Lovely Planet
Quicktequila’s Lovely Planet is the anti-modern FPS. Instead of being multiplayer, gritty, and easy, Lovely Planet is single player, cutesy, and incredibly difficult. Calum Bowen’s happy, catchy soundtrack only really fits the first couple worlds. After that, the game introduces cruel new mechanics that demand precision trick shots on the run. I couldn’t beat a single stage in world 5 except the ending. If your keyboard-and-mouse skills are awesome, give this game a shot. It’s different.
Source: http://www.quicktequila.com/lovelyplanet.html via their booth at PAX East 2015, also YouTube and Bandcamp