Sure! Here's an example of a simple math game about a lemon implemented as a single HTML file using JavaScript:
In this game, a random math question is asked with three possible answers. The player needs to select one of the answers, and the game checks if the player's answer is correct or not. The score is updated accordingly, and the difficulty of the questions increases every 3 levels. The player's current score and level are not displayed in this example, but you can easily add that feature if needed.
Note: This is just a basic implementation to give you an idea, and you can customize it further based on your requirements and add pictograms or any other enhancements you'd like.