Back in August game development duo Stabyourself revealed that they are working on a game where Mario meets Portal -- Mari0. Now the developers have begun a new motivational exercise to help them finish the game: they're posting a screenshot a day of their work-in-progress.
The game's creators say that Mari0 is a real, playable game they are working on that isn't a mod of any existing games or based on the original Super Mario Bros. code. The game is coded using Löve framework and all source code will be available after the release. It is currently being developed for Windows, OSX, and Linux-based systems, and will be completely free.
With a release deadline looming (the duo want to have the game out before the end of the year), Stabyourself are revealing parts of the game each day via their Mari0 Marathon page where people can follow their progress.
Develop of Mari0 continues to blow one's mind [GameSetWatch]