# Puzzle 156: Killer Sudoku

Next weekend I’m running a pure Killer Sudoku contest at logic-masters.de. The idea was to give our Killer Sudoku experts a chance to shine. It’s 9 puzzles in 90 minutes from 6 authors, see the instruction booklet for further details. Thank you to Tom Collyer, Stefan Heine, DavidMcNeill, Eva Schuckert and Bernhard Seckinger for their contribution!

To get you in the mood, here’s one Killer Sudoku.

Rules Solve as a regular Sudoku. In addition, some cages are given. The cage clues indicate the sum of the digits within the cage. Digits can’t repeat within a cage.

# Puzzle 153: Friendly Sudoku

Here’s a new (?) Sudoku variant. Inspired by Sudoku N from the upcoming Sudoku Mahabharat. The 6×6 example there also solves uniquely by these rules.

Rules Solve as a regular Sudoku. Some pairs of numbers are friends. Dots mark all spots where two friends are next to each other.

# Puzzle set: Classic Sudokus, 2017 East Asia Sudoku Championship

Last Sunday, South Korea hosted the Asian Sudoku Championship in Seoul, which included a set of classic Sudokus that I wrote.

These originally came out of practicing my Sudoku construction skills by writing a puzzle a day for a long week early last year. It’s still a hit-or-miss process for me, but I think there were some nice ones. Solve on PZV (a b c d e f g h i) or find the set below.

In other news, don’t forget to take part in Puzzle Ramayan at LMI this weekend: A set of easyish classics and region puzzles that I prepared, including some instructionless variants.

# Puzzle 141: Twin-Detector Sudoku (diagonal)

The WSC 2016 is over. I have a lot of puzzles left to solve, but I’m quite happy with my result (54th in the general ranking, after the 39th official participant, after 89/63 last year). Here’s a puzzle I made to help Martin to prepare to become the King of the Mountains (not sure that helped, considering I didn’t quite have the rules right). Test-solved by the new world champion Tiit Vunk of Estonia. Congratulations to both!

Rules Fill the cells with numbers 1 to 9, so that no number repeats in a row, column or outlined 3×3 square. Whenever a number is equal to the sum of some numbers in a diagonal direction, an arrow is placed pointing there.

(The standard rules also have arrows pointing horizontally and vertically.)

# Puzzle 136: External Sudoku

We’re running a small preview series on croco-puzzle for the 2016 WSC and WPC, which will take place in Slovakia soon. We’ll kick it off with an External Sudoku tomorrow. For this, I made an example puzzle which seems worth posting in its own right.

Rules Solve as a standard Sudoku, i.e., fill the grid with numbers 1-8 such that every row, column and outlined area contains each digit exactly once.

In addition, there is a diagonal rectangle of gray cells. Every edge of this rectangle must contain exactly the digits 1-(length of the edge). Diagonally adjacent digits in gray cells must not be consecutive.

Or see the instruction booklet.

# Puzzle 130: Divisor Sudoku

Here’s a Divisor Sudoku. I made this one for the 24h review series on croco earlier this year, but ended up making a second easier one. Please excuse the lazy rendering.

Rules Standard Sudoku rules. In addition, the givens indicate a divisor of the corresponding two-digit number (left-right or up-down).

# Puzzle 98: JaTaHoKu, cryptic

Last JaTaHoKu for now, a JaTaHoKu with cryptic clues. I made a triagonal one, too, but didn’t get around to rendering that yet. Maybe later.

Rules Place numbers from 1 to 6 into some empty cells, such that each row, column and region contains each number exactly once. Clues within the grid are Tapa clues; the numbered cells form a valid Tapa solution with respect to these. Clues along the bottom and right edges are skyscraper clues. Clues along the top and left are Japanese Sums clues, with question marks standing in for unspecified digits. (I.e., 10 would be two question marks.)

Some digits have been replaced by letters. Equal letters correspond to equal digits, different letters to different digits.