Calculation Solitaire is a pretty unusual solitaire card game. It has some features of Colorado Solitaire, but it really isn't much like any other solitaire card game I can think of. Suits are ignored, which isn't unheard of in games of Solitaire, but the 4 piles you build up are very strange. In addition, there are 5 piles of cards at the top of the game screen that behave like stacks where the last card you put on the pile has to be removed and moved to the foundations. You can't move cards between these stacks at all, and any card you take off the deck has to either be put into a foundation or on top of one of these stack piles. The trick is to put the cards on the stack in such a way that they can be taken off in a particular order and moved to the foundations. The foundations have to be built on alternating numbers (which is also kind of weird and hard to follow at first). To make that job easier, I display the next card that has to be placed in the pile to the left of the foundation pile.