Overall, very cool and unique idea! Was definitely shocked by change in genre (from chill to a monster blaster game).
1. I would say that the intro was a bit too long, because you might lose all people that like shooting games, when they see three levels and relaxed gameplay.
2. After shooting ever decaying tooth but one, the last one starts shooting WAY faster than at the start with all the other decaying teeth still alive. I'm sure this is intentional, but I does feel kinda unfair to the average player (especially with the jellyfish). Now correct me if I'm wrong, but you'er spawning the rockets with a set amount of time in-between each spawn, then spawning it at the location of one of the remaining teeth. If that is the way that you are doing it, then the last decaying tooth will be spawning rockets twice as fast as it was before the player destroyed the second to last tooth. That jump feels unnaturally fast and kinda annoying.
Hope this helps. Also, I joined the discord, so lmk if you want anymore feedback on newer levels/mechanics.