Sure! Here's an example of a text-based RPG game implemented as a single HTML file, using JavaScript:
In this game, the player starts by entering their character's name. Then, they engage in a battle with an enemy (a monster in this case) by attacking it. The game calculates the damage dealt by the player and the enemy, updates the health of both characters, and displays the results in the console. Once either the player's or enemy's health reaches zero or below, the game ends with the corresponding message.