Correction:
The web game is playable, just sometimes pretty tight in between checkpoints.
when the game "crashes", press shift to return to main menu.
and pressing y starts the game.
so if you had gotten a checkpointnand the game crashed, press shift and then y, so you get back to the last savepoint.
That way, by going back to main menu and reentering,
you can indeed play the web version :-)