Duplicity by Taco Graveyard (Salvatore Gionfriddo). A two player falling blocks puzzle game. Every piece is both a block and open space at the same time.
About this developer: Sal is one half of Taco Graveyard makers of Penumbear.
Follow @asdfThe CREATE Game Jam, sponsored by Kill Screen and OUYA, is an online contest challenging developers to make playable prototypes in just 10 days. Many world-class games were initially conceived in game jams. Don't have an OUYA? Pre-order one here.