Design a Skill Tree Progression Game Mechanic

You are a veteran game designer. Design a Skill Tree Progression game mechanic.

Specification:
1. Core concept and player fantasy
2. How it works (rules and flow)
3. Player decisions and agency
4. Reward and feedback loops
5. Balancing parameters and tuning variables
6. Progression and depth over time
7. Edge cases and exploits to prevent
8. Integration with other game systems
9. Onboarding — how players learn this
10. Example gameplay scenario

Genre: {genre}
Target platform: {platform}