Sure, here's an example of a simple open-world game where you can control a character running fast forever on a smartphone. The game utilizes pictograms for a visual interface. Simply copy the code below and save it as an HTML file on your device to play the game.
In this game, you control a character represented by a black square. The character will continuously run from left to right, and you can control its direction by tapping on the left or right half of the screen on a smartphone. It is an open-world game as there are no specific goals or obstacles implemented in this example. Feel free to enhance the game with additional features or elements according to your preferences.