This was a really fun gameplay loop! I spent quite a bit of time bouncing around and catching Z's (at first I was caught off-guard by how high I could jump, lol!). One thing I would have liked is some kind of indication (a little flash or sound effect or something) when the invincibility is just about to run out, because I occasionally got hit right after it ran out by taking a risk I might not have taken if I knew it was going to expire. I also feel like some kind of live score and/or leaderboard would also really add to the addictiveness of that core loop. But even without that, this is a really solid and fun game. Great work! :)