// This type represents a blue window closer. It takes, however, a generic window type,
// so it is capable of closing any type of window, not just a blue window. This is because
// the program will pass it a generic window; the program doesn't know there is a more
// specific type.
func (bwc *BlueWindowCloser) CloseWindow(w af.Window) string {
w.Close()
return "You closed a window with a blue window closer"
}
func (gwc *GreenWindowCloser) CloseWindow(w af.Window) string {
w.Close()
return "You closed a window with a green window closer"
}