This reminds me a lot of my first "game" I made with a buddy. We never finished it though, because of our lack of motivation. It also was about a robot who could shoot and jump and run and walljump (the same way as yours), so yeah, it was pretty much exactly the same.
That was about two years ago and we never made it as far as you have, we didn't even make a single level. Just wanted to point that out. Time teaches a lot of stuff, and I'm not at all an expert but I'll try to review it as good as I can (This is also my first review and english isn't my native language so don't expect much!).
First of all, the keyboard layout is just... bad. Shooting with space and interacting with "b"? On these kind of games you usually jump with "z", attack with "x" and interact with "c" (or sometimes the spacebar) so that you can rest your hand on the keyboard and can press shift to run. The order isn't that important and jumping with the up arrow is okay too, but stick with z, x and c when you use the arrow keys. I didn't read the description so it was my bad, but it'd be cool if you mentioned the keys and what objects you can interact with. I guessed you could make these platforms go down by pressing "b", but many people aren't as used to videogames so yeah, make that more clear.
The controls feel okay, but I don't like too much how enemies push you in the direction you're not facing and the walljump feels a bit weird. Adding a limit on how low you can jump would be good too. (tip ) I also don't like how much they push you, it's too much. Making it so you can shoot as fast as you can press the button is a choice, of course, but I ended up using my index and middle finger to spam the space bar and I don't know how good that is.
The art is okay, but if I can give one advice is make the size of each pixel consistent. On the death screen the wires have really small pixels, the outline of the character is enormous and the tear isn't even pixel art. You shouldn't do that. It doesn't look good and is frowned upon by pixel artists. The outline is well made though, so you got that right (at least on the byebye animation, don't remember the rest).
The level design is fine but at one moment I felt a bit lost on the second level. I did end up where I should've so I guess it's fine. One thing I didn't like too much is the lack of checkpoints on the first level. The level wasn't really hard so not having checkpoints made it more of a chore than anything else.
The music is good, I like it! Nothing bad to say about it, keep at it dude... But why the hell does jumping sound like a snare drum? That I'd change.
So, what else is there to say? Oh right, the boss. It was pretty cool! Definitely the best part of the game was the boss fight, it was really fun to dodge those projectiles.
I guess that's all. Hope it helps. The biggest mistake I made was never uploading my stuff anywhere so you're already on a better path than me. I suggest making many small things rather than one big thing though, so if you haven't already made a lot of small games I'd say start from there and retake on this project later. If you have any questions you can pm me btw. Have fun making stuff!