Add-to-13 Solitaire

Add-to-13 Solitaire is a solitaire card game also known as Pyramid Solitaire. Cards are placed in a pyramid shape of seven overlapping layers. The goal is to get all cards to the foundation. But cards can only be moved there in pairs when they add up to a value of 13. Cards in the stock can be turned if no moves are available. A turned card can be used to make a match, but if there is no valid move it's moved to the foundation regardless.