:)
Addictive. Still needs some help from frame-rate awareness. When a "slowdown" occures the game needs to be aware of it's processing slowdown and slow down the game fps to compensate otherwise things "jump".
I know I have troubles on Firefox on Windows 7.
I do compensation for actual elapsed time, but unfortunately this doesn't help when setInterval fires too late (in FF I can get occasional "jump" frame with 30x usual duration, I suspect due to garbage collection [1]).
Chrome and Opera are much more reliable in their JS timing.
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[1] You can check GC + animation test here:
http://hacks.mozilla.org/2010/01/javascript-speedups-in-fire...
FF (even version 3.6) performs pretty badly: I got 80-120 ms delay due to GC, Opera has 21ms, Chrome has 8 ms.
For my game it's even worse, normal frame can take 14 ms, garbage collected one 500 ms.