Unique use of the limitation, I like it!
The game feels very natural to control and the character is pretty charming, not to mention the effects (the stretch, the color fading as you age, etc). The visuals are simple but great. And I LOVE the jump SFX haha.
It's great that you're put on a safe spot to play with the controls before you enter the levels and have a time limit.
As it is, I found it pretty easy and straightforward, but I can absolutely see how this could be expanded and have lots of different challenges with different gimmicks and all. Good job!