Sure! Here's an example of a simple 3D video game about an empty office building with monsters, implemented as a single HTML file using JavaScript:
In this game, you'll see an empty office building represented by a black background. The player is represented by a player icon, and there are 10 monsters represented by monster icons scattered throughout the office building. The monsters will move towards the player, but the player cannot move. The game loop continuously updates the positions of the monsters and redraws them on the screen.
Please note that for a complete game, you would need additional functionality such as collision detection, scoring, game over conditions, and more. But this example should give you a starting point for building a 3D video game about an empty office building with monsters using JavaScript and HTML.