Cool, I guess. No instructions what-so-ever. Can we get some documentation on keys to use?
Edit: Yes, I did only test in Firefox and Chrome. According to the comments below, it appears to work for modern browsers except Firefox.
I can't understand this - in 2013, how on earth do you break mouse events in JavaScript? We've had events like onmousedown working reliably across browser implementations for a decade or more, what on earth is going on?
Firefox should just support offsetX as well, but they don't, for whatever reason.
Nothing else is implemented - and that much is probably obvious for people who played a hack'n slay before.
But thinking about it, it is interesting how games explain their shortcuts in the interface.