Sure! Here's an example of a simple shooting game implemented as a single HTML file with JavaScript:
In this game, you control a blue player using the left and right arrow keys. Your goal is to avoid getting hit by red bullets and earn score by colliding with them. The game ends when a bullet hits the player, and the gameover screen is shown.
You can copy the above code into an HTML file, save it, and open it in a web browser on your smartphone to play the game.