Enjoyed your game quite a bit. The gameplay felt tuned very well, and the feedback to the player was good. Every upgrade was balanced and felt meaningful. Cute little story. Cool thematic "invincibility" mechanic that gradually made it easier if you were struggling, though I felt it would have been a fun challenge even without that. (Maybe in a "hard mode" for a future version?)
I did notice that only the first enemy had on death sounds, guess they were bugged or didn't quite get into the game for the later enemies?
Speaking of which, it was great how more enemy types were added as the game went on, added variety and challenge.
Great job!