2 way, 3 way, 4 way lighting switching and other random stuff.

The mysteries of multi-way switching and some other loose odds and ends including RCD, GFI, GFCI controller chips with clever neutral to earth fault detection via inductive coupling.
Oh, and the previously awesome head torch that loses a point for not having lower voltage threshold cut-off to protect the lithium cell. But it's not super bad news, since the intensity diminishes significantly at that point, and you've got around 12 hours of use on a charge anyway.