After the initial contact, the cue ball will travel straight along the path defined by the horizontal alignment of the cue until the cue ball slows enough for the imparted vertical spin to take over. The cue ball will then curve onto a line defined by an angle described by the cue ball's initial resting point on the table and point on the table where the cue tip was aimed. The time before vertical spin overcomes horizontal movement is determined by the force with which the cue ball is struck. are quite difficult for non-experts, and are not allowed in some venues, as the table's can be easily damaged by unskilled players.
