Tiles that are below other tiles cannot be seen. The game is finished when all pairs of tiles have been removed from the board or when there are no exposed pairs remaining. The goal is to match open pairs of identical tiles and remove them from the board, exposing the tiles under them for play. A tile is said to be open or exposed if it can be moved either left or right without disturbing other tiles. The 144 tiles are arranged in a special four-layer pattern with their faces upwards. An untouched turtle formation, with exposed 'free' tiles highlighted in blue
