The idea behind this game is lovely, and I had quite an enjoyable time getting a hang of the mechanics. I like that the first level is an introduction to reinforce the mechanics found on the main menu, though I did find that the second level ramped up in difficulty quite quickly, an intermediate level between the first and second would help ease this.
It also seems that after the green trampoline has activacted, you need to touch the red button again before it will bounce you up another time. This was quite confusing as on the third level I stepped on the green platform whilst I was big, meaning that the tube blocked me from going to the exit. I thought the level bugged at first as it wouldn't bounce me up again, and I restarted the game a few times because of that. Some indication on that, or making it so the green trampoline always bounces you when the exit is open without having to touch the red button again would make sense in this case.
I loved the level design, and the music was nice too. Some audio feedback and visual feedback when jumping, touching buttons, and the exit opening could elevate this game from already enjoyable to a solid fun game, nice job!