const showlores = $C056
const keyboard  = $C000
const keystrobe = $C010
byte  exitmsg[] = "PRESS ANY KEY TO EXIT."
byte  goodbye[] = "THAT'S ALL FOLKS!"
byte  i, j, k, w, fmi, fmk, color

def textmode
  drop romcall(0, 0, 0, 0, $FB39)
end

def home
  drop romcall(0, 0, 0, 0, $FC58)
end

def gotoxy(x, y)
  ^($24) = x
  drop romcall(y, 0, 0, 0, $FB5B)
end

def grmode
  drop romcall(0, 0, 0, 0, $FB40)
  ^showlores
end

def colors
  while 1
    for w = 3 to 50
      for i = 1 to 19
        for j = 0 to 19
          k = i + j
          color = (j * 3) / (i + 3) + i * w / 12
          fmi = 40 - i
          fmk = 40 - k
          drop romcall(color, 0, 0,   0, $F864) ;grcolor(color);
          drop romcall(k,     0, i,   0, $F800) ;grplot(i, k);
          drop romcall(i,     0, k,   0, $F800) ;grplot(k, i);
          drop romcall(fmk,   0, fmi, 0, $F800) ;grplot(fmi, fmk);
          drop romcall(fmi,   0, fmk, 0, $F800) ;grplot(fmk, fmi);
          drop romcall(fmi,   0, k,   0, $F800) ;grplot(k, fmi);
          drop romcall(k,     0, fmi, 0, $F800) ;grplot(fmi, k);
          drop romcall(fmk,   0, i,   0, $F800) ;grplot(i, fmk);
          drop romcall(i,     0, fmk, 0, $F800) ;grplot(fmk, i);
          if ^keyboard >= 128
            drop ^keystrobe
            return
          fin
        next
      next
    next
  loop
end


grmode
home
gotoxy(10,22)
prstr(@exitmsg)
colors
textmode
home
prstr(@goodbye)
done