Explore how Duolingo balances teaching challenging subjects while maintaining user engagement in this 2019 GDC conference talk. Discover the strategies employed by Karin Tsai, senior director of engineering, to create an effective learning experience. Learn about competition for users' time, learning curves, metrics, and the impact of even the smallest changes in difficulty. Gain insights into measuring the right things, teaching immediately satisfying concepts, and disguising difficult ideas. Understand the importance of practice over instruction, offering exposure in different contexts, and making content memorable. Delve into difficulty scaffolding, pacing mechanics, and motivational messages. Acquire valuable advice for game developers on user engagement, including how to avoid overwhelming users and minimize reading requirements. Examine the "utterly screwed" test and the significance of streaks in maintaining user motivation.