Unlockable abilities

1. Player Roles vs Player Classes (Gamification Achievement Systems Tips)
2. Player Abilities vs Player Powers (Gamification Player Progression Tips)
3. Leveling Up vs Ranking Up (Gamification Player Progression Tips)
4. Skill Advancement vs Level Advancement (Gamification Player Progression Tips)
5. Skill Progression vs Ability Progression (Gamification Player Progression Tips)