Game mechanics optimization

1. Player Identification vs Player Authentication (Gamification Achievement Systems Tips)
2. Game Art vs Game Graphics (Player-Centric Gamification Tips)
3. Game Complexity vs Game Difficulty (Gamification Achievement Systems Tips)
4. Game Economy vs Virtual Economy (Player-Centric Gamification Tips)
5. Game Testing vs Play Testing (Player-Centric Gamification Tips)
6. Social Features vs Multiplayer Features (Player-Centric Gamification Tips)