Sure! Here's an example of a simple shooting game implemented as a single HTML file using JavaScript:
In this game, you control a player rectangle at the bottom of the canvas. The objective is to shoot the enemy square that moves randomly from top to bottom. Press the left and right arrow keys on your smartphone's keyboard to move the player, and press the spacebar to shoot bullets. If a bullet hits the enemy, it will be destroyed, and a new enemy will appear at a random position. The game continues until you close the browser window.