The best way to define how Hello Neighbor works is to compare it to games like Outlast, Penumbra, or Amnesia: the player gets under the skin of someone trying to unravel a dark secret hidden in a castle/asylum/scientific facility at the South Pole/home of a sinister being.
Although Hello Neighbor has been classified as a stealth horror game, the truth is that its strong point is not terror, but rather we should talk about tension. This tension becomes very tangible when the neighbor discovers us and starts to chase us.
The game has something in common with this kind of game: the number of secrets, traps, and obstacles that we will find along the way, and as expected, we will be defenseless against our main enemy.
However, what makes Hello Neighbor special is the artificial intelligence that controls our antagonist: it learns from the user's movements every time it catches it, making it capable of blocking our strategies and complicating the game a little more as it progresses.
According to the game developers, the neighbor has three basic states: at rest, hunting mode, when he detects the player, and attack mode, as soon as he starts chasing you. The rest mode ends as soon as the artificial intelligence receives a stimulus, triggering the hunting and attack modes. Also, there is an "offline" mode that allows the neighbor to set traps for the player.
What matters is that the neighbor is moving around the house no matter whether we see it or not; it is enough to analyze in detail what happens in each state of behavior of the artificial intelligence. In rest mode, you can find the story's antagonist going about his daily chores: eating, drinking, sleeping, showering, cleaning the house, and so on.
In hunting mode, he is looking for us. Let's suppose you walk into his house, and by accident, knock over a vase or make a particularly loud noise. That is the stimulus that breaks the state of rest and makes him stop what he is doing to try to find the player. The neighbor can investigate the noise and conclude that there is an intruder in his house.
Most interesting of all is the hunting mode. To talk about it, we first have to name several important points scattered throughout the neighbor's house. Artificial intelligence calculates the probabilities of the player passing through one or the other. He never knows where the player is, he only calculates the most likely places where we will try to sneak in and where to find us. This data improves as he finds us, and as he chases us in hunting mode, he can even predict our preferred escape routes. This means that he will try to guide us to them to catch us, or that he can even block them. In this phase of his behavior, artificial intelligence functions in a similar way as a human being would.
As you can see, Hello Neighbor is not just another horror game. Definitely, the game is very, very challenging, and will force you to restart a game several times until you find the right way to overcome it.