You can move a piece as many places as there are pieces on this line (line = row, column or diagonal).
If you land on a piece, it will be captured.
Two deletion rules apply:

Square-Deletion Rule:
If the target position contains a ball which is part of any 4-balls-in-a-square arrangement, then all 4 balls will be deleted. (Example: balls on a1, a3, c1, c3, or balls on a1, a9, i1, i9).
Note that the ball being moved cannot be part of such a arrangement if the 4-balls-in-a-square arrangement is to be deleted.
If the target ball is part of several such square arrangements, all those 4-ball arrangements will be deleted.

Diamond-Deletion Rule:
This rule is similar to the Square-Deletion Rule, but here the squares tilted by 45 degrees. (Example: balls on a2, b1, b3, c2 or balls on a3, c1, c5, e3).

Both rules apply in all variants of this game.

To make the solutions more difficult, after every second move a ball will be dropped randomly, but adjacent to an existing ball.
Half of the variants are marked as 'hard'. In those variants a ball will be dropped after every move. These hard variants might sometimes seem impossible to finish, but they are all solvable without exception.

The colour of the balls has no relevance in this game.
You win when only one piece is left.

 
Related Zillions games: Diball, Powerlines, Powerball, Squaredance.