diff --git a/GlitchyEngine/src/Math/BitArray.bf b/GlitchyEngine/src/Math/BitArray.bf
new file mode 100644
index 0000000..4f3b4ee
--- /dev/null
+++ b/GlitchyEngine/src/Math/BitArray.bf
@@ -0,0 +1,149 @@
+using System;
+
+namespace GlitchyEngine.Math
+{
+	public class BitArray
+	{
+		const int BitsPerInt = sizeof(uint) * 8;
+
+		private uint* _bits ~ Free(_);
+		private int _intCount;
+		private int _capacity;
+
+		public int Capacity
+		{
+			get => _capacity;
+			set => EnsureCapacity(value);
+		}
+
+		public this(int initialCapacity = sizeof(uint))
+		{
+			EnsureCapacity(initialCapacity);
+		}
+
+		[Inline]
+		static int IntCount(int bits)
+		{
+			int count = bits / BitsPerInt;
+
+			if(bits % BitsPerInt > 0)
+				count++;
+
+			return count;
+		}
+		
+		[LinkName("free")]
+		static extern void Free(void* memoryBlock);
+
+		[LinkName("realloc")]
+		static extern void* Realloc(void* memoryBlock, int size);
+
+		private void EnsureCapacity(int requestedCapacity)
+		{
+			if(requestedCapacity <= _capacity)
+				return;
+
+			int newIntCount = IntCount(requestedCapacity);
+
+			if(_intCount >= newIntCount)
+				return;
+			
+			int oldIntCount = _intCount;
+			_intCount = newIntCount;
+			_capacity = _intCount * BitsPerInt;
+
+			_bits = (.)Realloc(_bits, _intCount * sizeof(uint));
+
+			// Set new bits to 0
+			for(int i = oldIntCount; i < _intCount; i++)
+			{
+				_bits[i] = 0;
+			}
+		}
+
+		public bool this[int index]
+		{
+			get
+			{
+				Log.EngineLogger.AssertDebug(index >= 0);
+
+				if(index > _capacity)
+					return false;
+
+				int arrayIndex = index / _capacity;
+				int bitIndex = index % _capacity;
+
+				return ((_bits[arrayIndex] >> bitIndex) & 1) == 1;
+			}
+
+			set
+			{
+				Log.EngineLogger.AssertDebug(index >= 0);
+
+				if(index > _capacity)
+					EnsureCapacity(index);
+
+				int arrayIndex = index / _capacity;
+				int bitIndex = index % _capacity;
+
+				if(value)
+				{
+					_bits[arrayIndex] |= (1 << bitIndex);
+				}
+				else
+				{
+					// create a mask that is all 1 except for the bit at the specified index
+					uint mask = uint.MaxValue;
+					mask ^= (1 << bitIndex);
+
+					_bits[arrayIndex] &= mask;
+				}
+			}
+		}
+
+		/**
+		 * Sets all bits to given value.
+		 */
+		public void Clear(bool value = false)
+		{
+			if(value)
+			{
+				for(int i < _intCount)
+				{
+					_bits[i] = (uint)-1;
+				}
+			}
+			else
+			{
+				for(int i < _intCount)
+				{
+					_bits[i] = 0;
+				}
+			}
+		}
+
+		/**
+		 * Returns whether or not this bitarray is 1 for every 1 in mask.
+		 * i.e. mask == (this & mask)
+		*/
+		public bool MaskMatch(BitArray mask)
+		{
+			// The number of ints we can compare binary
+			int intCompares = Math.Min(mask._intCount, _intCount);
+			for(int i < intCompares)
+			{
+				if(mask._bits[i] != (_bits[i] & mask._bits[i]))
+					return false;
+			}
+
+			// if mask has more integers than "this", these integers must be 0
+			for(int i = _intCount; i < mask._intCount; i++)
+			{
+				if(mask._bits[i] > 0)
+					return false;
+			}
+
+			return true;
+		}
+	}
+}
diff --git a/GlitchyEngine/src/World/ComponentPool.bf b/GlitchyEngine/src/World/ComponentPool.bf
new file mode 100644
index 0000000..e8c4678
--- /dev/null
+++ b/GlitchyEngine/src/World/ComponentPool.bf
@@ -0,0 +1,30 @@
+using System;
+
+namespace GlitchyEngine.World
+{
+	public class ComponentPool
+	{
+		int _objectSize;
+		int _capacity;
+
+		int PoolSize => _objectSize * _capacity;
+
+		uint8* _rawData ~ delete _;
+
+		public this(int objectSize, int capacity)
+		{
+			_objectSize = objectSize;
+			_capacity = capacity;
+
+			_rawData = new uint8[_capacity * _objectSize]*;
+		}
+
+		[Inline]
+		public void* Get(int index)
+		{
+			Log.EngineLogger.AssertDebug(index >= 0 && index < _capacity);
+
+			return _rawData + index * _objectSize;
+		}
+	}
+}
diff --git a/GlitchyEngine/src/World/EcsWorld.bf b/GlitchyEngine/src/World/EcsWorld.bf
new file mode 100644
index 0000000..c034cf4
--- /dev/null
+++ b/GlitchyEngine/src/World/EcsWorld.bf
@@ -0,0 +1,250 @@
+using System;
+using System.Collections;
+using GlitchyEngine.Math;
+
+using internal GlitchyEngine.World;
+
+namespace GlitchyEngine.World
+{
+	public class EcsWorld
+	{
+		const int MaxEntities = 1024;
+		
+		typealias BitmaskEntry = (Entity ID, BitArray ComponentMask);
+		List<BitmaskEntry> _entities = new .();
+
+		List<uint32> _freeIndices = new List<uint32>() ~ delete _;
+
+		typealias ComponentPoolEntry = (uint32 Id, ComponentPool Pool);
+		Dictionary<Type, ComponentPoolEntry> _componentPools = new .();
+		
+		public ~this()
+		{
+			for(var entry in _componentPools)
+			{
+				delete entry.value.Pool;
+			}
+
+			delete _componentPools;
+
+			for(var entry in _entities)
+			{
+				delete entry.ComponentMask;
+			}
+
+			delete _entities;
+		}
+		
+		
+		/**
+		 * Registers a new Component.
+		 */
+		public void Register<T>() where T: struct
+		{
+			_componentPools.Add(typeof(T), ((uint32)_componentPools.Count, new ComponentPool(sizeof(T), MaxEntities)));
+		}
+
+		/**
+		 * Creates a new Entity and returns its ID.
+		 */
+		public Entity NewEntity()
+		{
+			Entity entity;
+
+			// Reuse freed entity slot
+			if(_freeIndices.Count > 0)
+			{
+				uint32 index = _freeIndices.PopBack();
+
+				entity = Entity.CreateEntityID(index, _entities[index].ID.Version);
+
+				_entities[index].ID = entity;
+			}
+			// Create new entity slot
+			else
+			{
+				entity = Entity.CreateEntityID((.)_entities.Count, 0);
+				_entities.Add((entity, new BitArray(_componentPools.Count)));
+			}
+
+			return entity;
+		}
+
+		/**
+		 * Removes the specified Entity from the World.
+		 */
+		public void RemoveEntity(Entity entity)
+		{
+			var listEntity = ref _entities[entity.Index];
+			if(entity != listEntity.ID)
+				return;
+
+			listEntity.ID = Entity.CreateEntityID(Entity.InvalidEntity.Index, entity.Version + 1);
+			
+			_entities[entity.Index].ComponentMask.Clear();
+			_freeIndices.Add(entity.Index);
+
+			// TODO: add "destructor" for components
+		}
+
+		/**
+		 * Assigns a component of type T to the specified entity and returns it.
+		 */
+		public T* AssignComponent<T>(Entity entity) where T : struct
+		{
+			if(entity.Index > _entities.Count)
+				return null;
+
+			var listEntity = ref _entities[entity.Index];
+
+			if(entity != listEntity.ID)
+				return null;
+
+			ComponentPoolEntry entry;
+			if(!_componentPools.TryGetValue(typeof(T), out entry))
+			{
+				entry = ((uint32)_componentPools.Count, new ComponentPool(sizeof(T), MaxEntities));
+
+				_componentPools.Add(typeof(T), entry);
+			}
+			
+			// TODO: maybe assert?
+			if(listEntity.ComponentMask[entry.Id])
+				return null;
+			
+			listEntity.ComponentMask[entry.Id] = true;
+			
+			return (.)entry.Pool.Get(entity.Index);
+		}
+
+		/**
+		 * Removes a component of type T from the specified entity.
+		 */
+		public void RemoveComponent<T>(Entity entity) where T : struct
+		{
+			if(entity.Index > _entities.Count)
+				return;
+
+			var listEntity = ref _entities[entity.Index];
+			if(entity != listEntity.ID)
+				return;
+			
+			ComponentPoolEntry entry;
+			if(!_componentPools.TryGetValue(typeof(T), out entry))
+				return;
+			
+			// TODO: maybe assert?
+			if(!listEntity.ComponentMask[entry.Id])
+				return;
+			
+			listEntity.ComponentMask[entry.Id] = false;
+		}
+
+		public T* GetComponent<T>(Entity entity) where T : struct
+		{
+			var listEntity = ref _entities[entity.Index];
+			if(entity != listEntity.ID)
+				return null;
+			
+			ComponentPoolEntry entry;
+			if(!_componentPools.TryGetValue(typeof(T), out entry))
+				return null;
+
+			// TODO: maybe assert?
+			if(!listEntity.ComponentMask[entry.Id])
+				return null;
+
+			return (.)entry.Pool.Get(entity.Index);
+		}
+		
+		public WorldEnumerator Enumerate(params Type[] componentTypes)
+		{
+			return WorldEnumerator(this, componentTypes);
+		}
+
+		public struct WorldEnumerator : IEnumerator<Entity>, IDisposable
+		{
+			private EcsWorld _world;
+			private BitArray _bitMask;
+			private BitmaskEntry* _currentEntry;
+			private BitmaskEntry* _endEntry;
+
+			public this(EcsWorld world, Type[] componentTypes)
+			{
+				_world = world;
+				_currentEntry = _world._entities.Ptr;
+				_endEntry = _world._entities.Ptr + _world._entities.Count;
+
+				_bitMask = new BitArray(_world._componentPools.Count);
+				for(var type in componentTypes)
+				{
+					Log.EngineLogger.AssertDebug(type.IsStruct, "Components can only be structs.");
+
+					var result = _world._componentPools.GetValue(type);
+
+					if(result case .Ok(let entry))
+					{
+						_bitMask[entry.Id] = true;
+					}
+					else
+					{
+						Log.EngineLogger.AssertDebug(false, "Queried component is not registered for this world. This is invalid because the query would never return any results.");
+					}
+				}
+			}
+
+			public Result<Entity> GetNext() mut
+			{
+				while(_currentEntry < _endEntry)
+				{
+					BitmaskEntry* entry = _currentEntry++;
+					// Check whether or not mask matches
+					if(entry.ComponentMask.MaskMatch(_bitMask))
+						return entry.ID;
+				}
+
+				return .Err;
+			}
+
+			public void Dispose()
+			{
+				delete _bitMask;
+			}
+		}
+
+		public static void Test()
+		{
+			EcsWorld world = new .();
+
+			world.Register<TransformComponent>();
+
+			Entity entity = world.NewEntity();
+
+			TransformComponent* myComp = world.AssignComponent<TransformComponent>(entity);
+			myComp.Transform = Matrix.Identity;
+
+			TransformComponent gotComp = *world.GetComponent<TransformComponent>(entity);
+
+			world.RemoveComponent<TransformComponent>(entity);
+
+			Entity entity2 = world.NewEntity();
+			world.AssignComponent<TransformComponent>(entity2);
+
+			world.RemoveEntity(entity);
+
+			entity = world.NewEntity();
+
+			world.RemoveEntity(entity);
+			world.RemoveComponent<TransformComponent>(entity);
+
+			entity = world.NewEntity();
+
+			for(let forenty in world.Enumerate(typeof(TransformComponent)))
+			{
+
+			}
+
+			delete world;
+		}
+	}
+}
diff --git a/GlitchyEngine/src/World/Entity.bf b/GlitchyEngine/src/World/Entity.bf
new file mode 100644
index 0000000..097eeb0
--- /dev/null
+++ b/GlitchyEngine/src/World/Entity.bf
@@ -0,0 +1,30 @@
+using System;
+
+using internal GlitchyEngine.World;
+
+namespace GlitchyEngine.World
+{
+	public struct Entity : uint64
+	{	
+		// Binary Format:
+		// Bits: [0 - 31] [32 - 64]
+		// Data: Version    Index
+
+		[Inline]
+		internal uint32 Version => (uint32)this;
+
+		[Inline]
+		internal uint32 Index => (uint32)(this >> 32);
+		
+		[Inline]
+		static internal Entity CreateEntityID(uint32 index, uint32 version)
+		{
+			return ((uint64)index << 32) | version;
+		}
+		
+		[Inline]
+		internal bool IsValid => Index != InvalidEntity.Index;
+
+		public const Entity InvalidEntity = ((uint64)uint32.MaxValue << 32) | 0;//TODO: Report bug: CreateEntityID(uint32.MaxValue, 0);
+	}
+}
diff --git a/GlitchyEngine/src/World/TransformComponent.bf b/GlitchyEngine/src/World/TransformComponent.bf
new file mode 100644
index 0000000..0ba7758
--- /dev/null
+++ b/GlitchyEngine/src/World/TransformComponent.bf
@@ -0,0 +1,19 @@
+using GlitchyEngine.Math;
+
+namespace GlitchyEngine.World
+{
+	public struct TransformComponent
+	{
+		static int _id;
+
+		public static int ID {get => _id; set => _id = value; }
+
+		internal Matrix _transform;
+
+		public Matrix Transform
+		{
+			get => _transform;
+			set mut => _transform = value;
+		}
+	}
+}