Sure, here's an example of a simple Solar System 3D game implemented as a single HTML file using JavaScript and enclosed in script tags:
This HTML file creates a canvas element and uses JavaScript to render the Sun, Earth, Mars, Venus, and a Moon around the Earth in a simple 3D representation of the Solar System. The objects' positions are updated using their respective speeds and angles. The `drawSolarSystem()` function is responsible for rendering the objects on the canvas, and the `animate()` function continuously updates and redraws the scene using the `requestAnimationFrame()` method.
Please note that this is a simplified example for demonstration purposes, and it can be further improved and enhanced according to your specific requirements.