As a language model AI, I can help you create a simple text-based game based on a scenario where two brothers are on opposite sides in a gun fight. Here's an example implementation in a single HTML file using JavaScript:
In this example, the game initializes two players (Brother A and Brother B) with their respective health, attack, and defense attributes. A simple game loop runs until one of the player's health reaches 0 or below. In each iteration of the loop, players attack each other based on their attack and defense attributes. When a player's health reaches 0 or below, the game ends, and the winner is announced on the webpage.
Please note that the game's logic is simple and doesn't involve any interactive buttons or graphical interface. It is a text-based game played out in the console log. You can modify and enhance this example according to your specific requirements.