HALDANE-4
Descend alone beneath the Antarctic ice and uncover what waits below in ASCII.
Genres
A horror game is a video game centered on horror fiction and designed to scare the player. It is defined more by tone and presentation than by one set of mechanics, so the core loop varies. In survival horror, the loop is to explore, find items and solve puzzles while avoiding or barely surviving enemies. Resident Evil (1996) and Silent Hill (1999) are well-known survival horror examples.
Horror leans on atmosphere, which is also a code problem: dim lighting that limits what the player sees, off-screen sounds and scripted encounters. Survival horror adds limited ammunition and health, a small inventory and save points, and some games use fixed camera angles to build tension.
Sound needs care in a browser. Browsers block audio until the player clicks or presses a key, so the first scare can't play on page load, and the Web Audio API's PannerNode places sounds in 3D space around the listener.

Descend alone beneath the Antarctic ice and uncover what waits below in ASCII.
Shoot your way out of a collapsing office nightmare as a burned-out worker.
Perform shady operations on patients with saws and shocks to earn money.
Bargain with a corrupted Andean deity by playing cards in a horror roguelite.
Explore a first-person memory from a 90s childhood and uncover what was buried.
Find seven blue flowers in a dark forest while spirits chase you.
Run from an evil clown that eats you if you slow down.
Survive a night in a forest tower by working a broken emergency phone.
Explore an unsettling house and solve its puzzles as the place seems to watch you.
Counted from the 9 games above. A game can name more than one tool or genre, so a list can add up to more than 9.