Sure! Here's a simple example of a 3D shooter game implemented as a single HTML file using JavaScript. Please note that a comprehensive 3D shooter game would require more complex code and resources, but this example will give you a basic understanding of how it can be achieved:
This HTML file creates a simple 3D shooter game where you control a blue player circle and need to shoot (click on) red target circles that randomly appear on the screen. The player circle can be controlled by dragging your finger on a smartphone, and the score is displayed in the browser's title bar.
Please note that this is a very basic implementation to demonstrate the concept. To create a more complex and feature-rich 3D shooter game, additional JavaScript libraries and techniques like WebGL or game engines would typically be used.