This last weekend I created a github project, picked the autogenerated name, and proceeded to create Furry Dangerzone.
Three and a half hours after getting familiar with Gosu I had a playable game. 24 hours later I had a polished game. ~48 hours later I had an optimsed, somewhat bug-free game. Since then I've been improving it here and there.
It's flappy-bird-esque: space to jump, don't touch the stars or the edges.