Sure! Here's a simple shooting game implemented as a single HTML file using JavaScript:
This game allows the player to move a square (player) horizontally using the left and right arrow keys. The player can also shoot bullets by pressing the spacebar. The objective is to shoot the falling bullet and increase the score. The game ends if the bullet hits the player or goes off the screen. The score is displayed at the top left corner, and "Game Over" is shown when the game ends.