I am looking for a sliding block puzzle named "the viking game".

competition/games/sliding.block New

New entry, edited from material collected for the archive and not yet in a released version.

Problem

I am looking for a sliding block puzzle named "the viking game".  The
game consists of 10 blocks inside a 5x5 wooden frame.  The blocks can
not be lifted, only slided, and not twisted.  [The idea is to get the
large 2x2 block out of the frame through the gap at the bottom by
sliding blocks around (no twisting or lifting allowed].

-- Darren Price <priced@cadvision.com>

[ Editor: the starting position, as redrawn by Gareth Rees, is the first
figure in the solution. ]

Show solution

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   X .__..______..__. X     X .__.        .__. X    X .__..______..__. X
   X |  ||      ||  | X     X |  |        |  | X    X |  ||      ||  | X
   X |  ||      ||  | X     X |  |        |  | X    X |__||      ||__| X
   X |  ||      ||  | X     X |  |.______.|  | X    X .__.|      |.__. X
   X |  ||      ||  | X     X |  ||      ||  | X    X |  ||      ||  | X
   X |__||______||__| X     X |__||      ||__| X    X |  ||______||  | X
   X .__..__..__..__. X     X .__.|      |.__. X    X |  |  .__.  |  | X
   X |  ||  ||  ||  | X     X |  ||      ||  | X    X |  |  |  |  |  | X
   X |  ||__||__||  | X     X |  ||______||  | X    X |__|  |  |  |__| X
   X |  |.__..__.|  | X     X |  |.______.|  | X    X .__.  |  |  .__. X
   X |  ||  ||  ||  | X     X |  ||      ||  | X    X |  |  |  |  |  | X
   X |__||__||__||__| X     X |__||______||__| X    X |__|  |__|  |__| X
   X     .______.     X     X .__..__..__..__. X    X .______..______. X
   X     |      |     X     X |  ||  ||  ||  | X    X |      ||      | X
   X     |______|     X     X |__||__||__||__| X    X |______||______| X
   XXXXXX        XXXXXX     XXXXXX        XXXXXX    XXXXXX        XXXXXX

     Darren Price's              "The Donkey"          "The Century"
        original

Darren Price's puzzle, which I've redrawn above, is just a variant
starting position of a puzzle which Berlekamp, Conway and Guy call "the
Donkey" on page 769 of their book "Winning Ways".  They present a
sketchy "map" of the obtainable configurations of that puzzle, and also
describe a much more challenging puzzle using the same pieces, called
"the Century", whose shortest solution requires 100 moves (and an
additional challenge - to invert the starting configuration - takes 150
moves).

-- Gareth Rees <gdr11@cl.cam.ac.uk>

[ Editor: no move-by-move solution was given in the collected postings.
See also competition/games/15.puzzle. ]