Sure! Here's an example of a simple planet simulation game implemented as a single HTML file using JavaScript and enclosed in script tags:
The above code sets up a simple planet simulation game where the planet's size gradually increases over time. The game canvas is represented by a `canvas` element, and the game state is updated inside the `update` function. The function continuously clears the canvas, draws the planet, and checks if the game is finished based on the planet size. The game loop is started by calling the `update` function, which will continue running until the game is finished.