Sure! Here's an example of a simple shooter game implemented as a single HTML file using JavaScript:
In this game, you control a player character using arrow keys to avoid colliding with enemy characters that descend from the top of the screen. You can also shoot bullets using the spacebar to destroy enemies. If a player collides with an enemy, it's game over and the page is reloaded.
Please note that this is a basic example. You can modify and enhance it to fit your needs and add more features or graphics accordingly.