feedback but error after conflict

61 files changed, 1998 insertions, 422 deletions

diff --git a/mwe/events/include/event.h b/mwe/events/include/event.h
index ee1bf52..e1b220b 100644
--- a/mwe/events/include/event.h
+++ b/mwe/events/include/event.h
@@ -148,7 +148,7 @@ private:
 };
 class ShutDownEvent : public Event {
 public:
-	ShutDownEvent() : Event("ShutDownEvent") {};
+	ShutDownEvent() : Event("ShutDownEvent"){};
 
 	REGISTER_EVENT_TYPE(ShutDownEvent)
 
diff --git a/src/crepe/CMakeLists.txt b/src/crepe/CMakeLists.txt
index da9d492..6cbb9fe 100644
--- a/src/crepe/CMakeLists.txt
+++ b/src/crepe/CMakeLists.txt
@@ -2,6 +2,7 @@ target_sources(crepe PUBLIC
 	Particle.cpp
 	Component.cpp
 	Collider.cpp
+	Resource.cpp
 )
 
 target_sources(crepe PUBLIC FILE_SET HEADERS FILES
@@ -9,6 +10,7 @@ target_sources(crepe PUBLIC FILE_SET HEADERS FILES
 	Collider.h
 	ValueBroker.h
 	ValueBroker.hpp
+	Resource.h
 )
 
 add_subdirectory(api)
diff --git a/src/crepe/Component.h b/src/crepe/Component.h
index c30419d..eff5a58 100644
--- a/src/crepe/Component.h
+++ b/src/crepe/Component.h
@@ -16,7 +16,12 @@ class Component {
 public:
 	//! Whether the component is active
 	bool active = true;
-	//! The id of the GameObject this component belongs to
+	/**
+	 * \brief The id of the GameObject this component belongs to
+	 *
+	 * \note Only systems are supposed to use this member, but since friend
+	 * relations aren't inherited this needs to be public.
+	 */
 	const game_object_id_t game_object_id;
 
 protected:
@@ -24,7 +29,7 @@ protected:
 	 * \param id The id of the GameObject this component belongs to
 	 */
 	Component(game_object_id_t id);
-	//! Only the ComponentManager can create components
+	//! Only ComponentManager can create components
 	friend class ComponentManager;
 
 	Component(const Component &) = delete;
diff --git a/src/crepe/Resource.cpp b/src/crepe/Resource.cpp
new file mode 100644
index 0000000..27b4c4b
--- /dev/null
+++ b/src/crepe/Resource.cpp
@@ -0,0 +1,5 @@
+#include "Resource.h"
+
+using namespace crepe;
+
+Resource::Resource(const Asset & asset) {}
diff --git a/src/crepe/Resource.h b/src/crepe/Resource.h
new file mode 100644
index 0000000..eceb15b
--- /dev/null
+++ b/src/crepe/Resource.h
@@ -0,0 +1,29 @@
+#pragma once
+
+namespace crepe {
+
+class ResourceManager;
+class Asset;
+
+/**
+ * \brief Resource interface
+ *
+ * Resource is an interface class used to represent a (deserialized) game resource (e.g.
+ * textures, sounds). Resources are always created from \ref Asset "assets" by ResourceManager.
+ *
+ * The game programmer has the ability to use the ResourceManager to keep instances of concrete
+ * resources between scenes, preventing them from being reinstantiated during a scene
+ * transition.
+ */
+class Resource {
+public:
+	Resource(const Asset & src);
+	virtual ~Resource() = default;
+
+	Resource(const Resource &) = delete;
+	Resource(Resource &&) = delete;
+	Resource & operator=(const Resource &) = delete;
+	Resource & operator=(Resource &&) = delete;
+};
+
+} // namespace crepe
diff --git a/src/crepe/api/AI.cpp b/src/crepe/api/AI.cpp
new file mode 100644
index 0000000..2195249
--- /dev/null
+++ b/src/crepe/api/AI.cpp
@@ -0,0 +1,89 @@
+#include <stdexcept>
+#include <type_traits>
+
+#include "AI.h"
+#include "types.h"
+
+namespace crepe {
+
+AI::AI(game_object_id_t id, float max_force) : Component(id), max_force(max_force) {}
+
+void AI::make_circle_path(float radius, const vec2 & center, float start_angle,
+						  bool clockwise) {
+	if (radius <= 0) {
+		throw std::runtime_error("Radius must be greater than 0");
+	}
+
+	// The step size is determined by the radius (step size is in radians)
+	float step = RADIUS_TO_STEP / radius;
+	// Force at least MIN_STEP steps (in case of a small radius)
+	if (step > 2 * M_PI / MIN_STEP) {
+		step = 2 * M_PI / MIN_STEP;
+	}
+	// The path node distance is determined by the step size and the radius
+	this->path_node_distance = radius * step * PATH_NODE_DISTANCE_FACTOR;
+
+	if (clockwise) {
+		for (float i = start_angle; i < 2 * M_PI + start_angle; i += step) {
+			path.push_back(vec2{static_cast<float>(center.x + radius * cos(i)),
+								static_cast<float>(center.y + radius * sin(i))});
+		}
+	} else {
+		for (float i = start_angle; i > start_angle - 2 * M_PI; i -= step) {
+			path.push_back(vec2{static_cast<float>(center.x + radius * cos(i)),
+								static_cast<float>(center.y + radius * sin(i))});
+		}
+	}
+}
+
+void AI::make_oval_path(float radius_x, float radius_y, const vec2 & center, float start_angle,
+						bool clockwise, float rotation) {
+	if (radius_x <= 0 && radius_y <= 0) {
+		throw std::runtime_error("Radius must be greater than 0");
+	}
+
+	float max_radius = std::max(radius_x, radius_y);
+	// The step size is determined by the radius (step size is in radians)
+	float step = RADIUS_TO_STEP / max_radius;
+	// Force at least MIN_STEP steps (in case of a small radius)
+	if (step > 2 * M_PI / MIN_STEP) {
+		step = 2 * M_PI / MIN_STEP;
+	}
+	// The path node distance is determined by the step size and the radius
+	this->path_node_distance = max_radius * step * PATH_NODE_DISTANCE_FACTOR;
+
+	std::function<vec2(vec2, vec2)> rotate_point = [rotation](vec2 point, vec2 center) {
+		float s = sin(rotation);
+		float c = cos(rotation);
+
+		// Translate point back to origin
+		point.x -= center.x;
+		point.y -= center.y;
+
+		// Rotate point
+		float xnew = point.x * c - point.y * s;
+		float ynew = point.x * s + point.y * c;
+
+		// Translate point back
+		point.x = xnew + center.x;
+		point.y = ynew + center.y;
+
+		return point;
+	};
+
+	if (clockwise) {
+		for (float i = start_angle; i < 2 * M_PI + start_angle; i += step) {
+			vec2 point = {static_cast<float>(center.x + radius_x * cos(i)),
+						  static_cast<float>(center.y + radius_y * sin(i))};
+			path.push_back(rotate_point(point, center));
+		}
+	} else {
+		for (float i = start_angle; i > start_angle - 2 * M_PI; i -= step) {
+			vec2 point = {static_cast<float>(center.x + radius_x * cos(i)),
+						  static_cast<float>(center.y + radius_y * sin(i))};
+			path.push_back(rotate_point(point, center));
+		}
+	}
+}
+
+} // namespace crepe
diff --git a/src/crepe/api/AI.h b/src/crepe/api/AI.h
new file mode 100644
index 0000000..c780a91
--- /dev/null
+++ b/src/crepe/api/AI.h
@@ -0,0 +1,128 @@
+#pragma once
+
+#include "Component.h"
+#include "types.h"
+
+namespace crepe {
+
+/**
+ * \brief The AI component is used to control the movement of an entity using AI.
+ *
+ * The AI component can be used to control the movement of an entity. The AI component can be used
+ * to implement different behaviors such as seeking, fleeing, arriving, and path following.
+ */
+class AI : public Component {
+public:
+	//! The different types of behaviors that can be used
+	enum BehaviorTypeMask {
+		SEEK = 0x00002,
+		FLEE = 0x00004,
+		ARRIVE = 0x00008,
+		PATH_FOLLOW = 0x00010,
+	};
+
+public:
+	/**
+	 * \param id The id of the game object
+	 * \param max_force The maximum force that can be applied to the entity
+	 */
+	AI(game_object_id_t id, float max_force);
+
+	/**
+	 * \brief Check if a behavior is on (aka activated)
+	 *
+	 * \param behavior The behavior to check
+	 * \return true if the behavior is on, false otherwise
+	 */
+	bool on(BehaviorTypeMask behavior) const { return (flags & behavior); }
+	//! Turn on the seek behavior
+	void seek_on() { flags |= SEEK; }
+	//! Turn off the seek behavior
+	void seek_off() { flags &= ~SEEK; }
+	//! Turn on the flee behavior
+	void flee_on() { flags |= FLEE; }
+	//! Turn off the flee behavior
+	void flee_off() { flags &= ~FLEE; }
+	//! Turn on the arrive behavior
+	void arrive_on() { flags |= ARRIVE; }
+	//! Turn off the arrive behavior
+	void arrive_off() { flags &= ~ARRIVE; }
+	//! Turn on the path follow behavior
+	void path_follow_on() { flags |= PATH_FOLLOW; }
+	//! Turn off the path follow behavior
+	void path_follow_off() { flags &= ~PATH_FOLLOW; }
+
+	/**
+	 * \brief Add a path node (for the path following behavior)
+	 *
+	 * \note The path is not relative to the entity's position (it is an absolute path)
+	 *
+	 * \param node The path node to add
+	 */
+	void add_path_node(const vec2 & node) { path.push_back(node); }
+	/**
+	 * \brief Make a circle path (for the path following behavior)
+	 *
+	 * \note The path is not relative to the entity's position (it is an absolute path)
+	 *
+	 * \param radius The radius of the circle (in game units)
+	 * \param center The center of the circle (in game units)
+	 * \param start_angle The start angle of the circle (in radians)
+	 * \param clockwise The direction of the circle
+	 */
+	void make_circle_path(float radius, const vec2 & center = {0, 0}, float start_angle = 0,
+						  bool clockwise = true);
+	/**
+	 * \brief Make an oval path (for the path following behavior)
+	 *
+	 * \note The path is not relative to the entity's position (it is an absolute path)
+	 *
+	 * \param radius_x The x radius of the oval (in game units)
+	 * \param radius_y The y radius of the oval (in game units)
+	 * \param center The center of the oval (in game units)
+	 * \param start_angle The start angle of the oval (in radians)
+	 * \param clockwise The direction of the oval
+	 * \param rotation The rotation of the oval (in radians)
+	 */
+	void make_oval_path(float radius_x, float radius_y, const vec2 & center = {0, 0},
+						float start_angle = 0, bool clockwise = true, float rotation = 0);
+
+public:
+	//! The maximum force that can be applied to the entity (higher values will make the entity adjust faster)
+	float max_force;
+
+	//! The target to seek at
+	vec2 seek_target;
+	//! The target to arrive at
+	vec2 arrive_target;
+	//! The target to flee from
+	vec2 flee_target;
+	//! The distance at which the entity will start to flee from the target
+	float square_flee_panic_distance = 200.0f * 200.0f;
+	//! The deceleration rate for the arrive behavior (higher values will make the entity decelerate faster (less overshoot))
+	float arrive_deceleration = 40.0f;
+	//! The path to follow (for the path following behavior)
+	std::vector<vec2> path;
+	//! The distance from the path node at which the entity will move to the next node (automatically set by make_circle_path())
+	float path_node_distance = 400.0f;
+	//! Looping behavior for the path
+	bool path_loop = true;
+
+private:
+	//! The flags for the behaviors
+	int flags = 0;
+	//! The current path index
+	size_t path_index = 0;
+
+	//! The AISystem is the only class that should access the flags and path_index variables
+	friend class AISystem;
+
+	//! The minimum amount of steps for the path following behavior
+	static constexpr int MIN_STEP = 16;
+	//! The radius to step size ratio for the path following behavior
+	static constexpr float RADIUS_TO_STEP = 400.0f;
+	//! The path node distance factor for the path following behavior
+	static constexpr float PATH_NODE_DISTANCE_FACTOR = 0.75f;
+};
+
+} // namespace crepe
diff --git a/src/crepe/api/AssetManager.cpp b/src/crepe/api/AssetManager.cpp
deleted file mode 100644
index 3925758..0000000
--- a/src/crepe/api/AssetManager.cpp
+++ /dev/null
@@ -1,17 +0,0 @@
-#include "util/Log.h"
-
-#include "AssetManager.h"
-
-using namespace crepe;
-
-AssetManager & AssetManager::get_instance() {
-	static AssetManager instance;
-	return instance;
-}
-
-AssetManager::~AssetManager() {
-	dbg_trace();
-	this->asset_cache.clear();
-}
-
-AssetManager::AssetManager() { dbg_trace(); }
diff --git a/src/crepe/api/AssetManager.h b/src/crepe/api/AssetManager.h
deleted file mode 100644
index 3b1cc4b..0000000
--- a/src/crepe/api/AssetManager.h
+++ /dev/null
@@ -1,62 +0,0 @@
-#pragma once
-
-#include <any>
-#include <memory>
-#include <string>
-#include <unordered_map>
-
-namespace crepe {
-
-/**
- * \brief The AssetManager is responsible for storing and managing assets over multiple scenes.
- *
- * The AssetManager ensures that assets are loaded once and can be accessed across different
- * scenes. It caches assets to avoid reloading them every time a scene is loaded. Assets are
- * retained in memory until the AssetManager is destroyed, at which point the cached assets are
- * cleared.
- */
-class AssetManager {
-
-private:
-	//! A cache that holds all the assets, accessible by their file path, over multiple scenes.
-	std::unordered_map<std::string, std::any> asset_cache;
-
-private:
-	AssetManager();
-	virtual ~AssetManager();
-
-public:
-	AssetManager(const AssetManager &) = delete;
-	AssetManager(AssetManager &&) = delete;
-	AssetManager & operator=(const AssetManager &) = delete;
-	AssetManager & operator=(AssetManager &&) = delete;
-
-	/**
-	 * \brief Retrieves the singleton instance of the AssetManager.
-	 *
-	 * \return A reference to the single instance of the AssetManager.
-	 */
-	static AssetManager & get_instance();
-
-public:
-	/**
-	 * \brief Caches an asset by loading it from the given file path.
-	 *
-	 * \param file_path The path to the asset file to load.
-	 * \param reload If true, the asset will be reloaded from the file, even if it is already
-	 * cached.
-	 * \tparam T The type of asset to cache (e.g., texture, sound, etc.).
-	 *
-	 * \return A shared pointer to the cached asset.
-	 *
-	 * This template function caches the asset at the given file path. If the asset is already
-	 * cached and `reload` is false, the existing cached version will be returned. Otherwise, the
-	 * asset will be reloaded and added to the cache.
-	 */
-	template <typename T>
-	std::shared_ptr<T> cache(const std::string & file_path, bool reload = false);
-};
-
-} // namespace crepe
-
-#include "AssetManager.hpp"
diff --git a/src/crepe/api/AssetManager.hpp b/src/crepe/api/AssetManager.hpp
deleted file mode 100644
index 1c0e978..0000000
--- a/src/crepe/api/AssetManager.hpp
+++ /dev/null
@@ -1,22 +0,0 @@
-#pragma once
-
-#include "AssetManager.h"
-
-namespace crepe {
-
-template <typename asset>
-std::shared_ptr<asset> AssetManager::cache(const std::string & file_path, bool reload) {
-	auto it = asset_cache.find(file_path);
-
-	if (!reload && it != asset_cache.end()) {
-		return std::any_cast<std::shared_ptr<asset>>(it->second);
-	}
-
-	std::shared_ptr<asset> new_asset = std::make_shared<asset>(file_path.c_str());
-
-	asset_cache[file_path] = new_asset;
-
-	return new_asset;
-}
-
-} // namespace crepe
diff --git a/src/crepe/api/AudioSource.cpp b/src/crepe/api/AudioSource.cpp
new file mode 100644
index 0000000..7b05cb1
--- /dev/null
+++ b/src/crepe/api/AudioSource.cpp
@@ -0,0 +1,15 @@
+#include "AudioSource.h"
+
+using namespace crepe;
+using namespace std;
+
+AudioSource::AudioSource(game_object_id_t id, const Asset & src)
+	: Component(id),
+	  source(src) {}
+
+void AudioSource::play(bool looping) {
+	this->loop = looping;
+	this->oneshot_play = true;
+}
+
+void AudioSource::stop() { this->oneshot_stop = true; }
diff --git a/src/crepe/api/AudioSource.h b/src/crepe/api/AudioSource.h
new file mode 100644
index 0000000..b20e490
--- /dev/null
+++ b/src/crepe/api/AudioSource.h
@@ -0,0 +1,74 @@
+#pragma once
+
+#include "../Component.h"
+#include "../facade/SoundHandle.h"
+#include "../types.h"
+
+#include "Asset.h"
+#include "GameObject.h"
+
+namespace crepe {
+
+class AudioSystem;
+
+//! Audio source component
+class AudioSource : public Component {
+	//! AudioSource components are handled by AudioSystem
+	friend class AudioSystem;
+
+protected:
+	/**
+	 * \param source Sound sample to load
+	 */
+	AudioSource(game_object_id_t id, const Asset & source);
+	//! Only ComponentManager creates components
+	friend class ComponentManager;
+
+public:
+	// std::unique_ptr needs to be able to destoy this component
+	virtual ~AudioSource() = default;
+
+public:
+	//! Start this audio source
+	void play(bool looping = false);
+	//! Stop this audio source
+	void stop();
+
+public:
+	//! Play when this component becomes active
+	bool play_on_awake = false;
+	//! Repeat the current audio clip during playback
+	bool loop = false;
+	//! Normalized volume (0.0 - 1.0)
+	float volume = 1.0;
+
+private:
+	//! This audio source's clip
+	const Asset source;
+
+	/**
+	 * \name One-shot state variables
+	 *
+	 * These variables trigger function calls when set to true, and are unconditionally reset on
+	 * every system update.
+	 *
+	 * \{
+	 */
+	//! Play this sample
+	bool oneshot_play = false;
+	//! Stop this sample
+	bool oneshot_stop = false;
+	//! \}
+	/**
+	 * \name State diffing variables
+	 * \{
+	 */
+	typeof(active) last_active = false;
+	typeof(volume) last_volume = volume;
+	typeof(loop) last_loop = loop;
+	//! \}
+	//! This source's voice handle
+	SoundHandle voice{};
+};
+
+} // namespace crepe
diff --git a/src/crepe/api/CMakeLists.txt b/src/crepe/api/CMakeLists.txt
index ca4edec..35161e4 100644
--- a/src/crepe/api/CMakeLists.txt
+++ b/src/crepe/api/CMakeLists.txt
@@ -1,5 +1,5 @@
 target_sources(crepe PUBLIC
-	# AudioSource.cpp
+	AudioSource.cpp
 	BehaviorScript.cpp
 	GameObject.cpp
 	Rigidbody.cpp
@@ -7,7 +7,6 @@ target_sources(crepe PUBLIC
 	Transform.cpp
 	Color.cpp
 	Texture.cpp
-	AssetManager.cpp
 	Sprite.cpp
 	Config.cpp
 	Metadata.cpp
@@ -21,10 +20,11 @@ target_sources(crepe PUBLIC
 	Script.cpp
 	Button.cpp
 	UIObject.cpp
+	AI.cpp
 )
 
 target_sources(crepe PUBLIC FILE_SET HEADERS FILES
-	# AudioSource.h
+	AudioSource.h
 	BehaviorScript.h
 	Config.h
 	Script.h
@@ -37,8 +37,6 @@ target_sources(crepe PUBLIC FILE_SET HEADERS FILES
 	Vector2.hpp
 	Color.h
 	Texture.h
-	AssetManager.h
-	AssetManager.hpp
 	Scene.h
 	Metadata.h
 	Camera.h
@@ -52,4 +50,5 @@ target_sources(crepe PUBLIC FILE_SET HEADERS FILES
 	Asset.h
 	Button.h
 	UIObject.h
+	AI.h
 )
diff --git a/src/crepe/api/Config.h b/src/crepe/api/Config.h
index a9745c3..6472270 100644
--- a/src/crepe/api/Config.h
+++ b/src/crepe/api/Config.h
@@ -15,20 +15,10 @@ namespace crepe {
  * modified *before* execution is handed over from the game programmer to the engine (i.e. the
  * main loop is started).
  */
-class Config final {
-public:
+struct Config final {
 	//! Retrieve handle to global Config instance
 	static Config & get_instance();
 
-private:
-	Config() = default;
-	~Config() = default;
-	Config(const Config &) = default;
-	Config(Config &&) = default;
-	Config & operator=(const Config &) = default;
-	Config & operator=(Config &&) = default;
-
-public:
 	//! Logging-related settings
 	struct {
 		/**
@@ -86,6 +76,12 @@ public:
 		 */
 		std::string root_pattern = ".crepe-root";
 	} asset;
+
+	//! Audio system settings
+	struct {
+		//! Max amount of simultanious voices
+		unsigned int voices = 32;
+	} audio;
 };
 
 } // namespace crepe
diff --git a/src/crepe/api/LoopManager.cpp b/src/crepe/api/LoopManager.cpp
index a1da8be..4ca9928 100644
--- a/src/crepe/api/LoopManager.cpp
+++ b/src/crepe/api/LoopManager.cpp
@@ -1,6 +1,7 @@
 #include "../facade/SDLContext.h"
-#include "../manager/EventManager.h"
+#include "../system/AISystem.h"
 #include "../system/AnimatorSystem.h"
+#include "../system/AudioSystem.h"
 #include "../system/CollisionSystem.h"
 #include "../system/InputSystem.h"
 #include "../system/ParticleSystem.h"
@@ -8,6 +9,7 @@
 #include "../system/RenderSystem.h"
 #include "../system/ScriptSystem.h"
 #include "../manager/EventManager.h"
+#include "../manager/LoopTimerManager.h"
 #include "../util/Log.h"
 
 #include "LoopManager.h"
@@ -25,6 +27,8 @@ LoopManager::LoopManager() {
 	this->load_system<InputSystem>();
 	this->event_manager.subscribe<ShutDownEvent>(
 		[this](const ShutDownEvent & event) { return this->on_shutdown(event); });
+	this->load_system<AudioSystem>();
+	this->load_system<AISystem>();
 }
 void LoopManager::start() {
 	this->setup();
@@ -62,8 +66,10 @@ void LoopManager::fixed_update() {
 	this->get_system<InputSystem>().update();
 	this->event_manager.dispatch_events();
 	this->get_system<ScriptSystem>().update();
+	this->get_system<AISystem>().update();
 	this->get_system<PhysicsSystem>().update();
 	this->get_system<CollisionSystem>().update();
+	this->get_system<AudioSystem>().update();
 }
 
 // will be called every frame
diff --git a/src/crepe/api/LoopManager.h b/src/crepe/api/LoopManager.h
index 2319d65..0110695 100644
--- a/src/crepe/api/LoopManager.h
+++ b/src/crepe/api/LoopManager.h
@@ -7,6 +7,8 @@
 #include "../manager/EventManager.h"
 #include "../manager/LoopTimerManager.h"
 #include "../manager/Mediator.h"
+#include "../manager/ResourceManager.h"
+#include "../manager/SaveManager.h"
 #include "../manager/SceneManager.h"
 #include "../system/System.h"
 
@@ -79,6 +81,10 @@ 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};
 
 	//! SDL context \todo no more singletons!
 	SDLContext & sdl_context = SDLContext::get_instance();
diff --git a/src/crepe/api/Script.cpp b/src/crepe/api/Script.cpp
index 4091fd4..753a9e3 100644
--- a/src/crepe/api/Script.cpp
+++ b/src/crepe/api/Script.cpp
@@ -8,8 +8,7 @@ using namespace crepe;
 using namespace std;
 
 Script::~Script() {
-	Mediator & mediator = this->mediator;
-	EventManager & mgr = mediator.event_manager;
+	EventManager & mgr = this->mediator->event_manager;
 	for (auto id : this->listeners) {
 		mgr.unsubscribe(id);
 	}
@@ -21,7 +20,8 @@ void Script::subscribe(const EventHandler<CollisionEvent> & callback) {
 }
 
 void Script::set_next_scene(const string & name) {
-	Mediator & mediator = this->mediator;
-	SceneManager & mgr = mediator.scene_manager;
+	SceneManager & mgr = this->mediator->scene_manager;
 	mgr.set_next_scene(name);
 }
+
+SaveManager & Script::get_save_manager() const { return this->mediator->save_manager; }
diff --git a/src/crepe/api/Script.h b/src/crepe/api/Script.h
index d99ab0e..668e5d1 100644
--- a/src/crepe/api/Script.h
+++ b/src/crepe/api/Script.h
@@ -86,6 +86,25 @@ protected:
 	RefVector<T> get_components() const;
 
 	/**
+	 * \copydoc ComponentManager::get_components_by_id
+	 * \see ComponentManager::get_components_by_id
+	 */
+	template <typename T>
+	RefVector<T> get_components_by_id(game_object_id_t id) const;
+	/**
+	 * \copydoc ComponentManager::get_components_by_name
+	 * \see ComponentManager::get_components_by_name
+	 */
+	template <typename T>
+	RefVector<T> get_components_by_name(const std::string & name) const;
+	/**
+	 * \copydoc ComponentManager::get_components_by_tag
+	 * \see ComponentManager::get_components_by_tag
+	 */
+	template <typename T>
+	RefVector<T> get_components_by_tag(const std::string & tag) const;
+
+	/**
 	 * \brief Log a message using Log::logf
 	 *
 	 * \tparam Args Log::logf parameters
@@ -113,6 +132,9 @@ protected:
 	 */
 	void set_next_scene(const std::string & name);
 
+	//! Retrieve SaveManager reference
+	SaveManager & get_save_manager() const;
+
 	//! \}
 
 private:
diff --git a/src/crepe/api/Script.hpp b/src/crepe/api/Script.hpp
index 45f1ff1..225a51c 100644
--- a/src/crepe/api/Script.hpp
+++ b/src/crepe/api/Script.hpp
@@ -20,10 +20,7 @@ T & Script::get_component() const {
 
 template <typename T>
 RefVector<T> Script::get_components() const {
-	Mediator & mediator = this->mediator;
-	ComponentManager & mgr = mediator.component_manager;
-
-	return mgr.get_components_by_id<T>(this->game_object_id);
+	return this->get_components_by_id<T>(this->game_object_id);
 }
 
 template <typename... Args>
@@ -34,8 +31,7 @@ void Script::logf(Args &&... args) {
 template <typename EventType>
 void Script::subscribe_internal(const EventHandler<EventType> & callback,
 								event_channel_t channel) {
-	Mediator & mediator = this->mediator;
-	EventManager & mgr = mediator.event_manager;
+	EventManager & mgr = this->mediator->event_manager;
 	subscription_t listener = mgr.subscribe<EventType>(
 		[this, callback](const EventType & data) -> bool {
 			bool & active = this->active;
@@ -56,4 +52,26 @@ void Script::subscribe(const EventHandler<EventType> & callback) {
 	this->subscribe_internal(callback, EventManager::CHANNEL_ALL);
 }
 
+template <typename T>
+RefVector<T> Script::get_components_by_id(game_object_id_t id) const {
+	Mediator & mediator = this->mediator;
+	ComponentManager & mgr = mediator.component_manager;
+
+	return mgr.get_components_by_id<T>(id);
+}
+template <typename T>
+RefVector<T> Script::get_components_by_name(const std::string & name) const {
+	Mediator & mediator = this->mediator;
+	ComponentManager & mgr = mediator.component_manager;
+
+	return mgr.get_components_by_name<T>(name);
+}
+template <typename T>
+RefVector<T> Script::get_components_by_tag(const std::string & tag) const {
+	Mediator & mediator = this->mediator;
+	ComponentManager & mgr = mediator.component_manager;
+
+	return mgr.get_components_by_tag<T>(tag);
+}
+
 } // namespace crepe
diff --git a/src/crepe/api/Vector2.h b/src/crepe/api/Vector2.h
index c278c87..bf9d124 100644
--- a/src/crepe/api/Vector2.h
+++ b/src/crepe/api/Vector2.h
@@ -66,6 +66,30 @@ struct Vector2 {
 
 	//! Checks if this vector is not equal to another vector.
 	bool operator!=(const Vector2<T> & other) const;
+
+	//! Truncates the vector to a maximum length.
+	void truncate(T max);
+
+	//! Normalizes the vector (resulting in vector with a length of 1).
+	void normalize();
+
+	//! Returns the length of the vector.
+	T length() const;
+
+	//! Returns the squared length of the vector.
+	T length_squared() const;
+
+	//! Returns the dot product (inwendig product) of this vector and another vector.
+	T dot(const Vector2<T> & other) const;
+
+	//! Returns the distance between this vector and another vector.
+	T distance(const Vector2<T> & other) const;
+
+	//! Returns the squared distance between this vector and another vector.
+	T distance_squared(const Vector2<T> & other) const;
+
+	//! Returns the perpendicular vector to this vector.
+	Vector2 perpendicular() const;
 };
 
 } // namespace crepe
diff --git a/src/crepe/api/Vector2.hpp b/src/crepe/api/Vector2.hpp
index cad15f8..ff53cb0 100644
--- a/src/crepe/api/Vector2.hpp
+++ b/src/crepe/api/Vector2.hpp
@@ -1,5 +1,7 @@
 #pragma once
 
+#include <cmath>
+
 #include "Vector2.h"
 
 namespace crepe {
@@ -115,4 +117,50 @@ bool Vector2<T>::operator!=(const Vector2<T> & other) const {
 	return !(*this == other);
 }
 
+template <class T>
+void Vector2<T>::truncate(T max) {
+	if (length() > max) {
+		normalize();
+		*this *= max;
+	}
+}
+
+template <class T>
+void Vector2<T>::normalize() {
+	T len = length();
+	if (len > 0) {
+		*this /= len;
+	}
+}
+
+template <class T>
+T Vector2<T>::length() const {
+	return std::sqrt(x * x + y * y);
+}
+
+template <class T>
+T Vector2<T>::length_squared() const {
+	return x * x + y * y;
+}
+
+template <class T>
+T Vector2<T>::dot(const Vector2<T> & other) const {
+	return x * other.x + y * other.y;
+}
+
+template <class T>
+T Vector2<T>::distance(const Vector2<T> & other) const {
+	return (*this - other).length();
+}
+
+template <class T>
+T Vector2<T>::distance_squared(const Vector2<T> & other) const {
+	return (*this - other).length_squared();
+}
+
+template <class T>
+Vector2<T> Vector2<T>::perpendicular() const {
+	return {-y, x};
+}
+
 } // namespace crepe
diff --git a/src/crepe/facade/Sound.cpp b/src/crepe/facade/Sound.cpp
index 4d3abf5..ad50637 100644
--- a/src/crepe/facade/Sound.cpp
+++ b/src/crepe/facade/Sound.cpp
@@ -1,59 +1,13 @@
+#include "../api/Asset.h"
 #include "../util/Log.h"
 
 #include "Sound.h"
-#include "SoundContext.h"
 
 using namespace crepe;
 using namespace std;
 
-Sound::Sound(unique_ptr<Asset> res) {
+Sound::Sound(const Asset & src) : Resource(src) {
+	this->sample.load(src.get_path().c_str());
 	dbg_trace();
-	this->load(std::move(res));
-}
-
-Sound::Sound(const char * src) {
-	dbg_trace();
-	this->load(make_unique<Asset>(src));
-}
-
-void Sound::load(unique_ptr<Asset> res) { this->sample.load(res->get_path().c_str()); }
-
-void Sound::play() {
-	SoundContext & ctx = SoundContext::get_instance();
-	if (ctx.engine.getPause(this->handle)) {
-		// resume if paused
-		ctx.engine.setPause(this->handle, false);
-	} else {
-		// or start new sound
-		this->handle = ctx.engine.play(this->sample, this->volume);
-		ctx.engine.setLooping(this->handle, this->looping);
-	}
-}
-
-void Sound::pause() {
-	SoundContext & ctx = SoundContext::get_instance();
-	if (ctx.engine.getPause(this->handle)) return;
-	ctx.engine.setPause(this->handle, true);
-}
-
-void Sound::rewind() {
-	SoundContext & ctx = SoundContext::get_instance();
-	if (!ctx.engine.isValidVoiceHandle(this->handle)) return;
-	ctx.engine.seek(this->handle, 0);
-}
-
-void Sound::set_volume(float volume) {
-	this->volume = volume;
-
-	SoundContext & ctx = SoundContext::get_instance();
-	if (!ctx.engine.isValidVoiceHandle(this->handle)) return;
-	ctx.engine.setVolume(this->handle, this->volume);
-}
-
-void Sound::set_looping(bool looping) {
-	this->looping = looping;
-
-	SoundContext & ctx = SoundContext::get_instance();
-	if (!ctx.engine.isValidVoiceHandle(this->handle)) return;
-	ctx.engine.setLooping(this->handle, this->looping);
 }
+Sound::~Sound() { dbg_trace(); }
diff --git a/src/crepe/facade/Sound.h b/src/crepe/facade/Sound.h
index ee43d94..85d141b 100644
--- a/src/crepe/facade/Sound.h
+++ b/src/crepe/facade/Sound.h
@@ -1,84 +1,30 @@
 #pragma once
 
-#include <memory>
 #include <soloud/soloud.h>
 #include <soloud/soloud_wav.h>
 
-#include "../api/Asset.h"
+#include "../Resource.h"
 
 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.
+ * 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:
-	/**
-	 * \brief Pause this sample
-	 *
-	 * Pauses this sound if it is playing, or does nothing if it is already paused. The playhead
-	 * position is saved, such that calling \c play() after this function makes the sound resume.
-	 */
-	void pause();
-	/**
-	 * \brief Play this sample
-	 *
-	 * Resume playback if this sound is paused, or start from the beginning of the sample.
-	 *
-	 * \note This class only saves a reference to the most recent 'voice' of this sound. Calling
-	 * \c play() while the sound is already playing causes multiple instances of the sample to
-	 * play simultaniously. The sample started last is the one that is controlled afterwards.
-	 */
-	void play();
-	/**
-	 * \brief Reset playhead position
-	 *
-	 * Resets the playhead position so that calling \c play() after this function makes it play
-	 * from the start of the sample. If the sound is not paused before calling this function,
-	 * this function will stop playback.
-	 */
-	void rewind();
-	/**
-	 * \brief Set playback volume / gain
-	 *
-	 * \param volume  Volume (0 = muted, 1 = full volume)
-	 */
-	void set_volume(float volume);
-	/**
-	 * \brief Get playback volume / gain
-	 *
-	 * \return Volume
-	 */
-	float get_volume() const { return this->volume; }
-	/**
-	 * \brief Set looping behavior for this sample
-	 *
-	 * \param looping  Looping behavior (false = one-shot, true = loop)
-	 */
-	void set_looping(bool looping);
-	/**
-	 * \brief Get looping behavior
-	 *
-	 * \return true if looping, false if one-shot
-	 */
-	bool get_looping() const { return this->looping; }
-
+class Sound : public Resource {
 public:
-	Sound(const char * src);
-	Sound(std::unique_ptr<Asset> res);
-
-private:
-	void load(std::unique_ptr<Asset> res);
+	Sound(const Asset & src);
+	~Sound(); // dbg_trace
 
 private:
+	//! Deserialized resource (soloud)
 	SoLoud::Wav sample;
-	SoLoud::handle handle;
-
-	float volume = 1.0f;
-	bool looping = false;
+	//! SoundContext uses \c sample
+	friend class SoundContext;
 };
 
 } // namespace crepe
diff --git a/src/crepe/facade/SoundContext.cpp b/src/crepe/facade/SoundContext.cpp
index deb2b62..b1f8cb3 100644
--- a/src/crepe/facade/SoundContext.cpp
+++ b/src/crepe/facade/SoundContext.cpp
@@ -4,17 +4,33 @@
 
 using namespace crepe;
 
-SoundContext & SoundContext::get_instance() {
-	static SoundContext instance;
-	return instance;
-}
-
 SoundContext::SoundContext() {
 	dbg_trace();
-	engine.init();
+	this->engine.init();
+	this->engine.setMaxActiveVoiceCount(this->config.audio.voices);
 }
 
 SoundContext::~SoundContext() {
 	dbg_trace();
-	engine.deinit();
+	this->engine.deinit();
+}
+
+SoundHandle SoundContext::play(Sound & resource) {
+	SoLoud::handle real_handle = this->engine.play(resource.sample, 1.0f);
+	SoundHandle handle = this->next_handle;
+	this->registry[handle] = real_handle;
+	this->next_handle++;
+	return handle;
+}
+
+void SoundContext::stop(const SoundHandle & handle) {
+	this->engine.stop(this->registry[handle]);
+}
+
+void SoundContext::set_volume(const SoundHandle & handle, float volume) {
+	this->engine.setVolume(this->registry[handle], volume);
+}
+
+void SoundContext::set_loop(const SoundHandle & handle, bool loop) {
+	this->engine.setLooping(this->registry[handle], loop);
 }
diff --git a/src/crepe/facade/SoundContext.h b/src/crepe/facade/SoundContext.h
index d703c16..d986c59 100644
--- a/src/crepe/facade/SoundContext.h
+++ b/src/crepe/facade/SoundContext.h
@@ -2,30 +2,80 @@
 
 #include <soloud/soloud.h>
 
+#include "../api/Config.h"
+
 #include "Sound.h"
+#include "SoundHandle.h"
 
 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.
+ * 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 {
-private:
-	// singleton
+public:
 	SoundContext();
 	virtual ~SoundContext();
+
 	SoundContext(const SoundContext &) = delete;
 	SoundContext(SoundContext &&) = delete;
 	SoundContext & operator=(const SoundContext &) = delete;
 	SoundContext & operator=(SoundContext &&) = delete;
 
+	/**
+	 * \brief Play a sample
+	 *
+	 * Plays a Sound from the beginning of the sample and returns a handle to control it later.
+	 *
+	 * \param resource Sound instance to play
+	 *
+	 * \returns Handle to control this voice
+	 */
+	virtual SoundHandle play(Sound & resource);
+	/**
+	 * \brief Stop a voice immediately if it is still playing
+	 *
+	 * \note This function does nothing if the handle is invalid or if the sound is already
+	 * stopped / finished playing.
+	 *
+	 * \param handle Voice handle returned by SoundContext::play
+	 */
+	virtual void stop(const SoundHandle & handle);
+	/**
+	 * \brief Change the volume of a voice
+	 *
+	 * \note This function does nothing if the handle is invalid or if the sound is already
+	 * stopped / finished playing.
+	 *
+	 * \param handle Voice handle returned by SoundContext::play
+	 * \param volume New gain value (0=silent, 1=default)
+	 */
+	virtual void set_volume(const SoundHandle & handle, float volume);
+	/**
+	 * \brief Set the looping behavior of a voice
+	 *
+	 * \note This function does nothing if the handle is invalid or if the sound is already
+	 * stopped / finished playing.
+	 *
+	 * \param handle Voice handle returned by SoundContext::play
+	 * \param loop Looping behavior (false=oneshot, true=loop)
+	 */
+	virtual void set_loop(const SoundHandle & handle, bool loop);
+
 private:
-	static SoundContext & get_instance();
+	//! Abstracted class
 	SoLoud::Soloud engine;
-	friend class Sound;
+
+	//! Config reference
+	Config & config = Config::get_instance();
+
+	//! Sound handle registry
+	std::unordered_map<SoundHandle, SoLoud::handle> registry;
+	//! Unique handle counter
+	SoundHandle next_handle = 0;
 };
 
 } // namespace crepe
diff --git a/src/crepe/facade/SoundHandle.h b/src/crepe/facade/SoundHandle.h
new file mode 100644
index 0000000..b7925fc
--- /dev/null
+++ b/src/crepe/facade/SoundHandle.h
@@ -0,0 +1,12 @@
+#pragma once
+
+#include <cstddef>
+
+namespace crepe {
+
+/**
+ * \brief Voice handle returned by
+ */
+typedef size_t SoundHandle;
+
+} // namespace crepe
diff --git a/src/crepe/manager/CMakeLists.txt b/src/crepe/manager/CMakeLists.txt
index 29d6df0..f73e165 100644
--- a/src/crepe/manager/CMakeLists.txt
+++ b/src/crepe/manager/CMakeLists.txt
@@ -5,6 +5,7 @@ target_sources(crepe PUBLIC
 	SaveManager.cpp
 	SceneManager.cpp
 	LoopTimerManager.cpp
+	ResourceManager.cpp
 )
 
 target_sources(crepe PUBLIC FILE_SET HEADERS FILES
@@ -18,5 +19,7 @@ target_sources(crepe PUBLIC FILE_SET HEADERS FILES
 	SceneManager.h
 	SceneManager.hpp
 	LoopTimerManager.h
+	ResourceManager.h
+	ResourceManager.hpp
 )
 
diff --git a/src/crepe/manager/ComponentManager.cpp b/src/crepe/manager/ComponentManager.cpp
index 80cf8b4..df30d27 100644
--- a/src/crepe/manager/ComponentManager.cpp
+++ b/src/crepe/manager/ComponentManager.cpp
@@ -1,4 +1,5 @@
 #include "../api/GameObject.h"
+#include "../api/Metadata.h"
 #include "../types.h"
 #include "../util/Log.h"
 
@@ -61,3 +62,13 @@ GameObject ComponentManager::new_object(const string & name, const string & tag,
 void ComponentManager::set_persistent(game_object_id_t id, bool persistent) {
 	this->persistent[id] = persistent;
 }
+
+set<game_object_id_t> ComponentManager::get_objects_by_name(const string & name) const {
+	return this->get_objects_by_predicate<Metadata>(
+		[name](const Metadata & data) { return data.name == name; });
+}
+
+set<game_object_id_t> ComponentManager::get_objects_by_tag(const string & tag) const {
+	return this->get_objects_by_predicate<Metadata>(
+		[tag](const Metadata & data) { return data.tag == tag; });
+}
diff --git a/src/crepe/manager/ComponentManager.h b/src/crepe/manager/ComponentManager.h
index 44429d9..19a8e81 100644
--- a/src/crepe/manager/ComponentManager.h
+++ b/src/crepe/manager/ComponentManager.h
@@ -1,6 +1,7 @@
 #pragma once
 
 #include <memory>
+#include <set>
 #include <typeindex>
 #include <unordered_map>
 #include <vector>
@@ -134,8 +135,77 @@ public:
 	 */
 	template <typename T>
 	RefVector<T> get_components_by_type() const;
+	/**
+	 * \brief Get all components of a specific type on a GameObject with name \c name
+	 * 
+	 * \tparam T The type of the component
+	 * \param name Metadata::name for the same game_object_id as the returned components
+	 * \return Components matching criteria
+	 */
+	template <typename T>
+	RefVector<T> get_components_by_name(const std::string & name) const;
+	/**
+	 * \brief Get all components of a specific type on a GameObject with tag \c tag
+	 * 
+	 * \tparam T The type of the component
+	 * \param name Metadata::tag for the same game_object_id as the returned components
+	 * \return Components matching criteria
+	 */
+	template <typename T>
+	RefVector<T> get_components_by_tag(const std::string & tag) const;
+
+private:
+	/**
+	 * \brief Get object IDs by predicate function
+	 *
+	 * This function calls the predicate function \c pred for all components matching type \c T,
+	 * and adds their parent game_object_id to a \c std::set if the predicate returns true.
+	 *
+	 * \tparam T The type of the component to check the predicate against
+	 * \param pred Predicate function
+	 *
+	 * \note The predicate function may be called for multiple components with the same \c
+	 * game_object_id. In this case, the ID is added if *any* call returns \c true.
+	 *
+	 * \returns game_object_id for all components where the predicate returned true
+	 */
+	template <typename T>
+	std::set<game_object_id_t>
+	get_objects_by_predicate(const std::function<bool(const T &)> & pred) const;
+
+	/**
+	 * \brief Get components of type \c T for multiple game object IDs
+	 *
+	 * \tparam T The type of the components to return
+	 * \param ids The object IDs
+	 *
+	 * \return All components matching type \c T and one of the IDs in \c ids
+	 */
+	template <typename T>
+	RefVector<T> get_components_by_ids(const std::set<game_object_id_t> & ids) const;
+
+	/**
+	 * \brief Get object IDs for objects with name \c name
+	 *
+	 * \param name Object name to match
+	 * \returns Object IDs where Metadata::name is equal to \c name
+	 */
+	std::set<game_object_id_t> get_objects_by_name(const std::string & name) const;
+	/**
+	 * \brief Get object IDs for objects with tag \c tag
+	 *
+	 * \param tag Object tag to match
+	 * \returns Object IDs where Metadata::tag is equal to \c tag
+	 */
+	std::set<game_object_id_t> get_objects_by_tag(const std::string & tag) const;
 
 private:
+	//! By Component \c std::type_index (readability helper type)
+	template <typename T>
+	using by_type = std::unordered_map<std::type_index, T>;
+	//! By \c game_object_id index (readability helper type)
+	template <typename T>
+	using by_id_index = std::vector<T>;
 	/**
 	 * \brief The components
 	 *
@@ -146,8 +216,7 @@ private:
 	 * The first vector is for the ids of the GameObjects and the second vector is for the
 	 * components (because a GameObject might have multiple components).
 	 */
-	std::unordered_map<std::type_index, std::vector<std::vector<std::unique_ptr<Component>>>>
-		components;
+	by_type<by_id_index<std::vector<std::unique_ptr<Component>>>> components;
 
 	//! Persistent flag for each GameObject
 	std::unordered_map<game_object_id_t, bool> persistent;
diff --git a/src/crepe/manager/ComponentManager.hpp b/src/crepe/manager/ComponentManager.hpp
index ffb38ec..9e70865 100644
--- a/src/crepe/manager/ComponentManager.hpp
+++ b/src/crepe/manager/ComponentManager.hpp
@@ -95,32 +95,25 @@ template <typename T>
 RefVector<T> ComponentManager::get_components_by_id(game_object_id_t id) const {
 	using namespace std;
 
-	// Determine the type of T (this is used as the key of the unordered_map<>)
-	type_index type = typeid(T);
-
-	// Create an empty vector<>
-	RefVector<T> component_vector;
-
-	if (this->components.find(type) == this->components.end()) return component_vector;
-
-	// Get the correct vector<>
-	const vector<vector<unique_ptr<Component>>> & component_array = this->components.at(type);
-
-	// Make sure that the id (that we are looking for) is within the boundaries of the vector<>
-	if (id >= component_array.size()) return component_vector;
-
-	// Loop trough the whole vector<>
-	for (const unique_ptr<Component> & component_ptr : component_array[id]) {
-		// Cast the unique_ptr to a raw pointer
-		T * casted_component = static_cast<T *>(component_ptr.get());
-
-		if (casted_component == nullptr) continue;
+	static_assert(is_base_of<Component, T>::value,
+				  "get_components_by_id must recieve a derivative class of Component");
 
-		// Add the dereferenced raw pointer to the vector<>
-		component_vector.push_back(*casted_component);
+	type_index type = typeid(T);
+	if (!this->components.contains(type)) return {};
+
+	const by_id_index<vector<unique_ptr<Component>>> & components_by_id
+		= this->components.at(type);
+	if (id >= components_by_id.size()) return {};
+
+	RefVector<T> out = {};
+	const vector<unique_ptr<Component>> & components = components_by_id.at(id);
+	for (auto & component_ptr : components) {
+		if (component_ptr == nullptr) continue;
+		Component & component = *component_ptr.get();
+		out.push_back(static_cast<T &>(component));
 	}
 
-	return component_vector;
+	return out;
 }
 
 template <typename T>
@@ -158,4 +151,46 @@ RefVector<T> ComponentManager::get_components_by_type() const {
 	return component_vector;
 }
 
+template <typename T>
+std::set<game_object_id_t>
+ComponentManager::get_objects_by_predicate(const std::function<bool(const T &)> & pred) const {
+	using namespace std;
+
+	set<game_object_id_t> objects = {};
+	RefVector<T> components = this->get_components_by_type<T>();
+
+	for (const T & component : components) {
+		game_object_id_t id = dynamic_cast<const Component &>(component).game_object_id;
+		if (objects.contains(id)) continue;
+		if (!pred(component)) continue;
+		objects.insert(id);
+	}
+
+	return objects;
+}
+
+template <typename T>
+RefVector<T>
+ComponentManager::get_components_by_ids(const std::set<game_object_id_t> & ids) const {
+	using namespace std;
+
+	RefVector<T> out = {};
+	for (game_object_id_t id : ids) {
+		RefVector<T> components = get_components_by_id<T>(id);
+		out.insert(out.end(), components.begin(), components.end());
+	}
+
+	return out;
+}
+
+template <typename T>
+RefVector<T> ComponentManager::get_components_by_name(const std::string & name) const {
+	return this->get_components_by_ids<T>(this->get_objects_by_name(name));
+}
+
+template <typename T>
+RefVector<T> ComponentManager::get_components_by_tag(const std::string & tag) const {
+	return this->get_components_by_ids<T>(this->get_objects_by_tag(tag));
+}
+
 } // namespace crepe
diff --git a/src/crepe/manager/Mediator.h b/src/crepe/manager/Mediator.h
index ad51cc6..dfb37dc 100644
--- a/src/crepe/manager/Mediator.h
+++ b/src/crepe/manager/Mediator.h
@@ -11,6 +11,8 @@ namespace crepe {
 
 class ComponentManager;
 class SceneManager;
+class SaveManager;
+class ResourceManager;
 
 class LoopTimerManager;
 class EventManager;
@@ -31,7 +33,8 @@ struct Mediator {
 	OptionalRef<SceneManager> scene_manager;
 	OptionalRef<EventManager> event_manager;
 	OptionalRef<LoopTimerManager> loop_timer;
-	OptionalRef<SaveManager> save_manager = SaveManager::get_instance();
+	OptionalRef<SaveManager> save_manager;
+	OptionalRef<ResourceManager> resource_manager;
 	OptionalRef<SDLContext> sdl_context = SDLContext::get_instance();
 };
 
diff --git a/src/crepe/manager/ResourceManager.cpp b/src/crepe/manager/ResourceManager.cpp
new file mode 100644
index 0000000..7c01808
--- /dev/null
+++ b/src/crepe/manager/ResourceManager.cpp
@@ -0,0 +1,30 @@
+#include "util/Log.h"
+
+#include "ResourceManager.h"
+
+using namespace crepe;
+using namespace std;
+
+ResourceManager::ResourceManager(Mediator & mediator) : Manager(mediator) {
+	mediator.resource_manager = *this;
+	dbg_trace();
+}
+ResourceManager::~ResourceManager() { dbg_trace(); }
+
+void ResourceManager::clear() {
+	std::erase_if(this->resources, [](const pair<const Asset, CacheEntry> & pair) {
+		const CacheEntry & entry = pair.second;
+		return entry.persistent == false;
+	});
+}
+
+void ResourceManager::clear_all() { this->resources.clear(); }
+
+void ResourceManager::set_persistent(const Asset & asset, bool persistent) {
+	this->get_entry(asset).persistent = persistent;
+}
+
+ResourceManager::CacheEntry & ResourceManager::get_entry(const Asset & asset) {
+	if (!this->resources.contains(asset)) this->resources[asset] = {};
+	return this->resources.at(asset);
+}
diff --git a/src/crepe/manager/ResourceManager.h b/src/crepe/manager/ResourceManager.h
new file mode 100644
index 0000000..84b275d
--- /dev/null
+++ b/src/crepe/manager/ResourceManager.h
@@ -0,0 +1,78 @@
+#pragma once
+
+#include <memory>
+#include <unordered_map>
+
+#include "../Resource.h"
+#include "../api/Asset.h"
+
+#include "Manager.h"
+
+namespace crepe {
+
+/**
+ * \brief Owner of concrete Resource instances
+ * 
+ * ResourceManager caches concrete Resource instances per Asset. Concrete resources are
+ * destroyed at the end of scenes by default, unless the game programmer marks them as
+ * persistent.
+ */
+class ResourceManager : public Manager {
+public:
+	ResourceManager(Mediator & mediator);
+	virtual ~ResourceManager(); // dbg_trace
+
+private:
+	//! Cache entry
+	struct CacheEntry {
+		//! Concrete resource instance
+		std::unique_ptr<Resource> resource = nullptr;
+		//! Prevent ResourceManager::clear from removing this entry
+		bool persistent = false;
+	};
+	//! Internal cache
+	std::unordered_map<const Asset, CacheEntry> resources;
+	/**
+	 * \brief Ensure a cache entry exists for this asset and return a mutable reference to it
+	 *
+	 * \param asset Asset the concrete resource is instantiated from
+	 *
+	 * \returns Mutable reference to cache entry
+	 */
+	CacheEntry & get_entry(const Asset & asset);
+
+public:
+	/**
+	 * \brief Mark a resource as persistent (i.e. used across multiple scenes)
+	 *
+	 * \param asset Asset the concrete resource is instantiated from
+	 * \param persistent Whether this resource is persistent (true=keep, false=destroy)
+	 */
+	void set_persistent(const Asset & asset, bool persistent);
+
+	/**
+	 * \brief Retrieve reference to concrete Resource by Asset
+	 *
+	 * \param asset Asset the concrete resource is instantiated from
+	 * \tparam Resource Concrete derivative of Resource
+	 *
+	 * This class instantiates the concrete resource if it is not yet stored in the internal
+	 * cache, or returns a reference to the cached resource if it already exists.
+	 *
+	 * \returns Reference to concrete resource
+	 *
+	 * \throws std::runtime_error if the \c Resource parameter does not match with the actual
+	 * type of the resource stored in the cache for this Asset
+	 */
+	template <typename Resource>
+	Resource & get(const Asset & asset);
+
+	//! Clear non-persistent resources from cache
+	void clear();
+	//! Clear all resources from cache regardless of persistence
+	void clear_all();
+};
+
+} // namespace crepe
+
+#include "ResourceManager.hpp"
diff --git a/src/crepe/manager/ResourceManager.hpp b/src/crepe/manager/ResourceManager.hpp
new file mode 100644
index 0000000..5167d71
--- /dev/null
+++ b/src/crepe/manager/ResourceManager.hpp
@@ -0,0 +1,27 @@
+#pragma once
+
+#include <format>
+
+#include "ResourceManager.h"
+
+namespace crepe {
+
+template <typename T>
+T & ResourceManager::get(const Asset & asset) {
+	using namespace std;
+	static_assert(is_base_of<Resource, T>::value,
+				  "cache must recieve a derivative class of Resource");
+
+	CacheEntry & entry = this->get_entry(asset);
+	if (entry.resource == nullptr) entry.resource = make_unique<T>(asset);
+
+	T * concrete_resource = dynamic_cast<T *>(entry.resource.get());
+	if (concrete_resource == nullptr)
+		throw runtime_error(format("ResourceManager: mismatch between requested type and "
+								   "actual type of resource ({})",
+								   asset.get_path()));
+
+	return *concrete_resource;
+}
+
+} // namespace crepe
diff --git a/src/crepe/manager/SaveManager.cpp b/src/crepe/manager/SaveManager.cpp
index d4ed1c1..691ea2f 100644
--- a/src/crepe/manager/SaveManager.cpp
+++ b/src/crepe/manager/SaveManager.cpp
@@ -1,13 +1,25 @@
 #include "../ValueBroker.h"
 #include "../api/Config.h"
 #include "../facade/DB.h"
-#include "../util/Log.h"
 
 #include "SaveManager.h"
 
 using namespace std;
 using namespace crepe;
 
+SaveManager::SaveManager(Mediator & mediator) : Manager(mediator) {
+	mediator.save_manager = *this;
+}
+
+DB & SaveManager::get_db() {
+	if (this->db == nullptr) {
+		Config & cfg = Config::get_instance();
+		this->db
+			= {new DB(cfg.savemgr.location), [](void * db) { delete static_cast<DB *>(db); }};
+	}
+	return *static_cast<DB *>(this->db.get());
+}
+
 template <>
 string SaveManager::serialize(const string & value) const noexcept {
 	return value;
@@ -90,22 +102,6 @@ int32_t SaveManager::deserialize(const string & value) const noexcept {
 	return deserialize<int64_t>(value);
 }
 
-SaveManager::SaveManager() { dbg_trace(); }
-
-SaveManager & SaveManager::get_instance() {
-	dbg_trace();
-	static SaveManager instance;
-	return instance;
-}
-
-DB & SaveManager::get_db() {
-	Config & cfg = Config::get_instance();
-	// TODO: make this path relative to XDG_DATA_HOME on Linux and whatever the
-	// default equivalent is on Windows using some third party library
-	static DB db(cfg.savemgr.location);
-	return db;
-}
-
 bool SaveManager::has(const string & key) {
 	DB & db = this->get_db();
 	return db.has(key);
@@ -155,7 +151,8 @@ ValueBroker<T> SaveManager::get(const string & key) {
 	return {
 		[this, key](const T & target) { this->set<T>(key, target); },
 		[this, key, value]() mutable -> const T & {
-			value = this->deserialize<T>(this->get_db().get(key));
+			DB & db = this->get_db();
+			value = this->deserialize<T>(db.get(key));
 			return value;
 		},
 	};
diff --git a/src/crepe/manager/SaveManager.h b/src/crepe/manager/SaveManager.h
index 3d8c852..61a978d 100644
--- a/src/crepe/manager/SaveManager.h
+++ b/src/crepe/manager/SaveManager.h
@@ -1,9 +1,12 @@
 #pragma once
 
+#include <functional>
 #include <memory>
 
 #include "../ValueBroker.h"
 
+#include "Manager.h"
+
 namespace crepe {
 
 class DB;
@@ -18,7 +21,7 @@ class DB;
  *
  * The underlying database is a key-value store.
  */
-class SaveManager {
+class SaveManager : public Manager {
 public:
 	/**
 	 * \brief Get a read/write reference to a value and initialize it if it does not yet exist
@@ -63,8 +66,8 @@ public:
 	 */
 	bool has(const std::string & key);
 
-private:
-	SaveManager();
+public:
+	SaveManager(Mediator & mediator);
 	virtual ~SaveManager() = default;
 
 private:
@@ -89,26 +92,13 @@ private:
 	template <typename T>
 	T deserialize(const std::string & value) const noexcept;
 
-public:
-	// singleton
-	static SaveManager & get_instance();
-	SaveManager(const SaveManager &) = delete;
-	SaveManager(SaveManager &&) = delete;
-	SaveManager & operator=(const SaveManager &) = delete;
-	SaveManager & operator=(SaveManager &&) = delete;
+protected:
+	//! Create or return DB
+	virtual DB & get_db();
 
 private:
-	/**
-	 * \brief Create an instance of DB and return its reference
-	 *
-	 * \returns DB instance
-	 *
-	 * This function exists because DB is a facade class, which can't directly be used in the API
-	 * without workarounds
-	 *
-	 * TODO: better solution
-	 */
-	static DB & get_db();
+	//! Database
+	std::unique_ptr<void, std::function<void(void *)>> db = nullptr;
 };
 
 } // namespace crepe
diff --git a/src/crepe/system/AISystem.cpp b/src/crepe/system/AISystem.cpp
new file mode 100644
index 0000000..e2e36a5
--- /dev/null
+++ b/src/crepe/system/AISystem.cpp
@@ -0,0 +1,185 @@
+#include <algorithm>
+#include <cmath>
+
+#include "api/LoopTimer.h"
+#include "manager/ComponentManager.h"
+#include "manager/Mediator.h"
+
+#include "AISystem.h"
+
+using namespace crepe;
+
+void AISystem::update() {
+	const Mediator & mediator = this->mediator;
+	ComponentManager & mgr = mediator.component_manager;
+	RefVector<AI> ai_components = mgr.get_components_by_type<AI>();
+
+	//TODO: Use fixed loop dt (this is not available at master at the moment)
+	double dt = LoopTimer::get_instance().get_delta_time();
+
+	// Loop through all AI components
+	for (AI & ai : ai_components) {
+		if (!ai.active) {
+			continue;
+		}
+
+		RefVector<Rigidbody> rigidbodies
+			= mgr.get_components_by_id<Rigidbody>(ai.game_object_id);
+		if (rigidbodies.empty()) {
+			throw std::runtime_error(
+				"AI component must be attached to a GameObject with a Rigidbody component");
+		}
+		Rigidbody & rigidbody = rigidbodies.front().get();
+		if (!rigidbody.active) {
+			continue;
+		}
+		if (rigidbody.data.mass <= 0) {
+			throw std::runtime_error("Mass must be greater than 0");
+		}
+
+		// Calculate the force to apply to the entity
+		vec2 force = this->calculate(ai, rigidbody);
+		// Calculate the acceleration (using the above calculated force)
+		vec2 acceleration = force / rigidbody.data.mass;
+		// Finally, update Rigidbody's velocity
+		rigidbody.data.linear_velocity += acceleration * dt;
+	}
+}
+
+vec2 AISystem::calculate(AI & ai, const Rigidbody & rigidbody) {
+	const Mediator & mediator = this->mediator;
+	ComponentManager & mgr = mediator.component_manager;
+	RefVector<Transform> transforms = mgr.get_components_by_id<Transform>(ai.game_object_id);
+	Transform & transform = transforms.front().get();
+
+	vec2 force;
+
+	// Run all the behaviors that are on, and stop if the force gets too high
+	if (ai.on(AI::BehaviorTypeMask::FLEE)) {
+		vec2 force_to_add = this->flee(ai, rigidbody, transform);
+
+		if (!this->accumulate_force(ai, force, force_to_add)) {
+			return force;
+		}
+	}
+	if (ai.on(AI::BehaviorTypeMask::ARRIVE)) {
+		vec2 force_to_add = this->arrive(ai, rigidbody, transform);
+
+		if (!this->accumulate_force(ai, force, force_to_add)) {
+			return force;
+		}
+	}
+	if (ai.on(AI::BehaviorTypeMask::SEEK)) {
+		vec2 force_to_add = this->seek(ai, rigidbody, transform);
+
+		if (!this->accumulate_force(ai, force, force_to_add)) {
+			return force;
+		}
+	}
+	if (ai.on(AI::BehaviorTypeMask::PATH_FOLLOW)) {
+		vec2 force_to_add = this->path_follow(ai, rigidbody, transform);
+
+		if (!this->accumulate_force(ai, force, force_to_add)) {
+			return force;
+		}
+	}
+
+	return force;
+}
+
+bool AISystem::accumulate_force(const AI & ai, vec2 & running_total, vec2 & force_to_add) {
+	float magnitude = running_total.length();
+	float magnitude_remaining = ai.max_force - magnitude;
+
+	if (magnitude_remaining <= 0.0f) {
+		// If the force is already at/above the max force, return false
+		return false;
+	}
+
+	float magnitude_to_add = force_to_add.length();
+	if (magnitude_to_add < magnitude_remaining) {
+		// If the force to add is less than the remaining force, add it
+		running_total += force_to_add;
+	} else {
+		// If the force to add is greater than the remaining force, add a fraction of it
+		force_to_add.normalize();
+		running_total += force_to_add * magnitude_remaining;
+	}
+
+	return true;
+}
+
+vec2 AISystem::seek(const AI & ai, const Rigidbody & rigidbody,
+					const Transform & transform) const {
+	// Calculate the desired velocity
+	vec2 desired_velocity = ai.seek_target - transform.position;
+	desired_velocity.normalize();
+	desired_velocity *= rigidbody.data.max_linear_velocity;
+
+	return desired_velocity - rigidbody.data.linear_velocity;
+}
+
+vec2 AISystem::flee(const AI & ai, const Rigidbody & rigidbody,
+					const Transform & transform) const {
+	// Calculate the desired velocity if the entity is within the panic distance
+	vec2 desired_velocity = transform.position - ai.flee_target;
+	if (desired_velocity.length_squared() > ai.square_flee_panic_distance) {
+		return vec2{0, 0};
+	}
+	desired_velocity.normalize();
+	desired_velocity *= rigidbody.data.max_linear_velocity;
+
+	return desired_velocity - rigidbody.data.linear_velocity;
+}
+
+vec2 AISystem::arrive(const AI & ai, const Rigidbody & rigidbody,
+					  const Transform & transform) const {
+	// Calculate the desired velocity (taking into account the deceleration rate)
+	vec2 to_target = ai.arrive_target - transform.position;
+	float distance = to_target.length();
+	if (distance > 0.0f) {
+		if (ai.arrive_deceleration <= 0.0f) {
+			throw std::runtime_error("Deceleration rate must be greater than 0");
+		}
+
+		float speed = distance / ai.arrive_deceleration;
+		speed = std::min(speed, rigidbody.data.max_linear_velocity.length());
+		vec2 desired_velocity = to_target * (speed / distance);
+
+		return desired_velocity - rigidbody.data.linear_velocity;
+	}
+
+	return vec2{0, 0};
+}
+
+vec2 AISystem::path_follow(AI & ai, const Rigidbody & rigidbody, const Transform & transform) {
+	if (ai.path.empty()) {
+		return vec2{0, 0};
+	}
+
+	// Get the target node
+	vec2 target = ai.path.at(ai.path_index);
+	// Calculate the force to apply to the entity
+	vec2 to_target = target - transform.position;
+	if (to_target.length_squared() > ai.path_node_distance * ai.path_node_distance) {
+		// If the entity is not close enough to the target node, seek it
+		ai.seek_target = target;
+		ai.arrive_target = target;
+	} else {
+		// If the entity is close enough to the target node, move to the next node
+		ai.path_index++;
+		if (ai.path_index >= ai.path.size()) {
+			if (ai.path_loop) {
+				// If the path is looping, reset the path index
+				ai.path_index = 0;
+			} else {
+				// If the path is not looping, arrive at the last node
+				ai.path_index = ai.path.size() - 1;
+				return this->arrive(ai, rigidbody, transform);
+			}
+		}
+	}
+
+	// Seek the target node
+	return this->seek(ai, rigidbody, transform);
+}
diff --git a/src/crepe/system/AISystem.h b/src/crepe/system/AISystem.h
new file mode 100644
index 0000000..d5f8a8e
--- /dev/null
+++ b/src/crepe/system/AISystem.h
@@ -0,0 +1,81 @@
+#pragma once
+
+#include "api/AI.h"
+#include "api/Rigidbody.h"
+
+#include "System.h"
+#include "api/Transform.h"
+#include "types.h"
+
+namespace crepe {
+
+/**
+ * \brief The AISystem is used to control the movement of entities using AI.
+ *
+ * The AISystem is used to control the movement of entities using AI. The AISystem can be used to
+ * implement different behaviors such as seeking, fleeing, arriving, and path following.
+ */
+class AISystem : public System {
+public:
+	using System::System;
+
+	//! Update the AI system
+	void update() override;
+
+private:
+	/**
+	 * \brief Calculate the total force to apply to the entity
+	 *
+	 * \param ai The AI component
+	 * \param rigidbody The Rigidbody component
+	 */
+	vec2 calculate(AI & ai, const Rigidbody & rigidbody);
+	/**
+	 * \brief Accumulate the force to apply to the entity
+	 *
+	 * \param ai The AI component
+	 * \param running_total The running total of the force
+	 * \param force_to_add The force to add
+	 * \return true if the force was added, false otherwise
+	 */
+	bool accumulate_force(const AI & ai, vec2 & running_total, vec2 & force_to_add);
+
+	/**
+	 * \brief Calculate the seek force
+	 *
+	 * \param ai The AI component
+	 * \param rigidbody The Rigidbody component
+	 * \param transform The Transform component
+	 * \return The seek force
+	 */
+	vec2 seek(const AI & ai, const Rigidbody & rigidbody, const Transform & transform) const;
+	/**
+	 * \brief Calculate the flee force
+	 *
+	 * \param ai The AI component
+	 * \param rigidbody The Rigidbody component
+	 * \param transform The Transform component
+	 * \return The flee force
+	 */
+	vec2 flee(const AI & ai, const Rigidbody & rigidbody, const Transform & transform) const;
+	/**
+	 * \brief Calculate the arrive force
+	 *
+	 * \param ai The AI component
+	 * \param rigidbody The Rigidbody component
+	 * \param transform The Transform component
+	 * \return The arrive force
+	 */
+	vec2 arrive(const AI & ai, const Rigidbody & rigidbody, const Transform & transform) const;
+	/**
+	 * \brief Calculate the path follow force
+	 *
+	 * \param ai The AI component
+	 * \param rigidbody The Rigidbody component
+	 * \param transform The Transform component
+	 * \return The path follow force
+	 */
+	vec2 path_follow(AI & ai, const Rigidbody & rigidbody, const Transform & transform);
+};
+
+} // namespace crepe
diff --git a/src/crepe/system/AudioSystem.cpp b/src/crepe/system/AudioSystem.cpp
new file mode 100644
index 0000000..b1aa0f8
--- /dev/null
+++ b/src/crepe/system/AudioSystem.cpp
@@ -0,0 +1,62 @@
+#include "AudioSystem.h"
+
+#include "../manager/ComponentManager.h"
+#include "../manager/ResourceManager.h"
+#include "../types.h"
+
+using namespace crepe;
+using namespace std;
+
+void AudioSystem::update() {
+	ComponentManager & component_manager = this->mediator.component_manager;
+	ResourceManager & resource_manager = this->mediator.resource_manager;
+	RefVector<AudioSource> components
+		= component_manager.get_components_by_type<AudioSource>();
+
+	for (AudioSource & component : components) {
+		Sound & resource = resource_manager.get<Sound>(component.source);
+
+		this->diff_update(component, resource);
+
+		this->update_last(component);
+	}
+}
+
+void AudioSystem::diff_update(AudioSource & component, Sound & resource) {
+	SoundContext & context = this->get_context();
+
+	if (component.active != component.last_active) {
+		if (!component.active) {
+			context.stop(component.voice);
+			return;
+		}
+		if (component.play_on_awake) component.oneshot_play = true;
+	}
+	if (!component.active) return;
+
+	if (component.oneshot_play) {
+		component.voice = context.play(resource);
+		component.oneshot_play = false;
+	}
+	if (component.oneshot_stop) {
+		context.stop(component.voice);
+		component.oneshot_stop = false;
+	}
+	if (component.volume != component.last_volume) {
+		context.set_volume(component.voice, component.volume);
+	}
+	if (component.loop != component.last_loop) {
+		context.set_loop(component.voice, component.loop);
+	}
+}
+
+void AudioSystem::update_last(AudioSource & component) {
+	component.last_active = component.active;
+	component.last_loop = component.loop;
+	component.last_volume = component.volume;
+}
+
+SoundContext & AudioSystem::get_context() {
+	if (this->context == nullptr) this->context = make_unique<SoundContext>();
+	return *this->context.get();
+}
diff --git a/src/crepe/system/AudioSystem.h b/src/crepe/system/AudioSystem.h
new file mode 100644
index 0000000..2ddc443
--- /dev/null
+++ b/src/crepe/system/AudioSystem.h
@@ -0,0 +1,51 @@
+#pragma once
+
+#include "../api/AudioSource.h"
+#include "../facade/Sound.h"
+#include "../facade/SoundContext.h"
+
+#include "System.h"
+
+namespace crepe {
+
+class AudioSystem : public System {
+public:
+	using System::System;
+	void update() override;
+
+private:
+	/**
+	 * \brief Update `last_*` members of \c component
+	 *
+	 * Copies all component properties stored for comparison between AudioSystem::update() calls
+	 *
+	 * \param component AudioSource component to update
+	 */
+	void update_last(AudioSource & component);
+
+	/**
+	 * \brief Compare update component
+	 *
+	 * Compares properties of \c component and \c data, and calls SoundContext functions where
+	 * applicable.
+	 *
+	 * \param component AudioSource component to update
+	 * \param resource Sound instance for AudioSource's Asset
+	 */
+	void diff_update(AudioSource & component, Sound & resource);
+
+protected:
+	/**
+	 * \brief Get SoundContext
+	 *
+	 * SoundContext is retrieved through this function instead of being a direct member of
+	 * AudioSystem to aid with testability.
+	 */
+	virtual SoundContext & get_context();
+
+private:
+	//! SoundContext
+	std::unique_ptr<SoundContext> context = nullptr;
+};
+
+} // namespace crepe
diff --git a/src/crepe/system/CMakeLists.txt b/src/crepe/system/CMakeLists.txt
index 95f6e33..0e2db76 100644
--- a/src/crepe/system/CMakeLists.txt
+++ b/src/crepe/system/CMakeLists.txt
@@ -5,8 +5,10 @@ target_sources(crepe PUBLIC
 	PhysicsSystem.cpp
 	CollisionSystem.cpp
 	RenderSystem.cpp
+	AudioSystem.cpp
 	AnimatorSystem.cpp
 	InputSystem.cpp
+	AISystem.cpp
 )
 
 target_sources(crepe PUBLIC FILE_SET HEADERS FILES
@@ -15,6 +17,8 @@ target_sources(crepe PUBLIC FILE_SET HEADERS FILES
 	PhysicsSystem.h
 	CollisionSystem.h
 	RenderSystem.h
+	AudioSystem.h
 	AnimatorSystem.h
 	InputSystem.h
+	AISystem.h
 )
diff --git a/src/crepe/system/System.cpp b/src/crepe/system/System.cpp
index f68549b..ecc740d 100644
--- a/src/crepe/system/System.cpp
+++ b/src/crepe/system/System.cpp
@@ -1,7 +1,5 @@
-#include "../util/Log.h"
-
 #include "System.h"
 
 using namespace crepe;
 
-System::System(const Mediator & mediator) : mediator(mediator) { dbg_trace(); }
+System::System(const Mediator & mediator) : mediator(mediator) {}
diff --git a/src/crepe/util/OptionalRef.h b/src/crepe/util/OptionalRef.h
index 3201667..1b2cb3f 100644
--- a/src/crepe/util/OptionalRef.h
+++ b/src/crepe/util/OptionalRef.h
@@ -25,7 +25,7 @@ public:
 	 */
 	OptionalRef<T> & operator=(T & ref);
 	/**
-	 * \brief Retrieve this reference
+	 * \brief Retrieve this reference (cast)
 	 *
 	 * \returns Internal reference if it is set
 	 *
@@ -33,6 +33,14 @@ public:
 	 */
 	operator T &() const;
 	/**
+	 * \brief Retrieve this reference (member access)
+	 *
+	 * \returns Internal reference if it is set
+	 *
+	 * \throws std::runtime_error if this function is called while the reference it not set
+	 */
+	T * operator->() const;
+	/**
 	 * \brief Check if this reference is not empty
 	 *
 	 * \returns `true` if reference is set, or `false` if it is not
diff --git a/src/crepe/util/OptionalRef.hpp b/src/crepe/util/OptionalRef.hpp
index 4608c9e..5e36b3a 100644
--- a/src/crepe/util/OptionalRef.hpp
+++ b/src/crepe/util/OptionalRef.hpp
@@ -19,6 +19,13 @@ OptionalRef<T>::operator T &() const {
 }
 
 template <typename T>
+T * OptionalRef<T>::operator->() const {
+	if (this->ref == nullptr)
+		throw std::runtime_error("OptionalRef: attempt to dereference nullptr");
+	return this->ref;
+}
+
+template <typename T>
 OptionalRef<T> & OptionalRef<T>::operator=(T & ref) {
 	this->ref = &ref;
 	return *this;
diff --git a/src/example/AITest.cpp b/src/example/AITest.cpp
new file mode 100644
index 0000000..f4efc9f
--- /dev/null
+++ b/src/example/AITest.cpp
@@ -0,0 +1,86 @@
+#include <crepe/api/AI.h>
+#include <crepe/api/BehaviorScript.h>
+#include <crepe/api/Camera.h>
+#include <crepe/api/Color.h>
+#include <crepe/api/GameObject.h>
+#include <crepe/api/LoopManager.h>
+#include <crepe/api/Rigidbody.h>
+#include <crepe/api/Scene.h>
+#include <crepe/api/Script.h>
+#include <crepe/api/Sprite.h>
+#include <crepe/api/Texture.h>
+#include <crepe/manager/Mediator.h>
+#include <crepe/types.h>
+
+using namespace crepe;
+using namespace std;
+
+class Script1 : public Script {
+	bool shutdown(const ShutDownEvent & event) {
+		// Very dirty way of shutting down the game
+		throw "ShutDownEvent";
+		return true;
+	}
+
+	bool mousemove(const MouseMoveEvent & event) {
+		/*RefVector<AI> aivec = this->get_components<AI>();
+		AI & ai = aivec.front().get();
+		ai.flee_target
+			= vec2{static_cast<float>(event.mouse_x), static_cast<float>(event.mouse_y)};*/
+		return true;
+	}
+
+	void init() {
+		subscribe<ShutDownEvent>(
+			[this](const ShutDownEvent & ev) -> bool { return this->shutdown(ev); });
+		subscribe<MouseMoveEvent>(
+			[this](const MouseMoveEvent & ev) -> bool { return this->mousemove(ev); });
+	}
+};
+
+class Scene1 : public Scene {
+public:
+	void load_scene() override {
+		Mediator & mediator = this->mediator;
+		ComponentManager & mgr = mediator.component_manager;
+
+		GameObject game_object1 = mgr.new_object("", "", vec2{0, 0}, 0, 1);
+		GameObject game_object2 = mgr.new_object("", "", vec2{0, 0}, 0, 1);
+
+		Texture img = Texture("asset/texture/test_ap43.png");
+		game_object1.add_component<Sprite>(img, Sprite::Data{
+													.color = Color::MAGENTA,
+													.flip = Sprite::FlipSettings{false, false},
+													.sorting_in_layer = 1,
+													.order_in_layer = 1,
+													.size = {0, 195},
+												});
+		AI & ai = game_object1.add_component<AI>(3000);
+		// ai.arrive_on();
+		// ai.flee_on();
+		ai.path_follow_on();
+		ai.make_oval_path(500, 1000, {0, -1000}, 1.5708, true);
+		ai.make_oval_path(1000, 500, {0, 500}, 4.7124, false);
+		game_object1.add_component<Rigidbody>(Rigidbody::Data{
+			.mass = 0.1f,
+			.max_linear_velocity = {40, 40},
+		});
+		game_object1.add_component<BehaviorScript>().set_script<Script1>();
+
+		game_object2.add_component<Camera>(ivec2{1080, 720}, vec2{5000, 5000},
+										   Camera::Data{
+											   .bg_color = Color::WHITE,
+											   .zoom = 1,
+										   });
+	}
+
+	string get_name() const override { return "Scene1"; }
+};
+
+int main() {
+	LoopManager engine;
+	engine.add_scene<Scene1>();
+	engine.start();
+
+	return 0;
+}
diff --git a/src/example/CMakeLists.txt b/src/example/CMakeLists.txt
index 8ef71bb..187ed46 100644
--- a/src/example/CMakeLists.txt
+++ b/src/example/CMakeLists.txt
@@ -16,8 +16,7 @@ function(add_example target_name)
 	add_dependencies(examples ${target_name})
 endfunction()
 
-add_example(asset_manager)
-add_example(savemgr)
 add_example(rendering_particle)
 add_example(game)
 add_example(button)
+add_example(AITest)
diff --git a/src/example/asset_manager.cpp b/src/example/asset_manager.cpp
deleted file mode 100644
index 917b547..0000000
--- a/src/example/asset_manager.cpp
+++ /dev/null
@@ -1,36 +0,0 @@
-#include <crepe/api/AssetManager.h>
-#include <crepe/api/Texture.h>
-#include <crepe/facade/Sound.h>
-
-using namespace crepe;
-
-int main() {
-
-	// this needs to be called before the asset manager otherwise the destructor of sdl is not in
-	// the right order
-	{ Texture test("../asset/texture/img.png"); }
-	// FIXME: make it so the issue described by the above comment is not possible (i.e. the order
-	// in which internal classes are instantiated should not impact the way the engine works).
-
-	auto & mgr = AssetManager::get_instance();
-
-	{
-		// TODO: [design] the Sound class can't be directly included by the user as it includes
-		// SoLoud headers.
-		auto bgm = mgr.cache<Sound>("../mwe/audio/bgm.ogg");
-		auto sfx1 = mgr.cache<Sound>("../mwe/audio/sfx1.wav");
-		auto sfx2 = mgr.cache<Sound>("../mwe/audio/sfx2.wav");
-
-		auto img = mgr.cache<Texture>("../asset/texture/img.png");
-		auto img1 = mgr.cache<Texture>("../asset/texture/second.png");
-	}
-
-	{
-		auto bgm = mgr.cache<Sound>("../mwe/audio/bgm.ogg");
-		auto sfx1 = mgr.cache<Sound>("../mwe/audio/sfx1.wav");
-		auto sfx2 = mgr.cache<Sound>("../mwe/audio/sfx2.wav");
-
-		auto img = mgr.cache<Texture>("../asset/texture/img.png");
-		auto img1 = mgr.cache<Texture>("../asset/texture/second.png");
-	}
-}
diff --git a/src/example/savemgr.cpp b/src/example/savemgr.cpp
deleted file mode 100644
index 65c4a34..0000000
--- a/src/example/savemgr.cpp
+++ /dev/null
@@ -1,44 +0,0 @@
-/** \file
- * 
- * Standalone example for usage of the save manager
- */
-
-#include <cassert>
-#include <crepe/api/Config.h>
-#include <crepe/api/SaveManager.h>
-#include <crepe/util/Log.h>
-#include <crepe/util/Proxy.h>
-
-using namespace crepe;
-
-// unrelated setup code
-int _ = []() {
-	// make sure all log messages get printed
-	auto & cfg = Config::get_instance();
-	cfg.log.level = Log::Level::TRACE;
-
-	return 0; // satisfy compiler
-}();
-
-int main() {
-	const char * key = "mygame.test";
-
-	SaveManager & mgr = SaveManager::get_instance();
-
-	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 = {}", mgr.get<int>(key).get());
-	prop.set(1);
-	dbg_logf("val = {}", mgr.get<int>(key).get());
-	val = 2;
-	dbg_logf("val = {}", mgr.get<int>(key).get());
-	mgr.set<int>(key, 3);
-	dbg_logf("val = {}", mgr.get<int>(key).get());
-
-	dbg_logf("has key = {}", mgr.has(key));
-	assert(true == mgr.has(key));
-
-	return 0;
-}
diff --git a/src/test/AudioTest.cpp b/src/test/AudioTest.cpp
new file mode 100644
index 0000000..48bba1b
--- /dev/null
+++ b/src/test/AudioTest.cpp
@@ -0,0 +1,161 @@
+#include <gmock/gmock.h>
+#include <gtest/gtest.h>
+
+#include <crepe/api/AudioSource.h>
+#include <crepe/api/GameObject.h>
+#include <crepe/manager/ComponentManager.h>
+#include <crepe/manager/ResourceManager.h>
+#include <crepe/system/AudioSystem.h>
+
+using namespace std;
+using namespace std::chrono_literals;
+using namespace crepe;
+using namespace testing;
+
+class AudioTest : public Test {
+private:
+	class TestSoundContext : public SoundContext {
+	public:
+		MOCK_METHOD(SoundHandle, play, (Sound & resource), (override));
+		MOCK_METHOD(void, stop, (const SoundHandle &), (override));
+		MOCK_METHOD(void, set_volume, (const SoundHandle &, float), (override));
+		MOCK_METHOD(void, set_loop, (const SoundHandle &, bool), (override));
+	};
+
+	class TestAudioSystem : public AudioSystem {
+	public:
+		using AudioSystem::AudioSystem;
+		StrictMock<TestSoundContext> context;
+		virtual SoundContext & get_context() { return this->context; }
+	};
+
+private:
+	Mediator mediator;
+	ComponentManager component_manager{mediator};
+	ResourceManager resource_manager{mediator};
+
+public:
+	TestAudioSystem system{mediator};
+	TestSoundContext & context = system.context;
+
+private:
+	GameObject entity = component_manager.new_object("name");
+
+public:
+	AudioSource & component = entity.add_component<AudioSource>("mwe/audio/bgm.ogg");
+};
+
+TEST_F(AudioTest, Default) {
+	EXPECT_CALL(context, play(_)).Times(0);
+	EXPECT_CALL(context, stop(_)).Times(0);
+	EXPECT_CALL(context, set_volume(_, _)).Times(0);
+	EXPECT_CALL(context, set_loop(_, _)).Times(0);
+	system.update();
+}
+
+TEST_F(AudioTest, Play) {
+	system.update();
+
+	{
+		InSequence seq;
+
+		EXPECT_CALL(context, play(_)).Times(0);
+		component.play();
+	}
+
+	{
+		InSequence seq;
+
+		EXPECT_CALL(context, play(_)).Times(1);
+		system.update();
+	}
+}
+
+TEST_F(AudioTest, Stop) {
+	system.update();
+
+	{
+		InSequence seq;
+
+		EXPECT_CALL(context, stop(_)).Times(0);
+		component.stop();
+	}
+
+	{
+		InSequence seq;
+
+		EXPECT_CALL(context, stop(_)).Times(1);
+		system.update();
+	}
+}
+
+TEST_F(AudioTest, Volume) {
+	system.update();
+
+	{
+		InSequence seq;
+
+		EXPECT_CALL(context, set_volume(_, _)).Times(0);
+		component.volume += 0.2;
+	}
+
+	{
+		InSequence seq;
+
+		EXPECT_CALL(context, set_volume(_, component.volume)).Times(1);
+		system.update();
+	}
+}
+
+TEST_F(AudioTest, Looping) {
+	system.update();
+
+	{
+		InSequence seq;
+
+		EXPECT_CALL(context, set_loop(_, _)).Times(0);
+		component.loop = !component.loop;
+	}
+
+	{
+		InSequence seq;
+
+		EXPECT_CALL(context, set_loop(_, component.loop)).Times(1);
+		system.update();
+	}
+}
+
+TEST_F(AudioTest, StopOnDeactivate) {
+	system.update();
+
+	{
+		InSequence seq;
+
+		EXPECT_CALL(context, stop(_)).Times(1);
+		component.active = false;
+		system.update();
+	}
+}
+
+TEST_F(AudioTest, PlayOnActive) {
+	component.active = false;
+	component.play_on_awake = true;
+	system.update();
+
+	{
+		InSequence seq;
+
+		EXPECT_CALL(context, play(_)).Times(1);
+		component.active = true;
+		system.update();
+	}
+}
+
+TEST_F(AudioTest, PlayImmediately) {
+	component.play_on_awake = false;
+	component.play();
+
+	EXPECT_CALL(context, play(_)).Times(1);
+
+	system.update();
+}
diff --git a/src/test/CMakeLists.txt b/src/test/CMakeLists.txt
index a6d3387..11b4ca9 100644
--- a/src/test/CMakeLists.txt
+++ b/src/test/CMakeLists.txt
@@ -4,7 +4,9 @@ target_sources(test_main PUBLIC
 	PhysicsTest.cpp
 	ScriptTest.cpp
 	ParticleTest.cpp
+	AudioTest.cpp
 	AssetTest.cpp
+	ResourceManagerTest.cpp
 	OptionalRefTest.cpp
 	RenderSystemTest.cpp
 	EventTest.cpp
@@ -19,4 +21,7 @@ target_sources(test_main PUBLIC
 	ScriptEventTest.cpp
 	ScriptSceneTest.cpp
 	Profiling.cpp
+	SaveManagerTest.cpp
+	ScriptSaveManagerTest.cpp
+	ScriptECSTest.cpp
 )
diff --git a/src/test/ECSTest.cpp b/src/test/ECSTest.cpp
index 3e6c61c..af2b7b0 100644
--- a/src/test/ECSTest.cpp
+++ b/src/test/ECSTest.cpp
@@ -1,6 +1,7 @@
 #include <gtest/gtest.h>
 
 #define protected public
+#define private public
 
 #include <crepe/api/GameObject.h>
 #include <crepe/api/Metadata.h>
@@ -16,6 +17,10 @@ class ECSTest : public ::testing::Test {
 
 public:
 	ComponentManager mgr{m};
+
+	class TestComponent : public Component {
+		using Component::Component;
+	};
 };
 
 TEST_F(ECSTest, createGameObject) {
@@ -387,3 +392,77 @@ TEST_F(ECSTest, resetPersistent) {
 	EXPECT_EQ(metadata.size(), 0);
 	EXPECT_EQ(transform.size(), 0);
 }
+
+TEST_F(ECSTest, IDByName) {
+	GameObject foo = mgr.new_object("foo");
+	GameObject bar = mgr.new_object("bar");
+
+	{
+		auto objects = mgr.get_objects_by_name("");
+		EXPECT_EQ(objects.size(), 0);
+	}
+
+	{
+		auto objects = mgr.get_objects_by_name("foo");
+		EXPECT_EQ(objects.size(), 1);
+		EXPECT_TRUE(objects.contains(foo.id));
+	}
+}
+
+TEST_F(ECSTest, IDByTag) {
+	GameObject foo = mgr.new_object("foo", "common tag");
+	GameObject bar = mgr.new_object("bar", "common tag");
+
+	{
+		auto objects = mgr.get_objects_by_tag("");
+		EXPECT_EQ(objects.size(), 0);
+	}
+
+	{
+		auto objects = mgr.get_objects_by_tag("common tag");
+		EXPECT_EQ(objects.size(), 2);
+		EXPECT_TRUE(objects.contains(foo.id));
+		EXPECT_TRUE(objects.contains(bar.id));
+	}
+}
+
+TEST_F(ECSTest, ComponentsByName) {
+	GameObject foo = mgr.new_object("foo");
+	foo.add_component<TestComponent>();
+	GameObject bar = mgr.new_object("bar");
+	bar.add_component<TestComponent>();
+	bar.add_component<TestComponent>();
+
+	{
+		auto objects = mgr.get_components_by_name<TestComponent>("");
+		EXPECT_EQ(objects.size(), 0);
+	}
+
+	{
+		auto objects = mgr.get_components_by_name<TestComponent>("foo");
+		EXPECT_EQ(objects.size(), 1);
+	}
+
+	{
+		auto objects = mgr.get_components_by_name<TestComponent>("bar");
+		EXPECT_EQ(objects.size(), 2);
+	}
+}
+
+TEST_F(ECSTest, ComponentsByTag) {
+	GameObject foo = mgr.new_object("foo", "common tag");
+	foo.add_component<TestComponent>();
+	GameObject bar = mgr.new_object("bar", "common tag");
+	bar.add_component<TestComponent>();
+	bar.add_component<TestComponent>();
+
+	{
+		auto objects = mgr.get_components_by_tag<TestComponent>("");
+		EXPECT_EQ(objects.size(), 0);
+	}
+
+	{
+		auto objects = mgr.get_components_by_tag<TestComponent>("common tag");
+		EXPECT_EQ(objects.size(), 3);
+	}
+}
diff --git a/src/test/ResourceManagerTest.cpp b/src/test/ResourceManagerTest.cpp
new file mode 100644
index 0000000..44a5921
--- /dev/null
+++ b/src/test/ResourceManagerTest.cpp
@@ -0,0 +1,81 @@
+#include <gtest/gtest.h>
+
+#define private public
+#define protected public
+
+#include <crepe/api/GameObject.h>
+#include <crepe/manager/ResourceManager.h>
+#include <crepe/util/Log.h>
+
+using namespace std;
+using namespace crepe;
+using namespace testing;
+
+class ResourceManagerTest : public Test {
+	Mediator mediator;
+
+public:
+	ResourceManager resource_manager{mediator};
+
+	class Unrelated : public Resource {
+		using Resource::Resource;
+	};
+
+	Asset asset_a{"asset/texture/img.png"};
+	Asset asset_b{"asset/texture/ERROR.png"};
+
+	class TestResource : public Resource {
+	public:
+		static unsigned instances;
+
+	public:
+		const unsigned instance;
+		TestResource(const Asset & src) : Resource(src), instance(this->instances++) {}
+		~TestResource() { this->instances--; }
+		bool operator==(const TestResource & other) const {
+			return this->instance == other.instance;
+		}
+	};
+
+private:
+	void SetUp() override { TestResource::instances = 0; }
+};
+unsigned ResourceManagerTest::TestResource::instances = 0;
+
+TEST_F(ResourceManagerTest, Default) {
+	TestResource & res_1 = resource_manager.get<TestResource>(asset_a);
+	TestResource & res_2 = resource_manager.get<TestResource>(asset_a);
+	TestResource & res_3 = resource_manager.get<TestResource>(asset_b);
+	TestResource & res_4 = resource_manager.get<TestResource>(asset_b);
+
+	ASSERT_EQ(res_1, res_2);
+	ASSERT_EQ(res_3, res_4);
+	EXPECT_NE(res_1, res_3);
+
+	EXPECT_EQ(TestResource::instances, 2);
+
+	resource_manager.clear();
+}
+
+TEST_F(ResourceManagerTest, Persistent) {
+	resource_manager.set_persistent(asset_a, true);
+	EXPECT_EQ(TestResource::instances, 0);
+
+	resource_manager.get<TestResource>(asset_a);
+	resource_manager.get<TestResource>(asset_a);
+	resource_manager.get<TestResource>(asset_b);
+	resource_manager.get<TestResource>(asset_b);
+	EXPECT_EQ(TestResource::instances, 2);
+
+	resource_manager.clear();
+	EXPECT_EQ(TestResource::instances, 1);
+
+	resource_manager.clear_all();
+	EXPECT_EQ(TestResource::instances, 0);
+}
+
+TEST_F(ResourceManagerTest, UnmatchedType) {
+	EXPECT_NO_THROW({ resource_manager.get<TestResource>(asset_a); });
+
+	EXPECT_THROW({ resource_manager.get<Unrelated>(asset_a); }, runtime_error);
+}
diff --git a/src/test/SaveManagerTest.cpp b/src/test/SaveManagerTest.cpp
new file mode 100644
index 0000000..e9b0c29
--- /dev/null
+++ b/src/test/SaveManagerTest.cpp
@@ -0,0 +1,40 @@
+#include <gtest/gtest.h>
+
+#include <crepe/ValueBroker.h>
+#include <crepe/facade/DB.h>
+#include <crepe/manager/SaveManager.h>
+
+using namespace std;
+using namespace crepe;
+using namespace testing;
+
+class SaveManagerTest : public Test {
+	Mediator m;
+	class TestSaveManager : public SaveManager {
+		using SaveManager::SaveManager;
+
+		// in-memory database for testing
+		DB db{};
+		virtual DB & get_db() override { return this->db; }
+	};
+
+public:
+	TestSaveManager mgr{m};
+};
+
+TEST_F(SaveManagerTest, ReadWrite) {
+	ASSERT_FALSE(mgr.has("foo"));
+	mgr.set<string>("foo", "bar");
+	ASSERT_TRUE(mgr.has("foo"));
+
+	ValueBroker value = mgr.get<string>("foo");
+	EXPECT_EQ(value.get(), "bar");
+}
+
+TEST_F(SaveManagerTest, DefaultValue) {
+	ValueBroker value = mgr.get<int>("foo", 3);
+
+	ASSERT_EQ(value.get(), 3);
+	value.set(5);
+	ASSERT_EQ(value.get(), 5);
+}
diff --git a/src/test/ScriptECSTest.cpp b/src/test/ScriptECSTest.cpp
new file mode 100644
index 0000000..1ec33ba
--- /dev/null
+++ b/src/test/ScriptECSTest.cpp
@@ -0,0 +1,41 @@
+#include <gtest/gtest.h>
+
+#define protected public
+
+#include <crepe/api/BehaviorScript.h>
+#include <crepe/api/GameObject.h>
+#include <crepe/api/Metadata.h>
+#include <crepe/api/Script.h>
+#include <crepe/manager/ComponentManager.h>
+#include <crepe/system/ScriptSystem.h>
+
+#include "ScriptTest.h"
+
+using namespace std;
+using namespace crepe;
+using namespace testing;
+
+class ScriptECSTest : public ScriptTest {
+public:
+	class TestComponent : public Component {
+		using Component::Component;
+	};
+};
+
+TEST_F(ScriptECSTest, GetOwnComponent) {
+	MyScript & script = this->script;
+	Metadata & metadata = script.get_component<Metadata>();
+
+	EXPECT_EQ(metadata.name, OBJ_NAME);
+}
+
+TEST_F(ScriptECSTest, GetOwnComponents) {
+	const unsigned COUNT = 4;
+
+	for (unsigned i = 0; i < COUNT; i++) entity.add_component<TestComponent>();
+
+	MyScript & script = this->script;
+	RefVector<TestComponent> components = script.get_components<TestComponent>();
+
+	EXPECT_EQ(components.size(), COUNT);
+}
diff --git a/src/test/ScriptEventTest.cpp b/src/test/ScriptEventTest.cpp
index 5da31e7..c1b4028 100644
--- a/src/test/ScriptEventTest.cpp
+++ b/src/test/ScriptEventTest.cpp
@@ -26,7 +26,7 @@ public:
 	class MyEvent : public Event {};
 };
 
-TEST_F(ScriptEventTest, Inactive) {
+TEST_F(ScriptEventTest, Default) {
 	BehaviorScript & behaviorscript = this->behaviorscript;
 	MyScript & script = this->script;
 	EventManager & evmgr = this->event_manager;
diff --git a/src/test/ScriptSaveManagerTest.cpp b/src/test/ScriptSaveManagerTest.cpp
new file mode 100644
index 0000000..64403c4
--- /dev/null
+++ b/src/test/ScriptSaveManagerTest.cpp
@@ -0,0 +1,35 @@
+#include <gtest/gtest.h>
+
+// stupid hack to allow access to private/protected members under test
+#define private public
+#define protected public
+
+#include <crepe/facade/DB.h>
+#include <crepe/manager/SaveManager.h>
+
+#include "ScriptTest.h"
+
+using namespace std;
+using namespace crepe;
+using namespace testing;
+
+class ScriptSaveManagerTest : public ScriptTest {
+public:
+	class TestSaveManager : public SaveManager {
+		using SaveManager::SaveManager;
+
+		// in-memory database for testing
+		DB db{};
+		virtual DB & get_db() override { return this->db; }
+	};
+
+	TestSaveManager save_mgr{mediator};
+};
+
+TEST_F(ScriptSaveManagerTest, GetSaveManager) {
+	MyScript & script = this->script;
+
+	SaveManager & mgr = script.get_save_manager();
+
+	EXPECT_EQ(&mgr, &save_mgr);
+}
diff --git a/src/test/ScriptSceneTest.cpp b/src/test/ScriptSceneTest.cpp
index 9ee1e52..2568049 100644
--- a/src/test/ScriptSceneTest.cpp
+++ b/src/test/ScriptSceneTest.cpp
@@ -18,7 +18,7 @@ public:
 	class MyScene : public Scene {};
 };
 
-TEST_F(ScriptSceneTest, Inactive) {
+TEST_F(ScriptSceneTest, Default) {
 	BehaviorScript & behaviorscript = this->behaviorscript;
 	MyScript & script = this->script;
 
diff --git a/src/test/ScriptTest.cpp b/src/test/ScriptTest.cpp
index 1d2d6dd..acdae70 100644
--- a/src/test/ScriptTest.cpp
+++ b/src/test/ScriptTest.cpp
@@ -6,7 +6,6 @@
 #define protected public
 
 #include "ScriptTest.h"
-#include <crepe/api/GameObject.h>
 
 using namespace std;
 using namespace crepe;
@@ -14,7 +13,6 @@ using namespace testing;
 
 void ScriptTest::SetUp() {
 	auto & mgr = this->component_manager;
-	GameObject entity = mgr.new_object("name");
 	BehaviorScript & component = entity.add_component<BehaviorScript>();
 
 	this->behaviorscript = component;
diff --git a/src/test/ScriptTest.h b/src/test/ScriptTest.h
index e0205ff..31fa7c9 100644
--- a/src/test/ScriptTest.h
+++ b/src/test/ScriptTest.h
@@ -11,11 +11,14 @@
 class ScriptTest : public testing::Test {
 protected:
 	crepe::Mediator mediator;
+	static constexpr const char * OBJ_NAME = "foo";
 
 public:
 	crepe::ComponentManager component_manager{mediator};
 	crepe::ScriptSystem system{mediator};
 	crepe::EventManager event_mgr{mediator};
+	crepe::GameObject entity = component_manager.new_object(OBJ_NAME);
+
 	class MyScript : public crepe::Script {
 		// NOTE: explicitly stating `public:` is not required on actual scripts
 
diff --git a/src/test/Vector2Test.cpp b/src/test/Vector2Test.cpp
index 17bca41..1e21af9 100644
--- a/src/test/Vector2Test.cpp
+++ b/src/test/Vector2Test.cpp
@@ -382,3 +382,151 @@ TEST_F(Vector2Test, NotEquals) {
 	EXPECT_FALSE(long_vec1 != long_vec1);
 	EXPECT_TRUE(long_vec1 != long_vec2);
 }
+
+TEST_F(Vector2Test, Truncate) {
+	Vector2<int> vec = {3, 4};
+	vec.truncate(3);
+	EXPECT_EQ(vec.x, 0);
+	EXPECT_EQ(vec.y, 0);
+
+	Vector2<double> vec2 = {3.0, 4.0};
+	vec2.truncate(3.0);
+	EXPECT_FLOAT_EQ(vec2.x, 1.8);
+	EXPECT_FLOAT_EQ(vec2.y, 2.4);
+
+	Vector2<long> vec3 = {3, 4};
+	vec3.truncate(3);
+	EXPECT_EQ(vec3.x, 0);
+	EXPECT_EQ(vec3.y, 0);
+
+	Vector2<float> vec4 = {3.0f, 4.0f};
+	vec4.truncate(3.0f);
+	EXPECT_FLOAT_EQ(vec4.x, 1.8f);
+	EXPECT_FLOAT_EQ(vec4.y, 2.4f);
+}
+
+TEST_F(Vector2Test, Normalize) {
+	Vector2<int> vec = {3, 4};
+	vec.normalize();
+	EXPECT_EQ(vec.x, 0);
+	EXPECT_EQ(vec.y, 0);
+
+	Vector2<double> vec2 = {3.0, 4.0};
+	vec2.normalize();
+	EXPECT_FLOAT_EQ(vec2.x, 0.6);
+	EXPECT_FLOAT_EQ(vec2.y, 0.8);
+
+	Vector2<long> vec3 = {3, 4};
+	vec3.normalize();
+	EXPECT_EQ(vec3.x, 0);
+	EXPECT_EQ(vec3.y, 0);
+
+	Vector2<float> vec4 = {3.0f, 4.0f};
+	vec4.normalize();
+	EXPECT_FLOAT_EQ(vec4.x, 0.6f);
+	EXPECT_FLOAT_EQ(vec4.y, 0.8f);
+}
+
+TEST_F(Vector2Test, Length) {
+	Vector2<int> vec = {3, 4};
+	EXPECT_EQ(vec.length(), 5);
+
+	Vector2<double> vec2 = {3.0, 4.0};
+	EXPECT_FLOAT_EQ(vec2.length(), 5.0);
+
+	Vector2<long> vec3 = {3, 4};
+	EXPECT_EQ(vec3.length(), 5);
+
+	Vector2<float> vec4 = {3.0f, 4.0f};
+	EXPECT_FLOAT_EQ(vec4.length(), 5.0f);
+}
+
+TEST_F(Vector2Test, LengthSquared) {
+	Vector2<int> vec = {3, 4};
+	EXPECT_EQ(vec.length_squared(), 25);
+
+	Vector2<double> vec2 = {3.0, 4.0};
+	EXPECT_FLOAT_EQ(vec2.length_squared(), 25.0);
+
+	Vector2<long> vec3 = {3, 4};
+	EXPECT_EQ(vec3.length_squared(), 25);
+
+	Vector2<float> vec4 = {3.0f, 4.0f};
+	EXPECT_FLOAT_EQ(vec4.length_squared(), 25.0f);
+}
+
+TEST_F(Vector2Test, Dot) {
+	Vector2<int> vec1 = {3, 4};
+	Vector2<int> vec2 = {5, 6};
+	EXPECT_EQ(vec1.dot(vec2), 39);
+
+	Vector2<double> vec3 = {3.0, 4.0};
+	Vector2<double> vec4 = {5.0, 6.0};
+	EXPECT_FLOAT_EQ(vec3.dot(vec4), 39.0);
+
+	Vector2<long> vec5 = {3, 4};
+	Vector2<long> vec6 = {5, 6};
+	EXPECT_EQ(vec5.dot(vec6), 39);
+
+	Vector2<float> vec7 = {3.0f, 4.0f};
+	Vector2<float> vec8 = {5.0f, 6.0f};
+	EXPECT_FLOAT_EQ(vec7.dot(vec8), 39.0f);
+}
+
+TEST_F(Vector2Test, Distance) {
+	Vector2<int> vec1 = {1, 1};
+	Vector2<int> vec2 = {4, 5};
+	EXPECT_EQ(vec1.distance(vec2), 5);
+
+	Vector2<double> vec3 = {1.0, 1.0};
+	Vector2<double> vec4 = {4.0, 5.0};
+	EXPECT_FLOAT_EQ(vec3.distance(vec4), 5.0);
+
+	Vector2<long> vec5 = {1, 1};
+	Vector2<long> vec6 = {4, 5};
+	EXPECT_EQ(vec5.distance(vec6), 5);
+
+	Vector2<float> vec7 = {1.0f, 1.0f};
+	Vector2<float> vec8 = {4.0f, 5.0f};
+	EXPECT_FLOAT_EQ(vec7.distance(vec8), 5.0f);
+}
+
+TEST_F(Vector2Test, DistanceSquared) {
+	Vector2<int> vec1 = {3, 4};
+	Vector2<int> vec2 = {5, 6};
+	EXPECT_EQ(vec1.distance_squared(vec2), 8);
+
+	Vector2<double> vec3 = {3.0, 4.0};
+	Vector2<double> vec4 = {5.0, 6.0};
+	EXPECT_FLOAT_EQ(vec3.distance_squared(vec4), 8.0);
+
+	Vector2<long> vec5 = {3, 4};
+	Vector2<long> vec6 = {5, 6};
+	EXPECT_EQ(vec5.distance_squared(vec6), 8);
+
+	Vector2<float> vec7 = {3.0f, 4.0f};
+	Vector2<float> vec8 = {5.0f, 6.0f};
+	EXPECT_FLOAT_EQ(vec7.distance_squared(vec8), 8.0f);
+}
+
+TEST_F(Vector2Test, Perpendicular) {
+	Vector2<int> vec = {3, 4};
+	Vector2<int> result = vec.perpendicular();
+	EXPECT_EQ(result.x, -4);
+	EXPECT_EQ(result.y, 3);
+
+	Vector2<double> vec2 = {3.0, 4.0};
+	Vector2<double> result2 = vec2.perpendicular();
+	EXPECT_FLOAT_EQ(result2.x, -4.0);
+	EXPECT_FLOAT_EQ(result2.y, 3.0);
+
+	Vector2<long> vec3 = {3, 4};
+	Vector2<long> result3 = vec3.perpendicular();
+	EXPECT_EQ(result3.x, -4);
+	EXPECT_EQ(result3.y, 3);
+
+	Vector2<float> vec4 = {3.0f, 4.0f};
+	Vector2<float> result4 = vec4.perpendicular();
+	EXPECT_FLOAT_EQ(result4.x, -4.0f);
+	EXPECT_FLOAT_EQ(result4.y, 3.0f);
+}
diff --git a/src/test/main.cpp b/src/test/main.cpp
index aece72d..ed2aed5 100644
--- a/src/test/main.cpp
+++ b/src/test/main.cpp
@@ -1,9 +1,5 @@
-#include <gtest/gtest.h>
-
-#define protected public
-#define private public
-
 #include <crepe/api/Config.h>
+#include <gtest/gtest.h>
 
 using namespace crepe;
 using namespace testing;
@@ -11,12 +7,14 @@ using namespace testing;
 class GlobalConfigReset : public EmptyTestEventListener {
 public:
 	Config & cfg = Config::get_instance();
-	Config cfg_default = Config();
 
 	// This function is called before each test
 	void OnTestStart(const TestInfo &) override {
-		cfg = cfg_default;
-		cfg.log.level = Log::Level::WARNING;
+		cfg = {
+			.log = {
+				.level = Log::Level::WARNING,
+			},
+		};
 	}
 };