The circular node based connections are a genius mechanic. It's really fun to expand outward to strategically place turrets. I think it would help if you moved the Credits to the bottom of the screen and place like with like, so you can view credits quickly without interrupting gameplay.
I think it would help to make the coins a little bit larger too, or make them stick around slightly longer.
Overall really excellent design and nice cute vibe. I could see this gameplay working well on mobile (tapping coins is so nice) and it's a nice mix of casual and frenzy style gameplay.