Currency systems

1. In-Game Purchases vs Microtransactions (Player-Centric Gamification Tips)
2. Tradable vs Sellable (Virtual Economy Gamification Tips)
3. Achievements vs Challenges (Gamification Achievement Systems Tips)
4. Leveling Up vs Ranking Up (Gamification Player Progression Tips)
5. Resource Allocation vs Wealth Distribution (Virtual Economy Gamification Tips)
6. Virtual Resources vs Game Resources (Virtual Economy Gamification Tips)