This program is the old Towers of Hanoi, judge as boring as ever, with the added twist that the "towers" are sliced up photos. The default appears to be the Memorial Tower in Kansas City, but there's also the Washington Monument and several others. That's nice. You can look up the history of this game at Wikipedia, but my favorite TOH anecdote is the one where the king/sultan/caliph/shogun/emporeror asks his vizier/counsellor/wiseman how to solve the game. The unfortunate stares at the puzzle a minute and replies, "Oh, that's easy! Just move n-1 discs from A to B." He-who-must-be-obeyed then disconnects the not-so-wise-one's head and plants it firmly on pole C as a warning to smart alecs. There's not enough memory (physical or virtual) to solve the 8-disk game on my iBook, where this implementation grinds to a sullen halt, but once you've seen the 4-disk version, you've got the principle.