Sure, here's an example of a simple bloody shooter game implemented as a single HTML file using JavaScript:
To run this game, simply copy and paste the above code into a text editor, save it as a ".html" file, and open it in a web browser. The game will start automatically, and you can move the blue player using your mouse. Clicking on the screen will trigger an alert indicating that the player shot. The game will end if the red enemy touches the blue player.