Sure, here's an example of a simple game implemented as a single HTML file using JavaScript. This game involves moving a particle (represented by a pictogram) on a smartphone screen:
In this game, you will see a game screen with a gray background. There is a particle (represented by a star emoji) at the center of the screen. You can control the movement of the particle by touching and dragging your finger on a smartphone's screen. The particle will move along with your finger's position.
Please note that this is a basic example of a game and can be expanded upon to include additional features and gameplay elements.