Sure! Here's an implementation of the game Flappy Bird using JavaScript within a single HTML file:
You can save the above code into an HTML file (e.g., `flappy_bird.html`) and open it in a web browser to play the Flappy Bird game. When played on a smartphone, you can tap the screen to make the bird jump. The goal is to navigate the bird through the gaps between the green pipes without touching them. The score will increase for each successfully passed pipe, and the game will end if the bird collides with a pipe.