Restarting frequently but keeping you coins across loops is a good idea, and for the most part you executed it well. The art was good and the background looked great. I particularly liked the effect of the pieces of the tower coming back together.
Where I think this game suffers is that it's slow for a game jam. It takes a while to get some money going, it takes a while to get to new waves, it takes a while for a lot of things, and in a game jam people are less willing to spend a bunch of time playing one game. A button to speed up the game would help immensely overall, as well as making it more jam friendly. The only other design element that I'd change is that it wasn't clear what a lot of the icons meant. Damage and money were clear right away, and I figured out projectile speed, but otherwise I wasn't sure what they meant. Stick a couple bits of text next to them and you should be good.
Overall it's a relatively strong design if you just tweak those two points, and I enjoyed checking it out. Thanks for making a game.