I beat it with a smile on my face the entire time. Very clever twist on the theme, nice aesthetics and and clever level design. I think you did a really good job of giving a lot of variety with a very simple idea.
The only gripe is it's very hard to tell just how low I need get to not hit ceiling spikes at time. Maybe you could shrink in stages instead of incrementally to give clearer changes is sizes, instead we're left just guessing and hoping. The quick reset button helped mitigate this issue a lot.
Very impressive for a first jam, keep it up!