Sure, here's an example of a simple horror game called "Skibidi Toilet" implemented as a single HTML file using JavaScript:
Skibidi Toilet - Horror Game
Tap on the toilet to start the horror!
In this game, all the game elements are contained within the `game-container` div. The gameplay starts when the player taps on the toilet icon, triggering the `startHorror()` function. Currently, it only displays a simple scary message, but you can build upon this by implementing more game logic, sound effects, animations, etc., depending on the complexity you desire for your horror game.