Sure, here's a simple example of a horror game implemented as a single HTML file using JavaScript:
Horror Game
To play the game, open this HTML file in a web browser, and it will present you with different choices as prompts. Depending on the choice you make, different outcomes will occur, resulting in either winning or losing the game. This is a very basic example, but you can expand on it to add more complex gameplay elements, graphics, and sound effects to make it more engaging.