The left player uses the keyboard. A number of white lines appear on the right end, and he must press the right key on the numpad or top row of numbers that matches it. Every time he does, he gets closer to catching the yellow player.
The yellow player uses the mouse to evade the green player for as long as possible. By clicking on the black or blue space to the right of the yellow character, she will keep out of reach of the greens. If she clicks the red parts, or to the other side of her character, she will drop back towards the green.
If the yellow player can evade the green player for long enough, she'll win. Otherwise, when the green player finally catches her, he'll win. DRAMA.