Key
Locked state
Several notched bars cross through a shared centre. Most pieces cannot move because another bar blocks their notch.
First release
The key piece has enough clearance to slide a short distance. That movement opens space for a second bar, and the structure changes from rigid to partially mobile.
Why reassembly is difficult
The same freedom must be preserved while pieces are added in reverse. Tightening the assembly too early can remove the route needed by the final key.
Animation pauses automatically when your device requests reduced motion.