TITLE HELP!!

Title please!?
It was like a action/fantasy or slice of life(?) manga and the art was absolutely stunning and breathtaking so I want to find it again. (Super detailed)
Anyways, it was about this young girl who ends up in this room and it’s labeled in a number and she has to go through rooms to be able to leave and escape. But the smaller the numbers become on the doors, the harder it is to pass through. And there’s one person protecting each room and by using their imagination or like personality, they can customize the room as they want. And at the last room/door, I think door #0, she has to defeat the game-master? (Someone rlly strong) but the girl had a secret and she was the one who made this whole system and in reality, she was the strongest person. And then she like transforms into a monster (I believe into a butterfly? I have absolute no clue)… I’m so sorry if this didn’t make sense. It’s completed with about 10 chapters or so… wasn’t very long.