Sure, here's an example of a game implemented in a single HTML file using JavaScript. It displays a rotating cube with a key on top of it.
To view this game, you can save the above code into a single HTML file (e.g., "game.html") and open it in a web browser. It will display a rotating cube with a key on top of it. Feel free to customize the cube rendering code to create a more visually appealing 3D shape.