Sure! Here's a simple implementation of the Flappy Bird game in a single HTML file using JavaScript:
You can copy the above code and save it as a single HTML file (e.g., `flappybird.html`). Open the file in any web browser on your smartphone, and you should be able to play the game. Tap the screen to make the bird jump and try to fit between the gaps between the pipes.
Note: This is a simple implementation of Flappy Bird and might not have all the features or graphics of the original game.