Sure, I can help you create a simple retro game using JavaScript within a single HTML file. Here's an example:
This example sets up a simple retro game where you control a red square using the arrow keys on your smartphone. The game canvas is displayed in the center, and the player can move the square around by pressing the arrow keys. The game loop updates the game logic and redraws the player every frame. You can enhance this game by adding additional features, levels, or enemies as per your preference.
Please note that this is just a basic example to demonstrate the concept. You can customize and add more features to make it a complete game with retro graphics and sounds if desired.