Sure, here's an example of a simple game implemented as a single HTML file using JavaScript:
In this game, you control a player represented by a red square. You can move the player using the arrow keys on your smartphone. The player moves at a fixed speed and the canvas is cleared and redrawn every frame to create the illusion of movement.
Please note that this is a basic example and can be further expanded to include various game mechanics, levels, and visual assets.