A free app for Android, by Mad Logic Games.
The Boxes are a very interesting and simple puzzle game.
The basic concept of the game is that every action has an equal and opposite reaction. It's very easy to understand, but hard to master. You have to move one of the boxes by dragging your finger from one corner to the other. Be careful, though, because the other box will move with you, and you'll have to deal with the mighty "Crushers" in order to advance further.
The game is based on the concept of relativity, which means that the movement of the boxes is not tied to any specific time, but to the time of your movement.
