Sure! Here's a basic example of a game implemented as a single HTML file using JavaScript:
In this example, there is a game container `<div>` element where all the game elements are placed, including the player, ground, blocks, enemies, and switch. The player character is represented by a blue square, the ground by a brown bar, the blocks by gray squares, the enemies by red squares, and the switch by a yellow bar.
You can control the player character using the up arrow key to make it jump. The player will jump 60 pixels up for 500 milliseconds when the up arrow key is pressed.
Feel free to modify and enhance this example according to your game requirements!