Maybe it's just me (Firefox 3.5.2 on WinXP), but the plus key ('+' and '=') doesn't seem to work, so I can't type 1+2 or x=1. Just tried it in Chrome, and that works fine. IE8 does too (though it's very slow).

Anyway, very neat project! How layered is it -- do you think it could approach the speed of JavaScript?