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