Most transitions are trivial to implement - you have a state A of your dialog that looks like this and a start B with your target look/layout - so the framework figures out what needs to move where, what needs to be hidden/shown and then animates that in a quick loop.

The complicated part is the fading of controls. There's no fine-grained control over when Windows repaints controls exactly, so unpainted parts of the background showing through is a nasty issue. Requires basically per-Windows version voodoo, because what works for W8, doesn't work for W10 and vice versa.