Most useless use of ZSH

I found neat ZSH hack:

 1 function most_useless_use_of_zsh {
 2     local lines columns colour a b p q i pnew
 3     ((columns=COLUMNS-1, lines=LINES-1, colour=0))
 4     for ((b=-1.5; b<=1.5; b+=3.0/lines)) do
 5         for ((a=-2.0; a<=1; a+=3.0/columns)) do
 6             for ((p=0.0, q=0.0, i=0; p*p+q*q < 4 && i < 32; i++)) do
 7                 ((pnew=p*p-q*q+a, q=2*p*q+b, p=pnew))
 8             done
 9             ((colour=(i/4)%8))
10             echo -n "\\e[4${colour}m " 
11         done
12         echo
13     done
14 }

What do you think this function does?

It draws Mandelbrot fractal :D This is possible because of ZSH floats support.