Sure, here's an example of a simple open-world 3D game implemented as a single HTML file using JavaScript and enclosed in script tags. Since it's a simple example, I won't be able to incorporate pictograms, but you can imagine the gameplay based on the description. Note that this is just a basic starting point and you can extend it further as per your requirements.
In this game example, you will see a blue background representing the open-world environment. The player is represented by a red square in the center of the screen. You can control the player's movement using the arrow keys on your smartphone. Pressing the up, down, left, and right keys will move the player accordingly, updating the player's position on the screen in real-time.
Please note that this is a very basic implementation, and to create a truly immersive open-world 3D game experience, you would need more complex code, graphics, and game logic.