Sure, here's an example of a simple game implemented as a single HTML file with JavaScript, suitable for smartphone operation:
In this example, the game is represented by a blue square (pictogram) inside a canvas element. The player's goal is to click on the square to win the game. When the player successfully clicks on the square, an alert message pops up notifying them that they have won.
You can copy the above code into a new HTML file and open it on a smartphone to play the game.