When I was in college I was working on an Ada interpreter. Ada was the new DoD 'official' language for embedded systems. Ada was a compiled language so an interpreter was an interesting idea.
"Here, as in natural science, is shown the correctness of the law discovered by Hegel (in his Logic), that merely quantitative differences beyond a certain point pass into qualitative changes."
When it was time to work on my dissertation, one of my faculty advisors, John King, told me to think about "when a difference in degree becomes a difference in kind." He didn't tell me this was a modification of a quote from Marx, who had modified something Hegel wrote.
His example was that a jet isn't just a fast airplane - to make a jet requires different control surfaces, different engines, different shape, different materials - just about everything needs to be re-engineered.
This insight has been hugely beneficial during my career. In the case of the Ada interpreter, it wasn't just a big interpreter for a normally compiled langauge - it evolved into something rather different, because to support Ada as an interpreted language without destroying its usefulness as a compiled language was a rather complex problem.
Later, when I worked on the B-2 Stealth "Spirit" Bomber, I realized that a stealth airplane wasn't just an invisible airplane - everything had to be reworked - materials, control surfaces, shape, engines - even the mission was different from a regular bomber. (My focus when working at the Northrop Research and Technology Center was computer graphics to support the 'new mission' of the B-2.)
When working on video and computer games, which are based on fast-moving computer technology, I have run up against this all the time. Each generation of gaming platform brings with it a whole new set of concerns. The old tools won't cut it - you generally need significantly enhanced or improved tools just to make the game.
Now I am working on an on-line music downloading service, and I can tell you that it's not just a music store without walls.
It's a completely different beast that has required re-engineering the entire model from the ground up.