Sure! Here's a simple example of an FPS (First Person Shooter) game implemented as a single HTML file using JavaScript and enclosed in script tags:
In this example, the game consists of a simple black game area (`game` div) with a red square representing the player (`player` div) in the center. The player can be controlled using the arrow keys on a smartphone.
You can further enhance this game by adding enemy characters, shooting mechanics, and more sophisticated gameplay features. But this provides a basic starting point for an FPS game using HTML, JavaScript, and smartphone operation.