Those eyes!!
This game feels like you took the best from Kirby, Gish! and Globdule and set them loose in a James Pond world. Everything matches everything. The character is cute, the music is catchy and the huge visuals are distinct. This aestetic is so well done. And the fact that eyes always face the right way up. Such a genius move.
I love it when there is no explanation whatsoever and within a minute you're only held back with by the puzzles. Everything makes sense. Each level has own small thing that is new, and than the next level stretches that to the max, while introducing some small new thing. That style of level design is almost perfect. The fail rate matches the interest to keep going. This is enhanced by restarting the whole room instead of using checkpoints. You force the user to get better and better in part they're not stuck, and use that skill in the part they are stuck.
Did I mention those eyes always face the right way up? Implementing physics (and the corresponding correct sound effect) is something every game should aspire. The more real they are, the more you brain starts to predict paths correctly and you start enjoying long intricate chains of actions.
You can extend this easily with loads of other forms, but I would keep restricted to a couple and doing those well instead of introducing 311 different shapes. Adding playable areas is way more worth the effort. As well as making the idea/story work with both the washing theme and what you're actually doing in the game. Bouncing goo, buzzsaws.. eh? The only thing you should never change are those eyes. ;)