Green Mountain Calculation is a solitaire card game with a fun frontier theme. When you play calculation, you're trying to order cards into piles skipping numbers based on the card to the left of the pile. These piles are located on the right side of the game screen. The pile with an Ace next to it only needs cards in Ascending order 2,3,4, etc. The card with the 2 next to it requires every other card 4,6,8, etc. without regard to suit.