StabYourself has released Mari0 for free downloading in Windows, Linux, Mac OS, and even source code. Mari0 combines Super Mario Bros. and Portal, which is as awesome as it sounds. It includes all the original Mario levels plus puzzle maps meant to resemble Aperture Labs, complete with elements of Portal 2 like repulsion gel, light bridges, companion cubes, lasers, etc.
The free game also includes four-player co-op play mode, although you’ll likely need USB game controllers and direct human contact (scary) to play that mode, as the online multiplayer isn’t available yet. The game also comes with a level editor, map packs, 33 fancy hats to differentiate players, and other game modifiers.
If the game is lagging for you, turn the sound off in the options menu. Also, you’ll need a 2-button mouse (control-click doesn’t register as a right click by the current version of the game). Other than that, this is an absurdly awesome freebie StabYourself.net put together. I definitely won’t be burning their houses down with lemons.
I haven’t played it through all the way yet, but I made this .gif in anticipation of how it probably ends:
Here’s the ridiculously well-made trailer, a speed run video, and some one-player gameplay:
Two more videos available here.