:-)) Yes, Microsoft Office is actually a perfect example for how not to do it and why:

What they do wrong is, how they partition the "state space" in the first place. They employ utterly absurd abstractions that fly in the face of rational usage. Then that "ribbon" nonsense observes the user stumbling though that mess and changes the arrangement on the fly, maximizing the confusion.

In other words, they have never conceptualized what it is their users actually want to do and why. Now they're "stuck" with "what users are habituated to" and each "optimization" makes things even more worse in other places.

To get a "fluid" interface right, you need to know that it makes sense only when there are distinct use cases. You then have to detect (or perhaps better: let the user decide) what use case you're in and shape the interface according to that. Making the user chase buttons certainly isn't the right way.