XOR0 game
I built an online version (single player and multi player) of a card game that my wife and I created the physical version of a few years ago: https://play.xor0game.com The game is basically the XOR operator combined with set-style game mechanics. What makes it better than other set style games, imho, is that there's a mathematical property of "projective sets" that guarantees that there is always at least one valid set on the table.