Sure, here's a simple RPG game implemented as a single HTML file with JavaScript code enclosed in script tags:
Wizard's Adventure RPG
This RPG game starts by displaying a welcome message and introducing the player to the wizard, Merlin. The player can click the "Start Adventure" button to begin the game.
Once the game starts, the player's wizard will encounter random enemies, represented by goblins. The player's wizard attacks the enemy, and the enemy counterattacks. Damage calculations are based on the player's attack and the enemy's defense.
The game continues until either the player's wizard or the enemy has been defeated. If the player's wizard's health reaches zero, the game is over. Otherwise, the player can click the "Continue Adventure" button to face a new enemy and continue the game.
Please note that this is a basic implementation to demonstrate the concept of an RPG game. It can be expanded and enhanced with additional features, graphics, and gameplay mechanics as desired.