Duolingo (2011)

Duolingo is a gamified language learning app, which works using the spaced repetition technique. In order to keep the learner engaged, Duolingo has leaderboards, daily objectives and rewards like badges, items, its own currency and experience points. As September 24th, 2024, Duolingo added a new lesson type called "Adventures", in which you can control one of Duolingo's mascots, while answering questions to make the scene play out. As of April 2025, Duolingo has added a Chess course for iOS.