CALCULATION SOLITAIRE is a challenging game that will keep you thinking. Like normal solitaire the objective is to move all cards onto the foundation, but unlike normal solitaire you don't build the foundation in-order (suits are ignored). Rather you step by a number with wrap around (modulo 13 for the mathies in the crowd). The first pile is built stepping by 1s. A 2 3 4 5 6 7 8 8 T J Q K The second pile is built stepping by 2s. 2 4 6 8 T Q A 3 5 7 9 J K The third pile is built stepping by 3s. 3 6 9 Q 2 5 8 J A 4 7 T K The fourth pile is built stepping by 4s. 4 8 Q 3 7 J 2 6 T A 5 9 K Sounds confusing, but we provide a helpful hint card which shows the progression so you know what is coming next and can plan to win the game... which you will need to do because it is very challenging. There are board columns where you can stash cards that don't yet go on the foundations. However cards on the board cannot be moved, unless they are promoted to the foundation. Totally free!! No in-app purchases. You can play an easier or a harder version plus a bonus game One234 where all the cards are laid out in a fan.