Sure! Here's a simple text-based world battle game implemented as a single HTML file using JavaScript:
This game allows you to attack an enemy, represented by an AI, and tries to defeat it by reducing its health to zero. Your health and the enemy's health are displayed on the screen. If either you or the enemy reach zero health, the game ends and displays the result. You can reset the game at any time.
Please note that this is a basic implementation and can be expanded upon with graphics, animations, and additional gameplay features as desired.