It's very cool, however I have yet to find an html5 game that will let me change the keybindings. Think of the people who don't use QWERTY!
And if you think about it, mario is usually played on a device where you only have a limited number of buttons. There's no reason to remap the keys if there's only 6 buttons to use.
It's a Tetris clone and very much a work in progress: Only "Standard" mode (and the controls menu) is implemented at all. There's also a simplistic AI and it saves your replays, but none of that is actually integrated into the game interface-wise yet :\