Our whole society is, and will be, deeply impacted by digital technologies and practices. This impact is taking a new qualitative and quantitative turn with what is named artificial intelligence (AI). We must allow everyone to master, thus understand and develop a creative and critical perspective and agency in the way AI is integrated in the different domains of our lives. We have built and now operate a citizen MOOC in AI in the broad sense, on AI foundations and applications, intended for a large public beyond the school domain, with more than 15000 participants engaged in the MOOC after three months. We report here on this project, detailing the didactic choices (linking everyday life elements to fundamental concepts, understanding the "how it works" via online or unplugged concrete activities, making explicit how understanding the "science underneath" allows to better discuss the societal impacts) and the pedagogical method (e.g.: small conceptual videos, contaminating activities to be redone in real life, ...). We finally share learning analytics, quantitative and qualitative evaluations and explain to which extent educational science research helps enlighten such large scale initiatives.