Algorithms

How would you judge a competition to draw a freehand square?

Third challenge cipher

Fourth challenge cipher

Fifth challenge cipher

Seventh challenge cipher

Can you crack these very difficult challenge ciphers? How might you systematise the cracking of unknown ciphers?

Second challenge cipher

Countries from across the world competed in a sports tournament. Can you devise an efficient strategy to work out the order in which they finished?

What day of the week were you born on? Do you know? Here's a way to find out.