10  REM (C) J. ILSLEY 1992.
   20  MODE0
   30  VDU23;8202;0;0;0;
   40  FOR X=-150 TO 0
   50  K=5:L=0:U=3E37:P=1:Z1=0
   60  Y1=K*INT(SQR(22500-X*X)/K)
   70  FOR Y=Y1 TO -Y1 STEP-K
   80  Z=INT(80+FNA(SQR(X*X+Y*Y))-.5*Y)
   90  IF Z<L THEN 150
  100  M=1
  110  L=Z
  120  PLOT69,640+M*X*4,Z*4+100
  130  IF M=1 THEN M=-1:GOTO 120
  140  GOTO 190
  150  IF Z=U THEN 190
  160  M=1:U=Z
  170  PLOT69,640+M*X*4,Z*4+100
  180  IF M=1 THEN M=-1 :GOTO 170
  190  NEXT
  200  NEXT
  210  END
  220  DEF FNA(Z)=38*(SIN(Z/20)+.48*SIN(3*Z/12))+2