The game, which comes from programmer Stefan Hedman, is playable online, and it will drive you bonkers.
This first thing you notice is that gravity's all wonky and Mario moves like a jellyfish. You control the game with the direction arrows on your keyboard, but I use the word "control" loosely.
Everything is squishy and the music goes out of tune as you move. It's Mario as a fever dream and it's incredibly entertaining.
The playable web demo, brought to our attention by Laughing Squid, is very short at the moment, but it will give you a good idea of the sheer challenge of the game. Mario bounces off the question-mark blocks, wanders off the top of the screen and explodes in a spray of colorful pixels on contact with a Goomba.
The maddening Mario game is in pre-alpha demo mode right now, but a fully playable level would be a delight for retro gaming fans and anybody who thought they had a handle on conquering the Nintendo classic.