I love the concept, though it almost feels like you abruptly started making a totally different game halfway through, where the races started?  I had to give up on the final one, alas, after throwing myself at the one before it an embarrassing number of times...

It might help if the background were more stable; sometimes it would change to horizontal stripes while I was moving along the ground, and it seemed like I wasn't moving at all, which was extra disorienting.

Hey, though, this is an entire complete game in only a week!  Great work!

Great idea for the core mechanic and I liked how your levels were designed around it as well. Nice job.