I was confused by equipping initially. I assumed the brighter golden outline was the equipped weapon instead of the darker crimson outline.

I found the flat shooters irritating because their movements seemed inconsistent with how much they moved forward between shots (i.e. sometimes not at all!)

Not sure why select needed to be held to keep the maps on the screen, pretty unusual.

i was able to use the air dash to get into the brown area since landing on spikes gives you invulnerability for a few seconds instead of resetting your position. There's not much you can do in the brown area.