Certainly! Here's a simple text-based Battle Royale game implemented as a single HTML file using JavaScript. Please note that this is a very simplified version of the game, and you can further expand and improve it as per your requirements.
To play the game, open the HTML file in a web browser. You'll be prompted to either attack the enemy or quit the game. Enter "attack" to initiate a battle turn, and try to defeat the enemy while keeping your own health above zero. If you choose to quit, the game will end. Health points and battle outcomes will be displayed through JavaScript alert boxes.
Please note that this is a basic implementation, and you can add more features, graphics, and interactivity as per your design preferences and requirements.