Didn't expect to see RPG Maker here. On to the feedback as I play through it!
-Title screen said press space to start, I pressed enter. It started. Wowwwww!
-Can't fast forward text, it's driving me crazy as I read at the speed of light.
-Blue key not auto-using was honestly annoying. I made a blind guess at what it wanted and it worked. Tbh I didn't even know I had a blue key.
-It took like 3 whole minutes to figure out that I was supposed to hold shift to exit gun mode. To be absolutely fair, I was trying it out before the tutorial. The method is pretty awkward though.
-The shooting in general is awkward, but I understand that's just the natural of RPGM.
-The hallway key thing is weird. It says "I'm not sure about this", but I expected that to mean a boss battle would start, not that it'd just instakill me. You put a save point right before it so that's fine, but something doesn't sit right about that with me.
-There's a spot in an early hallway that looks like there's a note on the floor, but you can't read the note. Weird.
-A little bit disappointed there's no easter egg for trying 6969 on the combo lock. Like "Nice, but it didn't work."
-When you re-enter the beginning area, the chains respawn and then fade away. I'd consider this a bug.
-The map doesn't seem to make much sense at the moment. I thought it was for the digits of the combo lock but it doesn't add up.
-Hmm, I'm giving up at the combo puzzle. I found the color code, then I guessed red was 3, blue was 8, and green I didn't know if 0, 1, or 4. It feels like some of these puzzles need some work as I don't really know what I'm doing and I played your game for over a half hour.
-On that note, so far, I don't see the point in the shooting at all, at least not with the normal enemies.
Overall, I think this will be pretty nice. Keep up the good work!