Sure! Here's an example of a simple 3D game implemented as a single HTML file using JavaScript. In this game, you'll be controlling a girl on a green walkway and collecting coins by swiping your finger:
To play the game on your smartphone, open any text editor, copy the entire code into a new file, and save it with an `.html` extension (e.g., `3DGame.html`). Then, you can open the file on your smartphone's browser, and the game will run.
In the game, you can control the girl's movement by swiping your finger across the screen. The objective is to collect coins on the green walkway. Your score increases each time you collect a coin.