The javascript speed war that's currently taking place amongst browsers may soon bring a javascript engine fast enough to have a pyromancer-like roguelike running in a browser.
http://www.chromeexperiments.com/browse/
That would be really cool. No more compilation/deployment/platform issue. I've been keeping an eye on browsers javascript speed for a few years, hoping that it would become fast enough one day for this :
http://jice.nospam.googlepages.com/rogue.htm
http://jice.nospam.googlepages.com/fire.htm
Well, that day seems really imminent...