New programs now open with a coach that walks you from your first contract through to your first debrief. Each step points at the button it's talking about rather than describing where to find it, and steps finish themselves when you do the thing — no pressing next to confirm what you just did.
It covers:
You can skip it, step back through it, or start it again at any time from the Escape menu.
Rockets now stand in clamps on the pad and are released at launch, instead of balancing there on their own.
A rocket can only fly with parts your program has actually researched, whichever way it reached the bench — and parts perform the way the catalogue says they do, with no exceptions.