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."