Indie game storeFree gamesFun gamesHorror games
Game developmentAssetsComics
SalesBundles
Jobs

Isn't it inspired by the Set card game? ;)
Anyways, what a fantastic execution! Once again amazing job done with minimalistic, yet thoughtful design. That's how (simple) games should be done!

Yes, and the Set card game was inspired by the Wisconsin Card Sorting Test (psychology)