Interesting minigame.
Art
Obviously, the visuals are very simple. I don't think that has to be a bad thing.
Look up "Thomas was Alone". Its a game that uses very basic shapes in a very visually pleasing way. Now, they had shadows going on, but I feel the core of what makes it look nice would be: proportional sizes, and a good color palette; less so the shadows.
The background did add some visual interesting but I feel it hurt the readability of the foreground objects a bit and added to the weirdness of the color palette.
Sound
The music was pretty neat. Aside from it looping when you respawned, you had a beat going.
The SFX were a bit lacking. There are good tools out there such as "bfxr" or the web version "jsfxr" that allow you to easily create nice sounding retro sounds. I'm not sure if you used it or not, if you did, then I would just suggest more "full" sounds; meaning sounds with a greater range of frequencies in them (instead of a very thin sounding sine-wave for instance).
For sounds, I used to use the retro style (and still do sometimes). Now-a-days I tend to prefer IRL SFX from various free sources (look up "zapsplat"). I feel it gives the simple graphics more "weight" by making it sound like its made of real-life materials (like rock or flesh).
Gameplay
First off, I'd like it if there was a WASD binding. Lots of people (especially in these kind of game jams) have lots of difference input preferences, so you can't please them all, but I feel WASD and arrow keys are a pretty safe bet (I actually forgot arrow keys on my game).
I didn't fully understand what to do. I tried it a couple times without much success. I found the prospect of gathering points while dodging projectiles. The weirdness of the movement system made that an engaging challenge.
Speaking of the movement system, I feel the inability to completely control it is perfectly fine, it adds to the challenge of this type of game. However, I would ideally, like to be able to press left or right while simultaneously pressing up or down. It seemed that pressing a movement key would override the previous movement even when they weren't direct opposites.
Overall, I think smaller style arcade games like this can work really well (especially for game jams). There's always things to improve on with literally anyone's game. The game I released for this jam was originally intended to be a lot more ambitious but it kept getting scoped down as I didn't want to stretch the polishing time for the game over several bosses; instead of one more polished boss for example.
If this is your first time completing a game for a game jam, then good job. It gets easier with time (sorta). I'm really curious what type of stuff you may produce in the future.