A square button that highlights when pressed.
Inherits from Button
Buttons generate callbacks when they are clicked by the user. You control exactly when and how by changing the values for type and when.
The Light_Button subclass display the "on" state by turning on a light, rather than drawing pushed in. The shape of the "light" is initially set to Boxtype.down. The color of the light when on is controlled with selection_color, which defaults to Color.yellow.