Sure! Here's a basic implementation of the Flappy Bird game in a single HTML file, using JavaScript and enclosed in script tags:
You can copy this code and save it as a single HTML file, then open it in your browser to play the Flappy Bird game. Use the spacebar to make the bird jump and avoid hitting the green pipes. If the bird collides with any obstacle, the game will end and you will be prompted with a "Game Over" alert.