Sure! I'll provide you with a basic template for an open-world game implemented as a single HTML file. Since your requirement is for a smartphone operation, I'll keep the design simple and use pictograms where possible. You can further build upon this template to create a more complex and interactive game.
Here's the code:
This basic game template sets up a canvas element where the game is rendered. It initializes a player object with coordinates and dimensions, and then continuously redraws the player on the canvas based on keyboard inputs for movement. In this example, the player moves using the arrow keys. You can expand this template by adding more game elements, interactive objects, and designing the game's world as per your requirements.
Keep in mind that this is a minimal implementation, and you'll need to further build upon it to create a full-fledged open-world game. Feel free to modify and enhance it according to your needs!