I really loved the sound design—super cool that you created it yourself!
I also really liked how well you teach the player the mechanics (the blue box). First, you introduce it in a safe zone, giving the player a chance to understand how it works and make mistakes. That’s a great design choice!
The controls felt a bit tricky at times, which made some puzzles harder to complete. Maybe making the gaps a little smaller would give players a better chance to jump across.
I’d recommend adding different states for the portal—closed until the players collect the balloons, and open after they’ve gathered them.
Overall, an awesome platformer for such a short development time. Well done!