For certain activities, you unlock Achievement Badges. Some of these are Inner Circle, Sharpshooter, Big Spender, Overachiever, Overtime, Friendlt, Wildfire and Champion.

Each badge has 3 levels that you progressively unlock.

More screenshots from‏‏‎ ‎

Duolingo

Learning experience
Gamification memes
Duolingo Clubs
Asking for notiification permissions during onboarding
Onboarding
Gamification: Streak, Lives and Gems
App Store screenshots
Duolingo Plus
2019 redesign
App icon change
Change or add language
Top level tabs
Create profile

More‏‏‎ ‎

Gamification

Gamification: Streak, Lives and Gems
Gamification with the translation camera
Redeeming reward
Card Gamification: Function Cards