Borrowing certain gameplay conventions from Qix, JezzBall presents another scenario forcing the player to divide and conquer a 2D playfield by whittling away slivers of it until it is at only 25% (or less) of its original size.
The complicating factor here are balls, more with every level, bouncing off the edges of the continuous playfield and, incidentally, quite lethal to the player's marker, only tangible while in the act of diminishing the playfield by marking off areas no longer to be used. The player can choose to trim horizontal or vertical segments -- depending on which axis they expect the bouncing ball to intercept soonest -- and the boring apparatus used fires off in opposite directions simultaneously, meaning the cross-section generally starts being cut from the middle and works its way toward the outside edges... all while keeping an eye on how close those balls are bouncing.
The apparatus is slow, and until the entire cross-section is completed, its entire span is at risk of being hit. The two sides of the dividing sweep are independent from each other, so if one side is intercepted by a ball while in the process of trimming, the other side continues unabated, resulting in a half-complete division.