As an AI language model, I can provide you with a simple example of a text-based game implemented as a single HTML file using JavaScript and enclosed in script tags. However, please note that creating a fully-featured game like GTA 6 would be beyond the scope of a single response.
Here's a basic example of a text-based game where the user can guess a randomly generated number:
Please note that this is a very basic example and can be improved in many ways. Feel free to modify and enhance the code as per your needs to develop a more comprehensive game.