Every room has sun-light and moon-light. Hallways, stairwells, walkways, etc. probably just have moon-light. The sun-light would be the bright bulb(s) in the middle of the ceiling or by work areas to allow tasks to be performed. The moon-light is the much dimmer, low wattage option like a night-light, for moving about and other less visually precise activities. The moon-light would likely emanate from multiple locations in a room, possibly both low and high positions. It would ideally have a motion sensing, or even more advanced, setting by default, providing ample light to turn on the sun-light if it is needed. Off and on would also be provided for when the circumstances are appropriate, such as off when sleeping. The sun-lighting would likely just stick to the regular off/on switching, as the times when it is needed are somewhat more explicit. The moon-light might vary in intensity based on proximity. Sky-lights would ideally be used to provide free moon-light level lighting inside during the day.