2020 Update: Given the huge number of requests we have received from teachers and students, will will be running a Challenge this year. Teachers can find details on the registration page.
Registration for the 2020 paper is now closed!
After five successful years of online challenges, there are 180 puzzles that are available to students and teachers. The entry level question for one of the challenges, chosen at random, is shown above. The other challenges can be found by clicking "The Online Challenge" panel below. We hope you have enjoyed the challenges as they came out, however, there are no plans to release new puzzles.