This is SCVNGR's version of that, in playing card format. https://techcrunch.com/2010/08/25/scvngr-game-mechanics/ https://techcrunch.com/2010/08/25/scvngr-gam

This is SCVNGR's version of that, in playing card format. https://techcrunch.com/2010/08/25/scvngr-game-mechanics/ https://techcrunch.com/2010/08/25/scvngr-game-mechanics/ I vaguely recall seeing that Zynga did something similar. Some of the mechanics revolve around the addictive and aspects of these type of games.