Thank you for the bug report! I have not tested on firefox, but sadly I expect it not to work because of certain gradient drawing things I do, which aren't supported.
Does it fail to run completely? Or does it just run in a way that is bad?
No fullscreen, but that's a good point.
The page was under construction when you first went to it I think, I've been editing it recently. The little playable 128px by 72px version is just there so the game is tagged as 'playable in browser'
The interface is supposed to be like a browser version of Smash bros, but yeah it's atypical to say the least.
Oh and the up-arrow thing with scrolling I can fix with CSS if I can figure out how to send the CSS file to the page.
Thank you for the information!