Sure! Here's an example of an incremental game implemented as a single HTML file with JavaScript:
In this game, the player starts with a score of 0 and can click on the "Click Me!" button to increase the score. The player can also spend 10 points to upgrade the multiplier, which will increase the score gained per click. The current score is displayed on the screen, and the player can reset the game at any time. The game is implemented using JavaScript and all the code is enclosed in script tags within the HTML file.