Many shooter games have traditionally calculated world collision and bullet impacts by modeling bullets as instantaneous line traces and characters as moving collision cylinders. In this case, the line-projecting cylinder is the fundamental nature of the character - the character's substance. The image of a fighter, the sounds he makes and the way he animates is the character's style.

A character can thus be, as a thought exercise, stripped of his style and considered simply as an abstract cylindrical game piece that slides around a level, attempting to project lines into other cylinders.