HappyTap

You're a little green square. You're constantly moving. Tap to go one way, tap again to go the other way. Tap once more to go the way you were going before you tapped again after you tapped the first time. Simple, right?

Don't hit the edge. Don't hit the brick walls. Oh, it looks like those red squares are angry with you. You shouldn't hit them either! Why are they mad? Tap away and find out!