
+/**
+ * \brief Optional reference utility
+ *
+ * This class doesn't need to know the full definition of \c T to be used.
+ *
+ * \tparam T Value type
+ */
+template <typename T>
+class OptionalRef {
+public:
+	//! Initialize empty (nonexistant) reference
+	OptionalRef() = default;
+	//! Initialize reference with value
+	OptionalRef(T & ref);
+	/**
+	 * \brief Assign new reference
+	 *
+	 * \param ref Reference to assign
+	 *
+	 * \return Reference to this (required for operator)
+	 */
+	OptionalRef<T> & operator=(T & ref);
+	/**
+	 * \brief Retrieve this reference
+	 *
+	 * \returns Internal reference if it is set
+	 *
+	 * \throws std::runtime_error if this function is called while the reference it not set
+	 */
+	operator T &() const;
+	/**
+	 * \brief Check if this reference is not empty
+	 *
+	 * \returns `true` if reference is set, or `false` if it is not
+	 */
+	explicit operator bool() const noexcept;
+
+	/**
+	 * \brief Make this reference empty
+	 */
+	void clear() noexcept;
+
+private:
+	/**
+	 * \brief Reference to the value of type \c T
+	 *
+	 * \note This raw pointer is *not* managed, and only used as a reference!
+	 */
+	T * ref = nullptr;
+};
+
+} // namespace crepe
+
+#include "OptionalRef.hpp"
diff --git a/src/crepe/util/OptionalRef.hpp b/src/crepe/util/OptionalRef.hpp
new file mode 100644
index 0000000..4608c9e
--- /dev/null
+++ b/src/crepe/util/OptionalRef.hpp
@@ -0,0 +1,37 @@
+#pragma once
+
+#include <stdexcept>
+
+#include "OptionalRef.h"
+
+namespace crepe {
+
+template <typename T>
+OptionalRef<T>::OptionalRef(T & ref) {
+	this->ref = &ref;
+}
+
+template <typename T>
+OptionalRef<T>::operator T &() const {
+	if (this->ref == nullptr)
+		throw std::runtime_error("OptionalRef: attempt to dereference nullptr");
+	return *this->ref;
+}
+
+template <typename T>
+OptionalRef<T> & OptionalRef<T>::operator=(T & ref) {
+	this->ref = &ref;
+	return *this;
+}
+
+template <typename T>
+OptionalRef<T>::operator bool() const noexcept {
+	return this->ref != nullptr;
+}
+
+template <typename T>
+void OptionalRef<T>::clear() noexcept {
+	this->ref = nullptr;
+}
+
+} // namespace crepe
diff --git a/src/crepe/util/Proxy.h b/src/crepe/util/Proxy.h
index b34f7c6..789144a 100644
--- a/src/crepe/util/Proxy.h
+++ b/src/crepe/util/Proxy.h
@@ -16,6 +16,8 @@ template <typename T>
 class Proxy {
 public:
 	//! Set operator
+	Proxy & operator=(Proxy &);
+	//! Set operator
 	Proxy & operator=(const T &);
 	//! Get operator
 	operator const T &();
diff --git a/src/crepe/util/Proxy.hpp b/src/crepe/util/Proxy.hpp
index b9923db..ef2b69f 100644
--- a/src/crepe/util/Proxy.hpp
+++ b/src/crepe/util/Proxy.hpp
@@ -14,6 +14,12 @@ Proxy<T> & Proxy<T>::operator=(const T & val) {
 }
 
 template <typename T>
+Proxy<T> & Proxy<T>::operator=(Proxy & proxy) {
+	this->broker.set(T(proxy));
+	return *this;
+}
+
+template <typename T>
 Proxy<T>::operator const T &() {
 	return this->broker.get();
 }
diff --git a/src/doc/feature/gameobject.dox b/src/doc/feature/gameobject.dox
new file mode 100644
index 0000000..c561874
--- /dev/null
+++ b/src/doc/feature/gameobject.dox
@@ -0,0 +1,18 @@
+// vim:ft=doxygen
+namespace crepe {
+/**
+
+\defgroup feature_gameobject GameObjects
+\ingroup feature
+\brief GameObject to create a Scene
+
+GameObjects are the fundamental building blocks of a Scene. They represent entities
+in the game world and can have various components attached to them to define their
+behavior and properties. GameObjects can be created and modified within the
+Scene, allowing for a flexible and dynamic game environment.
+
+\see Component
+\see Scene
+
+*/
+}
diff --git a/src/doc/feature/scene.dox b/src/doc/feature/scene.dox
new file mode 100644
index 0000000..5f34446
--- /dev/null
+++ b/src/doc/feature/scene.dox
@@ -0,0 +1,67 @@
+// vim:ft=doxygen
+namespace crepe {
+/**
+
+\defgroup feature_scene Scenes
+\ingroup feature
+\brief User-defined scenes
+
+Scenes can be used to implement game environments, and allow arbitrary game objects to be organized
+as part of the game structure. Scenes are implemented as derivative classes of Scene, which are
+added to the game using the SceneManager. Scenes describe the start of a Scene and cannot modify
+GameObjects during runtime of a Scene (use \ref feature_script "Scripting" for this purpose).
+
+\see SceneManager
+\see GameObject
+\see Script
+\see Scene
+
+\par Example
+
+This example demonstrates how to define and add scenes to the loop/scene manager in the `crepe` framework.
+Each concrete scene should be derived from Scene. In the example below, the concrete scene is named MyScene.
+A concrete scene should, at least, implement (override) two methods, namely load_scene() and get_name(). The
+scene is build (using GameObjects) in the load_scene() method. GameObjects should be made using the
+component_manager::new_object(). In the example below, two GameObjects (named object1 and object2) are added
+to MyScene. object1 and object2 do not have any non-default Components attached to them, however, if needed,
+this should also be done in load_scene(). Each concrete scene must have a unique name. This unique name is
+used to load a new concrete scene (via a Script). The unique name is set using the get_name() method. In the
+example below, MyScene's unique name is my_scene.
+After setting up one or more concrete scene(s), the concrete scene(s) should be added to the loop/scene manager.
+This is done in your main(). Firstly, the LoopManager should be instantiated. Than, all the concrete scene(s)
+should be added to the loop/scene manger via loop_mgr::add_scene<>(). The templated argument should define the
+concrete scene to be added.
+
+```cpp
+#include <crepe/api/LoopManager.h>
+#include <crepe/api/GameObject.h>
+#include <crepe/api/Scene.h>
+#include <crepe/api/Vector2.h>
+
+using namespace crepe;
+
+class MyScene : public Scene {
+public:
+	using Scene::Scene;
+
+	void load_scene() {
+		auto & mgr = this->component_manager;
+		GameObject object1 = mgr.new_object("object1", "tag_my_scene", Vector2{0, 0}, 0, 1);
+		GameObject object2 = mgr.new_object("object2", "tag_my_scene", Vector2{1, 0}, 0, 1);
+	}
+
+	string get_name() const { return "my_scene"; }
+};
+
+int main() {
+	LoopManager loop_mgr;
+	
+	// Add the scenes to the loop manager
+	loop_mgr.add_scene<MyScene>();
+
+	loop_mgr.start();
+}
+```
+
+*/
+}
diff --git a/src/example/CMakeLists.txt b/src/example/CMakeLists.txt
index 045f4d4..560e2bc 100644
--- a/src/example/CMakeLists.txt
+++ b/src/example/CMakeLists.txt
@@ -16,15 +16,8 @@ function(add_example target_name)
 	add_dependencies(examples ${target_name})
 endfunction()
 
-add_example(audio_internal)
-add_example(script)
-add_example(log)
-add_example(rendering)
 add_example(asset_manager)
 add_example(savemgr)
-add_example(proxy)
-add_example(db)
-add_example(game)
-add_example(events)
+add_example(rendering_particle)
 add_example(gameloop)
 
diff --git a/src/example/audio_internal.cpp b/src/example/audio_internal.cpp
deleted file mode 100644
index 661161a..0000000
--- a/src/example/audio_internal.cpp
+++ /dev/null
@@ -1,56 +0,0 @@
-/** \file
- * 
- * Standalone example for usage of the internal \c Sound class.
- */
-
-#include <crepe/api/Config.h>
-#include <crepe/facade/Sound.h>
-#include <crepe/util/Log.h>
-
-#include <thread>
-
-using namespace crepe;
-using namespace std;
-using namespace std::chrono_literals;
-using std::make_unique;
-
-// Unrelated stuff that is not part of this POC
-int _ = []() {
-	// Show dbg_trace() output
-	auto & cfg = Config::get_instance();
-	cfg.log.level = Log::Level::TRACE;
-
-	return 0; // satisfy compiler
-}();
-
-int main() {
-	// Load a background track (Ogg Vorbis)
-	auto bgm = Sound("../mwe/audio/bgm.ogg");
-	// Load three short samples (WAV)
-	auto sfx1 = Sound("../mwe/audio/sfx1.wav");
-	auto sfx2 = Sound("../mwe/audio/sfx2.wav");
-	auto sfx3 = Sound("../mwe/audio/sfx3.wav");
-
-	// Start the background track
-	bgm.play();
-
-	// Play each sample sequentially while pausing and resuming the background track
-	this_thread::sleep_for(500ms);
-	sfx1.play();
-	this_thread::sleep_for(500ms);
-	sfx2.play();
-	bgm.pause();
-	this_thread::sleep_for(500ms);
-	sfx3.play();
-	bgm.play();
-	this_thread::sleep_for(500ms);
-
-	// Play all samples simultaniously
-	sfx1.play();
-	sfx2.play();
-	sfx3.play();
-	this_thread::sleep_for(1000ms);
-
-	// Stop all audio and exit
-	return EXIT_SUCCESS;
-}
diff --git a/src/example/db.cpp b/src/example/db.cpp
deleted file mode 100644
index ee4e8fc..0000000
--- a/src/example/db.cpp
+++ /dev/null
@@ -1,30 +0,0 @@
-#include <crepe/api/Config.h>
-#include <crepe/facade/DB.h>
-#include <crepe/util/Log.h>
-
-using namespace crepe;
-using namespace std;
-
-// run before main
-static auto _ = []() {
-	auto & cfg = Config::get_instance();
-	cfg.log.level = Log::Level::TRACE;
-	return 0;
-}();
-
-int main() {
-	dbg_trace();
-
-	DB db("file.db");
-
-	const char * test_key = "test-key";
-	string test_data = "Hello world!";
-
-	dbg_logf("DB has key = {}", db.has(test_key));
-
-	db.set(test_key, test_data);
-
-	dbg_logf("key = \"{}\"", db.get(test_key));
-
-	return 0;
-}
diff --git a/src/example/log.cpp b/src/example/log.cpp
deleted file mode 100644
index 5baa021..0000000
--- a/src/example/log.cpp
+++ /dev/null
@@ -1,28 +0,0 @@
-/** \file
- * 
- * Standalone example for usage of the logging functions
- */
-
-#include <crepe/api/Config.h>
-#include <crepe/util/Log.h>
-
-using namespace crepe;
-
-// unrelated setup code
-int _ = []() {
-	// make sure all log messages get printed
-	auto & cfg = Config::get_instance();
-	cfg.log.level = Log::Level::TRACE;
-
-	return 0; // satisfy compiler
-}();
-
-int main() {
-	dbg_trace();
-	dbg_log("debug message");
-	Log::logf("info message with variable: {}", 3);
-	Log::logf(Log::Level::WARNING, "warning");
-	Log::logf(Log::Level::ERROR, "error");
-
-	return 0;
-}
diff --git a/src/example/proxy.cpp b/src/example/proxy.cpp
deleted file mode 100644
index 69451f8..0000000
--- a/src/example/proxy.cpp
+++ /dev/null
@@ -1,45 +0,0 @@
-/** \file
- * 
- * Standalone example for usage of the proxy type
- */
-
-#include <crepe/ValueBroker.h>
-#include <crepe/api/Config.h>
-#include <crepe/util/Log.h>
-#include <crepe/util/Proxy.h>
-
-using namespace std;
-using namespace crepe;
-
-void test_ro_ref(const int & val) {}
-void test_rw_ref(int & val) {}
-void test_ro_val(int val) {}
-
-int main() {
-	auto & cfg = Config::get_instance();
-	cfg.log.level = Log::Level::DEBUG;
-
-	int real_value = 0;
-
-	ValueBroker<int> broker{
-		[&real_value](const int & target) {
-			dbg_logf("set {} to {}", real_value, target);
-			real_value = target;
-		},
-		[&real_value]() -> const int & {
-			dbg_logf("get {}", real_value);
-			return real_value;
-		},
-	};
-
-	Proxy<int> proxy{broker};
-
-	broker.set(54);
-	proxy = 84;
-
-	test_ro_ref(proxy); // this is allowed
-	// test_rw_ref(proxy); // this should throw a compile error
-	test_ro_val(proxy);
-
-	return 0;
-}
diff --git a/src/example/rendering_particle.cpp b/src/example/rendering_particle.cpp
new file mode 100644
index 0000000..4571afb
--- /dev/null
+++ b/src/example/rendering_particle.cpp
@@ -0,0 +1,71 @@
+#include "api/Camera.h"
+#include "system/ParticleSystem.h"
+#include <SDL2/SDL_timer.h>
+#include <crepe/ComponentManager.h>
+
+#include <crepe/Component.h>
+#include <crepe/api/Color.h>
+#include <crepe/api/GameObject.h>
+#include <crepe/api/ParticleEmitter.h>
+#include <crepe/api/Rigidbody.h>
+#include <crepe/api/Sprite.h>
+#include <crepe/api/Texture.h>
+#include <crepe/api/Transform.h>
+#include <crepe/api/Vector2.h>
+#include <crepe/system/RenderSystem.h>
+
+#include <chrono>
+#include <iostream>
+#include <memory>
+
+using namespace crepe;
+using namespace std;
+
+int main(int argc, char * argv[]) {
+	ComponentManager mgr;
+	GameObject game_object = mgr.new_object("", "", Vector2{100, 100}, 0, 0.1);
+	RenderSystem sys{mgr};
+	ParticleSystem psys{mgr};
+
+	Color color(255, 255, 255, 255);
+
+	Sprite & test_sprite = game_object.add_component<Sprite>(
+		make_shared<Texture>("../asset/texture/img.png"), color, FlipSettings{false, false});
+	test_sprite.order_in_layer = 5;
+
+	auto & test = game_object.add_component<ParticleEmitter>(ParticleEmitter::Data{
+		.position = {0, 0},
+		.max_particles = 10,
+		.emission_rate = 0.1,
+		.min_speed = 6,
+		.max_speed = 20,
+		.min_angle = -20,
+		.max_angle = 20,
+		.begin_lifespan = 0,
+		.end_lifespan = 60,
+		.force_over_time = Vector2{0, 0},
+		.boundary{
+			.width = 1000,
+			.height = 1000,
+			.offset = Vector2{0, 0},
+			.reset_on_exit = false,
+		},
+		.sprite = test_sprite,
+	});
+	game_object.add_component<Camera>(Color::WHITE);
+
+	game_object
+		.add_component<Sprite>(make_shared<Texture>("../asset/texture/img.png"), color,
+							   FlipSettings{false, false})
+		.order_in_layer
+		= 6;
+
+	auto start = std::chrono::steady_clock::now();
+	while (std::chrono::steady_clock::now() - start < std::chrono::seconds(5)) {
+		psys.update();
+		sys.update();
+		SDL_Delay(10);
+	}
+
+	return 0;
+}
diff --git a/src/example/script.cpp b/src/example/script.cpp
deleted file mode 100644
index a23295b..0000000
--- a/src/example/script.cpp
+++ /dev/null
@@ -1,49 +0,0 @@
-/** \file
- * 
- * Standalone example for usage of the script component and system
- */
-
-#include <crepe/ComponentManager.h>
-#include <crepe/system/ScriptSystem.h>
-#include <crepe/util/Log.h>
-
-#include <crepe/api/BehaviorScript.h>
-#include <crepe/api/Config.h>
-#include <crepe/api/GameObject.h>
-#include <crepe/api/Script.h>
-#include <crepe/api/Transform.h>
-
-using namespace crepe;
-using namespace std;
-
-// Unrelated stuff that is not part of this POC
-int _ = []() {
-	// Show dbg_trace() output
-	auto & cfg = Config::get_instance();
-	cfg.log.level = Log::Level::TRACE;
-
-	return 0; // satisfy compiler
-}();
-
-// User-defined script:
-class MyScript : public Script {
-	void update() {
-		// Retrieve component from the same GameObject this script is on
-		Transform & test = get_component<Transform>();
-		dbg_logf("Transform({:.2f}, {:.2f})", test.position.x, test.position.y);
-	}
-};
-
-int main() {
-	ComponentManager component_manager{};
-	ScriptSystem system{component_manager};
-
-	// Create game object with Transform and BehaviorScript components
-	GameObject obj = component_manager.new_object("name");
-	obj.add_component<BehaviorScript>().set_script<MyScript>();
-
-	// Update all scripts. This should result in MyScript::update being called
-	system.update();
-
-	return EXIT_SUCCESS;
-}
diff --git a/src/test/AssetTest.cpp b/src/test/AssetTest.cpp
new file mode 100644
index 0000000..8aa7629
--- /dev/null
+++ b/src/test/AssetTest.cpp
@@ -0,0 +1,26 @@
+#include <gtest/gtest.h>
+
+#include <crepe/api/Asset.h>
+#include <crepe/api/Config.h>
+
+using namespace std;
+using namespace crepe;
+using namespace testing;
+
+class AssetTest : public Test {
+public:
+	Config & cfg = Config::get_instance();
+	void SetUp() override { this->cfg.asset.root_pattern = ".crepe-root"; }
+};
+
+TEST_F(AssetTest, Existant) { ASSERT_NO_THROW(Asset{"asset/texture/img.png"}); }
+
+TEST_F(AssetTest, Nonexistant) { ASSERT_ANY_THROW(Asset{"asset/nonexistant"}); }
+
+TEST_F(AssetTest, Rootless) {
+	cfg.asset.root_pattern.clear();
+
+	string arbitrary = "\\/this is / /../passed through as-is";
+	Asset asset{arbitrary};
+	ASSERT_EQ(arbitrary, asset.get_path());
+}
diff --git a/src/test/CMakeLists.txt b/src/test/CMakeLists.txt
index 14c5123..8be8252 100644
--- a/src/test/CMakeLists.txt
+++ b/src/test/CMakeLists.txt
@@ -4,7 +4,13 @@ target_sources(test_main PUBLIC
 	PhysicsTest.cpp
 	ScriptTest.cpp
 	ParticleTest.cpp
+	AssetTest.cpp
+	OptionalRefTest.cpp
+	RenderSystemTest.cpp
+	EventTest.cpp
 	ECSTest.cpp
 	SceneManagerTest.cpp
+	ValueBrokerTest.cpp
+	DBTest.cpp
 )
 
diff --git a/src/test/DBTest.cpp b/src/test/DBTest.cpp
new file mode 100644
index 0000000..e80814c
--- /dev/null
+++ b/src/test/DBTest.cpp
@@ -0,0 +1,28 @@
+#include <crepe/facade/DB.h>
+#include <gtest/gtest.h>
+
+using namespace std;
+using namespace crepe;
+using namespace testing;
+
+class DBTest : public Test {
+public:
+	DB db;
+};
+
+TEST_F(DBTest, ReadWrite) {
+	db.set("foo", "bar");
+	EXPECT_EQ(db.get("foo"), "bar");
+}
+
+TEST_F(DBTest, Nonexistant) {
+	EXPECT_THROW(db.get("foo"), std::out_of_range);
+	db.set("foo", "bar");
+	EXPECT_NO_THROW(db.get("foo"));
+}
+
+TEST_F(DBTest, Has) {
+	EXPECT_EQ(db.has("foo"), false);
+	db.set("foo", "bar");
+	EXPECT_EQ(db.has("foo"), true);
+}
diff --git a/src/test/EventTest.cpp b/src/test/EventTest.cpp
new file mode 100644
index 0000000..b0e6c9c
--- /dev/null
+++ b/src/test/EventTest.cpp
@@ -0,0 +1,254 @@
+
+#include "api/Event.h"
+#include "api/EventManager.h"
+#include "api/IKeyListener.h"
+#include "api/IMouseListener.h"
+#include <gmock/gmock.h>
+#include <gtest/gtest.h>
+using namespace std;
+using namespace std::chrono_literals;
+using namespace crepe;
+
+class EventManagerTest : public ::testing::Test {
+protected:
+	void SetUp() override {
+		// Clear any existing subscriptions or events before each test
+		EventManager::get_instance().clear();
+	}
+
+	void TearDown() override {
+		// Ensure cleanup after each test
+		EventManager::get_instance().clear();
+	}
+};
+class MockKeyListener : public IKeyListener {
+public:
+	MOCK_METHOD(bool, on_key_pressed, (const KeyPressEvent & event), (override));
+	MOCK_METHOD(bool, on_key_released, (const KeyReleaseEvent & event), (override));
+};
+
+class MockMouseListener : public IMouseListener {
+public:
+	MOCK_METHOD(bool, on_mouse_clicked, (const MouseClickEvent & event), (override));
+	MOCK_METHOD(bool, on_mouse_pressed, (const MousePressEvent & event), (override));
+	MOCK_METHOD(bool, on_mouse_released, (const MouseReleaseEvent & event), (override));
+	MOCK_METHOD(bool, on_mouse_moved, (const MouseMoveEvent & event), (override));
+};
+
+TEST_F(EventManagerTest, EventSubscription) {
+	EventHandler<KeyPressEvent> key_handler = [](const KeyPressEvent & e) {
+		std::cout << "Key Event Triggered" << std::endl;
+		return true;
+	};
+
+	// Subscribe to KeyPressEvent
+	EventManager::get_instance().subscribe<KeyPressEvent>(key_handler, 1);
+
+	// Verify subscription (not directly verifiable; test by triggering event)
+
+	EventManager::get_instance().trigger_event<KeyPressEvent>(
+		KeyPressEvent{
+			.repeat = true,
+			.key = Keycode::A,
+		},
+		1);
+	EventManager::get_instance().trigger_event<KeyPressEvent>(
+		KeyPressEvent{
+			.repeat = true,
+			.key = Keycode::A,
+
+		},
+		EventManager::CHANNEL_ALL);
+}
+TEST_F(EventManagerTest, EventManagerTest_trigger_all_channels) {
+	bool triggered = false;
+
+	EventHandler<MouseClickEvent> mouse_handler = [&](const MouseClickEvent & e) {
+		triggered = true;
+		EXPECT_EQ(e.mouse_x, 100);
+		EXPECT_EQ(e.mouse_y, 200);
+		EXPECT_EQ(e.button, MouseButton::LEFT_MOUSE);
+		return false;
+	};
+	EventManager::get_instance().subscribe<MouseClickEvent>(mouse_handler,
+															EventManager::CHANNEL_ALL);
+
+	MouseClickEvent click_event{
+		.mouse_x = 100, .mouse_y = 200, .button = MouseButton::LEFT_MOUSE};
+	EventManager::get_instance().trigger_event<MouseClickEvent>(click_event,
+																EventManager::CHANNEL_ALL);
+
+	EXPECT_TRUE(triggered);
+}
+TEST_F(EventManagerTest, EventManagerTest_trigger_one_channel) {
+	bool triggered = false;
+	int test_channel = 1;
+	EventHandler<MouseClickEvent> mouse_handler = [&](const MouseClickEvent & e) {
+		triggered = true;
+		EXPECT_EQ(e.mouse_x, 100);
+		EXPECT_EQ(e.mouse_y, 200);
+		EXPECT_EQ(e.button, MouseButton::LEFT_MOUSE);
+		return false;
+	};
+	EventManager::get_instance().subscribe<MouseClickEvent>(mouse_handler, test_channel);
+
+	MouseClickEvent click_event{
+		.mouse_x = 100, .mouse_y = 200, .button = MouseButton::LEFT_MOUSE};
+	EventManager::get_instance().trigger_event<MouseClickEvent>(click_event,
+																EventManager::CHANNEL_ALL);
+
+	EXPECT_FALSE(triggered);
+	EventManager::get_instance().trigger_event<MouseClickEvent>(click_event, test_channel);
+}
+
+TEST_F(EventManagerTest, EventManagerTest_callback_propagation) {
+	EventManager & event_manager = EventManager::get_instance();
+
+	// Flags to track handler calls
+	bool triggered_true = false;
+	bool triggered_false = false;
+
+	// Handlers
+	EventHandler<MouseClickEvent> mouse_handler_true = [&](const MouseClickEvent & e) {
+		triggered_true = true;
+		EXPECT_EQ(e.mouse_x, 100);
+		EXPECT_EQ(e.mouse_y, 200);
+		EXPECT_EQ(e.button, MouseButton::LEFT_MOUSE);
+		return true; // Stops propagation
+	};
+
+	EventHandler<MouseClickEvent> mouse_handler_false = [&](const MouseClickEvent & e) {
+		triggered_false = true;
+		EXPECT_EQ(e.mouse_x, 100);
+		EXPECT_EQ(e.mouse_y, 200);
+		EXPECT_EQ(e.button, MouseButton::LEFT_MOUSE);
+		return false; // Allows propagation
+	};
+
+	// Test event
+	MouseClickEvent click_event{
+		.mouse_x = 100, .mouse_y = 200, .button = MouseButton::LEFT_MOUSE};
+	event_manager.subscribe<MouseClickEvent>(mouse_handler_true, EventManager::CHANNEL_ALL);
+	event_manager.subscribe<MouseClickEvent>(mouse_handler_false, EventManager::CHANNEL_ALL);
+
+	// Trigger event
+	event_manager.trigger_event<MouseClickEvent>(click_event, EventManager::CHANNEL_ALL);
+
+	// Check that only the true handler was triggered
+	EXPECT_TRUE(triggered_true);
+	EXPECT_FALSE(triggered_false);
+
+	// Reset and clear
+	triggered_true = false;
+	triggered_false = false;
+	event_manager.clear();
+	event_manager.subscribe<MouseClickEvent>(mouse_handler_false, EventManager::CHANNEL_ALL);
+	event_manager.subscribe<MouseClickEvent>(mouse_handler_true, EventManager::CHANNEL_ALL);
+
+	// Trigger event again
+	event_manager.trigger_event<MouseClickEvent>(click_event, EventManager::CHANNEL_ALL);
+
+	// Check that both handlers were triggered
+	EXPECT_TRUE(triggered_true);
+	EXPECT_TRUE(triggered_false);
+}
+
+TEST_F(EventManagerTest, EventManagerTest_queue_dispatch) {
+	EventManager & event_manager = EventManager::get_instance();
+	bool triggered1 = false;
+	bool triggered2 = false;
+	int test_channel = 1;
+	EventHandler<MouseClickEvent> mouse_handler1 = [&](const MouseClickEvent & e) {
+		triggered1 = true;
+		EXPECT_EQ(e.mouse_x, 100);
+		EXPECT_EQ(e.mouse_y, 200);
+		EXPECT_EQ(e.button, MouseButton::LEFT_MOUSE);
+		return false; // Allows propagation
+	};
+	EventHandler<MouseClickEvent> mouse_handler2 = [&](const MouseClickEvent & e) {
+		triggered2 = true;
+		EXPECT_EQ(e.mouse_x, 100);
+		EXPECT_EQ(e.mouse_y, 200);
+		EXPECT_EQ(e.button, MouseButton::LEFT_MOUSE);
+		return false; // Allows propagation
+	};
+	event_manager.subscribe<MouseClickEvent>(mouse_handler1);
+	event_manager.subscribe<MouseClickEvent>(mouse_handler2, test_channel);
+
+	event_manager.queue_event<MouseClickEvent>(
+		MouseClickEvent{.mouse_x = 100, .mouse_y = 200, .button = MouseButton::LEFT_MOUSE});
+	event_manager.queue_event<MouseClickEvent>(
+		MouseClickEvent{.mouse_x = 100, .mouse_y = 200, .button = MouseButton::LEFT_MOUSE},
+		test_channel);
+	event_manager.dispatch_events();
+	EXPECT_TRUE(triggered1);
+	EXPECT_TRUE(triggered2);
+}
+
+TEST_F(EventManagerTest, EventManagerTest_unsubscribe) {
+	EventManager & event_manager = EventManager::get_instance();
+
+	// Flags to track if handlers are triggered
+	bool triggered1 = false;
+	bool triggered2 = false;
+
+	// Define EventHandlers
+	EventHandler<MouseClickEvent> mouse_handler1 = [&](const MouseClickEvent & e) {
+		triggered1 = true;
+		EXPECT_EQ(e.mouse_x, 100);
+		EXPECT_EQ(e.mouse_y, 200);
+		EXPECT_EQ(e.button, MouseButton::LEFT_MOUSE);
+		return false; // Allows propagation
+	};
+
+	EventHandler<MouseClickEvent> mouse_handler2 = [&](const MouseClickEvent & e) {
+		triggered2 = true;
+		EXPECT_EQ(e.mouse_x, 100);
+		EXPECT_EQ(e.mouse_y, 200);
+		EXPECT_EQ(e.button, MouseButton::LEFT_MOUSE);
+		return false; // Allows propagation
+	};
+	// Subscribe handlers
+	subscription_t handler1_id = event_manager.subscribe<MouseClickEvent>(mouse_handler1);
+	subscription_t handler2_id = event_manager.subscribe<MouseClickEvent>(mouse_handler2);
+
+	// Queue events
+	event_manager.queue_event<MouseClickEvent>(
+		MouseClickEvent{.mouse_x = 100, .mouse_y = 200, .button = MouseButton::LEFT_MOUSE});
+
+	// Dispatch events - both handlers should be triggered
+	event_manager.dispatch_events();
+	EXPECT_TRUE(triggered1); // Handler 1 should be triggered
+	EXPECT_TRUE(triggered2); // Handler 2 should be triggered
+
+	// Reset flags
+	triggered1 = false;
+	triggered2 = false;
+
+	// Unsubscribe handler1
+	event_manager.unsubscribe(handler1_id);
+
+	// Queue the same event again
+	event_manager.queue_event<MouseClickEvent>(
+		MouseClickEvent{.mouse_x = 100, .mouse_y = 200, .button = MouseButton::LEFT_MOUSE});
+
+	// Dispatch events - only handler 2 should be triggered, handler 1 should NOT
+	event_manager.dispatch_events();
+	EXPECT_FALSE(triggered1); // Handler 1 should NOT be triggered
+	EXPECT_TRUE(triggered2); // Handler 2 should be triggered
+
+	// Reset flags
+	triggered2 = false;
+
+	// Unsubscribe handler2
+	event_manager.unsubscribe(handler2_id);
+
+	// Queue the event again
+	event_manager.queue_event<MouseClickEvent>(
+		MouseClickEvent{.mouse_x = 100, .mouse_y = 200, .button = MouseButton::LEFT_MOUSE});
+
+	// Dispatch events - no handler should be triggered
+	event_manager.dispatch_events();
+	EXPECT_FALSE(triggered1); // Handler 1 should NOT be triggered
+	EXPECT_FALSE(triggered2); // Handler 2 should NOT be triggered
+}
diff --git a/src/test/OptionalRefTest.cpp b/src/test/OptionalRefTest.cpp
new file mode 100644
index 0000000..83f7b23
--- /dev/null
+++ b/src/test/OptionalRefTest.cpp
@@ -0,0 +1,42 @@
+#include <gtest/gtest.h>
+
+#include <crepe/util/OptionalRef.h>
+
+using namespace std;
+using namespace crepe;
+using namespace testing;
+
+TEST(OptionalRefTest, Normal) {
+	string value = "foo";
+	OptionalRef<string> ref = value;
+
+	EXPECT_TRUE(ref);
+	ASSERT_NO_THROW({
+		string & value_ref = ref;
+		EXPECT_EQ(value_ref, value);
+	});
+
+	ref.clear();
+	EXPECT_FALSE(ref);
+	ASSERT_THROW({ string & value_ref = ref; }, runtime_error);
+}
+
+TEST(OptionalRefTest, Empty) {
+	string value = "foo";
+	OptionalRef<string> ref;
+
+	EXPECT_FALSE(ref);
+	ASSERT_THROW({ string & value_ref = ref; }, runtime_error);
+}
+
+TEST(OptionalRefTest, Chain) {
+	string value = "foo";
+	OptionalRef<string> ref1 = value;
+	OptionalRef<string> ref2 = ref1;
+
+	EXPECT_TRUE(ref2);
+	string & value_ref = ref2;
+	EXPECT_EQ(value_ref, value);
+	value_ref = "bar";
+	EXPECT_EQ(value_ref, value);
+}
diff --git a/src/test/ParticleTest.cpp b/src/test/ParticleTest.cpp
index 4e655a9..eee022f 100644
--- a/src/test/ParticleTest.cpp
+++ b/src/test/ParticleTest.cpp
@@ -28,8 +28,8 @@ public:
 			GameObject game_object = mgr.new_object("", "", Vector2{0, 0}, 0, 0);
 
 			Color color(0, 0, 0, 0);
-			Sprite test_sprite = game_object.add_component<Sprite>(
-				make_shared<Texture>("../asset/texture/img.png"), color,
+			Sprite & test_sprite = game_object.add_component<Sprite>(
+				make_shared<Texture>("asset/texture/img.png"), color,
 				FlipSettings{true, true});
 
 			game_object.add_component<ParticleEmitter>(ParticleEmitter::Data{
diff --git a/src/test/SceneManagerTest.cpp b/src/test/SceneManagerTest.cpp
index 69e1171..1efcfb2 100644
--- a/src/test/SceneManagerTest.cpp
+++ b/src/test/SceneManagerTest.cpp
@@ -20,6 +20,8 @@ public:
 		GameObject object2 = mgr.new_object("scene_1", "tag_scene_1", Vector2{1, 0}, 0, 1);
 		GameObject object3 = mgr.new_object("scene_1", "tag_scene_1", Vector2{2, 0}, 0, 1);
 	}
+
+	string get_name() const { return "scene1"; }
 };
 
 class ConcreteScene2 : public Scene {
@@ -33,6 +35,8 @@ public:
 		GameObject object3 = mgr.new_object("scene_2", "tag_scene_2", Vector2{0, 2}, 0, 1);
 		GameObject object4 = mgr.new_object("scene_2", "tag_scene_2", Vector2{0, 3}, 0, 1);
 	}
+
+	string get_name() const { return "scene2"; }
 };
 
 class SceneManagerTest : public ::testing::Test {
@@ -42,8 +46,8 @@ public:
 };
 
 TEST_F(SceneManagerTest, loadScene) {
-	scene_mgr.add_scene<ConcreteScene1>("scene1");
-	scene_mgr.add_scene<ConcreteScene2>("scene2");
+	scene_mgr.add_scene<ConcreteScene1>();
+	scene_mgr.add_scene<ConcreteScene2>();
 
 	scene_mgr.load_next_scene();
 
diff --git a/src/test/ValueBrokerTest.cpp b/src/test/ValueBrokerTest.cpp
new file mode 100644
index 0000000..e6bb058
--- /dev/null
+++ b/src/test/ValueBrokerTest.cpp
@@ -0,0 +1,63 @@
+#include <gtest/gtest.h>
+
+#include <crepe/ValueBroker.h>
+#include <crepe/util/Proxy.h>
+
+using namespace std;
+using namespace crepe;
+using namespace testing;
+
+class ValueBrokerTest : public Test {
+public:
+	int read_count = 0;
+	int write_count = 0;
+	int value = 0;
+
+	ValueBroker<int> broker{
+		[this](const int & target) -> void {
+			this->write_count++;
+			this->value = target;
+		},
+		[this]() -> const int & {
+			this->read_count++;
+			return this->value;
+		},
+	};
+	Proxy<int> proxy{broker};
+
+	void SetUp() override {
+		ASSERT_EQ(read_count, 0);
+		ASSERT_EQ(write_count, 0);
+	}
+};
+
+TEST_F(ValueBrokerTest, BrokerWrite) {
+	broker.set(0);
+	EXPECT_EQ(read_count, 0);
+	EXPECT_EQ(write_count, 1);
+}
+
+TEST_F(ValueBrokerTest, BrokerRead) {
+	broker.get();
+	EXPECT_EQ(read_count, 1);
+	EXPECT_EQ(write_count, 0);
+}
+
+TEST_F(ValueBrokerTest, ProxyWrite) {
+	proxy = 0;
+	EXPECT_EQ(read_count, 0);
+	EXPECT_EQ(write_count, 1);
+}
+
+void dummy(int) {}
+TEST_F(ValueBrokerTest, ProxyRead) {
+	dummy(proxy);
+	EXPECT_EQ(read_count, 1);
+	EXPECT_EQ(write_count, 0);
+}
+
+TEST_F(ValueBrokerTest, ProxyReadWrite) {
+	proxy = proxy;
+	ASSERT_EQ(read_count, 1);
+	ASSERT_EQ(write_count, 1);
+}