This is a super fun game! Love the concept of it quite a lot. The pixel art graphic stands out and looks great, the sounds are nice and not too overwhelming, the gameplay is simple and easy to understand, the goal is clear, nice job. I also like the way the range of the turrets forms a nice contour, which I think looks quite cool. Would definitely play a bit more out or anger later (see below).
For criticism, I'd say the balancing of the game is a bit off. Without upgrades and such the game felt impossible at difficulty 10+. Turrets don't deal enough damage to fend off enemies, and the player character got insta killed :( I tried to build huge turret nests with 2 lasers, 3 fires and a bunch of normals all surrounding an unobtainium ore miner, but it still got destroyed for some reason. Spamming turrets everywhere doesn't even help, and it lags the game quite a bit. Resource comes a bit low too, Quinten said purple was the problematic one but I'd say yellow is the ultimate bottleneck given that every damn thing needs yellow. Tried a couple of times but still no luck, and pairing with a slow early game, it is a bit punishing if you lose a run. I'd also say spawning enemies directly at some walls catches me off guard. I am expecting a well-lit area should not spawn, but no, they spawned directly within a turret chain :( I think it throws tactical turret placement out the window, and I think it hurts the game a bit.
Anyway, I am seeing potential, and I think this is a pretty great entry! Well done!