Sure, I can help you create a simple one-player fighting game using JavaScript within a single HTML file. Here's an example implementation to get you started:
In this game, you control a blue player on the screen using left and right arrow keys to move, and the spacebar to punch. The objective is to avoid colliding with the red enemy character. If a collision occurs, the game ends and you will receive a "Game Over" alert message.
Please note that this is a very basic example and can be expanded upon to add more features such as multiple enemies, health bars, levels, etc., according to your requirements.