There seems to be some bug: the game loads and I see the "click mouse button" prompt, but then I never see anything in the viewport except the tan mouse pointer. (Web build, Chrome 128 on Mac.)
Nice concept and puzzle design, and amazing work for a 10-year-old!
Suggestions for improvement: the animations are slow enough to hinder play, and the controls are awkward (I'd suggest one set of arrow keys to move the whole player, and separate grow and shrink keys).
Interesting puzzle, but partway through I ran into what I take to be a bug where the player stopped interacting with anything and could float past the bounds of the playing field.