Definition
Plain language
A version of a puzzle where both the starting arrangement and the target arrangement are scattered, so there's no memorized recipe to fall back on.
As stated in the literature
A Tower of Hanoi variant with arbitrary start and goal configurations rather than the canonical all-on-one-peg endpoints, eliminating the standard recursive template and requiring genuine shortest-path search over the state graph.
Also called: flat to flat
Why it matters: It separates models that have memorized a standard solution recipe from those that can actually search for a path between two arbitrary situations.
For example, instead of moving all the disks from one peg to another, you are handed a jumbled starting layout and a jumbled target layout and must figure out the shortest route between them.
Heard on the show
“So they move to what they call flat-to-flat.”Episode 237 — The Model Built a Perfect Map of the Puzzle, Then Lost It