{{:en:kahn_joel_square_spiral.png?200|}}
Square Spiral by Joel Kahn  (June 2010)
<code>
# Contributed by Joel Kahn
fastgraphics
cls
clg
graphsize 512, 512
r=1:g=1:b=1
x=250
y=250
s=1
plot x, y
for a=1 to 511
   x1=x+s*a
   y1=y+s*a
   q=s*1
   g=((abs(g+a))%255)+1
   for xx=x to x1 step q
      b=((abs(b+xx))%255)+1
      color r, g, b
      plot xx, y
   next xx
   for yy=y to y1 step q
      r=((abs(r+yy))%255)+1
      color r, g, b
      plot x1, yy
   next yy
   x=x1
   y=y1
   s=-s
   r=1:g=1:b=1
   refresh
next a
</code>