Sure! Here's an example of a simple text-based fighting game similar to Dark Souls that can be implemented as a single HTML file using JavaScript:
Dark Souls Fighter
Instructions:
Tap buttons to attack and defend against enemies. Try to defeat all enemies!
This simple game allows you to tap on the "player" area to attack the enemy, and on the "enemy" area to defend against the enemy's attack. The game starts when you click the "Start Game" button. The player and enemy health bars are represented using pictograms. The game will continue until either the player or enemy health reaches 0, at which point the game becomes "Game Over" and you have to restart by clicking the "Start Game" button again.