Feed the Rats! Make 'em fat I say.
Not as creepy as it sounds, Feed the Rats is a puzzle game based on solving challenges using realistic physics. You've also got awesome inventions that you can use, such as cannons & conveyor belts!
The full price is $1.99, currently on launch sale at $0.99. I still have some promo codes tucked away though, so if you'd like the game for free please leave a comment below and I'd be happy to hook you up.