To change player color press number keys. The grey parts on walls is vent entrances, you can go in the vents even though you aren't impostor. You are trying to get to the task at the end. all levels are possible. in level if you die you will have to start over sorry for that glitch but if you think you know how to fix it please tell me in the comments. there are probably other glitches that might happen so please tell me in the comments if you find any.
