Wow, lots of content in here, but I'm not the first to point that out. Still playing on my other browser tab! I'm curious about which way y'all intended the theme interpretation. I could see it being the boots and "scaling" the walls is definitely a thing in here, but so is the "scale" of the game and worlds :).
Anyway, I second the great DOS vibes =D. One comment I have on the controls, it's a little counter-intuitive to have the jump be on the same hand as the directional controls (since you need your right hand for mouse/fire, or vice versa if left-handed). Personally, I actually sometimes like that kind of thing because it literally forces your brain to form connections that it didn't have before, but it did make the character a little tough to control, particularly on those skinny ledges!
Did not hurt my enjoyment of it though, I'm also curious which parts were procedurally generated. Saw that in the description, that's awesome.