Sure! Here's a simple text-based RPG game implemented in a single HTML file using JavaScript:
In this game, you play as a player battling against a monster. The character and enemy stats are defined using JavaScript objects. The `battle()` function simulates the battle by subtracting health points based on attack and defense values. The game ends when either the player or the enemy's health reaches 0.
Please note that this is a simplified example and does not include any graphical elements or extensive game mechanics. It's a basic implementation to illustrate the concept of an RPG game.