protected unsafe override void Update(float state, ReadOnlySpan <DefaultEntity> entities)
            {
                Components <DefaultSpeed>    speeds    = _world.GetComponents <DefaultSpeed>();
                Components <DefaultPosition> positions = _world.GetComponents <DefaultPosition>();

                foreach (ref readonly DefaultEntity entity in entities)
                {
                    DefaultSpeed        speed    = speeds[entity];
                    ref DefaultPosition position = ref positions[entity];

                    position.X += speed.X * state;
                    position.Y += speed.Y * state;
                }
            protected override void Update(int state, ReadOnlySpan <DefaultEntity> entities)
            {
                Components <DefaultComponent> components = _world.GetComponents <DefaultComponent>();

                foreach (ref readonly DefaultEntity entity in entities)
                {
                    ++components[entity].Value;
                }
            }