Here you can freely explore phase portraits of complex functions.
Variables accessible in the freely editable formula are $a,b,c,d,e$
Where $a,b,c,d$ depend on the position of the colored points
$A,B,C,D$. The dependence is
\[
a=z-A,
b=z-B,
c=z-C,
d=z-D.
\]
Here $z$ is the location in the image. Varable $e$ is a real scalar that can be adjusted
between $-1$ and $+1$.