Shifting guides for gutter ball prevention on a bowling alley

A bowling game apparatus utilizing a bowling ball, the bowling game apparatus comprising:

• an approach area where a player carries out bowling actions;
• a lane extending from said approach area and on which the bowling ball bowled by the player rolls;
• a plurality of pins arranged and placed on an end of said lane opposite said approach area;
• two guides provided longitudinally along the lane, the guides including at least one of a wire, a rope, a belt and a rod;
• two first retainers each including a first end retaining portion which retains a first end of one of said guides, said two first retainers being disposed on both outer sides of an approach side of said lane;
• two second retainers each including a second end retaining portion which retains a second end of one of said guides, said two second retainers being disposed above the lane at a position between said two first retainers and said plurality of pins, said second end retaining portions of said two second retainers being shiftable between (i) a guide position which is above the lane and between the plurality of pins and the approach, and (ii) a retract position away from the guide position;
• and
• a second retainer drive means for causing the second end retaining portions of said second retainers to shift between the retract position and the guide position;
• wherein when said second end retaining portions are in said guide position, axes of said guides intersect diagonally as viewed from overhead, such that said guides can contact a height-wise central position of the bowling ball so as to lead the bowling ball towards a middle position of the plurality of pins.