Sure! Here's an example of a simple 3D gun game implemented as a single HTML file using JavaScript and enclosed within script tags:
This code sets up a simple 3D gun game where a player represented by a blue triangle can move around on a canvas using the smartphone's motion sensors. The gun is represented by a gray shape attached to the player. The player's position and rotation are updated based on the device's movement, and the game is rendered continuously using the `render` function.
Please note that this implementation is just a basic example and can be further enhanced with additional features and gameplay mechanics as per your requirements.