The atmosphere felt throughout the film is restless and unsettled. It's not that scary for me tho, but yeah it's scary in the way it makes you stressed and "I don't want to be here" feeling, I think that's the point of the backroom, it always makes you uneasy. I think you need to think/search about the ending meaning if you don't get it in the first place, why did it happen, and at some scene I feel confused and "huh" moment. So, the moral of the story is don't turn on a switch that looks strange :)