Merge branch 'master' into niels/UI

27 files changed, 356 insertions, 149 deletions

diff --git a/src/crepe/api/Button.cpp b/src/crepe/api/Button.cpp
index 305922c..40153c9 100644
--- a/src/crepe/api/Button.cpp
+++ b/src/crepe/api/Button.cpp
@@ -2,9 +2,7 @@
 
 namespace crepe {
 
-Button::Button(game_object_id_t id, const vec2 & dimensions, const vec2 & offset,
-			   const std::function<void()> & on_click)
-	: UIObject(id, dimensions, offset),
-	  on_click(on_click) {}
+Button::Button(game_object_id_t id, const vec2 & dimensions, const vec2 & offset)
+	: UIObject(id, dimensions, offset) {}
 
 } // namespace crepe
diff --git a/src/crepe/api/Button.h b/src/crepe/api/Button.h
index 08f5dec..d42527e 100644
--- a/src/crepe/api/Button.h
+++ b/src/crepe/api/Button.h
@@ -2,11 +2,23 @@
 
 #include <functional>
 
+#include "Event.h"
 #include "UIObject.h"
 
 namespace crepe {
 
-//! Represents a clickable UI button, derived from the UiObject class.
+/**
+ * \brief Button component.
+ * 
+ * This component creates a clickable surface at the transform location with the specified width and height.
+ * 
+ * The Button can be used in scripts by subscribing a EventHandler to the following events:
+ * - ButtonPressEvent
+ * - ButtonEnterEvent
+ * - ButtonExitEvent
+ * \see EventManager
+ * 
+ */
 class Button : public UIObject {
 public:
 	/**
@@ -15,43 +27,22 @@ public:
 	 * \param id The unique ID of the game object associated with this button.
 	 * \param dimensions The width and height of the UIObject
 	 * \param offset The offset relative this GameObjects Transform
-	 * \param on_click callback function that will be invoked when the button is clicked.
 	 */
-	Button(game_object_id_t id, const vec2 & dimensions, const vec2 & offset,
-		   const std::function<void()> & on_click);
-
-	// TODO: create separate toggle button class
-	/**
-	 * \brief The callback function to be executed when the button is clicked.
-	 *
-	 * This function is invoked whenever the button is clicked. It can be set to any
-	 * function that matches the signature `void()`.
-	 */
-	std::function<void()> on_click = nullptr;
-
+	Button(game_object_id_t id, const vec2 & dimensions, const vec2 & offset);
 	/**
-	 * \brief Callback function to be executed when the mouse enters the button's boundaries.
+	 * \brief Get the maximum number of instances for this component
 	 *
-	 * This function is triggered when the mouse cursor moves over the button, allowing
-	 * custom actions like visual effects, highlighting, or sound effects.
+	 * Since the button Event transfers the GameObject Metadata it will be the same for each button so only one button is allowed per GameObject	
+	 * 
+	 * \return 1
 	 */
-	std::function<void()> on_mouse_enter = nullptr;
-
-	/**
-	 * \brief Callback function to be executed when the mouse exits the button's boundaries.
-	 *
-	 * This function is triggered when the mouse cursor moves out of the button's area,
-	 * allowing custom actions like resetting visual effects or playing exit-related effects.
-	 */
-	std::function<void()> on_mouse_exit = nullptr;
+	virtual int get_instances_max() const { return 1; }
 
 private:
-	//! friend relation for is_pressed and hover variables
+	//! friend relation hover variable
 	friend class InputSystem;
 	//! Indicates whether the mouse is currently hovering over the button
 	bool hover = false;
-
-public:
 };
 
 } // namespace crepe
diff --git a/src/crepe/api/Event.h b/src/crepe/api/Event.h
index 73bf461..8e38280 100644
--- a/src/crepe/api/Event.h
+++ b/src/crepe/api/Event.h
@@ -3,9 +3,10 @@
 
 #include <string>
 
-#include "api/KeyCodes.h"
 #include "types.h"
 
+#include "KeyCodes.h"
+
 namespace crepe {
 
 /**
@@ -95,15 +96,6 @@ public:
 };
 
 /**
- * \brief Event triggered when text is submitted, e.g., from a text input.
- */
-class TextSubmitEvent : public Event {
-public:
-	//! The submitted text.
-	std::string text = "";
-};
-
-/**
  * \brief Event triggered to indicate the application is shutting down.
  */
 class ShutDownEvent : public Event {};
diff --git a/src/crepe/api/LoopManager.h b/src/crepe/api/LoopManager.h
index 1d23cbf..124cd3a 100644
--- a/src/crepe/api/LoopManager.h
+++ b/src/crepe/api/LoopManager.h
@@ -71,9 +71,19 @@ private:
 private:
 	//! Global context
 	Mediator mediator;
+	/**
+	 * \brief Collection of System instances
+	 *
+	 * This map holds System instances indexed by the system's class typeid. It is filled in the
+	 * constructor of LoopManager using LoopManager::load_system.
+	 */
+	std::unordered_map<std::type_index, std::unique_ptr<System>> systems;
 
 	//! SDLContext instance
 	SDLContext sdl_context{mediator};
+	//! Resource manager instance
+	ResourceManager resource_manager{mediator};
+
 	//! Component manager instance
 	ComponentManager component_manager{mediator};
 	//! Scene manager instance
@@ -82,8 +92,6 @@ private:
 	LoopTimerManager loop_timer{mediator};
 	//! EventManager instance
 	EventManager event_manager{mediator};
-	//! Resource manager instance
-	ResourceManager resource_manager{mediator};
 	//! Save manager instance
 	SaveManager save_manager{mediator};
 
@@ -95,13 +103,6 @@ private:
 	 */
 	bool on_shutdown(const ShutDownEvent & e);
 	/**
-	 * \brief Collection of System instances
-	 *
-	 * This map holds System instances indexed by the system's class typeid. It is filled in the
-	 * constructor of LoopManager using LoopManager::load_system.
-	 */
-	std::unordered_map<std::type_index, std::unique_ptr<System>> systems;
-	/**
 	 * \brief Initialize a system
 	 * \tparam T System type (must be derivative of \c System)
 	 */
diff --git a/src/crepe/api/Script.cpp b/src/crepe/api/Script.cpp
index 583c04f..85016f5 100644
--- a/src/crepe/api/Script.cpp
+++ b/src/crepe/api/Script.cpp
@@ -26,6 +26,8 @@ void Script::set_next_scene(const string & name) {
 
 SaveManager & Script::get_save_manager() const { return this->mediator->save_manager; }
 
+LoopTimerManager & Script::get_loop_timer() const { return this->mediator->loop_timer; }
+
 const keyboard_state_t & Script::get_keyboard_state() const {
 	SDLContext & sdl_context = this->mediator->sdl_context;
 	return sdl_context.get_keyboard_state();
@@ -38,3 +40,4 @@ bool Script::get_key_state(Keycode key) const noexcept {
 		return false;
 	}
 }
+
diff --git a/src/crepe/api/Script.h b/src/crepe/api/Script.h
index 65306cd..a87af4e 100644
--- a/src/crepe/api/Script.h
+++ b/src/crepe/api/Script.h
@@ -4,6 +4,7 @@
 
 #include "../api/KeyCodes.h"
 #include "../manager/EventManager.h"
+#include "../manager/LoopTimerManager.h"
 #include "../manager/Mediator.h"
 #include "../system/CollisionSystem.h"
 #include "../types.h"
@@ -47,10 +48,12 @@ protected:
 	/**
 	 * \brief Script update function (empty by default)
 	 *
+	 * \param delta_time Time since last fixed update
+	 *
 	 * This function is called during the ScriptSystem::update() routine if the \c BehaviorScript
 	 * component holding this script instance is active.
 	 */
-	virtual void update() {}
+	virtual void update(duration_t delta_time) {}
 	//! \}
 
 	//! ScriptSystem calls \c init() and \c update()
@@ -135,6 +138,10 @@ protected:
 
 	//! Retrieve SaveManager reference
 	SaveManager & get_save_manager() const;
+
+	//! Retrieve LoopTimerManager reference
+	LoopTimerManager & get_loop_timer() const;
+
 	/**
 	 * \brief Utility function to retrieve the keyboard state
 	 * \see SDLContext::get_keyboard_state
@@ -151,7 +158,6 @@ protected:
 	 * 
 	 */
 	bool get_key_state(Keycode key) const noexcept;
-	//! \}
 
 private:
 	/**
diff --git a/src/crepe/api/Sprite.h b/src/crepe/api/Sprite.h
index a2409c2..a3fc319 100644
--- a/src/crepe/api/Sprite.h
+++ b/src/crepe/api/Sprite.h
@@ -66,6 +66,16 @@ public:
 
 		//! independent sprite offset position
 		vec2 position_offset;
+
+		/**
+		 * \brief gives the user the option to render this in world space or in camera space
+		 *
+		 * - if true will this be rendered in world space this means that the sprite can be
+		 *   rendered off the screen 
+		 * - if false --> will the sprite be rendered in camera space. this means that the
+		 *   coordinates given on the \c Sprite and \c Transform will be inside the camera 
+		 */
+		bool world_space = true;
 	};
 
 public:
diff --git a/src/crepe/facade/DB.cpp b/src/crepe/facade/DB.cpp
index 95cf606..ae2d4bc 100644
--- a/src/crepe/facade/DB.cpp
+++ b/src/crepe/facade/DB.cpp
@@ -21,12 +21,6 @@ DB::DB(const string & path) {
 	const char * file = path.empty() ? NULL : path.c_str();
 	ret = this->db->open(this->db.get(), NULL, file, NULL, libdb::DB_BTREE, DB_CREATE, 0);
 	if (ret != 0) throw runtime_error(format("db->open: {}", libdb::db_strerror(ret)));
-
-	// create cursor
-	libdb::DBC * cursor;
-	ret = this->db->cursor(this->db.get(), NULL, &cursor, 0);
-	if (ret != 0) throw runtime_error(format("db->cursor: {}", libdb::db_strerror(ret)));
-	this->cursor = {cursor, [](libdb::DBC * cursor) { cursor->close(cursor); }};
 }
 
 libdb::DBT DB::to_thing(const string & thing) const noexcept {
@@ -42,10 +36,10 @@ string DB::get(const string & key) {
 	libdb::DBT db_val;
 	memset(&db_val, 0, sizeof(libdb::DBT));
 
-	int ret = this->cursor->get(this->cursor.get(), &db_key, &db_val, DB_FIRST);
+	int ret = this->db->get(this->db.get(), NULL, &db_key, &db_val, 0);
 	if (ret == 0) return {static_cast<char *>(db_val.data), db_val.size};
 
-	string err = format("cursor->get: {}", libdb::db_strerror(ret));
+	string err = format("db->get: {}", libdb::db_strerror(ret));
 	if (ret == DB_NOTFOUND) throw out_of_range(err);
 	else throw runtime_error(err);
 }
@@ -54,7 +48,7 @@ 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 runtime_error(format("cursor->get: {}", libdb::db_strerror(ret)));
+	if (ret != 0) throw runtime_error(format("db->get: {}", libdb::db_strerror(ret)));
 }
 
 bool DB::has(const std::string & key) {
diff --git a/src/crepe/facade/DB.h b/src/crepe/facade/DB.h
index 115c0f1..84cdf19 100644
--- a/src/crepe/facade/DB.h
+++ b/src/crepe/facade/DB.h
@@ -61,8 +61,6 @@ public:
 private:
 	//! RAII wrapper around \c DB struct
 	std::unique_ptr<libdb::DB, std::function<void(libdb::DB *)>> db;
-	//! RAII wrapper around \c DBC struct
-	std::unique_ptr<libdb::DBC, std::function<void(libdb::DBC *)>> cursor;
 
 private:
 	/**
diff --git a/src/crepe/facade/SDLContext.cpp b/src/crepe/facade/SDLContext.cpp
index d352adc..642aef8 100644
--- a/src/crepe/facade/SDLContext.cpp
+++ b/src/crepe/facade/SDLContext.cpp
@@ -141,6 +141,8 @@ SDL_FRect SDLContext::get_dst_rect(const DestinationRectangleData & ctx) const {
 		= (ctx.sprite.aspect_ratio == 0) ? ctx.texture.get_ratio() : ctx.sprite.aspect_ratio;
 
 	vec2 size = data.size;
+	vec2 screen_pos = ctx.pos + data.position_offset;
+
 	if (data.size.x == 0 && data.size.y != 0) {
 		size.x = data.size.y * aspect_ratio;
 	}
@@ -149,9 +151,16 @@ SDL_FRect SDLContext::get_dst_rect(const DestinationRectangleData & ctx) const {
 	}
 	size *= cam_aux_data.render_scale * ctx.img_scale * data.scale_offset;
 
-	vec2 screen_pos = (ctx.pos - cam_aux_data.cam_pos + (cam_aux_data.zoomed_viewport) / 2)
-						  * cam_aux_data.render_scale
-					  - size / 2 + cam_aux_data.bar_size;
+	if (ctx.sprite.data.world_space) {
+		vec2 multiplier = cam_aux_data.cam_pos
+						  + (cam_aux_data.zoomed_viewport / 2) * cam_aux_data.render_scale
+						  - size / 2 + cam_aux_data.bar_size;
+		screen_pos += multiplier;
+	} else {
+		vec2 multiplier = (cam_aux_data.zoomed_viewport / 2) * cam_aux_data.render_scale
+						  - size / 2 + cam_aux_data.bar_size;
+		screen_pos += multiplier;
+	}
 
 	return SDL_FRect{
 		.x = screen_pos.x,
diff --git a/src/crepe/manager/SaveManager.cpp b/src/crepe/manager/SaveManager.cpp
index 691ea2f..f313ed2 100644
--- a/src/crepe/manager/SaveManager.cpp
+++ b/src/crepe/manager/SaveManager.cpp
@@ -129,9 +129,32 @@ template void SaveManager::set(const string &, const float &);
 template void SaveManager::set(const string &, const double &);
 
 template <typename T>
+T SaveManager::get(const string & key) {
+	return this->deserialize<T>(this->get_db().get(key));
+}
+template uint8_t SaveManager::get(const string &);
+template int8_t SaveManager::get(const string &);
+template uint16_t SaveManager::get(const string &);
+template int16_t SaveManager::get(const string &);
+template uint32_t SaveManager::get(const string &);
+template int32_t SaveManager::get(const string &);
+template uint64_t SaveManager::get(const string &);
+template int64_t SaveManager::get(const string &);
+template float SaveManager::get(const string &);
+template double SaveManager::get(const string &);
+template string SaveManager::get(const string &);
+
+template <typename T>
 ValueBroker<T> SaveManager::get(const string & key, const T & default_value) {
 	if (!this->has(key)) this->set<T>(key, default_value);
-	return this->get<T>(key);
+	T value;
+	return {
+		[this, key](const T & target) { this->set<T>(key, target); },
+		[this, key, value]() mutable -> const T & {
+			value = this->get<T>(key);
+			return value;
+		},
+	};
 }
 template ValueBroker<uint8_t> SaveManager::get(const string &, const uint8_t &);
 template ValueBroker<int8_t> SaveManager::get(const string &, const int8_t &);
@@ -144,27 +167,3 @@ template ValueBroker<int64_t> SaveManager::get(const string &, const int64_t &);
 template ValueBroker<float> SaveManager::get(const string &, const float &);
 template ValueBroker<double> SaveManager::get(const string &, const double &);
 template ValueBroker<string> SaveManager::get(const string &, const string &);
-
-template <typename T>
-ValueBroker<T> SaveManager::get(const string & key) {
-	T value;
-	return {
-		[this, key](const T & target) { this->set<T>(key, target); },
-		[this, key, value]() mutable -> const T & {
-			DB & db = this->get_db();
-			value = this->deserialize<T>(db.get(key));
-			return value;
-		},
-	};
-}
-template ValueBroker<uint8_t> SaveManager::get(const string &);
-template ValueBroker<int8_t> SaveManager::get(const string &);
-template ValueBroker<uint16_t> SaveManager::get(const string &);
-template ValueBroker<int16_t> SaveManager::get(const string &);
-template ValueBroker<uint32_t> SaveManager::get(const string &);
-template ValueBroker<int32_t> SaveManager::get(const string &);
-template ValueBroker<uint64_t> SaveManager::get(const string &);
-template ValueBroker<int64_t> SaveManager::get(const string &);
-template ValueBroker<float> SaveManager::get(const string &);
-template ValueBroker<double> SaveManager::get(const string &);
-template ValueBroker<string> SaveManager::get(const string &);
diff --git a/src/crepe/manager/SaveManager.h b/src/crepe/manager/SaveManager.h
index 61a978d..1e34bc0 100644
--- a/src/crepe/manager/SaveManager.h
+++ b/src/crepe/manager/SaveManager.h
@@ -36,17 +36,17 @@ public:
 	ValueBroker<T> get(const std::string & key, const T & default_value);
 
 	/**
-	 * \brief Get a read/write reference to a value
+	 * \brief Get a value directly
 	 *
 	 * \param key  The value key
 	 *
-	 * \return Read/write reference to the value
+	 * \return The value
 	 *
 	 * \note Attempting to read this value before it is initialized (i.e. set) will result in an
 	 * exception
 	 */
 	template <typename T>
-	ValueBroker<T> get(const std::string & key);
+	T get(const std::string & key);
 
 	/**
 	 * \brief Set a value directly
diff --git a/src/crepe/system/InputSystem.cpp b/src/crepe/system/InputSystem.cpp
index fca540f..60daa55 100644
--- a/src/crepe/system/InputSystem.cpp
+++ b/src/crepe/system/InputSystem.cpp
@@ -10,10 +10,8 @@ using namespace crepe;
 
 void InputSystem::update() {
 	ComponentManager & mgr = this->mediator.component_manager;
-
 	SDLContext & context = this->mediator.sdl_context;
 	std::vector<EventData> event_list = context.get_events();
-	RefVector<Button> buttons = mgr.get_components_by_type<Button>();
 	RefVector<Camera> cameras = mgr.get_components_by_type<Camera>();
 	OptionalRef<Camera> curr_cam_ref;
 
@@ -155,28 +153,25 @@ void InputSystem::handle_non_mouse_event(const EventData & event) {
 
 void InputSystem::handle_move(const EventData & event_data, const vec2 & mouse_pos) {
 	ComponentManager & mgr = this->mediator.component_manager;
-
+	EventManager & event_mgr = this->mediator.event_manager;
 	RefVector<Button> buttons = mgr.get_components_by_type<Button>();
 
 	for (Button & button : buttons) {
 		if (!button.active) continue;
-		RefVector<Transform> transform_vec
-			= mgr.get_components_by_id<Transform>(button.game_object_id);
-		Transform & transform(transform_vec.front().get());
-
+		Metadata & metadata
+			= mgr.get_components_by_id<Metadata>(button.game_object_id).front();
+		Transform & transform
+			= mgr.get_components_by_id<Transform>(button.game_object_id).front();
 		bool was_hovering = button.hover;
 		if (this->is_mouse_inside_button(mouse_pos, button, transform)) {
 			button.hover = true;
-			if (!button.on_mouse_enter) continue;
 			if (!was_hovering) {
-				button.on_mouse_enter();
+				event_mgr.trigger_event<ButtonEnterEvent>(metadata);
 			}
 		} else {
 			button.hover = false;
-			// Trigger the on_exit callback if the hover state just changed to false
-			if (!button.on_mouse_exit) continue;
 			if (was_hovering) {
-				button.on_mouse_exit();
+				event_mgr.trigger_event<ButtonExitEvent>(metadata);
 			}
 		}
 	}
@@ -184,19 +179,18 @@ void InputSystem::handle_move(const EventData & event_data, const vec2 & mouse_p
 
 void InputSystem::handle_click(const MouseButton & mouse_button, const vec2 & mouse_pos) {
 	ComponentManager & mgr = this->mediator.component_manager;
-
+	EventManager & event_mgr = this->mediator.event_manager;
 	RefVector<Button> buttons = mgr.get_components_by_type<Button>();
 
 	for (Button & button : buttons) {
 		if (!button.active) continue;
-		if (!button.on_click) continue;
-		RefVector<Transform> transform_vec
-			= mgr.get_components_by_id<Transform>(button.game_object_id);
-		Transform & transform = transform_vec.front().get();
+		Metadata & metadata
+			= mgr.get_components_by_id<Metadata>(button.game_object_id).front();
+		Transform & transform
+			= mgr.get_components_by_id<Transform>(button.game_object_id).front();
 
 		if (this->is_mouse_inside_button(mouse_pos, button, transform)) {
-
-			button.on_click();
+			event_mgr.trigger_event<ButtonPressEvent>(metadata);
 		}
 	}
 }
diff --git a/src/crepe/system/InputSystem.h b/src/crepe/system/InputSystem.h
index eefd9fe..e580d8e 100644
--- a/src/crepe/system/InputSystem.h
+++ b/src/crepe/system/InputSystem.h
@@ -3,6 +3,8 @@
 #include "../api/Config.h"
 #include "../facade/EventData.h"
 
+#include "../api/Event.h"
+#include "../api/Metadata.h"
 #include "../types.h"
 #include "../util/OptionalRef.h"
 
@@ -13,6 +15,37 @@ namespace crepe {
 class Camera;
 class Button;
 class Transform;
+//! Event triggered when a button is clicked
+class ButtonPressEvent : public Event {
+public:
+	//! Metadata of the button.
+	const Metadata & metadata;
+	/**
+	 * \param metadata Metadata of the button pressed
+	 */
+	ButtonPressEvent(const Metadata & metadata) : metadata(metadata){};
+};
+//! Event triggered when the mouse enters a button
+class ButtonEnterEvent : public Event {
+public:
+	//! Metadata of the button.
+	const Metadata & metadata;
+	/**
+	 * \param metadata Metadata of the button pressed
+	 */
+	ButtonEnterEvent(const Metadata & metadata) : metadata(metadata){};
+};
+//! Event triggered when the mouse leaves a button
+class ButtonExitEvent : public Event {
+public:
+	//! Metadata of the button.
+	const Metadata & metadata;
+	/**
+	 * \param metadata Metadata of the button pressed
+	 */
+	ButtonExitEvent(const Metadata & metadata) : metadata(metadata){};
+};
+
 /**
  * \brief Handles the processing of input events created by SDLContext
  *
diff --git a/src/crepe/system/RenderSystem.cpp b/src/crepe/system/RenderSystem.cpp
index b4b745f..3ec1922 100644
--- a/src/crepe/system/RenderSystem.cpp
+++ b/src/crepe/system/RenderSystem.cpp
@@ -118,12 +118,13 @@ bool RenderSystem::render_particle(const Sprite & sprite, const Transform & tm){
 
 		for (const Particle & p : em.particles) {
 			if (!p.active) continue;
+			if (p.time_in_life < em.data.begin_lifespan) continue;
 
 			ctx.draw(SDLContext::RenderContext{
 				.sprite = sprite,
 				.texture = res,
 				.pos = p.position,
-				.angle = p.angle,
+				.angle = p.angle + transform_angle,
 				.scale = tm.scale,
 			});
 		}
diff --git a/src/crepe/system/ScriptSystem.cpp b/src/crepe/system/ScriptSystem.cpp
index d6b2ca1..0605c7a 100644
--- a/src/crepe/system/ScriptSystem.cpp
+++ b/src/crepe/system/ScriptSystem.cpp
@@ -11,6 +11,7 @@ void ScriptSystem::update() {
 	dbg_trace();
 
 	ComponentManager & mgr = this->mediator.component_manager;
+	LoopTimerManager & timer = this->mediator.loop_timer;
 	RefVector<BehaviorScript> behavior_scripts = mgr.get_components_by_type<BehaviorScript>();
 
 	for (BehaviorScript & behavior_script : behavior_scripts) {
@@ -23,6 +24,8 @@ void ScriptSystem::update() {
 			script->init();
 			script->initialized = true;
 		}
-		script->update();
+
+		duration_t delta_time = timer.get_scaled_fixed_delta_time();
+		script->update(delta_time);
 	}
 }
diff --git a/src/doc/feature/proxy.dox b/src/doc/feature/proxy.dox
new file mode 100644
index 0000000..66bbd2f
--- /dev/null
+++ b/src/doc/feature/proxy.dox
@@ -0,0 +1,43 @@
+// vim:ft=doxygen
+namespace crepe {
+/**
+
+\defgroup feature_proxy Proxy utility
+\ingroup feature
+\brief Use ValueBroker as if it were a regular variable
+
+Proxy provides operators that allow you to use a ValueBroker instance as if it
+were a regular variable. Proxy implements a constructor that allows it to be
+used as a substitute return type for any function that returns ValueBroker.
+
+\see ValueBroker
+\see Proxy
+
+\par Example
+
+```cpp
+#include <crepe/util/Proxy.h>
+#include <crepe/ValueBroker.h>
+
+int calculation(int value) {
+	return 3 * value;
+}
+
+void anywhere() {
+	crepe::ValueBroker<int> foo_handle;
+	crepe::Proxy foo = foo_handle;
+
+	// implicitly calls .set()
+	foo += 10;
+
+	// implicitly calls .get()
+	int out = calculation(foo);
+
+	// explicitly cast (also calls .get())
+	int casted = int(foo);
+}
+
+```
+
+*/
+}
diff --git a/src/doc/feature/savemgr.dox b/src/doc/feature/savemgr.dox
new file mode 100644
index 0000000..6aeab03
--- /dev/null
+++ b/src/doc/feature/savemgr.dox
@@ -0,0 +1,80 @@
+// vim:ft=doxygen
+namespace crepe {
+/**
+
+\defgroup feature_savemgr Save data
+\ingroup feature
+\brief Functions to persistently store and retrieve arbitrary values
+
+The SaveManager may be used to persistently store game state such as player
+progress, statistics, achievements, etc. It works like a key-value store, where
+the key is a string and the value is an arbitrary type.
+
+SaveManager implements the following:
+
+- Storage and retrieval of primitive types and strings.
+- Automatic initialization of the database using default values.
+- The underlying database format is journaled, which reduces the likelihood of
+	players losing save data when an unexpected crash occurs while the SaveManager
+	is writing to disk.
+
+\see SaveManager
+
+\par Example
+
+The SaveManager instance reference may be retrieved by calling \c
+get_save_manager(). This function is available---
+
+- Within (derivatives of) Script
+
+- \todo Within (derivatives of) Scene
+
+- \todo As a public member function of LoopManager
+
+```cpp
+// Retrieve save manager
+crepe::SaveManager & save_manager = get_save_manager();
+```
+
+SaveManager may be used *explicitly*, using the \ref SaveManager::set "set()",
+\ref SaveManager::get "get()" and  \ref SaveManager::has "has()" methods:
+```cpp
+// Check if the key "foo" exists, and initialize it to 3 if it doesn't
+if (!save_manager.has("foo"))
+	save_manager.set<int>("foo", 3);
+// Get value of key "foo"
+int foo = save_manager.get<int>("foo");
+
+// ~~~ arbitrary game code ~~~
+foo += 10;
+// ~~~ arbitrary game code ~~~
+
+// Save "foo" back to database
+save_manager.set<int>("foo", foo);
+```
+
+Alternatively, SaveManager::get may be called with a default value as second
+parameter. This changes its return type to ValueBroker, which acts as a
+read/write handle to the specific key requested, and remembers the key and its
+value type for you:
+```cpp
+// Get a read/write handle to the value stored in key "foo", and initialize it
+// to 3 if it doesn't exist yet
+ValueBroker foo_handle = save_manager.get<int>("foo", 3);
+int foo = foo_handle.get();
+
+// ~~~ arbitrary game code ~~~
+foo += 10;
+// ~~~ arbitrary game code ~~~
+
+// Save back to database
+foo_handle.set(foo);
+```
+
+To further simplify game code, the return value of SaveManager::get may be
+implicitly cast to Proxy instead of ValueBroker. This allows the database value
+to be used as if it were a regular variable. This usage is detailed separately
+in \"\ref feature_proxy\".
+
+*/
+}
diff --git a/src/example/game.cpp b/src/example/game.cpp
index 22effd2..3975650 100644
--- a/src/example/game.cpp
+++ b/src/example/game.cpp
@@ -86,7 +86,7 @@ class MyScript1 : public Script {
 		subscribe<KeyPressEvent>(
 			[this](const KeyPressEvent & ev) -> bool { return this->keypressed(ev); });
 	}
-	void update() {
+	void update(duration_t) {
 		Rigidbody & tf = this->get_component<Rigidbody>();
 		Log::logf("linear_velocity.x {}", tf.data.linear_velocity.x);
 		Log::logf("linear_velocity.y {}", tf.data.linear_velocity.y);
diff --git a/src/example/rendering_particle.cpp b/src/example/rendering_particle.cpp
index 9cf25d7..07cfae2 100644
--- a/src/example/rendering_particle.cpp
+++ b/src/example/rendering_particle.cpp
@@ -39,6 +39,8 @@ public:
 					 .angle_offset = 0,
 					 .position_offset = {0, 1},
 				 });
+		auto & emitter
+			= game_object.add_component<ParticleEmitter>(test_sprite, ParticleEmitter::Data{});
 
 		Sprite & test_sprite1
 			= game_object.add_component<Sprite>(img, Sprite::Data{
diff --git a/src/test/CollisionTest.cpp b/src/test/CollisionTest.cpp
index ff9e7cc..baa95c1 100644
--- a/src/test/CollisionTest.cpp
+++ b/src/test/CollisionTest.cpp
@@ -54,6 +54,7 @@ public:
 	ComponentManager mgr{m};
 	CollisionSystem collision_sys{m};
 	ScriptSystem script_sys{m};
+	LoopTimerManager loop_timer{m};
 
 	GameObject world = mgr.new_object("world", "", {50, 50});
 	GameObject game_object1 = mgr.new_object("object1", "", {50, 50});
diff --git a/src/test/DBTest.cpp b/src/test/DBTest.cpp
index 99dedff..7f2c339 100644
--- a/src/test/DBTest.cpp
+++ b/src/test/DBTest.cpp
@@ -27,3 +27,11 @@ TEST_F(DBTest, Has) {
 	db.set("foo", "bar");
 	EXPECT_EQ(db.has("foo"), true);
 }
+
+TEST_F(DBTest, MultipleKeys) {
+	db.set("foo", "foo");
+	db.set("bar", "bar");
+
+	EXPECT_EQ(db.get("foo"), "foo");
+	EXPECT_EQ(db.get("bar"), "bar");
+}
diff --git a/src/test/InputTest.cpp b/src/test/InputTest.cpp
index 2d844d4..ce8ea44 100644
--- a/src/test/InputTest.cpp
+++ b/src/test/InputTest.cpp
@@ -2,7 +2,6 @@
 
 #include <crepe/manager/ResourceManager.h>
 #include <crepe/system/RenderSystem.h>
-
 #define protected public
 #define private public
 
@@ -214,8 +213,12 @@ TEST_F(InputTest, MouseClick) {
 TEST_F(InputTest, testButtonClick) {
 	GameObject button_obj = mgr.new_object("body", "person", vec2{0, 0}, 0, 1);
 	bool button_clicked = false;
-	std::function<void()> on_click = [&]() { button_clicked = true; };
-	auto & button = button_obj.add_component<Button>(vec2{100, 100}, vec2{0, 0}, on_click);
+	event_manager.subscribe<ButtonPressEvent>([&](const ButtonPressEvent & event) {
+		button_clicked = true;
+		EXPECT_EQ(event.metadata.game_object_id, button_obj.id);
+		return false;
+	});
+	auto & button = button_obj.add_component<Button>(vec2{100, 100}, vec2{0, 0});
 
 	bool hover = false;
 	button.active = true;
@@ -232,25 +235,19 @@ TEST_F(InputTest, testButtonClick) {
 
 TEST_F(InputTest, testButtonHover) {
 	GameObject button_obj = mgr.new_object("body", "person", vec2{0, 0}, 0, 1);
-	bool button_clicked = false;
-	std::function<void()> on_click = [&]() { button_clicked = true; };
-	auto & button = button_obj.add_component<Button>(vec2{100, 100}, vec2{0, 0}, on_click);
+	bool button_hover = false;
+	event_manager.subscribe<ButtonEnterEvent>([&](const ButtonEnterEvent & event) {
+		button_hover = true;
+		EXPECT_EQ(event.metadata.game_object_id, button_obj.id);
+		return false;
+	});
+	event_manager.subscribe<ButtonExitEvent>([&](const ButtonExitEvent & event) {
+		button_hover = false;
+		EXPECT_EQ(event.metadata.game_object_id, button_obj.id);
+		return false;
+	});
+	auto & button = button_obj.add_component<Button>(vec2{100, 100}, vec2{0, 0});
 	button.active = true;
-
-	// Mouse not on button
-	SDL_Event event;
-	SDL_zero(event);
-	event.type = SDL_MOUSEMOTION;
-	event.motion.x = 700;
-	event.motion.y = 700;
-	event.motion.xrel = 10;
-	event.motion.yrel = 10;
-	SDL_PushEvent(&event);
-
-	input_system.update();
-	event_manager.dispatch_events();
-	EXPECT_FALSE(button.hover);
-
 	// Mouse on button
 	SDL_Event hover_event;
 	SDL_zero(hover_event);
@@ -264,4 +261,19 @@ TEST_F(InputTest, testButtonHover) {
 	input_system.update();
 	event_manager.dispatch_events();
 	EXPECT_TRUE(button.hover);
+	EXPECT_TRUE(button_hover);
+	// Mouse not on button
+	SDL_Event event;
+	SDL_zero(event);
+	event.type = SDL_MOUSEMOTION;
+	event.motion.x = 500;
+	event.motion.y = 500;
+	event.motion.xrel = 10;
+	event.motion.yrel = 10;
+	SDL_PushEvent(&event);
+
+	input_system.update();
+	event_manager.dispatch_events();
+	EXPECT_FALSE(button.hover);
+	EXPECT_FALSE(button_hover);
 }
diff --git a/src/test/SaveManagerTest.cpp b/src/test/SaveManagerTest.cpp
index e9b0c29..7609e69 100644
--- a/src/test/SaveManagerTest.cpp
+++ b/src/test/SaveManagerTest.cpp
@@ -27,8 +27,8 @@ TEST_F(SaveManagerTest, ReadWrite) {
 	mgr.set<string>("foo", "bar");
 	ASSERT_TRUE(mgr.has("foo"));
 
-	ValueBroker value = mgr.get<string>("foo");
-	EXPECT_EQ(value.get(), "bar");
+	string value = mgr.get<string>("foo");
+	EXPECT_EQ(value, "bar");
 }
 
 TEST_F(SaveManagerTest, DefaultValue) {
@@ -36,5 +36,16 @@ TEST_F(SaveManagerTest, DefaultValue) {
 
 	ASSERT_EQ(value.get(), 3);
 	value.set(5);
-	ASSERT_EQ(value.get(), 5);
+	EXPECT_EQ(value.get(), 5);
+}
+
+TEST_F(SaveManagerTest, MultipleKeys) {
+	ValueBroker foo = mgr.get<int>("foo", 1);
+	ValueBroker bar = mgr.get<int>("bar", 2);
+
+	EXPECT_EQ(foo.get(), 1);
+	EXPECT_EQ(bar.get(), 2);
+
+	EXPECT_EQ(mgr.get<int>("foo"), 1);
+	EXPECT_EQ(mgr.get<int>("bar"), 2);
 }
diff --git a/src/test/ScriptTest.cpp b/src/test/ScriptTest.cpp
index acdae70..846e398 100644
--- a/src/test/ScriptTest.cpp
+++ b/src/test/ScriptTest.cpp
@@ -28,7 +28,7 @@ void ScriptTest::SetUp() {
 TEST_F(ScriptTest, Default) {
 	MyScript & script = this->script;
 	EXPECT_CALL(script, init()).Times(0);
-	EXPECT_CALL(script, update()).Times(0);
+	EXPECT_CALL(script, update(_)).Times(0);
 }
 
 TEST_F(ScriptTest, UpdateOnce) {
@@ -38,7 +38,7 @@ TEST_F(ScriptTest, UpdateOnce) {
 		InSequence seq;
 
 		EXPECT_CALL(script, init()).Times(1);
-		EXPECT_CALL(script, update()).Times(1);
+		EXPECT_CALL(script, update(_)).Times(1);
 		system.update();
 	}
 
@@ -46,7 +46,7 @@ TEST_F(ScriptTest, UpdateOnce) {
 		InSequence seq;
 
 		EXPECT_CALL(script, init()).Times(0);
-		EXPECT_CALL(script, update()).Times(1);
+		EXPECT_CALL(script, update(_)).Times(1);
 		system.update();
 	}
 }
@@ -59,7 +59,7 @@ TEST_F(ScriptTest, UpdateInactive) {
 		InSequence seq;
 
 		EXPECT_CALL(script, init()).Times(0);
-		EXPECT_CALL(script, update()).Times(0);
+		EXPECT_CALL(script, update(_)).Times(0);
 		behaviorscript.active = false;
 		system.update();
 	}
@@ -68,8 +68,20 @@ TEST_F(ScriptTest, UpdateInactive) {
 		InSequence seq;
 
 		EXPECT_CALL(script, init()).Times(1);
-		EXPECT_CALL(script, update()).Times(1);
+		EXPECT_CALL(script, update(_)).Times(1);
 		behaviorscript.active = true;
 		system.update();
 	}
 }
+
+TEST_F(ScriptTest, SaveManager) {
+	MyScript & script = this->script;
+
+	EXPECT_EQ(&script.get_save_manager(), &this->save_manager);
+}
+
+TEST_F(ScriptTest, LoopTimerManager) {
+	MyScript & script = this->script;
+
+	EXPECT_EQ(&script.get_loop_timer(), &this->loop_timer);
+}
diff --git a/src/test/ScriptTest.h b/src/test/ScriptTest.h
index 31fa7c9..f3dbda4 100644
--- a/src/test/ScriptTest.h
+++ b/src/test/ScriptTest.h
@@ -7,7 +7,10 @@
 #include <crepe/api/Script.h>
 #include <crepe/manager/ComponentManager.h>
 #include <crepe/manager/EventManager.h>
+#include <crepe/manager/LoopTimerManager.h>
+#include <crepe/manager/SaveManager.h>
 #include <crepe/system/ScriptSystem.h>
+
 class ScriptTest : public testing::Test {
 protected:
 	crepe::Mediator mediator;
@@ -17,6 +20,8 @@ public:
 	crepe::ComponentManager component_manager{mediator};
 	crepe::ScriptSystem system{mediator};
 	crepe::EventManager event_mgr{mediator};
+	crepe::LoopTimerManager loop_timer{mediator};
+	crepe::SaveManager save_manager{mediator};
 	crepe::GameObject entity = component_manager.new_object(OBJ_NAME);
 
 	class MyScript : public crepe::Script {
@@ -24,7 +29,7 @@ public:
 
 	public:
 		MOCK_METHOD(void, init, (), (override));
-		MOCK_METHOD(void, update, (), (override));
+		MOCK_METHOD(void, update, (crepe::duration_t), (override));
 	};
 
 	crepe::OptionalRef<crepe::BehaviorScript> behaviorscript;
diff --git a/src/test/main.cpp b/src/test/main.cpp
index ed2aed5..0e1bc75 100644
--- a/src/test/main.cpp
+++ b/src/test/main.cpp
@@ -1,6 +1,7 @@
-#include <crepe/api/Config.h>
 #include <gtest/gtest.h>
 
+#include <crepe/api/Config.h>
+
 using namespace crepe;
 using namespace testing;