I like the base components at work here! I enjoyed the ability to make my own towers. It's a very solid foundation to build up! I will add that the UI became cluttered if you had too many materials as it started rising over the "Forge Turret" button. I have to agree with the "click to refuel" not being obvious in game, but I also had enough turrets covering each other that I didn't have any energy issues until the last wave where the win screen comes up. It probably also helps that I had a lot of bouncy projectiles that ripped through the back lines!
Overall, great job, you definitely have something here to keep building with if you decide to expand the project's scope!
- ImPasta/Mica