More a movie that had to be a game than a true game, this is still one of the most impactful experiences I've ever had. It's been a long time since I felt such care for a protagonist and was so connected to her struggle.
Playing with headphones is an absolute must to experience the voices properly. As I trained myself to recognize which ones to ignore and which to listen to, I realized I was as close as I hopefully will ever get to knowing what its like.
As the player you struggle with her. The game's masterful environmental design is so oppressive that you feel her fear, her dread, and her pain just by existing within the game's world, and when you fight to overcome it you are aligned with her desires like few games have ever achieved. This is possible the most emotional final boss fight I've ever had the pleasure to experience, and while the game has little replay value, I will not forget it.