Okay, here's a simple implementation of the Flappy Bird game in a single HTML file using JavaScript:
To run the game, simply save the code above into a ".html" file and open it in a web browser that supports JavaScript. The game is designed for smartphone operation, so you can either tap the canvas or press the spacebar or the up arrow key to make the bird jump. The goal is to navigate through the green obstacles and survive as long as possible without hitting them. Your score will be displayed at the top left corner of the canvas. Enjoy playing Flappy Bird!