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24 December 2006

From Chessbase: A christmas tree themed chess puzzle for all your enjoyment

http://www.chessclub.com/mailing/2006/12d/diag3.gif

White to play and mate in two.

This puzzle requires some initial retrograde analysis to get the crucial concept required for mate in two, and a little more intensive retrograde analysis to narrow down the two apparantly possible solutions to the one genuine, unique solution. Created by a truly excellent and prodigious composer, Thomas Rayner Dawson.

<spoiler> At first sight there appears to be no solution as the knights can’t possibly check in two let alone deliver mate. However once we start thinking retrograde, Black could only have played d7-d5 or f7-f5 as his last move. Each allows an en passant capture and then mate next move.

But a true puzzle has but only one true solution, and so we actually require a little more retrograde analysis. The white pawns must have captured 10 times, which accounts for all the missing black pieces. That means Black's last move cannot have been d7-d5, because in that case the Bc8 was captured on its starting square, and a pawn could not have done that. Therefore, Black's last move was f7-f5, and White mates with 1.gxf6 and 2.f7 mate! </spoiler>

22 December 2006

Have (yet again) modified the layout for puzzles, solutions and discussions.

• Relocated all solutions to the Talk page instead of a spoiler in the puzzle page. This reduces the incentive to glance at the solution and also means that I can easily create a group ("test-solvers") that has read access to article pages but no access to Talk pages
• Included on the Talk page a specific section for "Solver discussions". This section contains a table with everybody's feedback on the puzzle so that the designer can refine it if necessary. Things like:
  • Percentage of puzzle completed without guidance
  • A score rating
  • Specific comments on the solver's thought process while solving the puzzle

19 December 2006

SectionProtection tags replaced with Spoiler tags.

• No user lists, no access protection.
• Just a simple javascript toggle to switch between visible / invisible.
• Supports all wiki-text/HTML

SectionProtection script has been updated.

• Newest version supports encryption and prevents the previous workarounds.
• However, doesn't behave well (high server load and session time out) when encrpyting large wiki-text blocks.
• Would strongly suggest that it only be used sparingly, with preference given to Spoiler tags instead.

Example: <spoiler> This is an example </spoiler>