Thanks so much for your kind words and detailed feedback!
You make a lot of very good points!
The limited aiming is something I could have handled much better. It does feel wrong when the enemies are coming at you from an angle that you can't hit them from. If I was to re-do it I would either implement diagonal aiming, or I would better design the rest of the game around the limitation like making enemies only come from cardinal directions.
I also agree with the movement space feeling quite limited, I was designing the game with the idea that the stand should always be visible and it wasn't until playing it after the deadline that I realized that you have very little space to move around in and that the invisible walls don't feel great to run into.
The feedback about the damage upgrade is spot on, I spent very little time on balancing which was a big mistake. The damage upgrade was kind of an afterthought to synergize with the piercing upgrade since piercing does less damage each pierce. But as you said, on it's own (without piercing or spread) it has some very redundant levels since they don't allow you to kill things quicker which was a huge oversight.
Upgrades being available between waves is a very good idea and something I definitely should have considered since going back to wave 1 is quite tedious if you've gotten far.
Now I am the one rambling...
Feedback is INCREDIBLY useful so I really appreciate your write up! <3