Sure! Here's an example of a simple Mario Runner game implemented as a single HTML file, using JavaScript and enclosed in script tags:
In this game, you control Mario by making him jump over an enemy (represented by red rectangle) that moves from right to left across the screen. If Mario collides with the enemy, the game will show a "Game Over" alert and then reset.
Please note that the provided implementation is a basic example to give you an idea of how a Mario Runner game can be created using JavaScript in a single HTML file. To create a more complex and visually appealing game, you would need to add additional features, levels, and artwork. Additionally, keep in mind that a 2 MB size restriction may limit the complexity and size of the game you can create.