The window this game uses it tiny, which means that it's difficult to impossible to actually see the different transformations.
Combine that with the incredibly obnoxious music and the fact that endings are just "you turned into X" and I found little reason to play it long enough to actually beat it.
You're not gonna win this in one go. This game is mostly trial and error, and then restarting with some given foresight from the last playthrough. It's a good puzzle, though.
This game is hard! But true to the retro japanese games, they have a lot of puzzles that requires you to actually plan ahead before attempting a puzzle. Kudos to the translator for translating everything including the omake!