Fill the screen with filler balls while avoiding the bouncing balls in this
voluminous arcade Xonix game! The goal of Filler is tu fill up 2/3 of the
screen while avoiding bouncing balls. Press down on the mouse to
create a filler ball. It will continue to grow until you release the mouse,
or it will explose if you run into a bouncy ball. There's a limited
number of filler balls you can use per level.