Challenge and difficulty

1. Game Tasks vs Game Objectives (Gamification Achievement Systems Tips)
2. Active Users vs Registered Users (Player-Centric Gamification Tips)
3. Game Playability vs Player Playability (Gamification Player Progression Tips)
4. Player Data vs Game Data (Gamification Achievement Systems Tips)
5. Player Interaction vs Player Activity (Gamification Player Progression Tips)
6. Individual Progress vs Team Progress (Gamification Player Progression Tips)
7. Player Actions vs Player Behavior (Gamification Player Progression Tips)
8. Player Competence vs Player Performance (Gamification Player Progression Tips)
9. Player Investment vs Player Commitment (Gamification Achievement Systems Tips)
10. Player Preferences vs Player Interests (Gamification Achievement Systems Tips)
11. Player Targets vs Player Goals (Gamification Player Progression Tips)
12. Progression System vs Achievement System (Gamification Player Progression Tips)