Digital currency systems

1. In-Game Currency vs Premium Currency (Player-Centric Gamification Tips)
2. Resource Allocation vs Wealth Distribution (Virtual Economy Gamification Tips)
3. Tangible Goods vs Intangible Goods (Virtual Economy Gamification Tips)
4. Barter System vs Trading System (Virtual Economy Gamification Tips)
5. Exchange Rate vs Conversion Rate (Virtual Economy Gamification Tips)