Sure! Here's an example of a simple game implemented as a single HTML file, using JavaScript and enclosed in script tags:
This example creates a simple game where you can control a blue square (player) using left and right arrow keys or by tapping the respective buttons on a smartphone. The player can move horizontally within the canvas boundaries.
Please note that for a complete game, you would need to add additional features such as obstacles, scoring, and win/lose conditions. This example demonstrates the basic structure to get started with a game implemented in a single HTML file using JavaScript.