Escape Room Mystery Key gives you a choice of setting — an abandoned school or a hospital — and locks you in it. Each room has puzzles between you and the next door: codes hidden in the environment, objects to find and combine, mechanisms to work out.
The horror is atmospheric: dim corridors, unsettling audio and the sense of a building that shouldn't be empty. The puzzles themselves are fair.
The school and the hospital have different puzzles and atmosphere but similar difficulty — pick whichever appeals; both are complete.
It relies on atmosphere and occasional scares rather than gore or chase sequences, which makes it more tense than frightening.
Yes — it runs in the browser with nothing to install.