In filler, your goal is to cover 2/3 of the playing field with circles, all the while avoiding collisions with the bouncing balls. Press down on the left mouse button to create a circle. The circle will continue to grow until you release the mouse button, you collide with another circle, or one of the bouncing balls hits you (for which you'll lose a life). Bonus points for large circles, covering more than 2/3 of the board, time remaining, and lives left.