Yeah that's the spirit! And maybe the behavior of the monster could work like this...
-the monster wanders through the environments hunting you whilst the player searches for upgrades to eventually defeat it.
-more powerful attacks make more noise, increasing the chance of the monster discovering your location
-maybe something like the power going out when the monster enters the room you're in could act as a visual warning that you need to hide now?
Also, I need to make it scary but not so frightening that nobody, including myself, will want to play it. I need to balance it somehow.