Sure! Here's a simple implementation of a Geometry Dash game using JavaScript in a single HTML file:
In this simple implementation, the game starts with a blue square (representing the player) moving from the left side of the canvas to the right side. You can modify and expand upon this code to add more gameplay elements, such as obstacles, scorekeeping, and player controls.
Please note that this is a basic implementation and does not include all the features of the actual Geometry Dash game. It's meant to give you a starting point to build upon.