This is a pretty fun game, even if it is very simple.
Click on the window below until you can start playing. Once the game starts, you need to press the space bar. One press represents one flap of the bird's wings.
Therefore, you need to keep pressing it or the bird will fall and the game will be over.
But don't fly too high, or you will crash into the green pipes. There are gaps in the pipes, and you need to fly just right so that you can go through the gaps.