Sure! Here's an example of a simple game in a single HTML file using JavaScript. The game is played on a smartphone and the objective is to catch 10 falling balls by moving the player left and right. The game ends when the player catches 10 balls.
Simply save the above code in an HTML file, open it in a web browser on your smartphone, and you should be able to play the game. The player can move left and right by dragging their finger on the screen. The balls fall randomly from the sky, and the game ends when the player catches 10 balls.