Great aesthetics and controls. I like the pilot's face in the bottom left corner, it gives the game more personality.
I don't think the random layouts really work for this kind of game, personally. Considering it's an action platformer, the usual feeling a player wants to feel going into the game is learning, and, eventually, mastery. But since the layout is random, the player can be forced into bad situations because of some bad enemy spawns (which I imagine you could fix, but I thought it should be mentioned), and, as a designer, you can't give the player more specific challenges or craft a proper interest curve. It would also be nice if the non-essential rooms had some value, because otherwise they just make the game feel empty.
The whole mech thing is a cool idea conceptually, and cool to play, but it would be nice if you implemented a real difference in gameplay. The mech is just objectively better than being on foot. If there were smaller areas or enemies that could only be killed with the lance, or something of that nature, I think this game could go from good to great.
Still though, the graphics, music, and shooting are all very well done and makes the game feel great to play. Keep it up!