Page 1: 第1页 Have you ever wondered what it takes for an educational app to become the most popular in the world? What kind of mission would drive a company to achieve such a massive scale, reaching millions of users and topping the charts? Page 2: 第2页 What happens when someone who has seen educational inequality firsthand teams up with someone who understands the power of games? How might their unique personal histories shape the very DNA of the product they create together? Page 3: 第3页 If you could get millions of people to do a small, useful task for free—like deciphering a word to digitize a book—what else could you achieve? How could you apply that same powerful principle to make something as valuable as education completely free for everyone? Page 4: 第4页 Why does earning a digital badge or keeping a streak alive feel so intensely rewarding? What is it about these simple, game-like features that can transform the chore of studying into something you genuinely want to do every single day? Page 5: 第5页 What if an app could predict what you're about to forget and give you the perfect exercise to remember it? How can technology be used not just to make learning fun, but to make it scientifically more effective and personalized just for you? Page 6: 第6页 What do you do when your brilliant idea to keep education free doesn't actually make any money? How do you pivot to a new business model involving ads and subscriptions without betraying your original mission? Page 7: 第7页 Can something truly be "free for all" if the free experience is intentionally made more difficult? Where is the line between encouraging users to pay and compelling them to pay, and how does a company navigate that without losing the trust of its community? Page 8: 第8页 What does this incredible financial success tell us? Does making billions of dollars from a learning app prove that the freemium model is the perfect solution, or does it raise even more questions about the true meaning of a "free education" mission? Page 9: 第9页 Why would a respectable education company want its mascot to be seen as "unhinged" and "threatening"? What does this bold style of marketing achieve that a traditional, friendly advertisement simply cannot? Page 10: 第10页 We all receive countless notifications every day, but what makes some feel helpful while others just feel like spam? How can an app use data to send you the perfect reminder at the perfect time, turning a potential annoyance into a valuable and motivating nudge? Page 11: 第11页 If you've already built a successful platform for learning, what's the next logical step? How can you leverage that same brand trust and technology to disrupt another expensive and inaccessible part of the education system, like standardized testing? Page 12: 第12页 Is a company that teaches languages also qualified to teach math and music? What does it take to successfully apply a winning formula to a completely different subject? And how might artificial intelligence completely change the rules of the game? Page 13: 第13页 Can an app truly replace a classroom? When we talk about "effectiveness," what do we really mean? Is it about feeling more confident, or is it about achieving true fluency, and can a single app be expected to do both? Page 14: 第14页 So, after examining its history, its technology, its business, and its challenges, what do you believe is the true legacy of Duolingo? Is it a story of a mission-driven company that found a way to be profitable, or a story of a business that uses a powerful mission to drive its profits? What is the most important lesson we can learn from its journey?