This is a really neat concept and the execution is superb/feels really polished. Ignoring the fact that there are no sound effects due to time constraints, here were some of the bigger issues I had: It feels like there should be a way to moves turrets after you've placed them. I placed one too far away on accident and it became essentially worthless to me. The turret aiming seemed a little strange at times. When the turret was firing perpendicular to the enemy's direction of movement, they seemed to lag behind them quite a bit. Perhaps making them lead the enemies would help. It's also unclear if they were doing damage there, so maybe some more feedback on whether or not the bullets are hitting the enemy would help.
Other than that, it was an excellent game and I hope you plan to continue working on it post-jam!