Sure, here's an example of a classic ping pong game implemented as a single HTML file using JavaScript:
To play the game on a smartphone, you can open this HTML file in the browser. The game will be displayed as a pong table with a ball and a paddle at the bottom. To control the paddle, simply touch and move it horizontally to hit the ball. The ball will bounce off the walls and the paddle. The game will continue until you close the browser or navigate away from the page.