You have 2 boxes and an even number ($2n$) of balls in the first box. Your goal is to distribute the balls equally into the two boxes, so that each box contains $n$ balls. You must obey the following protocol: Step 1, move exactly 1 ball from one box to the other box. Step 2, move exactly 2 balls...

The Olympic rock climbing competition has 20 climbers. Each climber competes in 3 separate events, where they rank from 1st to 20th. The final score of a climber is the product of their rankings from the 3 events, where lower is better. For example, if a climber finishes 5th, 3rd and 10th then th...

After defeating the octangular spirits, you find yourself needing some laundry powder. However, you can't find any at your usual shop, and so you have to ask one of the employees, who happens to be a serpent-tail. You know that serpent-tails have 5 tails, which can understand and answer questions...

Inspired by Stiv's fantastic Where? word association puzzle, I decided to create my own. Special thanks to Stiv for test-solving and general feedback! Instructions (adapted from The GCHQ Puzzle Book (2016) and Stiv's original puzzle): The words in the following list can be partitioned into equal-...

Let's have the following first four terms of a sequence that expands indefinitely. 224, 8280, 34968, ? What number replaces the question mark? Secondly, all the numbers of this infinite sequence have something in common. What trick is required to prove that commonality?