The first game to come out of XBox's Summer of Arcade was the most interesting game in the line up to me, and with it only costing 1200 points ($15) I'd say well worth the price. Limbo at its core is a simple platforming game with very simple controls, but is so much more, its main focus is in its puzzle solving the likes of which I haven't seen since Portal. Aside from left and right movement you only have a jump button and an interact button. This is one of the times that less is more, anything more might have made this game too complex for its own good.