Sure, here's an example of a simple billiards game implemented as a single HTML file using JavaScript:
This code will create a billiards game with a ball, three pockets, and a canvas on which everything is drawn. The ball will bounce off the walls and pockets until it gets pocketed, in which case the game will end and display an alert message. You can open this HTML file in a browser (preferably on a smartphone) to play the game.