Just typed up in a random phone application while I was thinking of it
cs setpc 3 make r 0 while r <= 4 [ make x 0.6 make itr 0 while itr < 64 [ make x x * r * (1-x) make itr itr + 1 ] while itr < 256 [ make x x * r * (1-x) make itr itr + 1 dot [r*500 x*1000] ] make r r + 0.005 ]