(Note: This is a review of the browser build, I went back to check and I think the Windows build is slightly different?)
Great game and cool implementation of the theme, not really much negative to say about it! The art style was simple but effective, and I liked the use of sparse background elements to give rooms more personality. The music seemed a bit disjointed at first, but it did grow on me over time. It did such a good job staying in the background that I'm not actually sure if there was more than one song, so I think a bit more "kick" in that area definitely could have helped!
As someone who's pretty bad at both making and solving puzzles, I thought the puzzles in the game were quite creative and just the right amount of mind-bending without ever taking too long to figure out. I also appreciate that the backtracking never got too bad, with the warp mechanic definitely being a big help there. I think my only issue was that some of the bounce timings were pretty strict and took a lot of attempts to pull off. I actually had to remap my controller to have the transformation ability on another button to pull off the various tricks comfortably. I think the deadzones on the analog stick might also have been a bit low, as trying to use the stick often resulted in jumping or transforming by accident. While I appreciate the dedication to the directions-only control scheme, I think more mappings for the jump and transform would definitely have helped!
I actually went back and played it in an incognito tab to make sure, and all the "powerups" indeed seem to be available from the start (at least in the web build, I think in the Windows build, the square form and the warp aren't unlocked by default?). The "Metroidvania" is purely based on player knowledge, which I think is super cool and great for replayability! Some mechanics and reveals were pretty easy to figure out by accident, like the bounce ability. Others, like the various checkpoint shenanigans, were genuinely jaw-dropping, and I think the game did a great job helping you discover them organically!
Either way, I had a great time and managed to find both secrets according to the credits (I'm guessing the frog at the start was one of them, honestly not sure what the other one was)!