As an AI text-based model, I can provide you with an example of a simple game implemented in a single HTML file using JavaScript. However, please note that this simple game won't resemble the complexity and scale of GTA 5, as its development requires much more resources and time. Here's an example of a simple game you can play on a smartphone:
Simple Game
This code sets up a simple game where you control a blue circle (representing the player) using touch input on a smartphone. The player's position is updated based on the touch events, and a basic game loop continuously updates and redraws the player's position on the canvas.
Please note that this is only a basic example to demonstrate how a simple game can be implemented in a single HTML file using JavaScript. To create a fully-featured game like GTA 5, it would require a much more complex and extensive development process.