Very fun game! It was incredibly satisfying to gain a bunch of height at a time. I would have loved a combo meter for lots of consecutive bounces quickly. It might have also been more interesting if you added some platforms that hurt the player, or some crumbling platforms that got destroyed after a single bounce, or some platforms that toggle on and off. Maybe you did add them and I just didn't get far enough to see them though lol
I did have a couple of minor problems while playing. I found that the player could be bounced INSANELY high if you placed the platforms a little bit inside him, but that would have probably been difficult to fix within the time limit. The problem with this is that the lava didn't seem to care about how high the player was, and you could get high enough to never have it reasonably catch up. The platforms also did not seem to work properly at the edges of the screen, and the player could get stuck falling indefinitely with no way to catch him. This is a very simply problem though and could probably be fixed very quickly once the jam is over. (edit: I read some of the other comments and noticed that this was seemingly intentional. I think a good alternative way to prevent the edges being abused would be to not allow tiles to be placed too close to each-other.) The final issue was that it was sometimes very frustrating to line up the platforms with the player due to how fast they moved, and I found myself using the slow-mo for longer than I would have liked to. Maybe making the platform move slower when in slow-mo could have helped with precision, and slowing down the music during slow-mo could have helped with feedback.
Despite the difficulty I had while playing, this was still incredibly fun. Great job overall! (and sorry for the paragraph of feedback lol)