Sure, here's a simple shooting game implemented as a single HTML file with JavaScript. Please note that this is a basic example and may not include all the features you might expect from a full-fledged game.
To play the game, open the HTML file in a web browser on your smartphone. You can move the ship by dragging your finger across the screen and tap anywhere to fire a bullet. The ship is represented by a square and the bullet by a smaller square that moves towards the top of the screen.