I am ashamed to account for  the hours I’ve spent playing Cisco’s tetris-like simplistic  masterpiece, the Binary Game.

In this game, you turn the “bits” on or off until you add up to the number on the right, or you add the bits and manually enter a number on the right based on the set bits on the left.  Pretty cool – as a side effect you get really good at binary math.  Win win right?