Thanks for playing! This is some very useful feedback, I really appreciate it :)
Glad you enjoyed the game as a whole, sounds as though you saw a lot of the content from your comment. I suspect you've probably got the secret character correct - the silhouette didn't turn out especially subtle. Also happy to hear you enjoyed the posters, they were a whole lot of fun to make.
Regarding difficulty, I found myself tweaking various settings to make it more or less difficult throughout development, and I'm honestly not sure I ever really found a balance I was fully happy with. Were there any rooms in particular besides not-Pyramid-Head that stood out to you as seeming out of place?
Delighted that you noticed the graphics menu, seem to remember getting the idea from a GMTK video and was really pleased with how it turned out.
It's definitely ended up more of an action title with a horror theme at this point, I was aiming for some kind of cross between Left 4 Dead and Enter the Gungeon but definitely ended up closer to the latter in terms of tone and feel. I think your comments regarding the main menu are spot on, I was always quite concerned that they didn't really fit the final game which is an issue given that they're the first thing a new player will see. I'll work on menu screens (and cover art, for that matter) on future projects, definitely an area for improvement.
Cheers for letting me know about the bugs too, I'll take a look and see if I can get them squashed at some point.