Friend lists

1. Player Challenges vs Game Challenges (Gamification Achievement Systems Tips)
2. Achievements vs Trophies (Player-Centric Gamification Tips)
3. Financial Risk vs Gaming Risk (Virtual Economy Gamification Tips)
4. Player Experience vs Player Engagement (Gamification Achievement Systems Tips)
5. Player Identification vs Player Authentication (Gamification Achievement Systems Tips)
6. Player Interaction vs Player Connectivity (Gamification Achievement Systems Tips)
7. Player Onboarding vs Player Tutorials (Player-Centric Gamification Tips)
8. Social Features vs Multiplayer Features (Player-Centric Gamification Tips)