Happy to be your 20th rater :) This game was a pleasant surprise for me, the main menu already grabbed my attention and served as an implicit tutorial for the core mechanic. You really managed to implement a nice visual style using only the most basic shapes.
At first, the isometric view was a bit weird for navigation but you can get used to it pretty fast. The color distortion effect in the main menu was a bit hard on the eyes, that's my only issue graphics-wise.
You could also add some indication on what the different colors represent in-game (sorry if it's there and I missed it).
Overall, a very simple and cool game, way to go! :)