merge `loek/cleanup` into `loek/audio`

92 files changed, 886 insertions, 564 deletions

diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index e4922df..445a8b2 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -38,6 +38,5 @@ install(
 
 target_link_libraries(test_main
 	PRIVATE gtest
-	PRIVATE gtest_main
 	PUBLIC crepe
 )
diff --git a/src/crepe/Asset.cpp b/src/crepe/Asset.cpp
index 3d4df53..9c41ecb 100644
--- a/src/crepe/Asset.cpp
+++ b/src/crepe/Asset.cpp
@@ -1,20 +1,16 @@
 #include <filesystem>
 
 #include "Asset.h"
-#include "Exception.h"
 
 using namespace crepe;
 using namespace std;
 
-Asset::Asset(const string & src) : src(src) {
-	try {
-		this->src = filesystem::canonical(src);
-	} catch (filesystem::filesystem_error & e) {
-		throw Exception("Asset error: %s", e.what());
-	}
-	this->file = ifstream(this->src, ios::in | ios::binary);
+// 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);
 }
 
-const istream & Asset::read() { return this->file; }
+istream & Asset::get_stream() { return this->file; }
 
-const char * Asset::canonical() const { return this->src.c_str(); }
+const string & Asset::get_canonical() const { return this->src; }
diff --git a/src/crepe/Asset.h b/src/crepe/Asset.h
index d4e4ba1..cb413f4 100644
--- a/src/crepe/Asset.h
+++ b/src/crepe/Asset.h
@@ -20,13 +20,21 @@ public:
 	Asset(const std::string & src);
 
 public:
-	//! Get an input stream to the contents of this resource
-	const std::istream & read();
-	//! Get the canonical path to this resource
-	const char * canonical() const;
+	/**
+	 * \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:
-	std::string src;
+	//! Canonical path to asset
+	const std::string src;
+	//! File handle (stream)
 	std::ifstream file;
 };
 
diff --git a/src/crepe/CMakeLists.txt b/src/crepe/CMakeLists.txt
index fc95bd3..52a781e 100644
--- a/src/crepe/CMakeLists.txt
+++ b/src/crepe/CMakeLists.txt
@@ -16,6 +16,7 @@ target_sources(crepe PUBLIC FILE_SET HEADERS FILES
 	ValueBroker.h
 	ValueBroker.hpp
 	Exception.h
+	Exception.hpp
 )
 
 add_subdirectory(api)
diff --git a/src/crepe/Collider.cpp b/src/crepe/Collider.cpp
index bbec488..113ba61 100644
--- a/src/crepe/Collider.cpp
+++ b/src/crepe/Collider.cpp
@@ -1,5 +1,3 @@
 #include "Collider.h"
 
 using namespace crepe;
-
-Collider::Collider(game_object_id_t id) : Component(id) {}
diff --git a/src/crepe/Collider.h b/src/crepe/Collider.h
index 827f83d..a1e9095 100644
--- a/src/crepe/Collider.h
+++ b/src/crepe/Collider.h
@@ -6,7 +6,7 @@ namespace crepe {
 
 class Collider : public Component {
 public:
-	Collider(game_object_id_t id);
+	using Component::Component;
 
 	int size;
 };
diff --git a/src/crepe/Component.cpp b/src/crepe/Component.cpp
index 73c2d07..acfd35c 100644
--- a/src/crepe/Component.cpp
+++ b/src/crepe/Component.cpp
@@ -1,5 +1,4 @@
 #include "Component.h"
-#include "types.h"
 
 using namespace crepe;
 
diff --git a/src/crepe/Component.h b/src/crepe/Component.h
index e8d18d9..12c10cb 100644
--- a/src/crepe/Component.h
+++ b/src/crepe/Component.h
@@ -13,16 +13,21 @@ class ComponentManager;
  * interface for all components.
  */
 class Component {
+public:
+	//! Whether the component is active
+	bool active = true;
+	//! The id of the GameObject this component belongs to
+	const game_object_id_t game_object_id;
+
 protected:
-	//! Only the ComponentManager can create components
-	friend class crepe::ComponentManager;
 	/**
 	 * \param id The id of the GameObject this component belongs to
 	 */
 	Component(game_object_id_t id);
+	//! Only the ComponentManager can create components
+	friend class ComponentManager;
 
 public:
-	virtual ~Component() = default;
 	/**
 	 * \brief Get the maximum number of instances for this component
 	 *
@@ -33,12 +38,6 @@ public:
 	 * \return The maximum number of instances for this component
 	 */
 	virtual int get_instances_max() const { return -1; }
-
-public:
-	//! The id of the GameObject this component belongs to
-	const game_object_id_t game_object_id;
-	//! Whether the component is active
-	bool active = true;
 };
 
 } // namespace crepe
diff --git a/src/crepe/ComponentManager.cpp b/src/crepe/ComponentManager.cpp
index 85149c8..7af0380 100644
--- a/src/crepe/ComponentManager.cpp
+++ b/src/crepe/ComponentManager.cpp
@@ -1,13 +1,10 @@
-#include "util/log.h"
+#include "api/GameObject.h"
+#include "util/Log.h"
 
 #include "ComponentManager.h"
 
 using namespace crepe;
-
-ComponentManager & ComponentManager::get_instance() {
-	static ComponentManager instance;
-	return instance;
-}
+using namespace std;
 
 void ComponentManager::delete_all_components_of_id(game_object_id_t id) {
 	// Loop through all the types (in the unordered_map<>)
@@ -26,5 +23,13 @@ void ComponentManager::delete_all_components() {
 }
 
 ComponentManager::ComponentManager() { dbg_trace(); }
-
 ComponentManager::~ComponentManager() { dbg_trace(); }
+
+GameObject ComponentManager::new_object(const string & name, const string & tag,
+										const Vector2 & position,
+										double rotation, double scale) {
+	GameObject object{*this,	this->next_id, name, tag,
+					  position, rotation,	   scale};
+	this->next_id++;
+	return object;
+}
diff --git a/src/crepe/ComponentManager.h b/src/crepe/ComponentManager.h
index c8c196c..51c84a4 100644
--- a/src/crepe/ComponentManager.h
+++ b/src/crepe/ComponentManager.h
@@ -1,15 +1,18 @@
 #pragma once
 
-#include <cstdint>
+#include <forward_list>
 #include <memory>
 #include <typeindex>
 #include <unordered_map>
 #include <vector>
 
 #include "Component.h"
+#include "api/Vector2.h"
 
 namespace crepe {
 
+class GameObject;
+
 /**
  * \brief Manages all components
  * 
@@ -18,18 +21,10 @@ namespace crepe {
  */
 class ComponentManager {
 public:
-	/**
-	 * \brief Get the instance of the ComponentManager
-	 * 
-	 * \return The instance of the ComponentManager
-	 */
-	static ComponentManager & get_instance();
-	ComponentManager(const ComponentManager &) = delete;
-	ComponentManager(ComponentManager &&) = delete;
-	ComponentManager & operator=(const ComponentManager &) = delete;
-	ComponentManager & operator=(ComponentManager &&) = delete;
-	~ComponentManager();
+	ComponentManager(); // dbg_trace
+	~ComponentManager(); // dbg_trace
 
+protected:
 	/**
 	 * \brief Add a component to the ComponentManager
 	 * 
@@ -44,6 +39,11 @@ public:
 	 */
 	template <typename T, typename... Args>
 	T & add_component(game_object_id_t id, Args &&... args);
+	//! GameObject is used as an interface to add components instead of the
+	// component manager directly
+	friend class GameObject;
+
+public:
 	/**
 	 * \brief Delete all components of a specific type and id
 	 * 
@@ -100,8 +100,11 @@ public:
 	template <typename T>
 	std::vector<std::reference_wrapper<T>> get_components_by_type() const;
 
-private:
-	ComponentManager();
+	// TODO: doxygen
+	GameObject new_object(const std::string & name,
+						  const std::string & tag = "",
+						  const Vector2 & position = {0, 0},
+						  double rotation = 0, double scale = 0);
 
 private:
 	/**
@@ -118,6 +121,10 @@ private:
 	std::unordered_map<std::type_index,
 					   std::vector<std::vector<std::unique_ptr<Component>>>>
 		components;
+
+	//! ID of next GameObject
+	game_object_id_t next_id = 0;
+	std::forward_list<std::unique_ptr<GameObject>> objects;
 };
 
 } // namespace crepe
diff --git a/src/crepe/Exception.cpp b/src/crepe/Exception.cpp
index dab8f2e..5a24e7e 100644
--- a/src/crepe/Exception.cpp
+++ b/src/crepe/Exception.cpp
@@ -1,16 +1,8 @@
-#include <cstdarg>
-
 #include "Exception.h"
-#include "util/fmt.h"
 
-using namespace std;
 using namespace crepe;
+using namespace std;
 
-const char * Exception::what() { return error.c_str(); }
+const char * Exception::what() const noexcept { return error.c_str(); }
 
-Exception::Exception(const char * fmt, ...) {
-	va_list args;
-	va_start(args, fmt);
-	this->error = va_stringf(args, fmt);
-	va_end(args);
-}
+Exception::Exception(const string & msg) { this->error = msg; }
diff --git a/src/crepe/Exception.h b/src/crepe/Exception.h
index 6473043..580fc16 100644
--- a/src/crepe/Exception.h
+++ b/src/crepe/Exception.h
@@ -1,22 +1,31 @@
 #pragma once
 
 #include <exception>
+#include <format>
 #include <string>
 
 namespace crepe {
 
-//! Exception class with printf-style constructor
+//! Exception class
 class Exception : public std::exception {
 public:
-	//! printf
-	Exception(const char * fmt, ...);
+	//! Exception with plain message
+	Exception(const std::string & msg);
+
+	//! Exception with \c std::format message
+	template <class... Args>
+	Exception(std::format_string<Args...> fmt, Args &&... args);
+
 	//! Get formatted error message
-	const char * what();
+	const char * what() const noexcept;
 
 protected:
 	Exception() = default;
+
 	//! Formatted error message
 	std::string error;
 };
 
 } // namespace crepe
+
+#include "Exception.hpp"
diff --git a/src/crepe/Exception.hpp b/src/crepe/Exception.hpp
new file mode 100644
index 0000000..7c462a3
--- /dev/null
+++ b/src/crepe/Exception.hpp
@@ -0,0 +1,12 @@
+#pragma once
+
+#include "Exception.h"
+
+namespace crepe {
+
+template <class... Args>
+Exception::Exception(std::format_string<Args...> fmt, Args &&... args) {
+	this->error = std::format(fmt, std::forward<Args>(args)...);
+}
+
+} // namespace crepe
diff --git a/src/crepe/api/Animator.cpp b/src/crepe/api/Animator.cpp
index 58fee2a..54b2ec3 100644
--- a/src/crepe/api/Animator.cpp
+++ b/src/crepe/api/Animator.cpp
@@ -1,7 +1,7 @@
 
 #include <cstdint>
 
-#include "util/log.h"
+#include "util/Log.h"
 
 #include "Animator.h"
 #include "Component.h"
@@ -9,7 +9,8 @@
 
 using namespace crepe;
 
-Animator::Animator(uint32_t id, Sprite & ss, int row, int col, int col_animator)
+Animator::Animator(game_object_id_t id, Sprite & ss, int row, int col,
+				   int col_animator)
 	: Component(id),
 	  spritesheet(ss),
 	  row(row),
diff --git a/src/crepe/api/Animator.h b/src/crepe/api/Animator.h
index def0240..75b8139 100644
--- a/src/crepe/api/Animator.h
+++ b/src/crepe/api/Animator.h
@@ -6,6 +6,7 @@
 #include "Sprite.h"
 
 namespace crepe {
+
 class AnimatorSystem;
 class SDLContext;
 
@@ -35,7 +36,7 @@ public:
 	 *
 	 * This constructor sets up the Animator with the given parameters, and initializes the animation system.
 	 */
-	Animator(uint32_t id, Sprite & spritesheet, int row, int col,
+	Animator(game_object_id_t id, Sprite & spritesheet, int row, int col,
 			 int col_animate);
 
 	~Animator(); // dbg_trace
diff --git a/src/crepe/api/AssetManager.cpp b/src/crepe/api/AssetManager.cpp
index b891760..3925758 100644
--- a/src/crepe/api/AssetManager.cpp
+++ b/src/crepe/api/AssetManager.cpp
@@ -1,4 +1,4 @@
-#include "util/log.h"
+#include "util/Log.h"
 
 #include "AssetManager.h"
 
diff --git a/src/crepe/api/BehaviorScript.cpp b/src/crepe/api/BehaviorScript.cpp
index e69de29..7bbace0 100644
--- a/src/crepe/api/BehaviorScript.cpp
+++ b/src/crepe/api/BehaviorScript.cpp
@@ -0,0 +1,15 @@
+#include "BehaviorScript.h"
+#include "Component.h"
+#include "GameObject.h"
+
+using namespace crepe;
+
+BehaviorScript::BehaviorScript(game_object_id_t id, ComponentManager & mgr)
+	: Component(id),
+	  component_manager(mgr) {}
+
+template <>
+BehaviorScript & GameObject::add_component<BehaviorScript>() {
+	ComponentManager & mgr = this->component_manager;
+	return mgr.add_component<BehaviorScript>(this->id, mgr);
+}
diff --git a/src/crepe/api/BehaviorScript.h b/src/crepe/api/BehaviorScript.h
index 6b1fec7..2982358 100644
--- a/src/crepe/api/BehaviorScript.h
+++ b/src/crepe/api/BehaviorScript.h
@@ -3,6 +3,7 @@
 #include <memory>
 
 #include "../Component.h"
+#include "GameObject.h"
 
 namespace crepe {
 
@@ -10,23 +11,61 @@ class ScriptSystem;
 class ComponentManager;
 class Script;
 
+/**
+ * \brief Script component
+ *
+ * This class acts as a (component) wrapper around an instance of (a class
+ * derivatived from) \c Script. \c BehaviorScript is the only ECS component
+ * that stores member function implementations as data.
+ */
 class BehaviorScript : public Component {
 protected:
-	friend class crepe::ComponentManager;
-	using Component::Component;
+	BehaviorScript(game_object_id_t id, ComponentManager & component_manager);
+	//! Only ComponentManager is allowed to instantiate BehaviorScript
+	friend class ComponentManager;
 
 public:
-	virtual ~BehaviorScript() = default;
+	~BehaviorScript() = default;
 
 public:
+	/**
+	 * \brief Set the concrete script of this component
+	 *
+	 * \tparam T Concrete script type (derived from \c crepe::Script)
+	 *
+	 * \returns Reference to BehaviorScript component (`*this`)
+	 */
 	template <class T>
 	BehaviorScript & set_script();
 
 protected:
-	friend class crepe::ScriptSystem;
+	//! ScriptSystem needs direct access to the script instance
+	friend class ScriptSystem;
+	//! Flag to indicate if script->init() has been called already
+	bool initialized = false;
+	//! Script instance
 	std::unique_ptr<Script> script = nullptr;
+	//! Reference to component manager
+	ComponentManager & component_manager;
+
+private:
+	//! Script accesses the component manager directly via its parent
+	// (BehaviorScript) reference
+	friend class Script;
 };
 
+/**
+ * \brief Add a BehaviorScript component to this game object
+ *
+ * The \c BehaviorScript class is the only exception to the ECS harmony, and
+ * requires a reference to the component manager passed to its constructor in
+ * order to function normally. This is because the \c BehaviorScript (and \c
+ * Script) classes are the only component-related classes that store
+ * implemented member functions as data.
+ */
+template <>
+BehaviorScript & GameObject::add_component<BehaviorScript>();
+
 } // namespace crepe
 
 #include "BehaviorScript.hpp"
diff --git a/src/crepe/api/BehaviorScript.hpp b/src/crepe/api/BehaviorScript.hpp
index 4751607..eec26da 100644
--- a/src/crepe/api/BehaviorScript.hpp
+++ b/src/crepe/api/BehaviorScript.hpp
@@ -2,7 +2,7 @@
 
 #include <type_traits>
 
-#include "../util/log.h"
+#include "../util/Log.h"
 
 #include "BehaviorScript.h"
 #include "Script.h"
@@ -11,10 +11,11 @@ namespace crepe {
 
 template <class T>
 BehaviorScript & BehaviorScript::set_script() {
-	static_assert(std::is_base_of<Script, T>::value);
 	dbg_trace();
+	static_assert(std::is_base_of<Script, T>::value);
 	Script * s = new T();
-	s->parent = this;
+	s->parent_ref = this;
+	s->component_manager_ref = &this->component_manager;
 	this->script = std::unique_ptr<Script>(s);
 	return *this;
 }
diff --git a/src/crepe/api/Camera.cpp b/src/crepe/api/Camera.cpp
index 6355a03..5835bdd 100644
--- a/src/crepe/api/Camera.cpp
+++ b/src/crepe/api/Camera.cpp
@@ -1,7 +1,4 @@
-
-#include <cstdint>
-
-#include "util/log.h"
+#include "util/Log.h"
 
 #include "Camera.h"
 #include "Color.h"
@@ -9,7 +6,7 @@
 
 using namespace crepe;
 
-Camera::Camera(uint32_t id, const Color & bg_color)
+Camera::Camera(game_object_id_t id, const Color & bg_color)
 	: Component(id),
 	  bg_color(bg_color) {
 	dbg_trace();
diff --git a/src/crepe/api/Camera.h b/src/crepe/api/Camera.h
index ba3a9ef..d8c08a6 100644
--- a/src/crepe/api/Camera.h
+++ b/src/crepe/api/Camera.h
@@ -23,7 +23,7 @@ public:
 	 * \param id Unique identifier for the camera component.
 	 * \param bg_color Background color for the camera view.
 	 */
-	Camera(uint32_t id, const Color & bg_color);
+	Camera(game_object_id_t id, const Color & bg_color);
 	~Camera(); // dbg_trace only
 
 public:
diff --git a/src/crepe/api/Config.h b/src/crepe/api/Config.h
index 8c9e643..e3f86bf 100644
--- a/src/crepe/api/Config.h
+++ b/src/crepe/api/Config.h
@@ -1,6 +1,6 @@
 #pragma once
 
-#include "../util/log.h"
+#include "../util/Log.h"
 
 namespace crepe {
 
@@ -26,10 +26,10 @@ public:
 		/**
 		 * \brief Log level
 		 *
-		 * Only messages with equal or higher priority than this value will be
+		 * Only messages with equal or higher severity than this value will be
 		 * logged.
 		 */
-		LogLevel level = LogLevel::INFO;
+		Log::Level level = Log::Level::INFO;
 		/**
 		 * \brief Colored log output
 		 *
diff --git a/src/crepe/api/GameObject.cpp b/src/crepe/api/GameObject.cpp
index d252e77..4f3c639 100644
--- a/src/crepe/api/GameObject.cpp
+++ b/src/crepe/api/GameObject.cpp
@@ -1,23 +1,27 @@
 #include "api/Transform.h"
 
+#include "BehaviorScript.h"
 #include "GameObject.h"
 #include "Metadata.h"
 
 using namespace crepe;
 using namespace std;
 
-GameObject::GameObject(game_object_id_t id, const std::string & name,
+GameObject::GameObject(ComponentManager & component_manager,
+					   game_object_id_t id, const std::string & name,
 					   const std::string & tag, const Vector2 & position,
 					   double rotation, double scale)
-	: id(id) {
+	: id(id),
+	  component_manager(component_manager) {
+
 	// Add Transform and Metadata components
-	ComponentManager & mgr = ComponentManager::get_instance();
+	ComponentManager & mgr = this->component_manager;
 	mgr.add_component<Transform>(this->id, position, rotation, scale);
 	mgr.add_component<Metadata>(this->id, name, tag);
 }
 
 void GameObject::set_parent(const GameObject & parent) {
-	ComponentManager & mgr = ComponentManager::get_instance();
+	ComponentManager & mgr = this->component_manager;
 
 	// Set parent on own Metadata component
 	vector<reference_wrapper<Metadata>> this_metadata
diff --git a/src/crepe/api/GameObject.h b/src/crepe/api/GameObject.h
index d703730..73ff0b8 100644
--- a/src/crepe/api/GameObject.h
+++ b/src/crepe/api/GameObject.h
@@ -2,11 +2,12 @@
 
 #include <string>
 
+#include "Vector2.h"
 #include "types.h"
 
 namespace crepe {
 
-class Vector2;
+class ComponentManager;
 
 /**
  * \brief Represents a GameObject
@@ -16,11 +17,12 @@ class Vector2;
  * done in the ComponentManager.
  */
 class GameObject {
-public:
+private:
 	/**
 	 * This constructor creates a new GameObject. It creates a new
 	 * Transform and Metadata component and adds them to the ComponentManager.
 	 * 
+	 * \param component_manager Reference to component_manager
 	 * \param id The id of the GameObject
 	 * \param name The name of the GameObject
 	 * \param tag The tag of the GameObject
@@ -28,9 +30,13 @@ public:
 	 * \param rotation The rotation of the GameObject
 	 * \param scale The scale of the GameObject
 	 */
-	GameObject(game_object_id_t id, const std::string & name,
-			   const std::string & tag, const Vector2 & position,
-			   double rotation, double scale);
+	GameObject(ComponentManager & component_manager, game_object_id_t id,
+			   const std::string & name, const std::string & tag,
+			   const Vector2 & position, double rotation, double scale);
+	//! ComponentManager instances GameObject
+	friend class ComponentManager;
+
+public:
 	/**
 	 * \brief Set the parent of this GameObject
 	 * 
@@ -58,6 +64,9 @@ public:
 public:
 	//! The id of the GameObject
 	const game_object_id_t id;
+
+protected:
+	ComponentManager & component_manager;
 };
 
 } // namespace crepe
diff --git a/src/crepe/api/GameObject.hpp b/src/crepe/api/GameObject.hpp
index bfba7fe..17b17d7 100644
--- a/src/crepe/api/GameObject.hpp
+++ b/src/crepe/api/GameObject.hpp
@@ -8,7 +8,7 @@ namespace crepe {
 
 template <typename T, typename... Args>
 T & GameObject::add_component(Args &&... args) {
-	ComponentManager & mgr = ComponentManager::get_instance();
+	ComponentManager & mgr = this->component_manager;
 	return mgr.add_component<T>(this->id, std::forward<Args>(args)...);
 }
 
diff --git a/src/crepe/api/LoopManager.cpp b/src/crepe/api/LoopManager.cpp
index 2e9823f..f0788ab 100644
--- a/src/crepe/api/LoopManager.cpp
+++ b/src/crepe/api/LoopManager.cpp
@@ -1,5 +1,9 @@
-
 #include "../facade/SDLContext.h"
+
+#include "../system/AnimatorSystem.h"
+#include "../system/CollisionSystem.h"
+#include "../system/ParticleSystem.h"
+#include "../system/PhysicsSystem.h"
 #include "../system/RenderSystem.h"
 #include "../system/ScriptSystem.h"
 
@@ -7,11 +11,25 @@
 #include "LoopTimer.h"
 
 using namespace crepe;
+using namespace std;
+
+LoopManager::LoopManager() {
+	this->load_system<AnimatorSystem>();
+	this->load_system<CollisionSystem>();
+	this->load_system<ParticleSystem>();
+	this->load_system<PhysicsSystem>();
+	this->load_system<RenderSystem>();
+	this->load_system<ScriptSystem>();
+}
+
+ComponentManager & LoopManager::get_component_manager() {
+	return this->component_manager;
+}
 
-LoopManager::LoopManager() {}
 void LoopManager::process_input() {
 	SDLContext::get_instance().handle_events(this->game_running);
 }
+
 void LoopManager::start() {
 	this->setup();
 	this->loop();
@@ -48,7 +66,7 @@ void LoopManager::setup() {
 
 void LoopManager::render() {
 	if (this->game_running) {
-		RenderSystem::get_instance().update();
+		this->get_system<RenderSystem>().update();
 	}
 }
 
diff --git a/src/crepe/api/LoopManager.h b/src/crepe/api/LoopManager.h
index 2f03193..288dca2 100644
--- a/src/crepe/api/LoopManager.h
+++ b/src/crepe/api/LoopManager.h
@@ -2,15 +2,9 @@
 
 #include <memory>
 
-class RenderSystem;
-class SDLContext;
-class LoopTimer;
-class ScriptSystem;
-class SoundSystem;
-class ParticleSystem;
-class PhysicsSystem;
-class AnimatorSystem;
-class CollisionSystem;
+#include "../ComponentManager.h"
+#include "../system/System.h"
+
 namespace crepe {
 
 class LoopManager {
@@ -73,7 +67,21 @@ private:
 	void render();
 
 	bool game_running = false;
-	//#TODO add system instances
+
+protected:
+	ComponentManager & get_component_manager();
+	template <class T>
+	T & get_system();
+
+private:
+	ComponentManager component_manager{};
+	std::unordered_map<std::type_index, std::unique_ptr<System>> systems;
+
+private:
+	template <class T>
+	void load_system();
 };
 
 } // namespace crepe
+
+#include "LoopManager.hpp"
diff --git a/src/crepe/api/LoopManager.hpp b/src/crepe/api/LoopManager.hpp
new file mode 100644
index 0000000..8fb9aa3
--- /dev/null
+++ b/src/crepe/api/LoopManager.hpp
@@ -0,0 +1,40 @@
+#pragma once
+
+#include <cassert>
+#include <memory>
+
+#include "../Exception.h"
+#include "../system/System.h"
+
+#include "LoopManager.h"
+
+namespace crepe {
+
+template <class T>
+T & LoopManager::get_system() {
+	using namespace std;
+	static_assert(is_base_of<System, T>::value,
+				  "get_system must recieve a derivative class of System");
+
+	const type_info & type = typeid(T);
+	if (!this->systems.contains(type))
+		throw Exception("LoopManager: %s is not initialized", type.name());
+
+	System * system = this->systems.at(type).get();
+	T * concrete_system = dynamic_cast<T *>(system);
+	assert(concrete_system != nullptr);
+
+	return *concrete_system;
+}
+
+template <class T>
+void LoopManager::load_system() {
+	using namespace std;
+	static_assert(is_base_of<System, T>::value,
+				  "load_system must recieve a derivative class of System");
+
+	System * system = new T(this->component_manager);
+	this->systems[typeid(T)] = unique_ptr<System>(system);
+}
+
+} // namespace crepe
diff --git a/src/crepe/api/LoopTimer.cpp b/src/crepe/api/LoopTimer.cpp
index 8f09e41..b3aec22 100644
--- a/src/crepe/api/LoopTimer.cpp
+++ b/src/crepe/api/LoopTimer.cpp
@@ -1,7 +1,7 @@
 #include <chrono>
 
 #include "../facade/SDLContext.h"
-#include "../util/log.h"
+#include "../util/Log.h"
 
 #include "LoopTimer.h"
 
diff --git a/src/crepe/api/Rigidbody.cpp b/src/crepe/api/Rigidbody.cpp
index 3bf1c5b..6b87695 100644
--- a/src/crepe/api/Rigidbody.cpp
+++ b/src/crepe/api/Rigidbody.cpp
@@ -2,8 +2,8 @@
 
 using namespace crepe;
 
-crepe::Rigidbody::Rigidbody(uint32_t game_object_id, const Data & data)
-	: Component(game_object_id),
+crepe::Rigidbody::Rigidbody(game_object_id_t id, const Data & data)
+	: Component(id),
 	  data(data) {}
 
 void crepe::Rigidbody::add_force_linear(const Vector2 & force) {
diff --git a/src/crepe/api/Rigidbody.h b/src/crepe/api/Rigidbody.h
index 68481f4..2e20288 100644
--- a/src/crepe/api/Rigidbody.h
+++ b/src/crepe/api/Rigidbody.h
@@ -82,7 +82,7 @@ public:
 	 * \param game_object_id id of the gameobject the rigibody is added to.
 	 * \param data struct to configure the rigidbody.
 	 */
-	Rigidbody(uint32_t game_object_id, const Data & data);
+	Rigidbody(game_object_id_t id, const Data & data);
 	//! struct to hold data of rigidbody
 	Data data;
 
diff --git a/src/crepe/api/SaveManager.cpp b/src/crepe/api/SaveManager.cpp
index 43276c5..2974b91 100644
--- a/src/crepe/api/SaveManager.cpp
+++ b/src/crepe/api/SaveManager.cpp
@@ -1,5 +1,5 @@
 #include "../facade/DB.h"
-#include "../util/log.h"
+#include "../util/Log.h"
 
 #include "Config.h"
 #include "SaveManager.h"
diff --git a/src/crepe/api/Scene.cpp b/src/crepe/api/Scene.cpp
index 933edf4..88aa82d 100644
--- a/src/crepe/api/Scene.cpp
+++ b/src/crepe/api/Scene.cpp
@@ -2,4 +2,6 @@
 
 using namespace crepe;
 
-Scene::Scene(const std::string & name) : name(name) {}
+Scene::Scene(ComponentManager & mgr, const std::string & name)
+	: component_manager(mgr),
+	  name(name) {}
diff --git a/src/crepe/api/Scene.h b/src/crepe/api/Scene.h
index f8bcc3d..334f306 100644
--- a/src/crepe/api/Scene.h
+++ b/src/crepe/api/Scene.h
@@ -4,14 +4,20 @@
 
 namespace crepe {
 
+class ComponentManager;
+
 class Scene {
 public:
-	Scene(const std::string & name);
+	Scene(ComponentManager & mgr, const std::string & name);
 	virtual ~Scene() = default;
+
 	virtual void load_scene() = 0;
 
 public:
-	std::string name;
+	const std::string name;
+
+protected:
+	ComponentManager & component_manager;
 };
 
 } // namespace crepe
diff --git a/src/crepe/api/SceneManager.cpp b/src/crepe/api/SceneManager.cpp
index dfed6ee..4a38787 100644
--- a/src/crepe/api/SceneManager.cpp
+++ b/src/crepe/api/SceneManager.cpp
@@ -8,10 +8,7 @@
 using namespace crepe;
 using namespace std;
 
-SceneManager & SceneManager::get_instance() {
-	static SceneManager instance;
-	return instance;
-}
+SceneManager::SceneManager(ComponentManager & mgr) : component_manager(mgr) {}
 
 void SceneManager::set_next_scene(const string & name) { next_scene = name; }
 
@@ -30,7 +27,7 @@ void SceneManager::load_next_scene() {
 	unique_ptr<Scene> & scene = *it;
 
 	// Delete all components of the current scene
-	ComponentManager & mgr = ComponentManager::get_instance();
+	ComponentManager & mgr = this->component_manager;
 	mgr.delete_all_components();
 
 	// Load the new scene
diff --git a/src/crepe/api/SceneManager.h b/src/crepe/api/SceneManager.h
index 1e0e670..553194f 100644
--- a/src/crepe/api/SceneManager.h
+++ b/src/crepe/api/SceneManager.h
@@ -8,14 +8,12 @@
 
 namespace crepe {
 
+class ComponentManager;
+
 class SceneManager {
 public:
-	// Singleton
-	static SceneManager & get_instance();
-	SceneManager(const SceneManager &) = delete;
-	SceneManager(SceneManager &&) = delete;
-	SceneManager & operator=(const SceneManager &) = delete;
-	SceneManager & operator=(SceneManager &&) = delete;
+	SceneManager(ComponentManager & mgr);
+	virtual ~SceneManager() = default;
 
 public:
 	/**
@@ -38,11 +36,11 @@ public:
 	void load_next_scene();
 
 private:
-	SceneManager() = default;
-
-private:
 	std::vector<std::unique_ptr<Scene>> scenes;
 	std::string next_scene;
+
+protected:
+	ComponentManager & component_manager;
 };
 
 } // namespace crepe
diff --git a/src/crepe/api/SceneManager.hpp b/src/crepe/api/SceneManager.hpp
index 8bad7b2..714f690 100644
--- a/src/crepe/api/SceneManager.hpp
+++ b/src/crepe/api/SceneManager.hpp
@@ -1,13 +1,16 @@
+#pragma once
+
 #include "SceneManager.h"
 
 namespace crepe {
 
 template <typename T>
 void SceneManager::add_scene(const std::string & name) {
-	static_assert(std::is_base_of<Scene, T>::value,
-				  "T must be derived from Scene");
+	using namespace std;
+	static_assert(is_base_of<Scene, T>::value, "T must be derived from Scene");
 
-	scenes.emplace_back(make_unique<T>(name));
+	Scene * scene = new T(this->component_manager, name);
+	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()) {
diff --git a/src/crepe/api/Script.h b/src/crepe/api/Script.h
index 49e625f..68a46d7 100644
--- a/src/crepe/api/Script.h
+++ b/src/crepe/api/Script.h
@@ -3,18 +3,36 @@
 #include <vector>
 
 namespace crepe {
-class ScriptSystem;
-}
-
-namespace crepe {
 
+class ScriptSystem;
 class BehaviorScript;
+class ComponentManager;
 
+/**
+ * \brief Script interface
+ *
+ * This class is used as a base class for user-defined scripts that can be
+ * added to game objects using the \c BehaviorScript component.
+ */
 class Script {
+	//! ScriptSystem calls \c update()
 	friend class crepe::ScriptSystem;
 
 protected:
+	/**
+	 * \brief Script initialization function
+	 *
+	 * This function is called during the ScriptSystem::update() routine *before*
+	 * Script::update() if it (a) has not yet been called and (b) the \c
+	 * BehaviorScript component holding this script instance is active.
+	 */
 	virtual void init() {}
+	/**
+	 * \brief Script update function
+	 *
+	 * This function is called during the ScriptSystem::update() routine if the
+	 * \c BehaviorScript component holding this script instance is active.
+	 */
 	virtual void update() {}
 	// NOTE: additional *events* (like unity's OnDisable and OnEnable) should be
 	// implemented as member methods in derivative user script classes and
@@ -22,15 +40,42 @@ protected:
 	// added event.
 
 protected:
+	/**
+	 * \brief Get single component of type \c T on this game object (utility)
+	 *
+	 * \tparam T Type of component
+	 *
+	 * \returns Reference to component
+	 *
+	 * \throws nullptr if this game object does not have a component matching
+	 * type \c T
+	 */
 	template <typename T>
-	T & get_component();
+	T & get_component() const;
 
+	/**
+	 * \brief Get all components of type \c T on this game object (utility)
+	 *
+	 * \tparam T Type of component
+	 *
+	 * \returns List of component references
+	 */
 	template <typename T>
-	std::vector<std::reference_wrapper<T>> get_components();
+	std::vector<std::reference_wrapper<T>> get_components() const;
+
+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.
+	Script() = default;
+	//! Only \c BehaviorScript instantiates Script
+	friend class BehaviorScript;
 
 private:
-	friend class crepe::BehaviorScript;
-	BehaviorScript * parent = nullptr;
+	// These references are set by BehaviorScript immediately after calling the
+	// constructor of Script.
+	BehaviorScript * parent_ref = nullptr;
+	ComponentManager * component_manager_ref = nullptr;
 };
 
 } // namespace crepe
diff --git a/src/crepe/api/Script.hpp b/src/crepe/api/Script.hpp
index d96c0e8..aceb38b 100644
--- a/src/crepe/api/Script.hpp
+++ b/src/crepe/api/Script.hpp
@@ -1,6 +1,7 @@
 #pragma once
 
 #include "../ComponentManager.h"
+#include "../Exception.h"
 
 #include "BehaviorScript.h"
 #include "Script.h"
@@ -8,18 +9,22 @@
 namespace crepe {
 
 template <typename T>
-T & Script::get_component() {
+T & Script::get_component() const {
 	std::vector<std::reference_wrapper<T>> all_components
 		= this->get_components<T>();
-	if (all_components.size() < 1) throw nullptr; // TODO
+	if (all_components.size() < 1)
+		throw Exception("Script: no component found with type = {}",
+						typeid(T).name());
 
 	return all_components.back().get();
 }
 
 template <typename T>
-std::vector<std::reference_wrapper<T>> Script::get_components() {
-	ComponentManager & mgr = ComponentManager::get_instance();
-	return mgr.get_components_by_id<T>(this->parent->game_object_id);
+std::vector<std::reference_wrapper<T>> Script::get_components() const {
+	auto & parent = *this->parent_ref;
+	auto & mgr = *this->component_manager_ref;
+
+	return mgr.get_components_by_id<T>(parent.game_object_id);
 }
 
 } // namespace crepe
diff --git a/src/crepe/api/Sprite.cpp b/src/crepe/api/Sprite.cpp
index 6f0433f..ac0079e 100644
--- a/src/crepe/api/Sprite.cpp
+++ b/src/crepe/api/Sprite.cpp
@@ -1,6 +1,6 @@
 #include <memory>
 
-#include "../util/log.h"
+#include "../util/Log.h"
 #include "facade/SDLContext.h"
 
 #include "Component.h"
diff --git a/src/crepe/api/Texture.cpp b/src/crepe/api/Texture.cpp
index 5ebd23d..de0d0ea 100644
--- a/src/crepe/api/Texture.cpp
+++ b/src/crepe/api/Texture.cpp
@@ -1,7 +1,7 @@
 #include <SDL2/SDL_render.h>
 
 #include "../facade/SDLContext.h"
-#include "../util/log.h"
+#include "../util/Log.h"
 
 #include "Asset.h"
 #include "Texture.h"
@@ -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->canonical()));
+	this->texture = std::move(ctx.texture_from_path(res->get_canonical()));
 }
 
 int Texture::get_width() const {
diff --git a/src/crepe/api/Transform.cpp b/src/crepe/api/Transform.cpp
index e401120..e9108c4 100644
--- a/src/crepe/api/Transform.cpp
+++ b/src/crepe/api/Transform.cpp
@@ -1,4 +1,4 @@
-#include "util/log.h"
+#include "../util/Log.h"
 
 #include "Transform.h"
 
diff --git a/src/crepe/api/Transform.h b/src/crepe/api/Transform.h
index 756e45b..902dafa 100644
--- a/src/crepe/api/Transform.h
+++ b/src/crepe/api/Transform.h
@@ -14,28 +14,26 @@ namespace crepe {
  */
 class Transform : public Component {
 public:
+	//! Translation (shift)
+	Vector2 position = {0, 0};
+	//! Rotation, in degrees
+	double rotation = 0;
+	//! Multiplication factor
+	double scale = 0;
+
+protected:
 	/**
 	 * \param id The id of the GameObject this component belongs to
 	 * \param point The position of the GameObject
 	 * \param rotation The rotation of the GameObject
 	 * \param scale The scale of the GameObject
 	 */
-	Transform(game_object_id_t id, const Vector2 & point, double rotation,
-			  double scale);
-	/**
-	 * \brief Get the maximum number of instances for this component
-	 *
-	 * \return The maximum number of instances for this component
-	 */
+	Transform(game_object_id_t id, const Vector2 & point, double rotation = 0,
+			  double scale = 0);
+	//! There is always exactly one transform component per entity
 	virtual int get_instances_max() const { return 1; }
-
-public:
-	//! Translation (shift)
-	Vector2 position;
-	//! Rotation, in degrees
-	double rotation;
-	//! Multiplication factor
-	double scale;
+	//! ComponentManager instantiates all components
+	friend class ComponentManager;
 };
 
 } // namespace crepe
diff --git a/src/crepe/api/Vector2.cpp b/src/crepe/api/Vector2.cpp
index 09b3fa3..97b74ac 100644
--- a/src/crepe/api/Vector2.cpp
+++ b/src/crepe/api/Vector2.cpp
@@ -1,57 +1,43 @@
 #include "Vector2.h"
 
-namespace crepe {
+using namespace crepe;
 
-// Constructor with initial values
-Vector2::Vector2(double x, double y) : x(x), y(y) {}
-
-// Subtracts another vector from this vector and returns the result.
 Vector2 Vector2::operator-(const Vector2 & other) const {
 	return {x - other.x, y - other.y};
 }
 
-// Adds another vector to this vector and returns the result.
 Vector2 Vector2::operator+(const Vector2 & other) const {
 	return {x + other.x, y + other.y};
 }
 
-// Multiplies this vector by a scalar and returns the result.
 Vector2 Vector2::operator*(double scalar) const {
 	return {x * scalar, y * scalar};
 }
 
-// Multiplies this vector by another vector element-wise and updates this vector.
 Vector2 & Vector2::operator*=(const Vector2 & other) {
 	x *= other.x;
 	y *= other.y;
 	return *this;
 }
 
-// Adds another vector to this vector and updates this vector.
 Vector2 & Vector2::operator+=(const Vector2 & other) {
 	x += other.x;
 	y += other.y;
 	return *this;
 }
 
-// Adds a scalar value to both components of this vector and updates this vector.
 Vector2 & Vector2::operator+=(double other) {
 	x += other;
 	y += other;
 	return *this;
 }
 
-// Returns the negation of this vector.
 Vector2 Vector2::operator-() const { return {-x, -y}; }
 
-// Checks if this vector is equal to another vector.
 bool Vector2::operator==(const Vector2 & other) const {
 	return x == other.x && y == other.y;
 }
 
-// Checks if this vector is not equal to another vector.
 bool Vector2::operator!=(const Vector2 & other) const {
 	return !(*this == other);
 }
-
-} // namespace crepe
diff --git a/src/crepe/api/Vector2.h b/src/crepe/api/Vector2.h
index 5a57484..2fb6136 100644
--- a/src/crepe/api/Vector2.h
+++ b/src/crepe/api/Vector2.h
@@ -2,19 +2,12 @@
 
 namespace crepe {
 
-//! Vector2 class
-class Vector2 {
-public:
+//! 2D vector
+struct Vector2 {
 	//! X component of the vector
-	double x;
+	double x = 0;
 	//! Y component of the vector
-	double y;
-
-	//! Default constructor
-	Vector2() = default;
-
-	//! Constructor with initial values
-	Vector2(double x, double y);
+	double y = 0;
 
 	//! Subtracts another vector from this vector and returns the result.
 	Vector2 operator-(const Vector2 & other) const;
diff --git a/src/crepe/facade/DB.cpp b/src/crepe/facade/DB.cpp
index 0a2f455..80047a6 100644
--- a/src/crepe/facade/DB.cpp
+++ b/src/crepe/facade/DB.cpp
@@ -1,7 +1,7 @@
 #include <cstring>
 
 #include "Exception.h"
-#include "util/log.h"
+#include "util/Log.h"
 
 #include "DB.h"
 
@@ -15,19 +15,18 @@ DB::DB(const string & path) {
 	// init database struct
 	libdb::DB * db;
 	if ((ret = libdb::db_create(&db, NULL, 0)) != 0)
-		throw Exception("db_create: %s", libdb::db_strerror(ret));
+		throw Exception("db_create: {}", libdb::db_strerror(ret));
 	this->db = {db, [](libdb::DB * db) { db->close(db, 0); }};
 
 	// load or create database file
-	if ((ret = this->db->open(this->db.get(), NULL, path.c_str(), NULL,
-							  libdb::DB_BTREE, DB_CREATE, 0))
-		!= 0)
-		throw Exception("db->open: %s", libdb::db_strerror(ret));
+	ret = this->db->open(this->db.get(), NULL, path.c_str(), NULL,
+						 libdb::DB_BTREE, DB_CREATE, 0);
+	if (ret != 0) throw Exception("db->open: {}", libdb::db_strerror(ret));
 
 	// create cursor
 	libdb::DBC * cursor;
-	if ((ret = this->db->cursor(this->db.get(), NULL, &cursor, 0)) != 0)
-		throw Exception("db->cursor: %s", libdb::db_strerror(ret));
+	ret = this->db->cursor(this->db.get(), NULL, &cursor, 0);
+	if (ret != 0) throw Exception("db->cursor: {}", libdb::db_strerror(ret));
 	this->cursor = {cursor, [](libdb::DBC * cursor) { cursor->close(cursor); }};
 }
 
@@ -45,7 +44,7 @@ string DB::get(const string & key) {
 	memset(&db_val, 0, sizeof(libdb::DBT));
 
 	int ret = this->cursor->get(this->cursor.get(), &db_key, &db_val, DB_FIRST);
-	if (ret != 0) throw Exception("cursor->get: %s", libdb::db_strerror(ret));
+	if (ret != 0) throw Exception("cursor->get: {}", libdb::db_strerror(ret));
 	return {static_cast<char *>(db_val.data), db_val.size};
 }
 
@@ -53,7 +52,7 @@ void DB::set(const string & key, const string & value) {
 	libdb::DBT db_key = this->to_thing(key);
 	libdb::DBT db_val = this->to_thing(value);
 	int ret = this->db->put(this->db.get(), NULL, &db_key, &db_val, 0);
-	if (ret != 0) throw Exception("cursor->get: %s", libdb::db_strerror(ret));
+	if (ret != 0) throw Exception("cursor->get: {}", libdb::db_strerror(ret));
 }
 
 bool DB::has(const std::string & key) noexcept {
diff --git a/src/crepe/facade/SDLContext.cpp b/src/crepe/facade/SDLContext.cpp
index 236bf8c..a68d940 100644
--- a/src/crepe/facade/SDLContext.cpp
+++ b/src/crepe/facade/SDLContext.cpp
@@ -15,7 +15,7 @@
 #include "../api/Sprite.h"
 #include "../api/Texture.h"
 #include "../api/Transform.h"
-#include "../util/log.h"
+#include "../util/Log.h"
 #include "Exception.h"
 
 #include "SDLContext.h"
@@ -171,7 +171,7 @@ SDLContext::texture_from_path(const std::string & path) {
 		this->game_renderer.get(), img_surface.get());
 
 	if (tmp_texture == nullptr) {
-		throw Exception("Texture cannot be load from %s", path.c_str());
+		throw Exception("Texture cannot be load from {}", path);
 	}
 
 	std::unique_ptr<SDL_Texture, std::function<void(SDL_Texture *)>>
diff --git a/src/crepe/facade/Sound.cpp b/src/crepe/facade/Sound.cpp
index b8ea71a..5cd31e8 100644
--- a/src/crepe/facade/Sound.cpp
+++ b/src/crepe/facade/Sound.cpp
@@ -1,7 +1,7 @@
 #include <memory>
 
 #include "../Asset.h"
-#include "../util/log.h"
+#include "../util/Log.h"
 
 #include "Sound.h"
 #include "SoundContext.h"
@@ -13,7 +13,7 @@ Sound::Sound(SoundContext & ctx) : context(ctx) { dbg_trace(); }
 
 unique_ptr<Resource> Sound::clone(const Asset & src) const {
 	auto instance = make_unique<Sound>(*this);
-	instance->sample.load(src.canonical());
+	instance->sample.load(src.get_canonical().c_str());
 	return instance;
 }
 
diff --git a/src/crepe/facade/Sound.h b/src/crepe/facade/Sound.h
index e5b2f19..8342b46 100644
--- a/src/crepe/facade/Sound.h
+++ b/src/crepe/facade/Sound.h
@@ -10,6 +10,12 @@ namespace crepe {
 
 class SoundContext;
 
+/**
+ * \brief Sound resource facade
+ *
+ * This class is a wrapper around a \c SoLoud::Wav instance, which holds a
+ * single sample. It is part of the sound facade.
+ */
 class Sound : public Resource {
 public:
 	/**
diff --git a/src/crepe/facade/SoundContext.cpp b/src/crepe/facade/SoundContext.cpp
index b5f3db3..b65dfb2 100644
--- a/src/crepe/facade/SoundContext.cpp
+++ b/src/crepe/facade/SoundContext.cpp
@@ -1,4 +1,4 @@
-#include "../util/log.h"
+#include "../util/Log.h"
 
 #include "SoundContext.h"
 
diff --git a/src/crepe/facade/SoundContext.h b/src/crepe/facade/SoundContext.h
index 8d9e396..d22ff7a 100644
--- a/src/crepe/facade/SoundContext.h
+++ b/src/crepe/facade/SoundContext.h
@@ -6,6 +6,12 @@
 
 namespace crepe {
 
+/**
+ * \brief Sound engine facade
+ *
+ * This class is a wrapper around a \c SoLoud::Soloud instance, which provides
+ * the methods for playing \c Sound instances. It is part of the sound facade.
+ */
 class SoundContext {
 public:
 	SoundContext();
diff --git a/src/crepe/system/AnimatorSystem.cpp b/src/crepe/system/AnimatorSystem.cpp
index bf45362..9d18873 100644
--- a/src/crepe/system/AnimatorSystem.cpp
+++ b/src/crepe/system/AnimatorSystem.cpp
@@ -1,27 +1,17 @@
-
 #include <cstdint>
 #include <functional>
 #include <vector>
 
 #include "api/Animator.h"
 #include "facade/SDLContext.h"
-#include "util/log.h"
 
 #include "AnimatorSystem.h"
 #include "ComponentManager.h"
 
 using namespace crepe;
 
-AnimatorSystem::AnimatorSystem() { dbg_trace(); }
-AnimatorSystem::~AnimatorSystem() { dbg_trace(); }
-
-AnimatorSystem & AnimatorSystem::get_instance() {
-	static AnimatorSystem instance;
-	return instance;
-}
-
 void AnimatorSystem::update() {
-	ComponentManager & mgr = ComponentManager::get_instance();
+	ComponentManager & mgr = this->component_manager;
 
 	std::vector<std::reference_wrapper<Animator>> animations
 		= mgr.get_components_by_type<Animator>();
diff --git a/src/crepe/system/AnimatorSystem.h b/src/crepe/system/AnimatorSystem.h
index 969e9d1..aa97084 100644
--- a/src/crepe/system/AnimatorSystem.h
+++ b/src/crepe/system/AnimatorSystem.h
@@ -17,16 +17,7 @@ namespace crepe {
 class AnimatorSystem : public System {
 
 public:
-	/**
-	 * \brief Retrieves the singleton instance of the AnimatorSystem.
-	 *
-	 * \return A reference to the single instance of the AnimatorSystem.
-	 *
-	 * This method ensures that there is only one instance of the AnimatorSystem, following the
-	 * singleton design pattern. It can be used to access the system globally.
-	 */
-	static AnimatorSystem & get_instance();
-
+	using System::System;
 	/**
 	 * \brief Updates the Animator components.
 	 *
@@ -34,11 +25,7 @@ public:
 	 * Animator components, moving the animations forward and managing their behavior (e.g., looping).
 	 */
 	void update() override;
-
-private:
-	// private because singleton
-	AnimatorSystem(); // dbg_trace
-	~AnimatorSystem(); // dbg_trace
+	// FIXME: never say "likely" in the documentation lmao
 };
 
 } // namespace crepe
diff --git a/src/crepe/system/AudioSystem.cpp b/src/crepe/system/AudioSystem.cpp
index 9fdd7eb..67967ef 100644
--- a/src/crepe/system/AudioSystem.cpp
+++ b/src/crepe/system/AudioSystem.cpp
@@ -6,10 +6,9 @@
 using namespace crepe;
 using namespace std;
 
-AudioSystem::AudioSystem(SoundContext & ctx) : ctx(ctx) {}
-
 void AudioSystem::update() {
-	vector<reference_wrapper<AudioSource>> components = this->compmgr.get_components_by_type<AudioSource>();
+	ComponentManager & mgr = this->component_manager;
+	vector<reference_wrapper<AudioSource>> components = mgr.get_components_by_type<AudioSource>();
 
 	for (auto component_ref : components) {
 		AudioSource & component = component_ref.get();
diff --git a/src/crepe/system/CollisionSystem.cpp b/src/crepe/system/CollisionSystem.cpp
index 55e0fdc..c74ca1d 100644
--- a/src/crepe/system/CollisionSystem.cpp
+++ b/src/crepe/system/CollisionSystem.cpp
@@ -2,6 +2,4 @@
 
 using namespace crepe;
 
-CollisionSystem::CollisionSystem() {}
-
 void CollisionSystem::update() {}
diff --git a/src/crepe/system/CollisionSystem.h b/src/crepe/system/CollisionSystem.h
index 1e9f1aa..c1a70d8 100644
--- a/src/crepe/system/CollisionSystem.h
+++ b/src/crepe/system/CollisionSystem.h
@@ -1,11 +1,13 @@
 #pragma once
 
+#include "System.h"
+
 namespace crepe {
 
-class CollisionSystem {
+class CollisionSystem : public System {
 public:
-	CollisionSystem();
-	void update();
+	using System::System;
+	void update() override;
 };
 
 } // namespace crepe
diff --git a/src/crepe/system/ParticleSystem.cpp b/src/crepe/system/ParticleSystem.cpp
index e7a3bec..33db52e 100644
--- a/src/crepe/system/ParticleSystem.cpp
+++ b/src/crepe/system/ParticleSystem.cpp
@@ -13,7 +13,7 @@ using namespace crepe;
 
 void ParticleSystem::update() {
 	// Get all emitters
-	ComponentManager & mgr = ComponentManager::get_instance();
+	ComponentManager & mgr = this->component_manager;
 	std::vector<std::reference_wrapper<ParticleEmitter>> emitters
 		= mgr.get_components_by_type<ParticleEmitter>();
 
diff --git a/src/crepe/system/ParticleSystem.h b/src/crepe/system/ParticleSystem.h
index d7ca148..0acc2b9 100644
--- a/src/crepe/system/ParticleSystem.h
+++ b/src/crepe/system/ParticleSystem.h
@@ -4,67 +4,83 @@
 
 #include "System.h"
 
+#include "System.h"
+
 namespace crepe {
+
 class ParticleEmitter;
 class Transform;
+
 /**
- 	* \brief ParticleSystem class responsible for managing particle emission, updates, and bounds checking.
+	* \brief ParticleSystem class responsible for managing particle emission,
+	* updates, and bounds checking.
  	*/
 class ParticleSystem : public System {
 public:
+	using System::System;
 	/**
-		* \brief Updates all particle emitters by emitting particles, updating particle states, and checking bounds.
-		*/
+	 * \brief Updates all particle emitters by emitting particles, updating
+	 * particle states, and checking bounds.
+	 */
 	void update() override;
 
 private:
 	/**
-		* \brief Emits a particle from the specified emitter based on its emission properties.
-		* 
-		* \param emitter Reference to the ParticleEmitter.
-		* \param transform Const reference to the Transform component associated with the emitter.
-		*/
+	 * \brief Emits a particle from the specified emitter based on its emission
+	 * properties.
+	 * 
+	 * \param emitter Reference to the ParticleEmitter.
+	 * \param transform Const reference to the Transform component associated
+	 * with the emitter.
+	 */
 	void emit_particle(ParticleEmitter & emitter, const Transform & transform);
 
 	/**
-		* \brief Calculates the number of times particles should be emitted based on emission rate and update count.
-		* 
-		* \param count Current update count.
-		* \param emission Emission rate.
-		* \return The number of particles to emit.
-		*/
+	 * \brief Calculates the number of times particles should be emitted based on
+	 * emission rate and update count.
+	 * 
+	 * \param count Current update count.
+	 * \param emission Emission rate.
+	 * \return The number of particles to emit.
+	 */
 	int calculate_update(int count, double emission) const;
 
 	/**
-		* \brief Checks whether particles are within the emitter’s boundary, resets or stops particles if they exit.
-		* 
-		* \param emitter Reference to the ParticleEmitter.
-		* \param transform Const reference to the Transform component associated with the emitter.
-		*/
+	 * \brief Checks whether particles are within the emitter’s boundary, resets
+	 * or stops particles if they exit.
+	 * 
+	 * \param emitter Reference to the ParticleEmitter.
+	 * \param transform Const reference to the Transform component associated
+	 * with the emitter.
+	 */
 	void check_bounds(ParticleEmitter & emitter, const Transform & transform);
 
 	/**
-		* \brief Generates a random angle for particle emission within the specified range.
-		* 
-		* \param min_angle Minimum emission angle in degrees.
-		* \param max_angle Maximum emission angle in degrees.
-		* \return Random angle in degrees.
-		*/
+	 * \brief Generates a random angle for particle emission within the specified
+	 * range.
+	 * 
+	 * \param min_angle Minimum emission angle in degrees.
+	 * \param max_angle Maximum emission angle in degrees.
+	 * \return Random angle in degrees.
+	 */
 	double generate_random_angle(double min_angle, double max_angle) const;
 
 	/**
-		* \brief Generates a random speed for particle emission within the specified range.
-		* 
-		* \param min_speed Minimum emission speed.
-		* \param max_speed Maximum emission speed.
-		* \return Random speed.
-		*/
+	 * \brief Generates a random speed for particle emission within the specified
+	 * range.
+	 * 
+	 * \param min_speed Minimum emission speed.
+	 * \param max_speed Maximum emission speed.
+	 * \return Random speed.
+	 */
 	double generate_random_speed(double min_speed, double max_speed) const;
 
 private:
-	//! Counter to count updates to determine how many times emit_particle is called.
+	//! Counter to count updates to determine how many times emit_particle is
+	// called.
 	unsigned int update_count = 0;
-	//! Determines the lowest amount of emission rate (1000 = 0.001 = 1 particle per 1000 updates).
+	//! Determines the lowest amount of emission rate (1000 = 0.001 = 1 particle
+	// per 1000 updates).
 	static constexpr unsigned int MAX_UPDATE_COUNT = 100;
 };
 
diff --git a/src/crepe/system/PhysicsSystem.cpp b/src/crepe/system/PhysicsSystem.cpp
index eb54ad3..da79707 100644
--- a/src/crepe/system/PhysicsSystem.cpp
+++ b/src/crepe/system/PhysicsSystem.cpp
@@ -11,7 +11,7 @@
 using namespace crepe;
 
 void PhysicsSystem::update() {
-	ComponentManager & mgr = ComponentManager::get_instance();
+	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
diff --git a/src/crepe/system/PhysicsSystem.h b/src/crepe/system/PhysicsSystem.h
index 038c120..5433a0f 100644
--- a/src/crepe/system/PhysicsSystem.h
+++ b/src/crepe/system/PhysicsSystem.h
@@ -3,6 +3,7 @@
 #include "System.h"
 
 namespace crepe {
+
 /**
  * \brief System that controls all physics
  * 
@@ -11,6 +12,7 @@ namespace crepe {
  */
 class PhysicsSystem : public System {
 public:
+	using System::System;
 	/**
 	 * \brief updates the physics system.
 	 * 
diff --git a/src/crepe/system/RenderSystem.cpp b/src/crepe/system/RenderSystem.cpp
index 10211a3..0d37808 100644
--- a/src/crepe/system/RenderSystem.cpp
+++ b/src/crepe/system/RenderSystem.cpp
@@ -5,21 +5,12 @@
 #include "../api/Sprite.h"
 #include "../api/Transform.h"
 #include "../facade/SDLContext.h"
-#include "../util/log.h"
+#include "../util/Log.h"
 
 #include "RenderSystem.h"
 
 using namespace crepe;
 
-RenderSystem::RenderSystem() { dbg_trace(); }
-
-RenderSystem::~RenderSystem() { dbg_trace(); }
-
-RenderSystem & RenderSystem::get_instance() {
-	static RenderSystem instance;
-	return instance;
-}
-
 void RenderSystem::clear_screen() const {
 	SDLContext::get_instance().clear_screen();
 }
@@ -28,7 +19,7 @@ void RenderSystem::present_screen() const {
 	SDLContext::get_instance().present_screen();
 }
 void RenderSystem::update_camera() {
-	ComponentManager & mgr = ComponentManager::get_instance();
+	ComponentManager & mgr = this->component_manager;
 
 	std::vector<std::reference_wrapper<Camera>> cameras
 		= mgr.get_components_by_type<Camera>();
@@ -39,8 +30,7 @@ void RenderSystem::update_camera() {
 	}
 }
 void RenderSystem::render_sprites() const {
-
-	ComponentManager & mgr = ComponentManager::get_instance();
+	ComponentManager & mgr = this->component_manager;
 
 	std::vector<std::reference_wrapper<Sprite>> sprites
 		= mgr.get_components_by_type<Sprite>();
diff --git a/src/crepe/system/RenderSystem.h b/src/crepe/system/RenderSystem.h
index 70db21a..da4e910 100644
--- a/src/crepe/system/RenderSystem.h
+++ b/src/crepe/system/RenderSystem.h
@@ -15,14 +15,8 @@ namespace crepe {
  * rendering services for the application.
  */
 class RenderSystem : public System {
-
 public:
-	/**
-	 * \brief Gets the singleton instance of RenderSystem.
-	 * \return Reference to the RenderSystem instance.
-	 */
-	static RenderSystem & get_instance();
-
+	using System::System;
 	/**
 	 * \brief Updates the RenderSystem for the current frame.
 	 * This method is called to perform all rendering operations for the current game frame.
@@ -30,10 +24,6 @@ public:
 	void update() override;
 
 private:
-	// Private constructor to enforce singleton pattern.
-	RenderSystem();
-	~RenderSystem();
-
 	//! Clears the screen in preparation for rendering.
 	void clear_screen() const;
 
@@ -61,4 +51,5 @@ private:
 	Camera * curr_cam = nullptr;
 	// TODO: needs a better solution
 };
+
 } // namespace crepe
diff --git a/src/crepe/system/ScriptSystem.cpp b/src/crepe/system/ScriptSystem.cpp
index 68fbb02..f4a826b 100644
--- a/src/crepe/system/ScriptSystem.cpp
+++ b/src/crepe/system/ScriptSystem.cpp
@@ -5,7 +5,6 @@
 #include "../ComponentManager.h"
 #include "../api/BehaviorScript.h"
 #include "../api/Script.h"
-#include "../util/log.h"
 
 #include "ScriptSystem.h"
 
@@ -13,24 +12,33 @@ using namespace std;
 using namespace crepe;
 
 void ScriptSystem::update() {
-	using namespace std;
 	dbg_trace();
 
-	forward_list<Script *> scripts = this->get_scripts();
-	for (Script * script : scripts) script->update();
+	forward_list<reference_wrapper<Script>> scripts = this->get_scripts();
+
+	for (auto & script_ref : scripts) {
+		Script & script = script_ref.get();
+		BehaviorScript & component = *script.parent_ref;
+		if (!component.initialized) {
+			script.init();
+			component.initialized = true;
+		}
+		script.update();
+	}
 }
 
-forward_list<Script *> ScriptSystem::get_scripts() {
-	forward_list<Script *> scripts = {};
+forward_list<reference_wrapper<Script>> ScriptSystem::get_scripts() const {
+	forward_list<reference_wrapper<Script>> scripts = {};
+	ComponentManager & mgr = this->component_manager;
 	vector<reference_wrapper<BehaviorScript>> behavior_scripts
-		= this->compmgr.get_components_by_type<BehaviorScript>();
+		= 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_front(*script);
 	}
 
 	return scripts;
diff --git a/src/crepe/system/ScriptSystem.h b/src/crepe/system/ScriptSystem.h
index 4fa6141..deb89cb 100644
--- a/src/crepe/system/ScriptSystem.h
+++ b/src/crepe/system/ScriptSystem.h
@@ -8,13 +8,32 @@ namespace crepe {
 
 class Script;
 
+/**
+ * \brief Script system
+ * 
+ * The script system is responsible for all \c BehaviorScript components, and
+ * calls the methods on classes derived from \c Script.
+ */
 class ScriptSystem : public System {
 public:
-	void update();
+	using System::System;
+	/**
+	 * \brief Call Script::update() on all active \c BehaviorScript instances
+	 *
+	 * This routine updates all scripts sequentially using the Script::update()
+	 * method. It also calls Script::init() if this has not been done before on
+	 * the \c BehaviorScript instance.
+	 */
+	void update() override;
 
 private:
-	// TODO: to forward_list<reference_wrapper>
-	std::forward_list<Script *> get_scripts();
+	/**
+	 * \brief Aggregate all active \c BehaviorScript components and return a list
+	 * of references to their \c Script instances (utility)
+	 *
+	 * \returns List of active \c Script instances
+	 */
+	std::forward_list<std::reference_wrapper<Script>> get_scripts() const;
 };
 
 } // namespace crepe
diff --git a/src/crepe/system/System.cpp b/src/crepe/system/System.cpp
index fa51d2f..937a423 100644
--- a/src/crepe/system/System.cpp
+++ b/src/crepe/system/System.cpp
@@ -1,7 +1,7 @@
+#include "../util/Log.h"
+
 #include "System.h"
 
 using namespace crepe;
 
-// TODO: ComponentManager shouldn't be a singleton
-System::System() : compmgr(ComponentManager::get_instance()) {}
-
+System::System(ComponentManager & mgr) : component_manager(mgr) { dbg_trace(); }
diff --git a/src/crepe/system/System.h b/src/crepe/system/System.h
index 5091977..36f7edc 100644
--- a/src/crepe/system/System.h
+++ b/src/crepe/system/System.h
@@ -4,19 +4,28 @@
 
 namespace crepe {
 
-//! ECS system base class
+class ComponentManager;
+
+/**
+ * \brief Base ECS system class
+ *
+ * This class is used as the base for all system classes. Classes derived from
+ * System must implement the System::update() method and copy Script::Script
+ * with the `using`-syntax.
+ */
 class System {
 public:
-	//! Process components belonging to this system
+	/**
+	 * \brief Process all components this system is responsible for.
+	 */
 	virtual void update() = 0;
 
 public:
-	System();
+	System(ComponentManager &);
 	virtual ~System() = default;
 
-public:
-	//! Reference to component manager
-	ComponentManager & compmgr;
+protected:
+	ComponentManager & component_manager;
 };
 
 } // namespace crepe
diff --git a/src/crepe/util/CMakeLists.txt b/src/crepe/util/CMakeLists.txt
index 0fa4343..4be738a 100644
--- a/src/crepe/util/CMakeLists.txt
+++ b/src/crepe/util/CMakeLists.txt
@@ -1,13 +1,12 @@
 target_sources(crepe PUBLIC
 	LogColor.cpp
-	log.cpp
-	fmt.cpp
+	Log.cpp
 )
 
 target_sources(crepe PUBLIC FILE_SET HEADERS FILES
 	LogColor.h
-	log.h
-	fmt.h
+	Log.h
+	Log.hpp
 	Proxy.h
 	Proxy.hpp
 )
diff --git a/src/crepe/util/log.cpp b/src/crepe/util/Log.cpp
index 4a8f8e8..e583734 100644
--- a/src/crepe/util/log.cpp
+++ b/src/crepe/util/Log.cpp
@@ -4,50 +4,35 @@
 #include <string>
 
 #include "../api/Config.h"
-#include "fmt.h"
-#include "log.h"
+#include "Log.h"
 
 using namespace crepe;
 using namespace std;
 
-string log_prefix(LogLevel level) {
+string Log::prefix(const Level & level) {
 	switch (level) {
-		case LogLevel::TRACE:
+		case Level::TRACE:
 			return LogColor().fg_white().str("[TRACE]") + " ";
-		case LogLevel::DEBUG:
+		case Level::DEBUG:
 			return LogColor().fg_magenta().str("[DEBUG]") + " ";
-		case LogLevel::INFO:
+		case Level::INFO:
 			return LogColor().fg_blue().str("[INFO]") + " ";
-		case LogLevel::WARNING:
+		case Level::WARNING:
 			return LogColor().fg_yellow().str("[WARN]") + " ";
-		case LogLevel::ERROR:
+		case Level::ERROR:
 			return LogColor().fg_red().str("[ERROR]") + " ";
 	}
 	return "";
 }
 
-static void log(LogLevel level, const string msg) {
+void Log::log(const Level & level, const string & msg) {
 	auto & cfg = Config::get_instance();
 	if (level < cfg.log.level) return;
 
-	string out = log_prefix(level) + msg;
+	string out = Log::prefix(level) + msg;
 	if (!out.ends_with("\n")) out += "\n";
 
 	// TODO: also log to file or smth
 	fwrite(out.c_str(), 1, out.size(), stdout);
 	fflush(stdout);
 }
-
-void crepe::logf(const char * fmt, ...) {
-	va_list args;
-	va_start(args, fmt);
-	log(LogLevel::DEBUG, va_stringf(args, fmt));
-	va_end(args);
-}
-
-void crepe::logf(LogLevel level, const char * fmt, ...) {
-	va_list args;
-	va_start(args, fmt);
-	log(level, va_stringf(args, fmt));
-	va_end(args);
-}
diff --git a/src/crepe/util/Log.h b/src/crepe/util/Log.h
new file mode 100644
index 0000000..01452b2
--- /dev/null
+++ b/src/crepe/util/Log.h
@@ -0,0 +1,85 @@
+#pragma once
+
+#include <format>
+
+// allow user to disable debug macros
+#ifndef CREPE_DISABLE_MACROS
+
+#include "LogColor.h"
+
+// utility macros
+#define _crepe_logf_here(level, fmt, ...) \
+	crepe::Log::logf( \
+		level, "{}" fmt, \
+		crepe::LogColor().fg_white(false).str(std::format( \
+			"{} ({}:{})", __PRETTY_FUNCTION__, __FILE_NAME__, __LINE__)), \
+		__VA_ARGS__)
+
+// very illegal global function-style macros
+// NOLINTBEGIN
+#define dbg_logf(fmt, ...) \
+	_crepe_logf_here(crepe::Log::Level::DEBUG, ": " fmt, __VA_ARGS__)
+#define dbg_log(str) _crepe_logf_here(crepe::Log::Level::DEBUG, ": {}", str)
+#define dbg_trace() _crepe_logf_here(crepe::Log::Level::TRACE, "", "")
+// NOLINTEND
+
+#endif
+
+namespace crepe {
+
+/**
+ * \brief Logging utility
+ *
+ * This class is used to output log messages to the console and/or log files.
+ */
+class Log {
+public:
+	//! Log message severity
+	enum Level {
+		TRACE, //< Include (internal) function calls
+		DEBUG, //< Include dbg_logf output
+		INFO, //< General-purpose messages
+		WARNING, //< Non-fatal errors
+		ERROR, //< Fatal errors
+	};
+
+	/**
+	 * \brief Log a formatted message
+	 *
+	 * \param level Message severity
+	 * \param msg Formatted message
+	 */
+	static void log(const Level & level, const std::string & msg);
+
+	/**
+	 * \brief Format a message and log it
+	 *
+	 * \param level Message severity
+	 * \param fmt Message format
+	 * \param args Format arguments
+	 */
+	template <class... Args>
+	static void logf(const Level & level, std::format_string<Args...> fmt,
+					 Args &&... args);
+
+	/**
+	 * \brief Format a message and log it (with default severity \c INFO)
+	 *
+	 * \param fmt Message format
+	 * \param args Format arguments
+	 */
+	template <class... Args>
+	static void logf(std::format_string<Args...> fmt, Args &&... args);
+
+private:
+	/**
+	 * \brief Output a message prefix depending on the log level
+	 *
+	 * \param level Message severity
+	 */
+	static std::string prefix(const Level & level);
+};
+
+} // namespace crepe
+
+#include "Log.hpp"
diff --git a/src/crepe/util/Log.hpp b/src/crepe/util/Log.hpp
new file mode 100644
index 0000000..651f076
--- /dev/null
+++ b/src/crepe/util/Log.hpp
@@ -0,0 +1,18 @@
+#pragma once
+
+#include "Log.h"
+
+namespace crepe {
+
+template <class... Args>
+void Log::logf(std::format_string<Args...> fmt, Args &&... args) {
+	Log::logf(Level::INFO, fmt, std::forward<Args>(args)...);
+}
+
+template <class... Args>
+void Log::logf(const Level & level, std::format_string<Args...> fmt,
+			   Args &&... args) {
+	Log::log(level, std::format(fmt, std::forward<Args>(args)...));
+}
+
+} // namespace crepe
diff --git a/src/crepe/util/LogColor.cpp b/src/crepe/util/LogColor.cpp
index b5fe3ea..ae44d72 100644
--- a/src/crepe/util/LogColor.cpp
+++ b/src/crepe/util/LogColor.cpp
@@ -3,14 +3,12 @@
 #include "../api/Config.h"
 #include "LogColor.h"
 
-#include "fmt.h"
-
 using namespace crepe;
 using namespace std;
 
 static constexpr const char * RESET_CODE = "\e[0m";
 
-const string LogColor::str(const string & content) {
+const string LogColor::str(const string & content) const {
 	auto & cfg = Config::get_instance();
 	string out = content;
 	if (cfg.log.color) out = this->code + out;
@@ -19,21 +17,8 @@ const string LogColor::str(const string & content) {
 	return out;
 }
 
-const char * LogColor::c_str(const char * content) {
-	this->final = this->str(content == NULL ? "" : content);
-	return this->final.c_str();
-}
-
-const char * LogColor::fmt(const char * fmt, ...) {
-	va_list args;
-	va_start(args, fmt);
-	string content = va_stringf(args, fmt);
-	va_end(args);
-	return this->c_str(content.c_str());
-}
-
 LogColor & LogColor::add_code(unsigned int code) {
-	this->code += stringf("\e[%dm", code);
+	this->code += format("\e[{}m", code);
 	return *this;
 }
 
diff --git a/src/crepe/util/LogColor.h b/src/crepe/util/LogColor.h
index c1170cb..4b65127 100644
--- a/src/crepe/util/LogColor.h
+++ b/src/crepe/util/LogColor.h
@@ -4,20 +4,19 @@
 
 namespace crepe {
 
+/**
+ * \brief Utility class for coloring text using ANSI escape codes
+ *
+ * \note Most methods in this class return a reference to \c this, which may be
+ * used to chain multiple display attributes.
+ */
 class LogColor {
 public:
-	LogColor() = default;
+	//! Get color code as stl string (or color content string)
+	const std::string str(const std::string & content = "") const;
 
 public:
-	//! get color code as c-style string (or color content string)
-	const char * c_str(const char * content = NULL);
-	//! color printf-style format string
-	const char * fmt(const char * fmt, ...);
-	//! get color code as stl string (or color content string)
-	const std::string str(const std::string & content = "");
-
-public:
-	//! reset color to default foreground and background color
+	//! Reset color to default foreground and background color
 	LogColor & reset();
 
 public:
@@ -41,11 +40,19 @@ public:
 	LogColor & bg_white(bool bright = false);
 
 private:
+	/**
+	 * \brief Append SGR escape sequence to \c this->code
+	 *
+	 * \param code SGR attribute number
+	 *
+	 * See <https://en.wikipedia.org/wiki/ANSI_escape_code> for magic number
+	 * reference.
+	 */
 	LogColor & add_code(unsigned int code);
 
 private:
+	//! Color escape sequence
 	std::string code = "";
-	std::string final = "";
 };
 
 } // namespace crepe
diff --git a/src/crepe/util/fmt.cpp b/src/crepe/util/fmt.cpp
deleted file mode 100644
index 4b50da8..0000000
--- a/src/crepe/util/fmt.cpp
+++ /dev/null
@@ -1,35 +0,0 @@
-#include <cstdarg>
-#include <cstdio>
-#include <string>
-
-#include "fmt.h"
-
-using namespace std;
-
-string crepe::va_stringf(va_list args, const char * fmt) {
-	string out;
-
-	va_list args_copy;
-	va_copy(args_copy, args);
-	size_t length = vsnprintf(NULL, 0, fmt, args_copy);
-	// resize to include terminating null byte
-	out.resize(length + 1);
-	va_end(args_copy);
-
-	// vsnprintf adds terminating null byte
-	vsnprintf(out.data(), out.size(), fmt, args);
-	// resize to actual length
-	out.resize(length);
-
-	va_end(args);
-
-	return out;
-}
-
-string crepe::stringf(const char * fmt, ...) {
-	va_list args;
-	va_start(args, fmt);
-	string out = va_stringf(args, fmt);
-	va_end(args);
-	return out;
-}
diff --git a/src/crepe/util/fmt.h b/src/crepe/util/fmt.h
deleted file mode 100644
index e319e6e..0000000
--- a/src/crepe/util/fmt.h
+++ /dev/null
@@ -1,10 +0,0 @@
-#pragma once
-
-#include <string>
-
-namespace crepe {
-
-std::string va_stringf(va_list args, const char * fmt);
-std::string stringf(const char * fmt, ...);
-
-} // namespace crepe
diff --git a/src/crepe/util/log.h b/src/crepe/util/log.h
deleted file mode 100644
index 5a1cf00..0000000
--- a/src/crepe/util/log.h
+++ /dev/null
@@ -1,39 +0,0 @@
-#pragma once
-
-// allow user to disable debug macros
-#ifndef CREPE_DISABLE_MACROS
-
-#include "LogColor.h"
-
-// utility macros
-#define _crepe_logf_here(level, format, ...) \
-	crepe::logf( \
-		level, "%s" format, \
-		crepe::LogColor().fg_white(false).fmt( \
-			"%s (%s:%d)", __PRETTY_FUNCTION__, __FILE_NAME__, __LINE__), \
-		__VA_ARGS__)
-
-// very illegal global function-style macros
-// NOLINTBEGIN
-#define dbg_logf(fmt, ...) \
-	_crepe_logf_here(crepe::LogLevel::DEBUG, ": " fmt, __VA_ARGS__)
-#define dbg_log(str) _crepe_logf_here(crepe::LogLevel::DEBUG, "%s: " str, "")
-#define dbg_trace() _crepe_logf_here(crepe::LogLevel::TRACE, "%s", "")
-// NOLINTEND
-
-#endif
-
-namespace crepe {
-
-enum LogLevel {
-	TRACE,
-	DEBUG,
-	INFO,
-	WARNING,
-	ERROR,
-};
-
-void logf(const char * fmt, ...);
-void logf(enum LogLevel level, const char * fmt, ...);
-
-} // namespace crepe
diff --git a/src/example/audio_internal.cpp b/src/example/audio_internal.cpp
index 1ea839d..ff55a59 100644
--- a/src/example/audio_internal.cpp
+++ b/src/example/audio_internal.cpp
@@ -5,7 +5,7 @@
 
 #include <crepe/api/Config.h>
 #include <crepe/facade/Sound.h>
-#include <crepe/util/log.h>
+#include <crepe/util/Log.h>
 
 #include <thread>
 
@@ -18,7 +18,7 @@ using std::make_unique;
 int _ = []() {
 	// Show dbg_trace() output
 	auto & cfg = Config::get_instance();
-	cfg.log.level = LogLevel::TRACE;
+	cfg.log.level = Log::Level::TRACE;
 
 	return 0; // satisfy compiler
 }();
diff --git a/src/example/components_internal.cpp b/src/example/components_internal.cpp
index ea1eaad..eeecdc0 100644
--- a/src/example/components_internal.cpp
+++ b/src/example/components_internal.cpp
@@ -13,7 +13,7 @@
 #include <crepe/api/Rigidbody.h>
 #include <crepe/api/Sprite.h>
 
-#include <crepe/util/log.h>
+#include <crepe/util/Log.h>
 
 using namespace crepe;
 using namespace std;
@@ -23,17 +23,16 @@ using namespace std;
 int main() {
 	dbg_trace();
 
-	auto & mgr = ComponentManager::get_instance();
+	ComponentManager mgr{};
 
 	auto start_adding = chrono::high_resolution_clock::now();
 
 	GameObject * game_object[OBJ_COUNT];
 
 	for (int i = 0; i < OBJ_COUNT; ++i) {
-		game_object[i] = new GameObject(i, "Name", "Tag", 0);
-
-		game_object[i]->add_component<Sprite>("test");
-		game_object[i]->add_component<Rigidbody>(0, 0, i);
+		GameObject obj = mgr.new_object("Name", "Tag");
+		obj.add_component<Sprite>("test");
+		obj.add_component<Rigidbody>(0, 0, i);
 	}
 
 	auto stop_adding = chrono::high_resolution_clock::now();
@@ -45,10 +44,6 @@ int main() {
 
 	auto stop_looping = chrono::high_resolution_clock::now();
 
-	for (int i = 0; i < OBJ_COUNT; ++i) {
-		delete game_object[i];
-	}
-
 	auto add_time = chrono::duration_cast<chrono::microseconds>(stop_adding
 																- start_adding);
 	auto loop_time = chrono::duration_cast<chrono::microseconds>(stop_looping
diff --git a/src/example/db.cpp b/src/example/db.cpp
index 8c06a84..ee4e8fc 100644
--- a/src/example/db.cpp
+++ b/src/example/db.cpp
@@ -1,6 +1,6 @@
 #include <crepe/api/Config.h>
 #include <crepe/facade/DB.h>
-#include <crepe/util/log.h>
+#include <crepe/util/Log.h>
 
 using namespace crepe;
 using namespace std;
@@ -8,7 +8,7 @@ using namespace std;
 // run before main
 static auto _ = []() {
 	auto & cfg = Config::get_instance();
-	cfg.log.level = LogLevel::TRACE;
+	cfg.log.level = Log::Level::TRACE;
 	return 0;
 }();
 
@@ -20,11 +20,11 @@ int main() {
 	const char * test_key = "test-key";
 	string test_data = "Hello world!";
 
-	dbg_logf("DB has key = %d", db.has(test_key));
+	dbg_logf("DB has key = {}", db.has(test_key));
 
 	db.set(test_key, test_data);
 
-	dbg_logf("key = \"%s\"", db.get(test_key).c_str());
+	dbg_logf("key = \"{}\"", db.get(test_key));
 
 	return 0;
 }
diff --git a/src/example/ecs.cpp b/src/example/ecs.cpp
index e61c398..5f83da1 100644
--- a/src/example/ecs.cpp
+++ b/src/example/ecs.cpp
@@ -9,13 +9,19 @@ using namespace crepe;
 using namespace std;
 
 int main() {
+	ComponentManager mgr{};
+
 	// Create a few GameObjects
 	try {
-		GameObject body(0, "body", "person", Vector2{0, 0}, 0, 1);
-		GameObject right_leg(1, "rightLeg", "person", Vector2{1, 1}, 0, 1);
-		GameObject left_leg(2, "leftLeg", "person", Vector2{1, 1}, 0, 1);
-		GameObject right_foot(3, "rightFoot", "person", Vector2{2, 2}, 0, 1);
-		GameObject left_foot(4, "leftFoot", "person", Vector2{2, 2}, 0, 1);
+		GameObject body = mgr.new_object("body", "person", Vector2{0, 0}, 0, 1);
+		GameObject right_leg
+			= mgr.new_object("rightLeg", "person", Vector2{1, 1}, 0, 1);
+		GameObject left_leg
+			= mgr.new_object("leftLeg", "person", Vector2{1, 1}, 0, 1);
+		GameObject right_foot
+			= mgr.new_object("rightFoot", "person", Vector2{2, 2}, 0, 1);
+		GameObject left_foot
+			= mgr.new_object("leftFoot", "person", Vector2{2, 2}, 0, 1);
 
 		// Set the parent of each GameObject
 		right_foot.set_parent(right_leg);
@@ -30,7 +36,6 @@ int main() {
 	}
 
 	// Get the Metadata and Transform components of each GameObject
-	ComponentManager & mgr = ComponentManager::get_instance();
 	vector<reference_wrapper<Metadata>> metadata
 		= mgr.get_components_by_type<Metadata>();
 	vector<reference_wrapper<Transform>> transform
diff --git a/src/example/log.cpp b/src/example/log.cpp
index db8aa48..5baa021 100644
--- a/src/example/log.cpp
+++ b/src/example/log.cpp
@@ -4,7 +4,7 @@
  */
 
 #include <crepe/api/Config.h>
-#include <crepe/util/log.h>
+#include <crepe/util/Log.h>
 
 using namespace crepe;
 
@@ -12,17 +12,17 @@ using namespace crepe;
 int _ = []() {
 	// make sure all log messages get printed
 	auto & cfg = Config::get_instance();
-	cfg.log.level = LogLevel::TRACE;
+	cfg.log.level = Log::Level::TRACE;
 
 	return 0; // satisfy compiler
 }();
 
 int main() {
 	dbg_trace();
-	dbg_logf("test printf parameters: %d", 3);
-	logf(LogLevel::INFO, "info message");
-	logf(LogLevel::WARNING, "warning");
-	logf(LogLevel::ERROR, "error");
+	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/physics.cpp b/src/example/physics.cpp
index 848f857..ad663a0 100644
--- a/src/example/physics.cpp
+++ b/src/example/physics.cpp
@@ -9,9 +9,10 @@ using namespace crepe;
 using namespace std;
 
 int main(int argc, char * argv[]) {
-	GameObject * game_object;
-	game_object = new GameObject(0, "Name", "Tag", Vector2{0, 0}, 0, 0);
-	game_object->add_component<Rigidbody>(Rigidbody::Data{
+	ComponentManager mgr{};
+
+	GameObject game_object = mgr.new_object("Name", "Tag", Vector2{0, 0}, 0, 0);
+	game_object.add_component<Rigidbody>(Rigidbody::Data{
 		.mass = 1,
 		.gravity_scale = 1,
 		.body_type = Rigidbody::BodyType::DYNAMIC,
@@ -19,6 +20,5 @@ int main(int argc, char * argv[]) {
 		.use_gravity = true,
 		.bounce = false,
 	});
-	delete game_object;
 	return 0;
 }
diff --git a/src/example/proxy.cpp b/src/example/proxy.cpp
index 0afff41..69451f8 100644
--- a/src/example/proxy.cpp
+++ b/src/example/proxy.cpp
@@ -5,8 +5,8 @@
 
 #include <crepe/ValueBroker.h>
 #include <crepe/api/Config.h>
+#include <crepe/util/Log.h>
 #include <crepe/util/Proxy.h>
-#include <crepe/util/log.h>
 
 using namespace std;
 using namespace crepe;
@@ -17,18 +17,17 @@ void test_ro_val(int val) {}
 
 int main() {
 	auto & cfg = Config::get_instance();
-	cfg.log.level = LogLevel::DEBUG;
+	cfg.log.level = Log::Level::DEBUG;
 
 	int real_value = 0;
 
 	ValueBroker<int> broker{
 		[&real_value](const int & target) {
-			dbg_logf("set %s to %s", to_string(real_value).c_str(),
-					 to_string(target).c_str());
+			dbg_logf("set {} to {}", real_value, target);
 			real_value = target;
 		},
 		[&real_value]() -> const int & {
-			dbg_logf("get %s", to_string(real_value).c_str());
+			dbg_logf("get {}", real_value);
 			return real_value;
 		},
 	};
diff --git a/src/example/rendering.cpp b/src/example/rendering.cpp
index 827ad07..abd11b1 100644
--- a/src/example/rendering.cpp
+++ b/src/example/rendering.cpp
@@ -2,7 +2,7 @@
 #include <crepe/ComponentManager.h>
 #include <crepe/api/GameObject.h>
 #include <crepe/system/RenderSystem.h>
-#include <crepe/util/log.h>
+#include <crepe/util/Log.h>
 
 #include <crepe/api/AssetManager.h>
 #include <crepe/api/Color.h>
@@ -20,9 +20,12 @@ using namespace crepe;
 int main() {
 	dbg_trace();
 
-	auto obj = GameObject(0, "name", "tag", Vector2{0, 0}, 1, 1);
-	auto obj1 = GameObject(1, "name", "tag", Vector2{500, 0}, 1, 0.1);
-	auto obj2 = GameObject(2, "name", "tag", Vector2{800, 0}, 1, 0.1);
+	ComponentManager mgr{};
+	RenderSystem sys{mgr};
+
+	GameObject obj = mgr.new_object("name", "tag", Vector2{0, 0}, 1, 1);
+	GameObject obj1 = mgr.new_object("name", "tag", Vector2{500, 0}, 1, 0.1);
+	GameObject obj2 = mgr.new_object("name", "tag", Vector2{800, 0}, 1, 0.1);
 
 	// Normal adding components
 	{
@@ -47,7 +50,6 @@ int main() {
 	}
 	*/
 
-	auto & sys = crepe::RenderSystem::get_instance();
 	auto start = std::chrono::steady_clock::now();
 	while (std::chrono::steady_clock::now() - start < std::chrono::seconds(5)) {
 		sys.update();
diff --git a/src/example/savemgr.cpp b/src/example/savemgr.cpp
index 436fb5a..65c4a34 100644
--- a/src/example/savemgr.cpp
+++ b/src/example/savemgr.cpp
@@ -6,8 +6,8 @@
 #include <cassert>
 #include <crepe/api/Config.h>
 #include <crepe/api/SaveManager.h>
+#include <crepe/util/Log.h>
 #include <crepe/util/Proxy.h>
-#include <crepe/util/log.h>
 
 using namespace crepe;
 
@@ -15,7 +15,7 @@ using namespace crepe;
 int _ = []() {
 	// make sure all log messages get printed
 	auto & cfg = Config::get_instance();
-	cfg.log.level = LogLevel::TRACE;
+	cfg.log.level = Log::Level::TRACE;
 
 	return 0; // satisfy compiler
 }();
@@ -25,19 +25,19 @@ int main() {
 
 	SaveManager & mgr = SaveManager::get_instance();
 
-	dbg_logf("has key = %s", mgr.has(key) ? "true" : "false");
+	dbg_logf("has key = {}", mgr.has(key));
 	ValueBroker<int> prop = mgr.get<int>(key, 0);
 	Proxy<int> val = mgr.get<int>(key, 0);
 
-	dbg_logf("val = %d", mgr.get<int>(key).get());
+	dbg_logf("val = {}", mgr.get<int>(key).get());
 	prop.set(1);
-	dbg_logf("val = %d", mgr.get<int>(key).get());
+	dbg_logf("val = {}", mgr.get<int>(key).get());
 	val = 2;
-	dbg_logf("val = %d", mgr.get<int>(key).get());
+	dbg_logf("val = {}", mgr.get<int>(key).get());
 	mgr.set<int>(key, 3);
-	dbg_logf("val = %d", mgr.get<int>(key).get());
+	dbg_logf("val = {}", mgr.get<int>(key).get());
 
-	dbg_logf("has key = %s", mgr.has(key) ? "true" : "false");
+	dbg_logf("has key = {}", mgr.has(key));
 	assert(true == mgr.has(key));
 
 	return 0;
diff --git a/src/example/scene_manager.cpp b/src/example/scene_manager.cpp
index f46dc36..24ab72e 100644
--- a/src/example/scene_manager.cpp
+++ b/src/example/scene_manager.cpp
@@ -12,40 +12,51 @@ using namespace std;
 
 class ConcreteScene1 : public Scene {
 public:
-	ConcreteScene1(string name) : Scene(name) {}
+	using Scene::Scene;
 
 	void load_scene() {
-		GameObject object1(0, "scene_1", "tag_scene_1", Vector2{0, 0}, 0, 1);
-		GameObject object2(1, "scene_1", "tag_scene_1", Vector2{1, 0}, 0, 1);
-		GameObject object3(2, "scene_1", "tag_scene_1", Vector2{2, 0}, 0, 1);
+		auto & mgr = this->component_manager;
+		GameObject object1
+			= mgr.new_object("scene_1", "tag_scene_1", Vector2{0, 0}, 0, 1);
+		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);
 	}
 };
 
 class ConcreteScene2 : public Scene {
 public:
-	ConcreteScene2(string name) : Scene(name) {}
+	using Scene::Scene;
 
 	void load_scene() {
-		GameObject object1(0, "scene_2", "tag_scene_2", Vector2{0, 0}, 0, 1);
-		GameObject object2(1, "scene_2", "tag_scene_2", Vector2{0, 1}, 0, 1);
-		GameObject object3(2, "scene_2", "tag_scene_2", Vector2{0, 2}, 0, 1);
-		GameObject object4(3, "scene_2", "tag_scene_2", Vector2{0, 3}, 0, 1);
+		auto & mgr = this->component_manager;
+		GameObject object1
+			= mgr.new_object("scene_2", "tag_scene_2", Vector2{0, 0}, 0, 1);
+		GameObject object2
+			= mgr.new_object("scene_2", "tag_scene_2", Vector2{0, 1}, 0, 1);
+		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);
 	}
 };
 
 int main() {
-	SceneManager & scene_mgr = SceneManager::get_instance();
+	ComponentManager component_mgr{};
+	SceneManager scene_mgr{component_mgr};
 
 	// Add the scenes to the scene manager
 	scene_mgr.add_scene<ConcreteScene1>("scene1");
 	scene_mgr.add_scene<ConcreteScene2>("scene2");
 
-	// There is no need to call set_next_scene() at the beginnen, because the first scene will be automatically set as the next scene
+	// There is no need to call set_next_scene() at the beginning because the
+	// first scene will be automatically set as the next scene
+
 	// Load scene1 (the first scene added)
 	scene_mgr.load_next_scene();
 
 	// Get the Metadata components of each GameObject of Scene1
-	ComponentManager & component_mgr = ComponentManager::get_instance();
 	vector<reference_wrapper<Metadata>> metadata
 		= component_mgr.get_components_by_type<Metadata>();
 
diff --git a/src/example/script.cpp b/src/example/script.cpp
index 9e8b147..a23295b 100644
--- a/src/example/script.cpp
+++ b/src/example/script.cpp
@@ -5,7 +5,7 @@
 
 #include <crepe/ComponentManager.h>
 #include <crepe/system/ScriptSystem.h>
-#include <crepe/util/log.h>
+#include <crepe/util/Log.h>
 
 #include <crepe/api/BehaviorScript.h>
 #include <crepe/api/Config.h>
@@ -20,7 +20,7 @@ using namespace std;
 int _ = []() {
 	// Show dbg_trace() output
 	auto & cfg = Config::get_instance();
-	cfg.log.level = LogLevel::TRACE;
+	cfg.log.level = Log::Level::TRACE;
 
 	return 0; // satisfy compiler
 }();
@@ -30,20 +30,20 @@ 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);
+		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
-	auto obj = GameObject(0, "name", "tag", Vector2{1.2, 3.4}, 0, 1);
+	GameObject obj = component_manager.new_object("name");
 	obj.add_component<BehaviorScript>().set_script<MyScript>();
 
-	// Get ScriptSystem singleton instance (this would normally be done from the
-	// game loop)
-	ScriptSystem sys;
 	// Update all scripts. This should result in MyScript::update being called
-	sys.update();
+	system.update();
 
 	return EXIT_SUCCESS;
 }
diff --git a/src/test/AudioTest.cpp b/src/test/AudioTest.cpp
index a9d5e6c..6e2706c 100644
--- a/src/test/AudioTest.cpp
+++ b/src/test/AudioTest.cpp
@@ -3,6 +3,7 @@
 
 #include <crepe/ComponentManager.h>
 #include <crepe/api/AudioSource.h>
+#include <crepe/api/GameObject.h>
 
 using namespace std;
 using namespace crepe;
@@ -16,6 +17,7 @@ public:
 	void SetUp() override {
 		auto & mgr = this->component_manager;
 		GameObject entity = mgr.new_object("name");
+		entity.add_component<AudioSource>("../mwe/audio/sfx1.wav");
 	}
 };
 
diff --git a/src/test/CMakeLists.txt b/src/test/CMakeLists.txt
index f63a733..1a986bd 100644
--- a/src/test/CMakeLists.txt
+++ b/src/test/CMakeLists.txt
@@ -1,6 +1,8 @@
 target_sources(test_main PUBLIC
-	# PhysicsTest.cpp
-	# ParticleTest.cpp
+	main.cpp
+	PhysicsTest.cpp
+	ScriptTest.cpp
+	ParticleTest.cpp
 	AudioTest.cpp
 )
 
diff --git a/src/test/ParticleTest.cpp b/src/test/ParticleTest.cpp
index 6fe3133..1a89e3a 100644
--- a/src/test/ParticleTest.cpp
+++ b/src/test/ParticleTest.cpp
@@ -16,15 +16,16 @@ using namespace std::chrono_literals;
 using namespace crepe;
 
 class ParticlesTest : public ::testing::Test {
-protected:
-	ParticleSystem particle_system;
+public:
+	ComponentManager component_manager;
+	ParticleSystem particle_system{component_manager};
+
 	void SetUp() override {
-		ComponentManager & mgr = ComponentManager::get_instance();
+		ComponentManager & mgr = this->component_manager;
 		std::vector<std::reference_wrapper<Transform>> transforms
 			= mgr.get_components_by_id<Transform>(0);
 		if (transforms.empty()) {
-
-			GameObject game_object(0, "", "", Vector2{0, 0}, 0, 0);
+			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>(
@@ -77,7 +78,7 @@ protected:
 
 TEST_F(ParticlesTest, spawnParticle) {
 	Config::get_instance().physics.gravity = 1;
-	ComponentManager & mgr = ComponentManager::get_instance();
+	ComponentManager & mgr = this->component_manager;
 	ParticleEmitter & emitter
 		= mgr.get_components_by_id<ParticleEmitter>(0).front().get();
 	emitter.data.end_lifespan = 5;
@@ -122,7 +123,7 @@ TEST_F(ParticlesTest, spawnParticle) {
 
 TEST_F(ParticlesTest, moveParticleHorizontal) {
 	Config::get_instance().physics.gravity = 1;
-	ComponentManager & mgr = ComponentManager::get_instance();
+	ComponentManager & mgr = this->component_manager;
 	ParticleEmitter & emitter
 		= mgr.get_components_by_id<ParticleEmitter>(0).front().get();
 	emitter.data.end_lifespan = 100;
@@ -140,7 +141,7 @@ TEST_F(ParticlesTest, moveParticleHorizontal) {
 
 TEST_F(ParticlesTest, moveParticleVertical) {
 	Config::get_instance().physics.gravity = 1;
-	ComponentManager & mgr = ComponentManager::get_instance();
+	ComponentManager & mgr = this->component_manager;
 	ParticleEmitter & emitter
 		= mgr.get_components_by_id<ParticleEmitter>(0).front().get();
 	emitter.data.end_lifespan = 100;
@@ -159,7 +160,7 @@ TEST_F(ParticlesTest, moveParticleVertical) {
 
 TEST_F(ParticlesTest, boundaryParticleReset) {
 	Config::get_instance().physics.gravity = 1;
-	ComponentManager & mgr = ComponentManager::get_instance();
+	ComponentManager & mgr = this->component_manager;
 	ParticleEmitter & emitter
 		= mgr.get_components_by_id<ParticleEmitter>(0).front().get();
 	emitter.data.end_lifespan = 100;
@@ -179,7 +180,7 @@ TEST_F(ParticlesTest, boundaryParticleReset) {
 
 TEST_F(ParticlesTest, boundaryParticleStop) {
 	Config::get_instance().physics.gravity = 1;
-	ComponentManager & mgr = ComponentManager::get_instance();
+	ComponentManager & mgr = this->component_manager;
 	ParticleEmitter & emitter
 		= mgr.get_components_by_id<ParticleEmitter>(0).front().get();
 	emitter.data.end_lifespan = 100;
diff --git a/src/test/PhysicsTest.cpp b/src/test/PhysicsTest.cpp
index 5385962..edb76e9 100644
--- a/src/test/PhysicsTest.cpp
+++ b/src/test/PhysicsTest.cpp
@@ -11,16 +11,17 @@ using namespace std::chrono_literals;
 using namespace crepe;
 
 class PhysicsTest : public ::testing::Test {
-protected:
-	GameObject * game_object;
-	PhysicsSystem physics_system;
+public:
+	ComponentManager component_manager;
+	PhysicsSystem system{component_manager};
+
 	void SetUp() override {
-		ComponentManager & mgr = ComponentManager::get_instance();
-		std::vector<std::reference_wrapper<Transform>> transforms
+		ComponentManager & mgr = this->component_manager;
+		vector<reference_wrapper<Transform>> transforms
 			= mgr.get_components_by_id<Transform>(0);
 		if (transforms.empty()) {
-			game_object = new GameObject(0, "", "", Vector2{0, 0}, 0, 0);
-			game_object->add_component<Rigidbody>(Rigidbody::Data{
+			auto entity = mgr.new_object("", "", Vector2{0, 0}, 0, 0);
+			entity.add_component<Rigidbody>(Rigidbody::Data{
 				.mass = 1,
 				.gravity_scale = 1,
 				.body_type = Rigidbody::BodyType::DYNAMIC,
@@ -36,7 +37,7 @@ protected:
 		transform.position.x = 0.0;
 		transform.position.y = 0.0;
 		transform.rotation = 0.0;
-		std::vector<std::reference_wrapper<Rigidbody>> rigidbodies
+		vector<reference_wrapper<Rigidbody>> rigidbodies
 			= mgr.get_components_by_id<Rigidbody>(0);
 		Rigidbody & rigidbody = rigidbodies.front().get();
 		rigidbody.data.angular_velocity = 0;
@@ -47,34 +48,38 @@ protected:
 
 TEST_F(PhysicsTest, gravity) {
 	Config::get_instance().physics.gravity = 1;
-	ComponentManager & mgr = ComponentManager::get_instance();
-	std::vector<std::reference_wrapper<Transform>> transforms
+	ComponentManager & mgr = this->component_manager;
+	vector<reference_wrapper<Transform>> transforms
 		= mgr.get_components_by_id<Transform>(0);
 	const Transform & transform = transforms.front().get();
 	ASSERT_FALSE(transforms.empty());
 	EXPECT_EQ(transform.position.y, 0);
-	physics_system.update();
+
+	system.update();
 	EXPECT_EQ(transform.position.y, 1);
-	physics_system.update();
+
+	system.update();
 	EXPECT_EQ(transform.position.y, 3);
 }
 
 TEST_F(PhysicsTest, max_velocity) {
-	ComponentManager & mgr = ComponentManager::get_instance();
-	std::vector<std::reference_wrapper<Rigidbody>> rigidbodies
+	ComponentManager & mgr = this->component_manager;
+	vector<reference_wrapper<Rigidbody>> rigidbodies
 		= mgr.get_components_by_id<Rigidbody>(0);
 	Rigidbody & rigidbody = rigidbodies.front().get();
 	ASSERT_FALSE(rigidbodies.empty());
 	EXPECT_EQ(rigidbody.data.linear_velocity.y, 0);
+
 	rigidbody.add_force_linear({100, 100});
 	rigidbody.add_force_angular(100);
-	physics_system.update();
+	system.update();
 	EXPECT_EQ(rigidbody.data.linear_velocity.y, 10);
 	EXPECT_EQ(rigidbody.data.linear_velocity.x, 10);
 	EXPECT_EQ(rigidbody.data.angular_velocity, 10);
+
 	rigidbody.add_force_linear({-100, -100});
 	rigidbody.add_force_angular(-100);
-	physics_system.update();
+	system.update();
 	EXPECT_EQ(rigidbody.data.linear_velocity.y, -10);
 	EXPECT_EQ(rigidbody.data.linear_velocity.x, -10);
 	EXPECT_EQ(rigidbody.data.angular_velocity, -10);
@@ -82,39 +87,44 @@ TEST_F(PhysicsTest, max_velocity) {
 
 TEST_F(PhysicsTest, movement) {
 	Config::get_instance().physics.gravity = 0;
-	ComponentManager & mgr = ComponentManager::get_instance();
-	std::vector<std::reference_wrapper<Rigidbody>> rigidbodies
+	ComponentManager & mgr = this->component_manager;
+	vector<reference_wrapper<Rigidbody>> rigidbodies
 		= mgr.get_components_by_id<Rigidbody>(0);
 	Rigidbody & rigidbody = rigidbodies.front().get();
-	std::vector<std::reference_wrapper<Transform>> transforms
+	vector<reference_wrapper<Transform>> transforms
 		= mgr.get_components_by_id<Transform>(0);
 	const Transform & transform = transforms.front().get();
 	ASSERT_FALSE(rigidbodies.empty());
 	ASSERT_FALSE(transforms.empty());
+
 	rigidbody.add_force_linear({1, 1});
 	rigidbody.add_force_angular(1);
-	physics_system.update();
+	system.update();
 	EXPECT_EQ(transform.position.x, 1);
 	EXPECT_EQ(transform.position.y, 1);
 	EXPECT_EQ(transform.rotation, 1);
+
 	rigidbody.data.constraints = {1, 1, 1};
 	EXPECT_EQ(transform.position.x, 1);
 	EXPECT_EQ(transform.position.y, 1);
 	EXPECT_EQ(transform.rotation, 1);
+
 	rigidbody.data.linear_damping.x = 0.5;
 	rigidbody.data.linear_damping.y = 0.5;
 	rigidbody.data.angular_damping = 0.5;
-	physics_system.update();
+	system.update();
 	EXPECT_EQ(rigidbody.data.linear_velocity.x, 0.5);
 	EXPECT_EQ(rigidbody.data.linear_velocity.y, 0.5);
 	EXPECT_EQ(rigidbody.data.angular_velocity, 0.5);
+
 	rigidbody.data.constraints = {1, 1, 0};
 	rigidbody.data.angular_damping = 0;
 	rigidbody.data.max_angular_velocity = 1000;
 	rigidbody.data.angular_velocity = 360;
-	physics_system.update();
+	system.update();
 	EXPECT_EQ(transform.rotation, 1);
+
 	rigidbody.data.angular_velocity = -360;
-	physics_system.update();
+	system.update();
 	EXPECT_EQ(transform.rotation, 1);
 }
diff --git a/src/test/ScriptTest.cpp b/src/test/ScriptTest.cpp
new file mode 100644
index 0000000..19fef6d
--- /dev/null
+++ b/src/test/ScriptTest.cpp
@@ -0,0 +1,72 @@
+#include <gtest/gtest.h>
+
+// stupid hack to allow access to private/protected members under test
+#define private public
+#define protected public
+
+#include <crepe/ComponentManager.h>
+#include <crepe/api/BehaviorScript.h>
+#include <crepe/api/GameObject.h>
+#include <crepe/api/Script.h>
+#include <crepe/api/Vector2.h>
+#include <crepe/system/ScriptSystem.h>
+
+using namespace std;
+using namespace crepe;
+using namespace testing;
+
+class ScriptTest : public Test {
+public:
+	ComponentManager component_manager{};
+	ScriptSystem system{component_manager};
+
+	class MyScript : public Script {
+		// NOTE: default (private) visibility of init and update shouldn't cause
+		// issues!
+		void init() { this->init_count++; }
+		void update() { this->update_count++; }
+
+	public:
+		unsigned init_count = 0;
+		unsigned update_count = 0;
+	};
+
+	BehaviorScript * behaviorscript_ref = nullptr;
+	MyScript * script_ref = nullptr;
+
+	void SetUp() override {
+		auto & mgr = this->component_manager;
+		GameObject entity = mgr.new_object("name");
+		BehaviorScript & component = entity.add_component<BehaviorScript>();
+
+		this->behaviorscript_ref = &component;
+		EXPECT_EQ(this->behaviorscript_ref->script.get(), nullptr);
+		component.set_script<MyScript>();
+		ASSERT_NE(this->behaviorscript_ref->script.get(), nullptr);
+
+		this->script_ref = (MyScript *) this->behaviorscript_ref->script.get();
+		ASSERT_NE(this->script_ref, nullptr);
+	}
+};
+
+TEST_F(ScriptTest, Default) {
+	EXPECT_EQ(0, this->script_ref->init_count);
+	EXPECT_EQ(0, this->script_ref->update_count);
+}
+
+TEST_F(ScriptTest, UpdateOnce) {
+	EXPECT_EQ(0, this->script_ref->init_count);
+	EXPECT_EQ(0, this->script_ref->update_count);
+
+	this->system.update();
+	EXPECT_EQ(1, this->script_ref->init_count);
+	EXPECT_EQ(1, this->script_ref->update_count);
+}
+
+TEST_F(ScriptTest, ListScripts) {
+	size_t script_count = 0;
+	for (auto & _ : this->system.get_scripts()) {
+		script_count++;
+	}
+	ASSERT_EQ(1, script_count);
+}
diff --git a/src/test/main.cpp b/src/test/main.cpp
new file mode 100644
index 0000000..241015d
--- /dev/null
+++ b/src/test/main.cpp
@@ -0,0 +1,15 @@
+#include <crepe/api/Config.h>
+
+#include <gtest/gtest.h>
+
+using namespace crepe;
+using namespace testing;
+
+int main(int argc, char ** argv) {
+	InitGoogleTest(&argc, argv);
+
+	auto & cfg = Config::get_instance();
+	cfg.log.level = Log::Level::ERROR;
+
+	return RUN_ALL_TESTS();
+}