Sure! Here's an example of a simple RPG game implemented as a single HTML file with JavaScript:
This example sets up a simple RPG game where you control a player represented by a blue square, and you encounter an enemy represented by a red square. The player and enemy have basic attributes like level, health, attack, and defense. The game logic includes moving the player and handling combat between the player and enemy.
Please note that this is a barebones example and the game can be expanded and enhanced as per your requirements.