Source Free is a shunting puzzle app game: https://itunes.apple.com/us/app/source-free/id791918168?mt=8
Your task is to get a blue dot from the factory to the blue home. You must turn pipes so the dot can travel.
Along the way, you will have to pass through a machine that will change the color of your dot. There is also a device that will provide a ricochet action that you will need.
There are 60 levels. I've done 40 of them. They're not terribly hard. However, on the timed levels, I'm too slow!