All the challenges are available in the Online Challenge Archive. Each challenge have five levels. You can use whatever means you like to solve the problems, just type your answer in the box and click Submit. If your answer is correct, you will progress to the next level.
If you get stuck, typing HINT will give you some help to answer the question; typing ANSWER will give you the answer, leading you to the page with the fully explained solution.
To play a challenge follow one of these links:
- Play one of the past challenges in the challenge archive
- Try a question from one of the past challenges according to the rank:
- Choose an entry level question
- Choose a copper level question
- Choose a silver level question
- Choose a gold level question
- Choose a roentgenium level question