Gameplay wise it is difficult to some extent. You can get stuck on a couple of levels due to narrow platforms and inconvenient camera placement like Cam 12 but you can get over it if you put yourself to it.
Suprisingly enough the game was easier to beat in Ghost Mode with that thing flying right behind you mainly because throughout the whole time you must run non-stop (where that is possible) and I got really anxious running away from that eye-light monster. That anxiousness also helped go through the same narrow platforms with ease. End result was me getting twice as less deaths in Ghost Mode rather than Normal.
The Horror aspect of this game is not the best but it certainly adds a grim layer when you get immersed into it. Especially Ghost Mode. "A Mysterious Character" is creepy as well, no backstory whatsoever, bizarre interior and dangers contribute to the strangeness of the whole situation.
From what I can gather, the main lady we're in control of eventually reaches the only real door, enters the almost empty room and finds a person sitting at a computer, watching her every move via the cameras and real-time (in that room). Then you press X to "finish it" but who gets "finished" exactly? We can assume that it's the woman protagonist who says "Hello, Nice to meet you" since we're not given the cameraman's identity which kind of gives the idea that the person trapped (Lady Protagonis) is not the one who kills as well as that she willingly put herself through this endeavor to meet the person behind that little dangerous adventure. At the same time, I might be overthinking this but the confusion about the end is caused by the fact that you're controlling the lady this whole time so when you press X, you're "finishing" it as herself. Of course, there's also the possibility that it was the Mastermind who said "Nice to meet you" and the Lady killed her (since the voice is female) or backwards.
I would like to explore further on that matter and get more info if possible (although 6 years don't really guarantee that I'll get the satisfaction of uncovering the mystery) but I've wasted too much time writing this review. Overall, a good mysterious game, not too long but not too easy.