Nice entry! As other have mentioned, this ran extremely slow on my machine every time the rain particles came on screen. It made attempting to aim the "home" projectile very difficult. I also had a bit of a hard time figuring out what I was supposed to do - it took me a couple playthroughs before I realized you can upgrade towers and also re-aim them by pressing A/D. I would recommend at least adding a "pause" screen that tells the players all of these things while they're in-game.
The theme was a bit understated as well - the "calm" period was fairly standard tower defense gameplay. It would be nice to incorporate a bit more emphasis on the "calm before the storm" for the purpose of the game jam (but of course after the jam is over, it's completely unnecessary)
I think some minimal improvements would make this game really great though!
- Fix the framerate issues
- Add a small tutorial (text dump is honestly fine, but a quick "show and tell" of each tower would be even better)
- Give the player a chance to position their weapons before starting a round
- Bowling alley OP! I beat it with 100% bowling alleys XD