An Eisenstein triple is related to 60 degree triangles and a special case of the cosine law. But we need not worry about that except to note that a specific example of an Eisenstein triple is $7^2 = 5^2 - 5\times8 + 8^2$ which we can rewrite as $7^2 + 5\times8 = 5^2 + 8^2$ Which means we can hav...

This puzzle is part 5 of the Double feature series (first part here). The series will continue in "Double feature: Legal trouble". Rules of Nurikabe1 Shade some cells in the grid. Numbered cells are unshaded. Unshaded cells are divided into continuous regions, all of which...

There is a smooth dance, a ball sport, a country's capital, a month, and a drink. What's the drink?

This puzzle is not very difficult but yes it is a knowledge base. There are 4 switches & 4 right combinations of the switch to open the gate to the control room. you can either on the switch(green) or you can turn it off(red) but if you try any of the wrong switch combinations the room security ...

This puzzle is part of the ‘Twelve Labours’ series. Previous instalments can be found here: Prologue | 01 | 02 Hercules was grateful the morning sun wasn’t hotter as he pulled the heavy flatbed trolley laden with crates up Hippocrates Hill and along Aristotle Avenue to the Golden Hind. Arriv...

Standing next in turn in good mood; finished "Straight, No Chaser" with a fast tempo. What the Thelonious are we describing?

I'm solving an enigmatic-puzzle, in particular, this. If I found routes that ended up in a dead-end, but which I am sure that was deliberately added in by the puzzle creator, should I post them as an answer? Thanks! The number of red herrings was significant.

Can your criticisms please stop? All you say are crap Robert, stop teasing me for my height Raphaelle, i don’t care if I ressemble a Cheetos Oh my dear lord, I’m Tearing myself apart What am I?

It’s Black to move. What must Black do in order to help White castle queenside?

Two people in particular have come to my Codes and Ciphers Club almost every week. One of them is always expecting a certain message to appear in the weekly puzzles, so of course I can't include it, unless I find a really clever way of disguising it so they won't be able to read it until they wor...

There are 1600 people sitting around a circular table. The first person (person 1) has a sword and kills the second person then hands it to the next alive person (in this case person 3). Person 3 stabs person 4 and gives the sword to person 5. This goes on until person 1599 kills person 1600. The...

Fill in ~ with letters to create a real words vertically, horizontally, and diagonally. Vertical and horizontal words have to be the same: ~ A ~ ~ A X L E ~ L ~ ~ ~ E ~ ~

There are two columns (two sets), in each set there is a pattern among the elements. The elements are not arranged in any order, the two patterns are not necessarily the same, but they are related to each other some way. In one of the columns/set one single element breaks the pattern, and this el...

In the spirit of the What is a Word™/Phrase™ series started by JLee, a special brand of Phrase™ and Word™ puzzles. If a word conforms to a special rule, I call it a Spaceman Word™. Use the following examples below to find the rule. $$ % set Title text. (spaces around the text ARE important;...