I love the concept of the game. It is a neat idea and I think it could make for a great game!
... That being said, I think the execution of the concept could have been much better. On some of the jumps, I had to restart 5 or more times, usually just because I placed something a few pixels too high. I feel like, were you to publish this outside of the jam, you would need a mechanic that either makes you lose less time if you place something down wrong or some kind of time-slowing mechanic that would give the player time to back out of their placement if they quickly realize it is not good enough. As it is, the game is somewhat frustrating to play due to this (or maybe I'm just bad). Additionally, I think the jumping sound effect is just a little bit too loud (although this is a far more minor comment). For being made within 80 hours, though, this is a great start that just needs a little bit of extra help for the player in order to be less frustrating.
I did not dislike the game, and I hope it does not come off as if I did. The concept is great and the levels are well thought out. I simply wanted to bring a major flaw to your attention and some potential solutions should you choose to develop this further after the jam. Overall, great job!