Solution to Standard Sudoku no 515

Standard Sudoku no 515 (Tough)

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Solution to Sudoku no 514

Here is my original version of the solution:

...and here is another from Ferz Verdan Dizon, a member of the Sudoku Puzzles Facebook group:

Sudoku no 514 (Diabolical)

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Solution to Sudoku no 513

Here is my original version of the solution:

Here is Andrew Stuart's version. His solver will not finish a puzzle if it believes it has more than one solution:

The solver at https://www.sudoku-solutions.com/ was able to work out the answer by brute force but it didn't know how to get to it using human logic. That's perfectly reasonable. Writing a solver to use all known human solving strategies is a major undertaking:

This is what John Musgrave, a member of the Sudoku Puzzles Facebook group, had to say about this puzzle. You can see his own puzzles at http://www.manifestmaster.com  

Sudoku no 513 (Extreme)

Warning:

This puzzle is called extreme for a reason. In addition to naked and hidden singles it may require 48 other steps to solve. The exact figure will depend on how you approach it.  

The puzzle should only be attempted if you understand the BUG (bi-value universal grave) solving technique.

If you type this puzzle into an online solver or app which does not know about this technique, it will probably give up and may even suggest that the puzzle has more than one solution:

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Solution to Standard Sudoku no 512

Standard Sudoku no 512 (Easy)

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Solution to Standard Sudoku no 511

Standard Sudoku no 511 (Tough)

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Solution to Standard Sudoku no 510

Standard Sudoku no 510 (Extreme)

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Solution to Standard Sudoku 509

Standard Sudoku no 509 (Diabolical)

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Solution to Standard Sudoku no 508

Standard Sudoku no 508 (Moderate)

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Solution to Codeword no 1

Codeword no 1

The white rectangles in the 13 by 13 grid below contain every number from 1 to 26 at least once. Each number represents a letter of the alphabet. Each letter is represented by only 1 number so the whole alphabet is used.

The 13 by 2 grid allows you to record the letter corresponding to each number and I have given you 3 of these already.

Replace each number in the 13 by 13 grid with the letter it refers to so that you spell out words from left to right and top to bottom.

The line of letters allows you to cross out each one as you find it.

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Solution to Puzzle no 507

Sudoku Puzzle no 507 (Extreme)

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Solution to Puzzle no 506

Sudoku Puzzle no 506 (Extreme)

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Solution to Above, Below, Left and Right Puzzle no 1

Here is my original version of the solution:

This puzzle has also been solved by two members of the Sudoku Puzzles Facebook group.

Adelina Zaballero provided this version of the answer:

...and John Palmer supplied this one:

Above, Below, Left and Right Puzzle no 1

I created this puzzle using Oracle Database Version 18 Express Edition.

Use each of the numbers 1 to 9 exactly once to fill in the empty squares in the grid below.

I can tell you that:

9 is to the right of 6.
8 is above 4.
1 is to the left of 3.
4 is below 1.
2 is to the right of 4.
3 is above 9.
5 is below 3.

Numbers which are above or below one another are in the same column but do not have to be in adjacent squares.

Numbers which are to the left or right of each other are in the same row but do not have to be in adjacent squares.

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Solution to Puzzle no 505

Sudoku Puzzle no 505 (Diabolical)

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Solution to Puzzle no 504

Sudoku Puzzle no 504 (Diabolical)

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Solution to Puzzle no 503

Sudoku Puzzle no 503 (Easy)

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Chess Solution no 2

1. Bg7+  Rxg7
2. fxg7+  Kg8
3. Bh7+  Kxh7
4. g8=Q+  Kh6
5. Qh8#   

Chess Puzzle no 2

White to play and checkmate in 5:

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