Addition of complex numbers

This figure shows how to compute the addition of two complex numbers. Click the animate button!
-) Add two complex numbers, you can choose them. -) Search two complex numbers, to get 0 as the result of the addition. -) Search two complex numbers, to get 0 at the imaginary part . -) Search two complex numbers, to get 0 at the real part. -) Try to find out, how to subtract two complex numbers.