Congrats on finishing your game!
Controlling an entire planet as a gun, shooting down giant space bombs? Absurd! I love it. The music and initial placement of a giant cannon on the north pole set forth a whacky and epic premise, and I was excited to see what was in store.
But I sat still at the start of the game for a full minute before anything happened. Nothing was on screen at all. And then I got bombarded by enemies and lost most of my health immediately. The tank controls were slow and clunky, making dodging anything or lining up a shot feel more luck than ability. But I think a lot of that felt worse because there wasn't a background. It was really hard to tell if I was moving or how fast or how the enemies were actually moving. Yes, I had a blue tail to give me a hint, but it wasn't a clear indication of speed, only direction. And did nothing to help me understand how enemies were moving. I just felt lost and confused and unable to really feel like I was doing anything. I gave it a few gos, but never quite got the hang of it. Stuff like this can be really hard to get right in any game, but a limited time jam? Super tough. The more playtesting you can have others do, the better. But even that can be difficult to find time for. It's worth it!
Still, be proud of the thing you made! Jams are an incredible place to learn and grow as a developer. There are some cool ideas in here. Keep doing game jams! Keep making games! :)