Appendix F — Glossary

One word for each idea, used the same way everywhere in the game and in this book.

Blank: The empty Slot (stored as 0).
Board: The 3 x 3 puzzle as stored: nine Slots.
Board State: The nine digits of the Board in reading order, as one number.
Estimate: The heuristic: Manhattan distance (default) or misplaced Tiles.
estimatedMovesLeft: h: the Estimate for a Search State.
Expand: Take the best open Search State, close it, and look at its neighbors.
Finished: The solver’s situation when a Step has nothing more to do: the search stopped or the Route has been played (Mode of Run Search).
Frontier: The Search States still open (found but not yet Expanded).
Goal: The Board State the puzzle is solved at: Puzzle Settings / goalBoard (123456780).
Goal Cell: One cell of the Goal Picture; its placement sets its Slot (Data Structure Goal Slot).
Goal Picture: The small picture of the Goal (nine Goal Cell placements; each shows the Goal’s Tile in its Slot, from goalBoard).
Inversion: A pair of Tiles where the larger number comes first in reading order (the Blank is not counted); counted by Count Inversions.
Jump: How New puzzle and Reset show a Board: Tiles go straight to their Slots.
Message Line: The sentence that explains the last Step.
Move: One Tile sliding into the Blank; costs 1. A hand Move is made by the player; a Route Move by playback.
movesSoFar: g: the Moves from the Start Board to a Search State by its stored route.
Neighbor: A Board one Move away from another Board.
New puzzle: Make a new solvable Board by random legal Moves from the Goal.
Pause: Stop Solve and keep all progress.
player: The person playing (never a game piece).
Puzzle Button: One button Object; each placement sends its own Custom Event.
Puzzle Rules: The Object that owns the Board State and the search.
Reset: Put back the Board of the last New puzzle (or the Start Board).
Route: The chain of Board States from the Start Board to the Goal.
Route record: One row of the Solution Route table.
score: f = movesSoFar + estimatedMovesLeft; the lowest is Expanded next.
Search: One A* run from the current Board, from the first Step until the Goal is accepted, it stops, or it is cancelled.
Search State: One record in the Search States table: a Board State the Search found.
Slide: How a Move is shown: the Tile glides to its new Slot in slideSeconds.
Slot: One cell of the Board, numbered 0 to 8 in reading order (0 top-left).
Slot Position: The one Function that turns a Slot into a screen position.
Solve: Repeat Step on a timer until done or paused.
Start Board: The Board State the game opens with (542703816).
States checked: The count of Search States Expanded (shown on screen).
Status Line: The short text that says what the solver is doing (“Searching…”).
statusRow: The Messages row of what the solver is doing; the Status Line shows its words, or its pausedWords while Solve is paused.
Step: Do one transition: an Expand, accepting the Goal, copying one Route record, or one Route Move.
Tile: A numbered piece, 1 to 8, shown in one Slot. One Object, eight placements.