Sure, here's an example of a simple game implemented as a single HTML file with JavaScript:
Emoji Catch Game
In this game, emojis randomly appear on the screen, and the player's goal is to click on them to make them disappear. Every second, a new emoji is created at a random position. The game continues until the player decides to stop.
Please note that the code snippet needs to be saved as an HTML file and opened in a web browser to be played.