Single player game
* Two or more balls of the same color that form a connected region
constitute a block.
* Hovering the mouse over a ball will highlight the block that the
ball belongs to.
* Clicking on a ball removes that ball's block.
* You get (n-2)^2 points for removing a block with n balls in it.
* You get a 1000 point bonus if you remove all the balls.
* The goal is to maximize your score.
* As balls are removed, balls above fall down to take their place. If
a column is removed, the column to its right moves to the left.
* Try to identify the color which occurs the most number of times.
* Remove balls of the other 2 colors until all the balls of the most
frequent color (or as many of them as possible) form a single block.
* Remove this block. Now do the same with the remaining two colors.
* Avoid getting into a situation in which there is a single ball of
some color. If this happens you won't be able to clear the entire board.