Block Off is a cross between a puzzle and a strategy game. The objective is to clear up a pile of blocks by removing them one by one, without disturbing the red ones which are also in the pile. It may be the most uncomplicated game out there but it certainly takes some concentration.
The good thing about Block Off is that you can theoretically play forever. You will, however, make a mistake after a couple of minutes and your game will come tumbling down.