How a monster knows it can see you

Under the hood · line of sight in AISLE 7

AISLE 7 is a horror game with one verb: break line of sight. Everything else is decoration on that. Which raises a fair question, because "it can see me" is an obvious idea to a person standing in a supermarket and a completely non-obvious idea to a computer, which has no eyes and no intuition about shelves.

The obvious way, and the cheaper way

The standard technique is a raycast. You fire an invisible ray from the monster's eyes toward the player and ask the 3D scene whether anything is in the way. It is accurate, it handles any shape, and it is not free, because the answer involves testing that ray against a lot of triangles.

AISLE 7 does something simpler, because the store is already a grid. The floor plan is made of two metre squares, and each square is either walkable or it is not. So instead of testing a ray against geometry, the game walks the straight line from the monster's square to your square, one square at a time, using nothing but whole-number addition. If any square along the way is solid, sight is blocked. If it gets all the way to you, it can see you.

That is a handful of additions and comparisons, and it is honest here for a specific reason: the shelves in this supermarket are taller than the camera. A shelf square really does block the view, all the way up, so treating the square as solid is not an approximation. It is just true.

What counts as cover

The monster floats, and it has a list of fixtures low enough to float over: produce bins, deli counters and checkout lanes. It crosses those, and it also sees across them. Everything else is a wall as far as sight is concerned.

This produces one delightfully strange consequence. A table in this store is 0.95 metres tall and blocks the monster's view completely. A produce bin is 1.0 metres tall, and the monster sees straight over it. The taller object is better cover, because cover here is decided by a short list of fixture types and not by comparing heights. Once you learn which furniture hides you, you stop thinking about how tall things look and start reading the store as a map of squares that work and squares that do not.

There is also no height in the check at all. The line is walked flat across the floor plan, from your square to its square, so crouching does nothing and standing on something does nothing. You are either behind a blocking square or you are not.

It does not need to be facing you

Most stealth games give the enemy a view cone, so you can slip behind it. The Employee has no cone. Line of sight plus distance is the whole test, and the distance is 16 metres. It is always turned toward you anyway.

There is a second, shorter threshold for actually committing to a chase, and that one tightens as the nights go on: 8 metres on the first night, climbing to 13 by the sixth. Being seen and being hunted are two different events, and the gap between them is where the tension lives.

Sixty times a second

The sight check runs every single frame, so on a normal machine it is being asked and answered sixty times a second, and the game guarantees at least thirty even when frames are slow. That is the payoff for making the test cheap. A more expensive check would have to be throttled, and a throttled check means moments where you have been seen and the game does not know it yet.

For contrast, the monster only recalculates its route through the store twice a second. It senses you sixty times a second and thinks about how to reach you twice. Perception is cheap, pathfinding is not.

The moment it sees you

The instant sight connects inside chase range, three things happen. A sting plays, once, on that exact edge. The monster changes state from stalking to chasing. And then it stops dead and stares at you for a full second before moving.

That second is deliberate. It is the telegraph, the beat where you understand what has happened and choose a direction. Its patrol speed is 2.2 metres per second, its stalk is 3.2, and its chase is 4.5, against your walk of 4.2 and your sprint of 6.3. For the first couple of nights a sprinting player reliably opens a gap. That stops being true from the third night on, once the per-night multiplier, the items you are carrying and the eye-contact bonus stack up, and by the sixth it is simply faster than you. Sprinting also runs on a short stamina budget, so it was never a solution anyway.

Unbroken eye contact during a chase makes it faster, slowly, the longer you look at it. Breaking sight makes that bonus decay. The game is quietly telling you that staring is the wrong instinct.

The twist in all of this

Which brings us to what the sight system is not doing. It is not how the monster finds you. The monster always knows which square you are standing in. Always. There is no last known position and no searching, because it never lost you in the first place.

What line of sight decides is whether it is allowed to close. Undetected, it paths honestly toward you and then stops seven squares short, prowling around that leash and picking spots in a different aisle to wait. Sight is the permission slip for the last fourteen metres.

Once sight is broken, 1.5 seconds without it drops it out of the chase and back to that patient distance. Not gone. Waiting.

Two more senses to worry about

Hearing is a completely separate system with its own radii. Walking carries 5 metres, sprinting carries 14, the checkout scanner 18, and knocking over a stack of cans carries 22, which makes it the loudest thing you can do. Your own panicked breathing carries 7, so being frightened gives you away.

Noise alone will only start a chase if it happens within 3 metres. Further away, it just redirects the monster's slow approach toward the sound. This is why sprinting around a corner and getting behind a freezer genuinely works: the noise tells it roughly where you went, and only sight would let it commit.

The last sense is yours. Looking at the monster slows it to a third of its speed, and the game spends the first three nights teaching you that. From the fourth night the slow still applies, but a second rule is layered on top of it: hold the stare for more than about two and a half seconds and it lunges, at double speed for a moment, before settling back. The lesson is not cancelled, it is complicated. All of it switches off in a blackout, when it cannot tell that you are watching.