Visualizing Complex Polynomials
This sketch uses to graphics windows to show what complex input and output look like for real coefficient polynomials. (One exception, can have a complex constant.)
This sketch can be used to find real and complex roots, visualize orbits and even see winding numbers.
It works in the online version (student page) but it works a bit better if you download.
There is a blogpost about using this sketch and the Numberphile video that inspired it:
http://mathhombre.blogspot.com/2014/07/complex-instruction.html