Taco Graveyard's Duplicity is an OUYA Create entry (and possible PC game) that involves versus puzzle play on a horizontal Tetris-like board. Every piece acts as both a block and open space simultaneously.

Taco explained more to me via Twitter: "When you clear a row, it fills their row. You lose when you don't have room for your next block to spawn." They say that it gets tricky because "you have to see it from both perspectives, there is a bit of figure-ground illusion/multistability going on."

I'm dizzy watching it, but anyone interested in learning more should check out this Duplicity postmortem. Sal of Taco said he'll likely release Duplicity on OUYA, PC, and maybe mobile. "I also have a half backed idea to release it on mobile devices and have multiplayer over Bluetooth."