16 files changed, 599 insertions, 146 deletions

diff --git a/src/crepe/Particle.cpp b/src/crepe/Particle.cpp
index 4810e80..582edf4 100644
--- a/src/crepe/Particle.cpp
+++ b/src/crepe/Particle.cpp
@@ -2,19 +2,32 @@
 
 using namespace crepe;
 
-Particle::Particle() { this->active = false; }
-
-void Particle::reset(float lifespan, Position position, Position velocity) {
+void Particle::reset(uint32_t lifespan, const Vector2 & position,
+					 const Vector2 & velocity, double angle) {
+	// Initialize the particle state
 	this->time_in_life = 0;
 	this->lifespan = lifespan;
 	this->position = position;
 	this->velocity = velocity;
+	this->angle = angle;
 	this->active = true;
+	// Reset force accumulation
+	this->force_over_time = {0, 0};
+}
+
+void Particle::update() {
+	// Deactivate particle if it has exceeded its lifespan
+	if (++time_in_life >= lifespan) {
+		this->active = false;
+		return;
+	}
+
+	// Update velocity based on accumulated force and update position
+	this->velocity += force_over_time;
+	this->position += velocity;
 }
 
-void Particle::update(float deltaTime) {
-	time_in_life += deltaTime;
-	position.x += velocity.x * deltaTime;
-	position.y += velocity.y * deltaTime;
-	if (time_in_life >= lifespan) this->active = false;
+void Particle::stop_movement() {
+	// Reset velocity to halt movement
+	this->velocity = {0, 0};
 }
diff --git a/src/crepe/Particle.h b/src/crepe/Particle.h
index 21e691d..3eaebc3 100644
--- a/src/crepe/Particle.h
+++ b/src/crepe/Particle.h
@@ -1,22 +1,64 @@
 #pragma once
 
-#include "Position.h"
+#include <cstdint>
+
+#include "api/Vector2.h"
 
 namespace crepe {
 
+/**
+ * \brief Represents a particle in the particle emitter.
+ *
+ * This class stores information about a single particle, including its position,
+ * velocity, lifespan, and other properties. Particles can be updated over time
+ * to simulate movement and can also be reset or stopped.
+ */
 class Particle {
+	// TODO: add friend particleSsytem and rendersystem. Unit test will fail.
+
 public:
-	Position position;
-	// FIXME: `Position` is an awkward name for a 2D vector. See FIXME comment in
-	// api/Transform.h for fix proposal.
-	Position velocity;
-	float lifespan;
-	bool active;
+	//! Position of the particle in 2D space.
+	Vector2 position;
+	//! Velocity vector indicating the speed and direction of the particle.
+	Vector2 velocity;
+	//! Accumulated force affecting the particle over time.
+	Vector2 force_over_time;
+	//! Total lifespan of the particle in milliseconds.
+	uint32_t lifespan;
+	//! Active state of the particle; true if it is in use, false otherwise.
+	bool active = false;
+	//! The time the particle has been alive, in milliseconds.
+	uint32_t time_in_life = 0;
+	//! The angle at which the particle is oriented or moving.
+	double angle = 0;
 
-	Particle();
-	void reset(float lifespan, Position position, Position velocity);
-	void update(float deltaTime);
-	float time_in_life;
+	/**
+	 * \brief Resets the particle with new properties.
+	 *
+	 * This method initializes the particle with a specific lifespan, position,
+	 * velocity, and angle, marking it as active and resetting its life counter.
+	 *
+	 * \param lifespan  The lifespan of the particle in amount of updates.
+	 * \param position  The starting position of the particle.
+	 * \param velocity  The initial velocity of the particle.
+	 * \param angle     The angle of the particle's trajectory or orientation.
+	 */
+	void reset(uint32_t lifespan, const Vector2 & position,
+			   const Vector2 & velocity, double angle);
+	/**
+	 * \brief Updates the particle's state.
+	 *
+	 * Advances the particle's position based on its velocity and applies accumulated forces. 
+	 * Deactivates the particle if its lifespan has expired.
+	 */
+	void update();
+	/**
+	 * \brief Stops the particle's movement.
+	 *
+	 * Sets the particle's velocity to zero, effectively halting any further
+	 * movement.
+	 */
+	void stop_movement();
 };
 
 } // namespace crepe
diff --git a/src/crepe/api/AssetManager.h b/src/crepe/api/AssetManager.h
index dbfaef3..86a9902 100644
--- a/src/crepe/api/AssetManager.h
+++ b/src/crepe/api/AssetManager.h
@@ -56,7 +56,8 @@ public:
 	 * cache.
 	 */
 	template <typename T>
-	std::shared_ptr<T> cache(const std::string & file_path, bool reload = false);
+	std::shared_ptr<T> cache(const std::string & file_path,
+							 bool reload = false);
 };
 
 } // namespace crepe
diff --git a/src/crepe/api/ParticleEmitter.cpp b/src/crepe/api/ParticleEmitter.cpp
index 0bc2197..35f960d 100644
--- a/src/crepe/api/ParticleEmitter.cpp
+++ b/src/crepe/api/ParticleEmitter.cpp
@@ -1,41 +1,12 @@
-#include <ctime>
-#include <iostream>
-
-#include "Particle.h"
 #include "ParticleEmitter.h"
 
 using namespace crepe;
 
-ParticleEmitter::ParticleEmitter(game_object_id_t id, uint32_t max_particles,
-								 uint32_t emission_rate, uint32_t speed,
-								 uint32_t speed_offset, uint32_t angle,
-								 uint32_t angleOffset, float begin_lifespan,
-								 float end_lifespan)
-	: Component(id),
-	  max_particles(max_particles),
-	  emission_rate(emission_rate),
-	  speed(speed),
-	  speed_offset(speed_offset),
-	  position{0, 0},
-	  begin_lifespan(begin_lifespan),
-	  end_lifespan(end_lifespan) {
-	std::srand(
-		static_cast<uint32_t>(std::time(nullptr))); // initialize random seed
-	std::cout << "Create emitter" << std::endl;
-	// FIXME: Why do these expressions start with `360 +`, only to be `% 360`'d
-	// right after? This does not make any sense to me.
-	min_angle = (360 + angle - (angleOffset % 360)) % 360;
-	max_angle = (360 + angle + (angleOffset % 360)) % 360;
-	position.x = 400; // FIXME: what are these magic values?
-	position.y = 400;
-	for (size_t i = 0; i < max_particles; i++) {
-		this->particles.emplace_back();
-	}
-}
-
-ParticleEmitter::~ParticleEmitter() {
-	std::vector<Particle>::iterator it = this->particles.begin();
-	while (it != this->particles.end()) {
-		it = this->particles.erase(it);
+ParticleEmitter::ParticleEmitter(game_object_id_t game_object_id,
+								 const Data & data)
+	: Component(game_object_id),
+	  data(data) {
+	for (size_t i = 0; i < this->data.max_particles; i++) {
+		this->data.particles.emplace_back();
 	}
 }
diff --git a/src/crepe/api/ParticleEmitter.h b/src/crepe/api/ParticleEmitter.h
index 5939723..a9e872f 100644
--- a/src/crepe/api/ParticleEmitter.h
+++ b/src/crepe/api/ParticleEmitter.h
@@ -1,42 +1,85 @@
 #pragma once
 
-#include <cstdint>
 #include <vector>
 
 #include "Component.h"
 #include "Particle.h"
+#include "Vector2.h"
 
 namespace crepe {
 
+class Sprite;
+
+/**
+ * \brief Data holder for particle emission parameters.
+ *
+ * The ParticleEmitter class stores configuration data for particle properties,
+ * defining the characteristics and boundaries of particle emissions.
+ */
 class ParticleEmitter : public Component {
 public:
-	ParticleEmitter(game_object_id_t id, uint32_t max_particles,
-					uint32_t emission_rate, uint32_t speed,
-					uint32_t speed_offset, uint32_t angle, uint32_t angleOffset,
-					float begin_lifespan, float end_lifespan);
-	~ParticleEmitter();
-
-	//! position of the emitter
-	Position position;
-	//! maximum number of particles
-	uint32_t max_particles;
-	//! rate of particle emission
-	uint32_t emission_rate;
-	//! base speed of the particles
-	uint32_t speed;
-	//! offset for random speed variation
-	uint32_t speed_offset;
-	//! min angle of particle emission
-	uint32_t min_angle;
-	//! max angle of particle emission
-	uint32_t max_angle;
-	//! begin Lifespan of particle (only visual)
-	float begin_lifespan;
-	//! begin Lifespan of particle
-	float end_lifespan;
-
-	//! collection of particles
-	std::vector<Particle> particles;
+	/**
+	 * \brief Defines the boundary within which particles are constrained.
+	 *
+	 * This structure specifies the boundary's size and offset, as well as the
+	 * behavior of particles upon reaching the boundary limits.
+	 */
+	struct Boundary {
+		//! boundary width (midpoint is emitter location)
+		double width = 0.0;
+		//! boundary height (midpoint is emitter location)
+		double height = 0.0;
+		//! boundary offset from particle emitter location
+		Vector2 offset;
+		//! reset on exit or stop velocity and set max postion
+		bool reset_on_exit = false;
+	};
+
+	/**
+	 * \brief Holds parameters that control particle emission.
+	 *
+	 * Contains settings for the emitter’s position, particle speed, angle, lifespan,
+	 * boundary, and the sprite used for rendering particles.
+	 */
+	struct Data {
+		//! position of the emitter
+		Vector2 position;
+		//! maximum number of particles
+		const unsigned int max_particles = 0;
+		//! rate of particle emission per update (Lowest value = 0.001 any lower is ignored)
+		double emission_rate = 0;
+		//! min speed of the particles
+		double min_speed = 0;
+		//! min speed of the particles
+		double max_speed = 0;
+		//! min angle of particle emission
+		double min_angle = 0;
+		//! max angle of particle emission
+		double max_angle = 0;
+		//! begin Lifespan of particle (only visual)
+		double begin_lifespan = 0.0;
+		//! end Lifespan of particle
+		double end_lifespan = 0.0;
+		//! force over time (physics)
+		Vector2 force_over_time;
+		//! particle boundary
+		Boundary boundary;
+		//! collection of particles
+		std::vector<Particle> particles;
+		//! sprite reference
+		const Sprite & sprite;
+	};
+
+public:
+	/**
+	 * \param game_object_id  Identifier for the game object using this emitter.
+	 * \param data            Configuration data defining particle properties.
+	 */
+	ParticleEmitter(game_object_id_t game_object_id, const Data & data);
+
+public:
+	//! Configuration data for particle emission settings.
+	Data data;
 };
 
 } // namespace crepe
diff --git a/src/crepe/api/Vector2.cpp b/src/crepe/api/Vector2.cpp
index 09bb59b..09b3fa3 100644
--- a/src/crepe/api/Vector2.cpp
+++ b/src/crepe/api/Vector2.cpp
@@ -3,7 +3,7 @@
 namespace crepe {
 
 // Constructor with initial values
-Vector2::Vector2(float x, float y) : x(x), y(y) {}
+Vector2::Vector2(double x, double y) : x(x), y(y) {}
 
 // Subtracts another vector from this vector and returns the result.
 Vector2 Vector2::operator-(const Vector2 & other) const {
@@ -16,7 +16,7 @@ Vector2 Vector2::operator+(const Vector2 & other) const {
 }
 
 // Multiplies this vector by a scalar and returns the result.
-Vector2 Vector2::operator*(float scalar) const {
+Vector2 Vector2::operator*(double scalar) const {
 	return {x * scalar, y * scalar};
 }
 
@@ -35,7 +35,7 @@ Vector2 & Vector2::operator+=(const Vector2 & other) {
 }
 
 // Adds a scalar value to both components of this vector and updates this vector.
-Vector2 & Vector2::operator+=(float other) {
+Vector2 & Vector2::operator+=(double other) {
 	x += other;
 	y += other;
 	return *this;
diff --git a/src/crepe/api/Vector2.h b/src/crepe/api/Vector2.h
index 741951b..5a57484 100644
--- a/src/crepe/api/Vector2.h
+++ b/src/crepe/api/Vector2.h
@@ -6,15 +6,15 @@ namespace crepe {
 class Vector2 {
 public:
 	//! X component of the vector
-	float x;
+	double x;
 	//! Y component of the vector
-	float y;
+	double y;
 
 	//! Default constructor
 	Vector2() = default;
 
 	//! Constructor with initial values
-	Vector2(float x, float y);
+	Vector2(double x, double y);
 
 	//! Subtracts another vector from this vector and returns the result.
 	Vector2 operator-(const Vector2 & other) const;
@@ -23,7 +23,7 @@ public:
 	Vector2 operator+(const Vector2 & other) const;
 
 	//! Multiplies this vector by a scalar and returns the result.
-	Vector2 operator*(float scalar) const;
+	Vector2 operator*(double scalar) const;
 
 	//! Multiplies this vector by another vector element-wise and updates this vector.
 	Vector2 & operator*=(const Vector2 & other);
@@ -32,7 +32,7 @@ public:
 	Vector2 & operator+=(const Vector2 & other);
 
 	//! Adds a scalar value to both components of this vector and updates this vector.
-	Vector2 & operator+=(float other);
+	Vector2 & operator+=(double other);
 
 	//! Returns the negation of this vector.
 	Vector2 operator-() const;
diff --git a/src/crepe/facade/SDLContext.cpp b/src/crepe/facade/SDLContext.cpp
index 46230b4..236bf8c 100644
--- a/src/crepe/facade/SDLContext.cpp
+++ b/src/crepe/facade/SDLContext.cpp
@@ -159,7 +159,7 @@ SDLContext::texture_from_path(const std::string & path) {
 
 	SDL_Surface * tmp = IMG_Load(path.c_str());
 	if (tmp == nullptr) {
-		tmp = IMG_Load("../asset/texture/ERROR.png");	
+		tmp = IMG_Load("../asset/texture/ERROR.png");
 	}
 
 	std::unique_ptr<SDL_Surface, std::function<void(SDL_Surface *)>>
diff --git a/src/crepe/system/ParticleSystem.cpp b/src/crepe/system/ParticleSystem.cpp
index 397b586..e7a3bec 100644
--- a/src/crepe/system/ParticleSystem.cpp
+++ b/src/crepe/system/ParticleSystem.cpp
@@ -1,62 +1,141 @@
 #include <cmath>
+#include <cstdlib>
 #include <ctime>
 
-#include "../ComponentManager.h"
-#include "../api/ParticleEmitter.h"
+#include "api/ParticleEmitter.h"
+#include "api/Transform.h"
+#include "api/Vector2.h"
 
+#include "ComponentManager.h"
 #include "ParticleSystem.h"
 
 using namespace crepe;
 
-ParticleSystem::ParticleSystem() : elapsed_time(0.0f) {}
-
 void ParticleSystem::update() {
+	// Get all emitters
 	ComponentManager & mgr = ComponentManager::get_instance();
 	std::vector<std::reference_wrapper<ParticleEmitter>> emitters
 		= mgr.get_components_by_type<ParticleEmitter>();
-	float delta_time = 0.10;
+
 	for (ParticleEmitter & emitter : emitters) {
-		float update_amount = 1 / static_cast<float>(emitter.emission_rate);
-		for (float i = 0; i < delta_time; i += update_amount) {
-			emit_particle(emitter);
+		// Get transform linked to emitter
+		const Transform & transform
+			= mgr.get_components_by_id<Transform>(emitter.game_object_id)
+				  .front()
+				  .get();
+
+		// Emit particles based on emission_rate
+		int updates
+			= calculate_update(this->update_count, emitter.data.emission_rate);
+		for (size_t i = 0; i < updates; i++) {
+			emit_particle(emitter, transform);
 		}
-		for (size_t j = 0; j < emitter.particles.size(); j++) {
-			if (emitter.particles[j].active) {
-				emitter.particles[j].update(delta_time);
+
+		// Update all particles
+		for (Particle & particle : emitter.data.particles) {
+			if (particle.active) {
+				particle.update();
 			}
 		}
+
+		// Check if within boundary
+		check_bounds(emitter, transform);
 	}
+
+	this->update_count = (this->update_count + 1) % this->MAX_UPDATE_COUNT;
 }
 
-void ParticleSystem::emit_particle(ParticleEmitter & emitter) {
-	Position initial_position = {emitter.position.x, emitter.position.y};
-	float random_angle = 0.0f;
-	if (emitter.max_angle < emitter.min_angle) {
-		random_angle = ((emitter.min_angle
-						 + (std::rand()
-							% (static_cast<uint32_t>(emitter.max_angle + 360
-													 - emitter.min_angle + 1))))
-						% 360);
-	} else {
-		random_angle = emitter.min_angle
-					   + (std::rand()
-						  % (static_cast<uint32_t>(emitter.max_angle
-												   - emitter.min_angle + 1)));
-	}
-	float angle_in_radians = random_angle * (M_PI / 180.0f);
-	float random_speed_offset = (static_cast<float>(std::rand()) / RAND_MAX)
-									* (2 * emitter.speed_offset)
-								- emitter.speed_offset;
-	float velocity_x
-		= (emitter.speed + random_speed_offset) * std::cos(angle_in_radians);
-	float velocity_y
-		= (emitter.speed + random_speed_offset) * std::sin(angle_in_radians);
-	Position initial_velocity = {velocity_x, velocity_y};
-	for (size_t i = 0; i < emitter.particles.size(); i++) {
-		if (!emitter.particles[i].active) {
-			emitter.particles[i].reset(emitter.end_lifespan, initial_position,
-									   initial_velocity);
+void ParticleSystem::emit_particle(ParticleEmitter & emitter,
+								   const Transform & transform) {
+	constexpr double DEG_TO_RAD = M_PI / 180.0;
+
+	Vector2 initial_position = emitter.data.position + transform.position;
+	double random_angle
+		= generate_random_angle(emitter.data.min_angle, emitter.data.max_angle);
+
+	double random_speed
+		= generate_random_speed(emitter.data.min_speed, emitter.data.max_speed);
+	double angle_radians = random_angle * DEG_TO_RAD;
+
+	Vector2 velocity = {random_speed * std::cos(angle_radians),
+						random_speed * std::sin(angle_radians)};
+
+	for (Particle & particle : emitter.data.particles) {
+		if (!particle.active) {
+			particle.reset(emitter.data.end_lifespan, initial_position,
+						   velocity, random_angle);
 			break;
 		}
 	}
 }
+
+int ParticleSystem::calculate_update(int count, double emission) const {
+	double integer_part = std::floor(emission);
+	double fractional_part = emission - integer_part;
+
+	if (fractional_part > 0) {
+		int denominator = static_cast<int>(1.0 / fractional_part);
+		return (count % denominator == 0) ? 1 : 0;
+	}
+
+	return static_cast<int>(emission);
+}
+
+void ParticleSystem::check_bounds(ParticleEmitter & emitter,
+								  const Transform & transform) {
+	Vector2 offset = emitter.data.boundary.offset + transform.position
+					 + emitter.data.position;
+	double half_width = emitter.data.boundary.width / 2.0;
+	double half_height = emitter.data.boundary.height / 2.0;
+
+	const double LEFT = offset.x - half_width;
+	const double RIGHT = offset.x + half_width;
+	const double TOP = offset.y - half_height;
+	const double BOTTOM = offset.y + half_height;
+
+	for (Particle & particle : emitter.data.particles) {
+		const Vector2 & position = particle.position;
+		bool within_bounds = (position.x >= LEFT && position.x <= RIGHT
+							  && position.y >= TOP && position.y <= BOTTOM);
+
+		if (!within_bounds) {
+			if (emitter.data.boundary.reset_on_exit) {
+				particle.active = false;
+			} else {
+				particle.velocity = {0, 0};
+				if (position.x < LEFT) particle.position.x = LEFT;
+				else if (position.x > RIGHT) particle.position.x = RIGHT;
+				if (position.y < TOP) particle.position.y = TOP;
+				else if (position.y > BOTTOM) particle.position.y = BOTTOM;
+			}
+		}
+	}
+}
+
+double ParticleSystem::generate_random_angle(double min_angle,
+											 double max_angle) const {
+	if (min_angle == max_angle) {
+		return min_angle;
+	} else if (min_angle < max_angle) {
+		return min_angle
+			   + static_cast<double>(std::rand()
+									 % static_cast<int>(max_angle - min_angle));
+	} else {
+		double angle_offset = (360 - min_angle) + max_angle;
+		double random_angle = min_angle
+							  + static_cast<double>(
+								  std::rand() % static_cast<int>(angle_offset));
+		return (random_angle >= 360) ? random_angle - 360 : random_angle;
+	}
+}
+
+double ParticleSystem::generate_random_speed(double min_speed,
+											 double max_speed) const {
+	if (min_speed == max_speed) {
+		return min_speed;
+	} else {
+		return min_speed
+			   + static_cast<double>(std::rand()
+									 % static_cast<int>(max_speed - min_speed));
+	}
+}
diff --git a/src/crepe/system/ParticleSystem.h b/src/crepe/system/ParticleSystem.h
index 3ac1d3f..d7ca148 100644
--- a/src/crepe/system/ParticleSystem.h
+++ b/src/crepe/system/ParticleSystem.h
@@ -1,18 +1,71 @@
 #pragma once
 
-#include "../api/ParticleEmitter.h"
+#include <cstdint>
 
-namespace crepe {
+#include "System.h"
 
-class ParticleSystem {
+namespace crepe {
+class ParticleEmitter;
+class Transform;
+/**
+ 	* \brief ParticleSystem class responsible for managing particle emission, updates, and bounds checking.
+ 	*/
+class ParticleSystem : public System {
 public:
-	ParticleSystem();
-	void update();
+	/**
+		* \brief Updates all particle emitters by emitting particles, updating particle states, and checking bounds.
+		*/
+	void update() override;
 
 private:
-	void emit_particle(ParticleEmitter & emitter); //emits a new particle
+	/**
+		* \brief Emits a particle from the specified emitter based on its emission properties.
+		* 
+		* \param emitter Reference to the ParticleEmitter.
+		* \param transform Const reference to the Transform component associated with the emitter.
+		*/
+	void emit_particle(ParticleEmitter & emitter, const Transform & transform);
+
+	/**
+		* \brief Calculates the number of times particles should be emitted based on emission rate and update count.
+		* 
+		* \param count Current update count.
+		* \param emission Emission rate.
+		* \return The number of particles to emit.
+		*/
+	int calculate_update(int count, double emission) const;
+
+	/**
+		* \brief Checks whether particles are within the emitter’s boundary, resets or stops particles if they exit.
+		* 
+		* \param emitter Reference to the ParticleEmitter.
+		* \param transform Const reference to the Transform component associated with the emitter.
+		*/
+	void check_bounds(ParticleEmitter & emitter, const Transform & transform);
 
-	float elapsed_time; //elapsed time since the last emission
+	/**
+		* \brief Generates a random angle for particle emission within the specified range.
+		* 
+		* \param min_angle Minimum emission angle in degrees.
+		* \param max_angle Maximum emission angle in degrees.
+		* \return Random angle in degrees.
+		*/
+	double generate_random_angle(double min_angle, double max_angle) const;
+
+	/**
+		* \brief Generates a random speed for particle emission within the specified range.
+		* 
+		* \param min_speed Minimum emission speed.
+		* \param max_speed Maximum emission speed.
+		* \return Random speed.
+		*/
+	double generate_random_speed(double min_speed, double max_speed) const;
+
+private:
+	//! Counter to count updates to determine how many times emit_particle is called.
+	unsigned int update_count = 0;
+	//! Determines the lowest amount of emission rate (1000 = 0.001 = 1 particle per 1000 updates).
+	static constexpr unsigned int MAX_UPDATE_COUNT = 100;
 };
 
 } // namespace crepe
diff --git a/src/crepe/system/PhysicsSystem.h b/src/crepe/system/PhysicsSystem.h
index cc13b70..038c120 100644
--- a/src/crepe/system/PhysicsSystem.h
+++ b/src/crepe/system/PhysicsSystem.h
@@ -1,5 +1,7 @@
 #pragma once
 
+#include "System.h"
+
 namespace crepe {
 /**
  * \brief System that controls all physics
@@ -7,18 +9,14 @@ namespace crepe {
  * This class is a physics system that uses a rigidbody and transform
  * to add physics to a game object.
  */
-class PhysicsSystem {
+class PhysicsSystem : public System {
 public:
 	/**
-	 * Constructor is default
-	 */
-	PhysicsSystem() = default;
-	/**
 	 * \brief updates the physics system.
 	 * 
 	 * It calculates new velocties and changes the postion in the transform.
 	 */
-	void update();
+	void update() override;
 };
 
 } // namespace crepe
diff --git a/src/example/CMakeLists.txt b/src/example/CMakeLists.txt
index bf12ff3..ddb0262 100644
--- a/src/example/CMakeLists.txt
+++ b/src/example/CMakeLists.txt
@@ -29,5 +29,6 @@ add_example(db)
 add_example(ecs)
 add_example(scene_manager)
 add_example(events)
+add_example(particles)
 add_example(gameloop)
 
diff --git a/src/example/particles.cpp b/src/example/particles.cpp
new file mode 100644
index 0000000..6eab046
--- /dev/null
+++ b/src/example/particles.cpp
@@ -0,0 +1,43 @@
+#include <crepe/ComponentManager.h>
+#include <crepe/api/AssetManager.h>
+
+#include <crepe/Component.h>
+#include <crepe/api/Color.h>
+#include <crepe/api/GameObject.h>
+#include <crepe/api/ParticleEmitter.h>
+#include <crepe/api/Rigidbody.h>
+#include <crepe/api/Sprite.h>
+#include <crepe/api/Texture.h>
+#include <crepe/api/Transform.h>
+
+using namespace crepe;
+using namespace std;
+
+int main(int argc, char * argv[]) {
+	GameObject game_object(0, "", "", Vector2{0, 0}, 0, 0);
+	Color color(0, 0, 0, 0);
+	Sprite test_sprite = game_object.add_component<Sprite>(
+		make_shared<Texture>("../asset/texture/img.png"), color,
+		FlipSettings{true, true});
+	game_object.add_component<ParticleEmitter>(ParticleEmitter::Data{
+		.position = {0, 0},
+		.max_particles = 100,
+		.emission_rate = 0,
+		.min_speed = 0,
+		.max_speed = 0,
+		.min_angle = 0,
+		.max_angle = 0,
+		.begin_lifespan = 0,
+		.end_lifespan = 0,
+		.force_over_time = Vector2{0, 0},
+		.boundary{
+			.width = 0,
+			.height = 0,
+			.offset = Vector2{0, 0},
+			.reset_on_exit = false,
+		},
+		.sprite = test_sprite,
+	});
+
+	return 0;
+}
diff --git a/src/example/rendering.cpp b/src/example/rendering.cpp
index e02f6a3..827ad07 100644
--- a/src/example/rendering.cpp
+++ b/src/example/rendering.cpp
@@ -34,7 +34,9 @@ int main() {
 	}
 	{
 		Color color(0, 0, 0, 0);
-		obj1.add_component<Sprite>(make_shared<Texture>("../asset/texture/second.png"), color, FlipSettings{true, true});
+		obj1.add_component<Sprite>(
+			make_shared<Texture>("../asset/texture/second.png"), color,
+			FlipSettings{true, true});
 	}
 
 	/*
diff --git a/src/test/CMakeLists.txt b/src/test/CMakeLists.txt
index 0e4eaed..acab388 100644
--- a/src/test/CMakeLists.txt
+++ b/src/test/CMakeLists.txt
@@ -1,6 +1,7 @@
 target_sources(test_main PUBLIC
 	dummy.cpp
 	# audio.cpp
-	PhysicsTest.cpp
+	# PhysicsTest.cpp
+	ParticleTest.cpp
 )
 
diff --git a/src/test/ParticleTest.cpp b/src/test/ParticleTest.cpp
new file mode 100644
index 0000000..6fe3133
--- /dev/null
+++ b/src/test/ParticleTest.cpp
@@ -0,0 +1,206 @@
+#include "api/Vector2.h"
+#include <crepe/ComponentManager.h>
+#include <crepe/Particle.h>
+#include <crepe/api/Config.h>
+#include <crepe/api/GameObject.h>
+#include <crepe/api/ParticleEmitter.h>
+#include <crepe/api/Rigidbody.h>
+#include <crepe/api/Sprite.h>
+#include <crepe/api/Transform.h>
+#include <crepe/system/ParticleSystem.h>
+#include <gtest/gtest.h>
+#include <math.h>
+
+using namespace std;
+using namespace std::chrono_literals;
+using namespace crepe;
+
+class ParticlesTest : public ::testing::Test {
+protected:
+	ParticleSystem particle_system;
+	void SetUp() override {
+		ComponentManager & mgr = ComponentManager::get_instance();
+		std::vector<std::reference_wrapper<Transform>> transforms
+			= mgr.get_components_by_id<Transform>(0);
+		if (transforms.empty()) {
+
+			GameObject game_object(0, "", "", Vector2{0, 0}, 0, 0);
+
+			Color color(0, 0, 0, 0);
+			Sprite test_sprite = game_object.add_component<Sprite>(
+				make_shared<Texture>("../asset/texture/img.png"), color,
+				FlipSettings{true, true});
+
+			game_object.add_component<ParticleEmitter>(ParticleEmitter::Data{
+				.position = {0, 0},
+				.max_particles = 100,
+				.emission_rate = 0,
+				.min_speed = 0,
+				.max_speed = 0,
+				.min_angle = 0,
+				.max_angle = 0,
+				.begin_lifespan = 0,
+				.end_lifespan = 0,
+				.force_over_time = Vector2{0, 0},
+				.boundary{
+					.width = 0,
+					.height = 0,
+					.offset = Vector2{0, 0},
+					.reset_on_exit = false,
+				},
+				.sprite = test_sprite,
+			});
+		}
+		transforms = mgr.get_components_by_id<Transform>(0);
+		Transform & transform = transforms.front().get();
+		transform.position.x = 0.0;
+		transform.position.y = 0.0;
+		transform.rotation = 0.0;
+		std::vector<std::reference_wrapper<ParticleEmitter>> rigidbodies
+			= mgr.get_components_by_id<ParticleEmitter>(0);
+		ParticleEmitter & emitter = rigidbodies.front().get();
+		emitter.data.position = {0, 0};
+		emitter.data.emission_rate = 0;
+		emitter.data.min_speed = 0;
+		emitter.data.max_speed = 0;
+		emitter.data.min_angle = 0;
+		emitter.data.max_angle = 0;
+		emitter.data.begin_lifespan = 0;
+		emitter.data.end_lifespan = 0;
+		emitter.data.force_over_time = Vector2{0, 0};
+		emitter.data.boundary = {0, 0, Vector2{0, 0}, false};
+		for (auto & particle : emitter.data.particles) {
+			particle.active = false;
+		}
+	}
+};
+
+TEST_F(ParticlesTest, spawnParticle) {
+	Config::get_instance().physics.gravity = 1;
+	ComponentManager & mgr = ComponentManager::get_instance();
+	ParticleEmitter & emitter
+		= mgr.get_components_by_id<ParticleEmitter>(0).front().get();
+	emitter.data.end_lifespan = 5;
+	emitter.data.boundary.height = 100;
+	emitter.data.boundary.width = 100;
+	emitter.data.max_speed = 0.1;
+	emitter.data.max_angle = 0.1;
+	emitter.data.max_speed = 10;
+	emitter.data.max_angle = 10;
+	particle_system.update();
+	//check if nothing happend
+	EXPECT_EQ(emitter.data.particles[0].active, false);
+	emitter.data.emission_rate = 1;
+	//check particle spawnes
+	particle_system.update();
+	EXPECT_EQ(emitter.data.particles[0].active, true);
+	particle_system.update();
+	EXPECT_EQ(emitter.data.particles[1].active, true);
+	particle_system.update();
+	EXPECT_EQ(emitter.data.particles[2].active, true);
+	particle_system.update();
+	EXPECT_EQ(emitter.data.particles[3].active, true);
+
+	for (auto & particle : emitter.data.particles) {
+		// Check velocity range
+		EXPECT_GE(particle.velocity.x, emitter.data.min_speed);
+		// Speed should be greater than or equal to min_speed
+		EXPECT_LE(particle.velocity.x, emitter.data.max_speed);
+		// Speed should be less than or equal to max_speed
+		EXPECT_GE(particle.velocity.y, emitter.data.min_speed);
+		// Speed should be greater than or equal to min_speed
+		EXPECT_LE(particle.velocity.y, emitter.data.max_speed);
+		// Speed should be less than or equal to max_speed
+
+		// Check angle range
+		EXPECT_GE(particle.angle, emitter.data.min_angle);
+		// Angle should be greater than or equal to min_angle
+		EXPECT_LE(particle.angle, emitter.data.max_angle);
+		// Angle should be less than or equal to max_angle
+	}
+}
+
+TEST_F(ParticlesTest, moveParticleHorizontal) {
+	Config::get_instance().physics.gravity = 1;
+	ComponentManager & mgr = ComponentManager::get_instance();
+	ParticleEmitter & emitter
+		= mgr.get_components_by_id<ParticleEmitter>(0).front().get();
+	emitter.data.end_lifespan = 100;
+	emitter.data.boundary.height = 100;
+	emitter.data.boundary.width = 100;
+	emitter.data.min_speed = 1;
+	emitter.data.max_speed = 1;
+	emitter.data.max_angle = 0;
+	emitter.data.emission_rate = 1;
+	for (int a = 1; a < emitter.data.boundary.width / 2; a++) {
+		particle_system.update();
+		EXPECT_EQ(emitter.data.particles[0].position.x, a);
+	}
+}
+
+TEST_F(ParticlesTest, moveParticleVertical) {
+	Config::get_instance().physics.gravity = 1;
+	ComponentManager & mgr = ComponentManager::get_instance();
+	ParticleEmitter & emitter
+		= mgr.get_components_by_id<ParticleEmitter>(0).front().get();
+	emitter.data.end_lifespan = 100;
+	emitter.data.boundary.height = 100;
+	emitter.data.boundary.width = 100;
+	emitter.data.min_speed = 1;
+	emitter.data.max_speed = 1;
+	emitter.data.min_angle = 90;
+	emitter.data.max_angle = 90;
+	emitter.data.emission_rate = 1;
+	for (int a = 1; a < emitter.data.boundary.width / 2; a++) {
+		particle_system.update();
+		EXPECT_EQ(emitter.data.particles[0].position.y, a);
+	}
+}
+
+TEST_F(ParticlesTest, boundaryParticleReset) {
+	Config::get_instance().physics.gravity = 1;
+	ComponentManager & mgr = ComponentManager::get_instance();
+	ParticleEmitter & emitter
+		= mgr.get_components_by_id<ParticleEmitter>(0).front().get();
+	emitter.data.end_lifespan = 100;
+	emitter.data.boundary.height = 10;
+	emitter.data.boundary.width = 10;
+	emitter.data.boundary.reset_on_exit = true;
+	emitter.data.min_speed = 1;
+	emitter.data.max_speed = 1;
+	emitter.data.min_angle = 90;
+	emitter.data.max_angle = 90;
+	emitter.data.emission_rate = 1;
+	for (int a = 0; a < emitter.data.boundary.width / 2 + 1; a++) {
+		particle_system.update();
+	}
+	EXPECT_EQ(emitter.data.particles[0].active, false);
+}
+
+TEST_F(ParticlesTest, boundaryParticleStop) {
+	Config::get_instance().physics.gravity = 1;
+	ComponentManager & mgr = ComponentManager::get_instance();
+	ParticleEmitter & emitter
+		= mgr.get_components_by_id<ParticleEmitter>(0).front().get();
+	emitter.data.end_lifespan = 100;
+	emitter.data.boundary.height = 10;
+	emitter.data.boundary.width = 10;
+	emitter.data.boundary.reset_on_exit = false;
+	emitter.data.min_speed = 1;
+	emitter.data.max_speed = 1;
+	emitter.data.min_angle = 90;
+	emitter.data.max_angle = 90;
+	emitter.data.emission_rate = 1;
+	for (int a = 0; a < emitter.data.boundary.width / 2 + 1; a++) {
+		particle_system.update();
+	}
+	const double TOLERANCE = 0.01;
+	EXPECT_NEAR(emitter.data.particles[0].velocity.x, 0, TOLERANCE);
+	EXPECT_NEAR(emitter.data.particles[0].velocity.y, 0, TOLERANCE);
+	if (emitter.data.particles[0].velocity.x != 0)
+		EXPECT_NEAR(std::abs(emitter.data.particles[0].position.x),
+					emitter.data.boundary.height / 2, TOLERANCE);
+	if (emitter.data.particles[0].velocity.y != 0)
+		EXPECT_NEAR(std::abs(emitter.data.particles[0].position.y),
+					emitter.data.boundary.width / 2, TOLERANCE);
+}