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Plank Puzzle No.15 - Fiendish

History (2000/2001)

Fiendish was devised by hand over a period of several days. My sole aim was to improve on my previous best (Route-66) which I had stumbled on more by luck than judgement and was a big leap forward in its time. A nifty windows-based (C++) plank-puzzle editor/solver (by applet author, Graham) was used to verify the solution. Fiendish is actually shorter than Route-66, but more complex and compact, as (hopefully) illustrated in the following table.

During the first few heady months of plank puzzle exploration I fixed on the notion that the best way to measure plank puzzle complexity was by move-over-span ratio which is why I initially ranked Fiendish above Route-66. Until March 2001 Fiendish and Route-66 were the only two puzzles with a move-over-span ratio greater than 1 (meaning the number of moves actually exceeds the number of possible plank positions).

  Route-66 Fiendish
Grid 9x9 (square) 8x8 (square)
Planks 3 (1+2+3) 4 (1+2+3+4)
Shortest solution 66 moves 57 moves
Span count 54 40
Move/span ratio 1.22 1.42

However... In March 2001 Pascal Wassong well and truly smashed my move-over-span ratio record with a plank-puzzle of his own design entitled The Centrifugal Force (TCF for short). TCF requires an incredible 342 moves and has a move-over-span ratio of 4.62.

concept & maze design - © Andrea Gilbert 2000-2001
HTML5 implementation - © Jeremy D. Miller - 2017
hosted with permission from Jeremy D. Miller