The birds are flying above your head. Press the rectangle with the same color of the nearest bird to remove them and fly up.
If you miss-press the rectangle up to 3 times, the game is over.
You have 30 seconds to remove the bird. But if you remove 10 birds without miss-pressing and bird, you got 5 seconds of playing time bonus.
Try to get highest score, and if you are good enough, the time could be infinite.