You wouldn't know it by looking at it, but Source started out as an iPhone game. As indie developer Fenix Fire explains, it grew from a simple mobile idea to a full-fledged metroidvania, which is now headed to Steam Greenlight. It has a unique and beautiful look that reminds me of something between Tron and Descent. If that doesn't sound interesting to you, I bet the trailer will change your mind.
You play as a kind of firefly, flying around in a strange, bioluminescent world that is being corrupted by a dark energy. If you've never played a Metroid or Castlevania, the gist is that the game takes place in one big, connected world, which opens up as you earn new skills that allow you to enter new areas. I'm not even close to being sick of that formula, and the idea of mixing it with the freedom of a flying game looks really smart.
If you're lucky enough to be going to PAX East this week, you should make time to check out Source at the Indie Megabooth. And if you're already there, don't forget PC Gamer's panel on The (Incredible) Future of PC Gaming and the PAX East Afterparty .