One lesson, exactly as a student gets it.

• Seven and a half minutes of order book, narrated — and five questions inside the video, which stops until you answer.
• Three of them ask you to point at the screen: where the diagonal imbalance is, where the others are, which one would take you out.
• And the distinction the rest of the course turns on: the same two levels, the same diagonal, read as a twin or as an imbalance depending on one ratio.

The voice is French, and only French — there is no English or Spanish audio track. Everything else follows the language you pick: subtitles, summaries, written pages, quizzes. You can switch at any time.