Great concept. Not a game for me, but even I can appreciate how it's made.
Controls are very smooth and responsive. Checkpoint after every screen, no waiting for the game to load or transit pointlessly between deaths (I sincerely thank you for this, many games fail by wasting time because they add needless animations), not lagging and we can even change the framerate if we have any problem (to be honest, that's the first time I heard about changing fps in a browser game).
Wonderful game, just not my type.