The art and animation were fantastic and the music felt great for the action and setting! I liked the bit of world building with the contract as well.
It was a bit difficult to keep track of the mouse cursor with all the action so you want to look into adding a custom cursor in the project settings or hide it completely during gameplay to make people look at the floating guns (depends what style of shooter you're going for). For the flying enemies, I wasn't quite sure when it was safe to jump or if they were about to swoop down so you might want to telegraph when they're about to like what you do with the ground enemies. On the upgrade screen, I didn't realize "collect" was a button so skipped the upgrades thinking I hadn't gotten any items. Disabling the exit button until you collect everything and adding hover states to the collect button would definitely help.
Overall though, this is a beautiful game and congrats on your first solo submission!