// Initialize variables var line zigzag = na var line ghost_level = na var max = 0., var min = 0. var max_x1 = 0, var min_x1 = 0 var follow_max = 0., var follow_max_x1 = 0 var follow_min = 0., var follow_min_x1 = 0 var os = 0, var py1 = 0., var px1 = 0