I quite like the idea of this game, and think it fits the theme pretty well.
I feel like that currently, the camera moves a bit too slowly, especially considering the fact most people would take at least 3-4 cycles to deal 50 damage.
It might be interesting to more strongly limit the player movement (since generally in tower-defense games, enemies approach the base in a pre-determined line), and require the player to fully focus on moving up / down to dodge enemy projectiles (and if you wanted to take this further, you could lean even harder into the tower offense concept by having the player actually try and construct waves of enemies to take down a tower, with the win condition being destroying the tower (or pc in this case) in as few waves as possible).
One final note, please put the explanation screen right after the 'play' button as well, so players are forced to look at the rules (in my personal game jam experience, people want to start playing these games as fast as possible, so even when controls are explained separately in a different menu, most people won't take the time to go through them if not forced to).