Sure, here's an example of a simple 3D shooting game implemented as a single HTML file using JavaScript:
This game creates a canvas element and renders a blue square representing the player's character. The player can control the character using the arrow keys on a smartphone, and shoot bullets by tapping the screen. The bullets are represented by red squares. The game continuously updates the game state and renders it using the `requestAnimationFrame` method. This is a simple implementation and can be expanded upon to add more features such as enemies, scoring, and levels.