Nice game and idea! You can feel it's polished from the beginning and it's a joy to play overal. The mechanic if fun, but I had issues that sometimesi felt two effects were applied at once, and I didn't know some power was changed. Somehow the tight timer kept me addicted to the game for quite a bit. Well done!

I found this game super challenging! The squishy cube is very satisfying to watch and it's fun to try and move fast. Nice game!

This game was fun!
I reached 204 points!

I love what you've done with the player, this squishy square changing it shapes while jumping is really juicy!
All mechanics are well implemented, double jump is cool to use and we can really feel the debuff on the low jump!

Bugs are kind of common in Game Jams, so I won't focus on it, even though it didn't prevent me from playing and enjoying your game.
It took me some times to understand what to do on the game over screen, maybe some UI text may help?
As you say, sounds are missing and could improve juiciness on your game.

Anyway, this is a nice game for your first entry!