It doesn't seem to have the Abominable Snow Monster (TM)
It's amusing that the original (native) version ran smoothly on a 286 with EGA but this JS version gets the CPU running hard enough to turn on the fans on my 2014 MBP.
I would guess it's running at like a thousand FPS, could be wrong though.
That looks like it's a recreation, though. Shouldn't it be possible to create an Emscripten port of the original? :)
Many of the normal rules aren't implemented (flips in the air, jumping off of rocks if you click at the right time, etc.).