Frogatto & Friends
Frogatto is an open-source platformer. You're given a cross-section view into the world, and you help a small green fellow named Frogatto walk and jump between solid platforms without getting hurt.
Frogatto is a finished, fully-playable game. We're planning to add a bunch of other stuff to it, but we have a complete start-to-finish single-player story you can play right now.
Developer: Various / open source
Download in the open source Indie Game Installer