Sure! Here's an example of a simple Rocket League game implemented as a single HTML file using JavaScript.
This is a basic version of a Rocket League game where you control a rocket (represented by a filled square) using the up and down arrow keys. The objective is to prevent the ball (represented by a red circle) from scoring a goal by reflecting it with the rocket. The goal (represented by a blue rectangle) is stationary. If the ball scores a goal, an alert will be shown, and the game will be reset.
Note: This is a simplified example and does not include advanced game mechanics or features like multiplayer. Feel free to modify and enhance the game as per your requirements.