Sure, here is a simple text-based Pokemon game implemented as a single HTML file using JavaScript:
In this game, we start by defining three available Pokemon with their names, types, and power. Then, we randomly select a Pokemon for both the player and the opponent. The game logic compares the power of the player's Pokemon with the opponent's Pokemon to determine the result (win, lose, or tie). The result is then printed in the console.
Please note that this is a very basic implementation of a Pokemon game and doesn't include any interactive elements or visual representation. It's more of a text-based simulation.