We apologise for the late rating:
You did an excellent job for your first game jam! The implementation of the controls and progressive introduction of game mechanics is great! The addition of your body only becoming "solid" in a way shortly after using your gun to move is a great idea. The solid black and white art makes the game easy to look at and makes the boundaries and objectives easy to understand. The art is simple, but your sprites are also good. The music is also simple, but not too much. I like the theme, but I think the loop needs to be about 30-50% longer before it repeats to keep it from sounding too repetitive. The mechanics of movement feel really solid and polished, and they are easy to understand.
I like that your GDD lists your assets along with your development software. Adding some graphics that show your art design and how the mechanics work would be a nice addition. The design goals and ToDo list are nice to see, and an addition of goal/completion dates would also be good to go along with those. Everything else is described thoroughly and well.
You are a boss for doing so well for your first jam. You have a great sense of what good gameplay mechanics feel like, and I see that you took criticism from gameplay testers well and changed unintuitive mechanics to be more fun. Great job, and I am excited to see where you go with your future game dev career!