That is one hard game.
I love the style of it, and the mechanics are fluid but you seriously effed up when creating the cave-in system. It was completely random at times, sometimes I would have had a perfect run, powersliding as much as I could, and it would catch up to me still. Others I would mess up 3 or 4 times and it was hardly a problem.
It makes the game impossible unless you absolutely grind the hell out of it, and these games are designed to be casual fun, not something you sink hours into.
I like the idea, but barring any idea of the total length, any checkpoint system and the completely unbeatable cave-in, it makes the game intensely not fun.
Make some tweaks and I would definitely come back to give this a round 2, but for now it is unplayable.