I took part in the 23rd Ludum Dare competition, where you have 48 hours to complete a game based on a theme which is set just before the competition begins.
It isn't very complete (as you can imagine with a timescale like that) but the platforming actually turned out pretty good.
It's written in Love2D. I used aseprite to draw the graphics, LapChirp to generate the sound effects, Tiled map editor to edit the map and the AdvTileRenderer library to render them.
You can view my entry, and play my game here.