Super niche art style and game design! I am impressed by all the different kinds of games I see in game jams and this is definitely one of the most unique ones.
My only suggestion is to mix up the gameplay more with more levels, obstacles, interactable objects, multiple contacts, moving the player during the game, etc. This is a simple idea that you could take very far. You could choose to add a new mechanic in each level and keep adding mechanics, or you could swap out mechanics in each level and make each level very different from the rest. It would be cool to require the player to bounce their bullet off of bouncing walls in order to kill their targets without touching the contact, or a level where you have to go into slow motion because the targets and contact are constantly moving around, or where the player moves in a circle around the targets, etc.