Sure! Here's an example of a simple platformer game implemented as a single HTML file using JavaScript, enclosed in script tags:
In this example, the player (represented by a blue div) can move left and right using the Arrow keys and jump by pressing the Arrow Up key. The player can interact with a platform (represented by a green div) and will collide with it, stopping its vertical movement. Gravity is also applied to the player, causing it to fall downward when not on the platform.
This is a basic demonstration of a platformer game and can be expanded upon to add more features such as multiple platforms, enemies, collectibles, and levels.