Duolingo's rise to #1 wasn't by chance. What design choices got them there?

Duolingo revenue for the twelve months ending June 30, 2023 was $0.442B, a 44.47% increase year-over-year. Duolingo annual revenue for 2022 was $0.369B, a 47.34% increase from 2021.
‍

I was curious how they think about their design. I observed 5 points that were consistent:

‍

1. "Level-Up" Mentality: Fostered “urge” among users to progress through levels. This could be a potential reason for skyrocketing user retention. 

‍

2. Refinement at all stages: Persistent look on user-centric data. I learnt they’ve a 20 member dedicated team devoted to unceasing product enhancement.

‍

3. Simple, not minimalistic: Welcoming users from various backgrounds. Not making it region specific. 

‍

4. Building narrative for long-term: Habit building through triggers like emotive notifications.
   
   
5. Behavioural Blueprint: I suspect if they’ve psychologists in their team. They've included aspects like fear of loss to boost user engagement. Increases LTV

As nascent startups, these design tenets could be helpful.

I’ll keep going through other apps that've tasted success, and try to put my honest insights on their design from a user perspective.

‍