Image: Wikimedia Commons

Canadian puzzle designer Jeff Widderich invented this game in 2007. The goal is to place a digit 1-9 in each white cell so that each crossword-style “word” contains a straight, that is, a set of consecutive numbers in some order. For example, the top row of five digits might contain 62534, but not 91548.

One other constraint: Each full row or column must contain no repeated digits. That means, for example, that each of the two long vertical “words” will contain all nine digits. The digits in black cells count toward this constraint — the 9 in the black cell near the center means that no 9 appears elsewhere in its row or column. Can you complete the rest of the diagram?

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An Unsolved Puzzle

Sam Loyd’s 1903 Eighth Book of Tan explores the world of tangrams, the pastime of constructing specified shapes from a given set of seven pieces:

The book includes a few “paradoxes,” two of which I’ve mentioned here before. But here’s another:

“The seventh and eighth figures represent the mysterious square, built with seven pieces; then with one corner clipped off, and still the same seven pieces employed.”

The book includes no solution. The square on the left is just the regular “block” formation above. But if anyone has discovered how Loyd produced a “clipped” square using the same seven pieces, I haven’t been able to find it.


From a collection in Frank Mittler’s Little Book of Word Tricks (1958):

1. Pray tell me, listener, if you can,
Who is that highly-favored man
Who, though he marries many a wife,
May still stay single all his life?

2. I sit in fire, but not in the flame;
I follow the master, but not the dame;
I’m found in the church, but not in the steeple;
I belong to the monarch, but not the people.

3. Its light was mellow, soft and lazy;
One foot broke off — and it went crazy!

4. What is found in the very center of both America and Australia?

5. What divides by uniting and unites by dividing?

6. Why is a popular crooner like a doctor in an asylum?

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keith chessametic

Mike Keith published this remarkable invention in the Journal of Recreational Mathematics in 1975. Suppose a chess game goes:

P-K4   P-K4 
B-B4   P-R4 
Q-B3   P-R4 

This is checkmate, so White says “I win!” Now if the game score is written out in one column, including White’s exclamation:


… we get a solvable alphametic — replace each letter (and the symbols x and -) with a unique digit and you get a valid sum. (The digits already shown count as numbers, and those numbers also remain available to replace letters.)

This example isn’t quite perfect — the two moves P-R4 are ambiguous, as is the final pawn capture. Keith’s Alphametics Page has an even better specimen, a pretty variation from a real 1912 game by Siegbert Tarrasch. It’s 13 moves long and forms a perfect alphametic with a unique solution.

Image: Wikimedia Commons

In this original logic puzzle by the Japanese publisher Nikoli, the goal is to connect lattice points to draw a closed loop so that each number in the grid denotes the number of sides on which the finished loop bounds its cell, as above: Each cell bearing a “1” is bounded on 1 side, a “2” on 2 sides, and so on.

Here’s a moderately difficult puzzle. Can you solve it? (A loop that merely touches a cell’s corner point without passing along any side is not considered to bound it.)
Image: Wikimedia Commons