This does three things:

* When it is too dark, the lights will go into a shut down mode, where
  the maximum amount of brightness is graudally reduced to zero. This will
  allow me to let the project run all the time, while shutting down when I
  go to bed.
* When it is dim (again), the process is reversed (but faster)
* When there is too much light, the lights will be directly set to zero.
  This means that the house won't be lit if I switch on the lights in my
  room.