As an AI language model, I can help you with the structure and provide a basic template for the game you described. However, it is not possible to write the complete code for a 3D game like Fortnite in a single HTML file using only JavaScript, especially with smartphone operation and pictograms. Developing a complex game like Fortnite requires advanced development techniques and frameworks.
Nonetheless, here's a simplified HTML template with some JavaScript code that could serve as a starting point for a simple gun game:
This basic template sets up a canvas for rendering the game, provides a `gameLoop` function as the entry point for game logic, and starts the game loop using `requestAnimationFrame`. You would need to implement the game mechanics, controls, and 3D rendering using appropriate frameworks or libraries tailored for game development.
Keep in mind that creating a complex 3D game like Fortnite requires expertise in game development and significant effort. It's recommended to use professional game development tools and frameworks to achieve the desired results.