This was pretty fun, and I with some balancing could be nice little TD game. In my game for some reason repair wasn't working (was always red), so it was somewhat hard to survive without that for long. I also didn't understand building placement requirements, so I just put towers wherever it allowed me, which was usually not the place I'd actually want them.
Visuals are basic, music is fine, and controls are OK, but it's a bit annoying without minimap and with buttons on the side it's easy to scroll sideways unintentionally.
Great game overall!