How lessons work
A lesson can have three parts: a short explanation, a quiz and a coding challenge. Press Run Code to check your challenge against its tests. Hints are free, and the solution is there if you need it.
Updated October 17, 2026
The parts of a lesson
- Theory: a short explanation with examples.
- Quiz: a few questions, such as multiple choice, fill in the blank or putting code in order.
- Challenge: a task you solve by writing code in the editor.
Your course is made of sections, sections of chapters, and chapters of lessons. You earn a certificate for each section you finish.
Running your code
Press Run Code to check your challenge. Your code runs against the challenge's tests, and the TEST CASES tab shows each one: the input, the expected output and yours. When a test fails, DIFFERENCES shows exactly where your output differs. Some tests are hidden, so you can't pass by printing the expected answer.
A failed run costs nothing. A passed challenge or a finished quiz uses 1 energy on the free plan.
Stuck?
- Hints are free. Reveal them one by one, and they don't lower your rewards.
- Bugsy, the AI tutor, can explain the challenge or why your code failed. See Bugsy, the AI tutor.
- Solution: the SOLUTION tab shows the answer. Revealing it before you pass means you earn no tokens and less XP for that challenge.
First try
Pass a challenge with no failed run before it, and without revealing the solution, and you earn more XP and tokens for it.
Skipping a quiz
On the website, a lesson with both a quiz and a challenge has SKIP QUIZ. To always skip quizzes, turn on Always skip quizzes in Preferences.
Think your answer is right but it fails? See My answer is marked wrong.