to yuan :r
 repeat 30[fd 2*3.14*:r/2/30 lt 360/30] 
end 
to zfx :b 
repeat 4[fd :b lt 90] 
end 
to sjx :b
 lt 30 repeat 3[fd :b lt 120] rt 30 
end
 to tu :x
 if :x<5 then [rt 90 yuan :x stop] 
zfx :x sjx :x fd :x lt 90 fd :x/4 rt 90 tu :x/2
end