Sure, here's an example of a simplified 3D gun game using JavaScript and HTML:
This is a basic example of a game in which you control a blue player square using the arrow keys on your smartphone. The objective is to avoid colliding with the red enemy square. When a collision occurs, the player resets to the start and the enemy position changes randomly. The game loop continuously updates the game state, clears the canvas, and redraws the player and enemy.
Please note that this is a simplified version and lacks many features present in actual games like Fortnite. However, it demonstrates the basic mechanics of player movement, collision detection, and canvas rendering.