Combining Enum Value using Bitmask

I understand it's possible to use bitmasks in enum values, but I don't know how to create it.

I have a simple enum :

enum State
{
    minimizing = 0,
    maximizing,

    minimized,
    maximized
};

A state is always State.minimized or State.maximized, and can have additional state on resize. So something can be Maximized and minimizing