Sure! Here's an example of a simple shooting game implemented as a single HTML file using JavaScript:
In this game, you control a blue circle (representing the player) with your finger on a touchscreen device. The player can move horizontally and vertically by dragging their finger. By tapping on the screen, you shoot red bullets to destroy green circles (enemies). The goal is to score as many points as possible by hitting the enemies without getting hit. The score is displayed at the top left corner of the screen.
Please note that this is a simple example and can be expanded further based on your specific requirements and preferences.