gfxdemo1.prg ==2001==
   10 rem ** 320x200x32col fractal(?)
   20 rem **
   30 rem ** this is a little demonstration how to do a formula-based
   40 rem ** computer graphic using the screen instructions of the 65
   50 rem ** calculation will last about 20 minutes. basic is sloooow
   60 rem ** coded for the c65 information page at
   70 rem ** http://www.toxic-waste.de/c65/
   80 rem **
   90 rem ** contact me: michael@toxic-waste.de
  100 rem
  110 trap 330                  : rem ** in case of error want text screen
  120 graphic clr               : rem ** initialize graphics
  130 screen def 1,0,0,5        : rem ** define 320x200x5 graphics screen
  140 screen open 1             : rem ** open it
  150 for i=1 to 31
  160 read a,b,c
  170 palette 1,i,a,b,c
  180 next i
  190 screen set 1,1            : rem ** make screen 1 the view screen
  200 scnclr 0                  : rem ** clear screen with color 0
  210 border 0                  : rem ** set border color to 0
  220 pen 0,15
  230 char 15,2,2,2,2,"toxic waste"
  240 char 15,20,1,1,2,"calculating 20 minutes"
  250 for x=1 to 320
  260 for y=1 to 190
  270 c=(x*x+y*y)/600           : rem ** draw the fractal
  280 pen 0,c
  290 draw x,y
  300 next y
  310 next x
  320 get a$:if a$="" goto 320  : rem ** wait for key press
  330 screen close 1            : rem ** close graphic, get text screen
  340 palette restore           : rem ** restore normal system colors
  350 border 6                  : rem ** restore normal border color
  360 end
  370 data 1,0,1,3,0,3,5,0,5,7,0,7,9,0,9,11,0,11,13,0,13,15,0,15
  380 data 15,0,13,15,0,11,15,0,9,15,0,7,15,0,5,15,0,3,15,0,1
  390 data 13,0,3,11,0,5,9,0,7,7,0,9,5,0,11,3,0,13,1,0,15,0,0,13
  400 data 0,0,11,0,0,9,0,0,7,0,0,5,0,0,3,0,0,1,0,0,0,0,0,0