Great job submitting a game! I think what you've managed to create here is great for a second game. As others have pointed out, once you figure out that everything else but turrets loses you money you can't lose. I think you've done a great job with the visuals, everything is very clear and minimal. Also great work fitting in the upgrade theme although it didn't seem like my turrets needed them since the default fire rate could keep up with the enemy spawn rate. With some simple balancing I think this would be a very polished experience. Hope you were able to learn a lot and thanks for participating!