I really like the concept, the theme, and the way you implemented the limitation! Your art is so cute and I love it.
Gameplay wise, just as others say, I feel like the speed of the character could use some adjustment. Right now it requires a LOT of precision, which is not necessarily bad; however, it does mean the character ends up feeling a little slippery. I think it has something to do with the start and stop; if there's a way to slow down the character when they're just starting or just stopping, I think it would feel better?
Additionally, I got to a level that used the yellow squares in the circle, but they mostly don't seem to do anything for me. I got them to work once, where I jumped directly on top of it and bounced off, but couldn't replicate it despite trying multiple times.
Just one more thing regarding gameplay; on some levels, there's a little bit of a stutter when moving from a position to the left of the screen to a position more to the right of the screen. This could have something to do with my WiFi or it being an HTML build, but I found it happened consistently in the same spot on one of the levels.
Regarding audio, I do agree that the sound effects are a little loud; but more than that, I think it has to do with their balance. The level clear sound effect is quite a bit louder than the jump sound effect, so there's a bit of imbalance there. I think editing this to be more balanced would make the game a lot more enjoyable. This could be easier to do from a development perspective if you have some background music as your anchor for your audio levels, although this isn't necessary :)
Despite these things, I did really enjoy the concept, the gameplay, and the art. I think there's a real gem of a game here waiting to be polished!