An adventure puzzle/platformer for the Game Boy. The mechanics are fun, and has you transforming between a human, frog, and snake to get through various areas. I'm about an hour in and the puzzles are fairly simple, but the charming writing and art design carry the game for me. I'd recommend it if you're looking for something somewhat casual. I have laughed out loud a few times while playing it.
If you want to check it out, you'll need to run it on an emulator.
The game is a Japan-only release, but there's an English fan patch you can find on here
You'll need the base ROM for the game, which you can find here
Once you download both of those, use this to mash them together and you're good to go.