Card can be selected if and only if, it is called 'available'. Availability is, no other card does cover the blocks no other on the right and the left. You can change the background image or the type of card. I still kept the option of playing with tiles of classic Mahjong for fans of the original game. The current game can be saved automatically when you exit the game to replay later. So good fun, and tell me if you like the idea?