Sure, here's an example of a basic Gorilla Tag horror game implemented as a single HTML file using JavaScript:
In this game, you control a green square (representing a player) on a canvas, and you need to avoid colliding with a red square (representing a ghost). The game starts automatically when the HTML page is loaded, and you can control the player's movement on a touchscreen device by tapping on the screen.
Please note that this is a very basic example and can be further expanded and enhanced to create a more feature-rich and engaging game experience.