bbox -100,-100,200,200,true l = 99.99; wall (-1, 0, 1*l), -1*l, 1*l, green wall ( 1, 0, 1*l), -1*l, 1*l, green wall ( 0,-1, 1*l), -1*l, 1*l, green wall ( 0, 1, 1*l), -1*l, 1*l, green bmin = -0.8*l; bmax = 0.8*l; rr = (bmax-bmin)/20; d = 0.49*rr; balltype t1, d, d, black balltype t2, 2*d, 2*d, magenta for y (bmin:rr:bmax) { for x (bmin:rr:bmax) { ball (x,y), (0,0), t1 } } ball (0,l-1.1*2*d), (randn*l,-1*l), t2