Sure! Here is an example of a simple game implemented as a single HTML file using JavaScript:
SO COOL!
When you open this HTML file in a web browser, you will see a black background with bouncing colored cubes. The background continuously updates, providing a flashing effect. At the center of the screen, there is rainbow text saying "SO COOL". The balls bounce off the edges of the screen.
Please note that this is just a basic example and you can modify it to add more features or customize it further based on your requirements.