public struct Speed : IComponent
{
	public float value;

	public Speed(float value) // Optional, syntactic sugar for later
	{
		this.value = value;
	}
}

// IMPORTANT: You need to pass the count of component types you will use to the context
const int COMPONENT_TYPES_COUNT = 9;

var context = new Context(Constants.COMPONENT_TYPES_COUNT);

var entity = context.CreateEntity();

entity.Add(new Speed(2f));

entity.Add(new Position(3, 7));
entity.Replace(new Health(10));
entity.Remove<Speed>();

var hasSpeed = entity.Has<Speed>();
var healthData = entity.Get<Health>();

// You can also chain methods!
context.CreateEntity()
	.Add(new Speed(2f))
	.Add(new Position(3, 7))
	.Replace(new Health(10)) // Note: Replace will add the component if doesn't have it yet
	.Remove<Speed>();

// Returns a group containing always all entities with Position and Speed components.
var group = context.GetGroup(MatcherGenerator.AllOf<Position, Speed>());

var entities = group.GetEntities();

foreach (var e in entities)
{
	// ...
}

// You can also use IInitializeSystem, ICleanupSystem and ITearDownSystem systems
public class MovementSystem : IExecuteSystem
{
	private IGroup group;

	public MovementSystem(IContext context)
	{
		// You can also use a shorthand for AllOf components!
		// This is equivalent to: GetGroup(MatcherGenerator.AllOf<Position, Speed>())
		group = context.GetGroup<Position, Speed>();
	}

	public void Execute()
	{
		foreach (var e in group.GetEntities())
		{
			var position = e.Get<Position>();
			var speed = e.Get<Speed>().value;
			position.x += speed;

			e.Replace(position);
		}
	}
}

public class RenderPositionSystem : ReactiveSystem
{
	private IContext context;
	private IGroup group;

	public RenderPositionSystem(IContext context) : base(context)
	{
		this.context = context;
	}

	protected override ICollector GetTrigger(IContext context)
	{
		return context.GetGroup<Position, View>().CreateCollector(GroupEvent.Added);
	}

	protected override bool Filter(IEntity entity)
	{
		// Yes, you can use multiple types in Has<T> method !
		return entity.Has<Position, View>();
	}

	protected override void Execute(List<IEntity> entities)
	{
		foreach (var e in entities)
		{
			var position = e.Get<Position>();
			e.Get<View>().gameObject.transform.position = new Vector3(position.x, position.y, position.z);
		}
	}
}