As an AI language model, I can provide you with an example of a simple game implemented as a single HTML file using JavaScript. Please find the code below:
The provided code creates a simple open-world game interface on a smartphone. The player is represented by a pictogram ("
👤") and can be moved using the arrow keys or by tapping on the screen in the desired direction. Whenever the player interacts with the character by clicking on it, an alert message is shown.
Please note that this is just a simplified example to give you an idea of how to start building a game using HTML and JavaScript. You can extend and modify the code according to your specific game requirements and design.