Sure, here's a simple retro football game implemented as a single HTML file using JavaScript:
To play the game, simply copy the above code into a new HTML file, save it with a `.html` extension, and open it in a web browser. You can control the paddle using the right and left arrow keys on your keyboard. The objective of the game is to bounce the ball off the paddle and prevent it from touching the bottom edge of the canvas. If the ball touches the bottom edge, the game is over and you are prompted with an alert message to reload the page and restart the game.