A super cool twist on tower defense and bullet hell! As the comments below stated, there are so many things done right.
Trying to add something aside from those comments here. **Nitpick alert!
My optimization brain told me to aim for tower predictfulness, which leads to picking aim + barricades (to my surprise the barricades do have health lol) and finally switched to spamming quads leaving only a safe spot near the track.
My thought is that the tower defense aspect is well done, however the bullet hell part could use for some working. I think it is indeed a great challenge to do so! Since bullet hell requires player to move a lot, while the enemies in a TD tends to follow a set track. As a result, player would try to go back to the picking spot but the bullets may not allow so. There's a contradiction here, a double edged sword that may induce interesting gameplays or disruption of flow.
Maybe that's why i opted for the strategy to remove one part of the contradiction to allow for the ease of the main TD game.
I really hope that your team can expand this to a full game!
The bullets get "out of control" very quickly, which highly limits the maneuvers player can do, maybe each type of turrets can shoot in consecutive turns, and in small bursts, which can be more forgiving in bullet hell gameplay, and encourages players to place different kinds of turrets instead of optimmizing for a single one.
Sorry for the long post, but i'm very impressed by the potential of this game.