I didn't think that a bird collecting berries would hit this hard with nostalgia and difficulty, but here we are!
This game felt really well designed and fun to play; in my playthrough, there wasn't anything that I found (be it glitch or game design) that caught my eye negatively. The gameplay felt fluid, the rooms progressed with a good difficulty curve and gave you enough instructions to help you get ahead.
I can't say much towards secrets; while I was able to find the hidden stars room, I couldn't get all 9 berries nor beat the game on no-hit difficulty. Even with this in mind, it's great to see a non-completion Easter Egg like that in the game!
My playthrough: