diff --git a/source/Game.cpp b/source/Game.cpp
index d423f87..3577650 100644
--- a/source/Game.cpp
+++ b/source/Game.cpp
@@ -12,7 +12,8 @@
 #include <Thor/Graphics.hpp>
 
 #include "abstract/Character.h"
-#include "sprites/Enemy.h"
+#include "sprites/Enemy.h"
+#include "sprites/Player.h"
 #include "util/Loader.h"
 #include "util/ResourceManager.h"
 #include "util/Yaml.h"
diff --git a/source/Game.h b/source/Game.h
index e997bcf..8fd86e0 100644
--- a/source/Game.h
+++ b/source/Game.h
@@ -8,15 +8,7 @@
 #ifndef DG_GAME_H_
 #define DG_GAME_H_
 
-#include <string>
-
-#include <SFML/System.hpp>
-#include <SFML/Graphics.hpp>
-
-#include <Thor/Resources.hpp>
-
 #include "sprites/TileManager.h"
-#include "sprites/Player.h"
 #include "World.h"
 
 class TileManager;
diff --git a/source/World.h b/source/World.h
index 973f210..35a7b83 100755
--- a/source/World.h
+++ b/source/World.h
@@ -8,8 +8,8 @@
 #ifndef DG_WORLD_H_
 #define DG_WORLD_H_
 
-#include "abstract/Sprite.h"
 #include "abstract/Character.h"
+#include "abstract/Sprite.h"
 
 class Character;
 class Sprite;
diff --git a/source/abstract/Character.cpp b/source/abstract/Character.cpp
index fc63a26..692e572 100644
--- a/source/abstract/Character.cpp
+++ b/source/abstract/Character.cpp
@@ -16,6 +16,7 @@
 #include "../sprites/Corpse.h"
 #include "../util/Log.h"
 #include "../util/Yaml.h"
+#include "../World.h"
 
 const std::string Character::KEY_HEALTH = "health";
 const int Character::DEFAULT_HEALTH = 100;
diff --git a/source/abstract/Character.h b/source/abstract/Character.h
index 332c54a..7b73e64 100644
--- a/source/abstract/Character.h
+++ b/source/abstract/Character.h
@@ -8,14 +8,10 @@
 #ifndef DG_ACTOR_H_
 #define DG_ACTOR_H_
 
-#include <string>
-#include <vector>
-
 #include "Sprite.h"
 
 class World;
 class Weapon;
-class Sprite;
 class Yaml;
 
 /**
diff --git a/source/abstract/Singleton.h b/source/abstract/Singleton.h
index e275ca4..0bd8fb7 100644
--- a/source/abstract/Singleton.h
+++ b/source/abstract/Singleton.h
@@ -8,8 +8,6 @@
 #ifndef DG_SINGLETON_H_
 #define DG_SINGLETON_H_
 
-#include <SFML/System.hpp>
-
 /**
  * Template class for inheriting singleton behaviour.
  *
diff --git a/source/effects/Bullet.cpp b/source/effects/Bullet.cpp
index 9b646fa..31d496a 100755
--- a/source/effects/Bullet.cpp
+++ b/source/effects/Bullet.cpp
@@ -12,6 +12,7 @@
 #include "../abstract/Character.h"
 #include "../util/Loader.h"
 #include "../util/ResourceManager.h"
+#include "../util/Yaml.h"
 
 const std::string Bullet::KEY_DAMAGE = "damage";
 const int Bullet::DEFAULT_DAMAGE = 10;
diff --git a/source/effects/Bullet.h b/source/effects/Bullet.h
index 3a70a0e..57d3c1d 100755
--- a/source/effects/Bullet.h
+++ b/source/effects/Bullet.h
@@ -8,12 +8,8 @@
 #ifndef DG_BULLET_H_
 #define DG_BULLET_H_
 
-#include <string>
-
 #include "../particle/Particle.h"
-#include "../util/Yaml.h"
 
-class Particle;
 class Yaml;
 
 /**
diff --git a/source/items/Weapon.cpp b/source/items/Weapon.cpp
index d93c1b0..eaadea5 100755
--- a/source/items/Weapon.cpp
+++ b/source/items/Weapon.cpp
@@ -13,6 +13,7 @@
 
 #include "../World.h"
 #include "../effects/Bullet.h"
+#include "../util/Yaml.h"
 
 const std::string Weapon::KEY_BULLET = "bullet";
 const std::string Weapon::DEFAULT_BULLET = "bullet.yaml";
@@ -78,11 +79,11 @@ Weapon::onThink(int elapsed) {
 	}
 }
 
-std::shared_ptr<Particle>
+std::shared_ptr<Sprite>
 Weapon::createParticle() {
 	// Minus to account for positive y-axis going downwards in SFML.
 	sf::Vector2f offset(- mOffset);
 	thor::rotate(offset, mHolder.getAngle());
-	return std::shared_ptr<Particle>(new Bullet(mHolder.getPosition() + offset,
+	return std::shared_ptr<Sprite>(new Bullet(mHolder.getPosition() + offset,
 			mHolder, mHolder.getAngle(), Yaml(mBullet)));
 }
diff --git a/source/items/Weapon.h b/source/items/Weapon.h
index e8720b9..3179b89 100755
--- a/source/items/Weapon.h
+++ b/source/items/Weapon.h
@@ -8,7 +8,9 @@
 #ifndef DG_WEAPON_H_
 #define DG_WEAPON_H_
 
-#include <Thor/Particles.hpp>
+#include <string>
+
+#include <SFML/System.hpp>
 
 #include "../particle/Emitter.h"
 
@@ -33,7 +35,7 @@ public:
 
 // Protected functions.
 protected:
-	std::shared_ptr<Particle> createParticle();
+	std::shared_ptr<Sprite> createParticle();
 
 // Private variables.
 private:
diff --git a/source/particle/Emitter.cpp b/source/particle/Emitter.cpp
index 6118a8a..542787a 100755
--- a/source/particle/Emitter.cpp
+++ b/source/particle/Emitter.cpp
@@ -7,8 +7,10 @@
 
 #include "Emitter.h"
 
-Emitter::Emitter(World& collection) :
-		mCollection(collection) {
+#include "../World.h"
+
+Emitter::Emitter(World& world) :
+		mWorld(world) {
 }
 
 Emitter::~Emitter() {
@@ -19,5 +21,5 @@ Emitter::~Emitter() {
  */
 void
 Emitter::emit() {
-	mCollection.insert(createParticle());
+	mWorld.insert(createParticle());
 }
diff --git a/source/particle/Emitter.h b/source/particle/Emitter.h
index e25fad8..f96de2f 100755
--- a/source/particle/Emitter.h
+++ b/source/particle/Emitter.h
@@ -8,27 +8,27 @@
 #ifndef DG_EMITTER_H_
 #define DG_EMITTER_H_
 
-#include "../World.h"
-#include "Particle.h"
+#include <memory>
 
 class World;
 class Particle;
+class Sprite;
 
 class Emitter {
 // Public functions.
 public:
-	Emitter(World& collection);
+	Emitter(World& world);
 	virtual ~Emitter();
 
 // Protected functions.
 protected:
 	void emit();
 	/// Creates a particle. Allows to use a user-defined particle class and custom settings.
-	virtual std::shared_ptr<Particle> createParticle() = 0;
+	virtual std::shared_ptr<Sprite> createParticle() = 0;
 
 // Private variables.
 private:
-	World& mCollection;
+	World& mWorld;
 };
 
 #endif /* DG_EMITTER_H_ */
diff --git a/source/particle/Particle.h b/source/particle/Particle.h
index 3612b0c..6639b1d 100755
--- a/source/particle/Particle.h
+++ b/source/particle/Particle.h
@@ -9,9 +9,7 @@
 #define DG_PARTICLE_H_
 
 #include "../abstract/Sprite.h"
-#include "../util/Yaml.h"
 
-class Sprite;
 class Yaml;
 
 /**
diff --git a/source/sprites/Corpse.h b/source/sprites/Corpse.h
index c67e5cf..e82c970 100644
--- a/source/sprites/Corpse.h
+++ b/source/sprites/Corpse.h
@@ -10,7 +10,6 @@
 
 #include "../abstract/Sprite.h"
 
-class Sprite;
 class Yaml;
 
 class Corpse : public Sprite {
diff --git a/source/sprites/Enemy.h b/source/sprites/Enemy.h
index c813283..8d2c57d 100644
--- a/source/sprites/Enemy.h
+++ b/source/sprites/Enemy.h
@@ -10,7 +10,6 @@
 
 #include "../abstract/Character.h"
 
-class Character;
 class World;
 class Yaml;
 
diff --git a/source/sprites/Player.h b/source/sprites/Player.h
index b0e2dfd..4569e9e 100644
--- a/source/sprites/Player.h
+++ b/source/sprites/Player.h
@@ -8,13 +8,10 @@
 #ifndef DG_PLAYER_H_
 #define DG_PLAYER_H_
 
-#include <SFML/System.hpp>
-#include <SFML/Graphics.hpp>
-
 #include "../abstract/Character.h"
 
-class Character;
 class Yaml;
+class World;
 
 /**
  * Player object.
diff --git a/source/sprites/TileManager.cpp b/source/sprites/TileManager.cpp
index bf1f4bd..e69382a 100644
--- a/source/sprites/TileManager.cpp
+++ b/source/sprites/TileManager.cpp
@@ -16,6 +16,7 @@
 #include "../util/Loader.h"
 #include "../util/ResourceManager.h"
 #include "../util/Yaml.h"
+#include "../World.h"
 
 const sf::Vector2i TileManager::TILE_SIZE = sf::Vector2i(100, 100);
 
diff --git a/source/sprites/TileManager.h b/source/sprites/TileManager.h
index 78e68c8..0bf66c1 100644
--- a/source/sprites/TileManager.h
+++ b/source/sprites/TileManager.h
@@ -8,15 +8,9 @@
 #ifndef DG_TILEMANAGER_H_
 #define DG_TILEMANAGER_H_
 
-#include <map>
-#include <vector>
-
-#include "../World.h"
 #include "../abstract/Sprite.h"
-#include <string>
 
 class World;
-class Sprite;
 
 class TileManager : public sf::Drawable {
 // Public types.
diff --git a/source/util/Loader.h b/source/util/Loader.h
index b4801ae..fe29035 100755
--- a/source/util/Loader.h
+++ b/source/util/Loader.h
@@ -8,19 +8,10 @@
 #ifndef DG_LOADER_H_
 #define DG_LOADER_H_
 
-#include <string>
-#include <map>
-#include <memory>
-
-#include <SFML/System.hpp>
-
 #include <Thor/Resources.hpp>
 
 #include "../abstract/Singleton.h"
 
-template <class T>
-class Singleton;
-
 /**
  * This class allows to set default resource folders and subfolders, which means that these
  * folders only have to be set once, and not be included in the creation of every single
diff --git a/source/util/Log.h b/source/util/Log.h
index f364eea..f4d00bf 100644
--- a/source/util/Log.h
+++ b/source/util/Log.h
@@ -8,8 +8,6 @@
 #ifndef DG_LOG_H_
 #define DG_LOG_H_
 
-#include <iostream>
-
 /**
  * Logging functions for different levels.
  *
diff --git a/source/util/ResourceManager.h b/source/util/ResourceManager.h
index aa5743d..38d50a9 100644
--- a/source/util/ResourceManager.h
+++ b/source/util/ResourceManager.h
@@ -8,15 +8,8 @@
 #ifndef DG_RESOURCEMANAGER_H_
 #define DG_RESOURCEMANAGER_H_
 
-#include <SFML/Graphics.hpp>
-
-#include <Thor/Resources.hpp>
-
 #include "../abstract/Singleton.h"
 
-template <class T>
-class Singleton;
-
 /**
  * Loads and manages all resources by providing Singleton access to Thor ResourceManager.
  */