This HTML5 app shows how the *basic arithmetic operations* with *complex numbers*
can be interpreted geometrically. In the green control panel the type of operation and the coordinate system can be set.
The first operand is represented by a blue point in the complex plane (Gauss plane), the second by a red one.
Both operands can be varied by dragging the mouse with pressed mouse button. The result can be seen from the position
of the point in black.