It's great to see more unreal games in the jam! This is a fun tower defense game and seems like a lot of work in just 7 days! I lasted until wave 25. Once I learned you could send the next wave before the previous one was done I was happy, that's a nice feature.
I think what would improve this game the most is some clarity. It needs some UI elements explaining the difference between each type of turret. The range of them all seems the same, but there isn't much feedback on what makes them different besides ice slows. A tiny bit of polish that will help a surprising amount is a little more variety in sound effects as well. For sounds you'll hear very often you'll want to have multiple different sound effects if you can. However even if you only have one you can vary it a little bit. In the sound cue for you turret shot I'd add a modulator node. There you can make it so the pitch varies a little bit every time it's played making even a single repeated sound effect nicer on the ears!
Awesome job, I look forward to seeing more!