ARCHIMEDES SPIRAL from Analog Magazine, adapted for Apple II

archimedes.bas

100 REM ARCHIMEDES SPIRAL
110 REM 
120 REM ANALOG MAGAZINE
130 REM 
140 HGR2: HCOLOR =3:XS=0.85:YS=0.9
150 XP=139:XR=4.71238905:XF=XR/XP
160 FOR ZI=-64 TO 64
170 ZT=ZI*2.25:ZS=ZT*ZT
180 XL=INT(SQR(20736-ZS)+0.5)
190 FOR XI=0-XL TO XL
200 XT=SQR(XI*XI+ZS)*XF
210 YY=(SIN(XT)+SIN(XT*3)*0.4)*56
220 X1=XI+ZI+160:Y1=90-YY+ZI-1
225 X1=X1*XS: Y1=Y1*YS : REM SCALED A BIT FOR HGR RESOLUTION
230 HPLOT X1,Y1
235 REM COMMENT THE NEXT LINE TO MAKE IT SEE-THROUGH (ALSO FASTER DRAW)
240 HCOLOR=0:HPLOT X1,Y1+1 TO X1,191: HCOLOR =3
250 NEXT XI:NEXT ZI