This was a fun concept, but I had a lot of issues with it. The first is the scaling of the game. The itch.io embed viewport is set too small to see everything. You say to play in fullscreen, but I play on a 4K screen so we can play and rate as a group, and in fullscreen the game is completely unplayable. The projectiles cannot reach the enemies. It would be helpful if you could adjust the embed viewport settings on your itch.io page to match the intended size for the game. I used to be a web developer, so was able to use browser tools to adjust the viewport size in the HTML to allow me to play the game.
In addition to the scaling issue, when 3 enemies reached the edge of the screen, the game stopped. I lost a life, and then could no longer interact with the game and nothing else happening in game. The music kept playing, but that was it.
When moving left and firing with the mouse to the right of the player, my shots often went down left, instead of up. Moving to the right my shots always went up, even if on the wrong side of the player. This made dodging while shooting back difficult.
After closing the upgrade screen the player weapon is firing automatically as if holding the attack button. This isn't a real problem since I was always firing anyway. It stops after receiving other inputs.
It would be nice if the UI was updated to have important parts always showing, and the rest in a scroll container. Things like buttons to close the screen, or the amount of currency available.
I like the overall idea. There were a lot of neat upgrades, and I was able to get a number of them. There is a good start here.