The movement is smooth, and the shooting sound effect is good, but I do want to comment on some aspects that can be improved, if you plan on continuing developing this game :)
The jumping is a little funky, so I guess playing with some parameters might be worth trying. The things shooting at me were extremely difficult to avoid and not get insta-killed from. Perhaps adding a life meter would fix the issue. On, say, five hits you respawn, instead of one. Also, a little visual improvement I think would fit really nicely is some splotches of color. The bullets look like paint balls, so I think it would be super cool to see them land and splatter on the wall for a few seconds before they disappear. Not only it would look really cool, but it would also be a visual marker of where the hit landed, so you can fix the aim.
Another issue I had is not related to gameplay, but rather the theme and story. I'm not saying a shooter can't qualify for the jam's theme, though it's probably more difficult to achieve, but it needs a context, a story to explain where you are and what you're doing there. Beyond helping to relate to the theme, it will also make your game feel more than just a pocket dimension with nothing beyond it. It will keep the player invested, because they know who they are playing as, and that they have a purpose.
I hope some of this, at least, is helpful if you do come back to develop this. Or even for future projects.