Here is a simple example of a game implemented as a single HTML file, using JavaScript and enclosed within script tags:
This game features a simple player object represented by a blue rectangle, which can be controlled using the arrow keys on a smartphone. The player can move up, down, left, and right within the boundaries of the canvas. The game continuously redraws the player's position on the canvas using the `gameLoop` function and handles user input through the `updatePlayer` function.