Really nice game! All the feels of Mole Mania, too!
Anyway, I'm on planet 3 now, and I do wonder what that zone 2s on the second planet is for. You can't enter it until you finish the last level of the planet, but there's nothing you can do there other than take off. (You can't even go back left.)
Is that a bug?
The game is really enjoyable and I'll play more later. :)