Forms like tetris, there are 20 number (1-20), each number corresponds to a square, square random drops, and the bottom, there are two locations, one put the odd one put even, from the top down according to the number of squares, accidentally fell into the corresponding location, fall out of position and falling into the wrong is the end of the game, the square can be or so key move, can accelerate the key drop,

O great god answer