While the game is normally priced at $20 Nimblebit is letting folks download and play the full game for free from now until Sunday. That's ususally reserved for a game that's been released for at least a few months to gain promotion. If you like the game you can either get it for $20 or get a four pack for $40 (which means you are getting two copies of the game for free). It's not the world's hardest game, but it is free for a few days. Enjoy.
Gallery: Zero Gear Screenshots