delta_y 70 usr/sample/balls/balls.c int delta_x, delta_y; delta_y 79 usr/sample/balls/balls.c delta_y = (random() % 10) + 1; delta_y 96 usr/sample/balls/balls.c y += delta_y; delta_y 100 usr/sample/balls/balls.c delta_y = -delta_y;