Sure! Here's a simple implementation of Flappy Bird as a single HTML file using JavaScript:
To play the game, you can save this code as a .html file, open it in a web browser on your smartphone, and touch the screen to make the bird jump. The goal is to navigate the bird through the gaps between the pipes without colliding with them. The game will keep track of your score. If you collide with a pipe or go out of bounds, the game will end and display your score.