You are an email marketing innovation expert. Write a detailed, 2300-word guide on gamification. The guide must cover: 1) What is gamification and why it works, 2) Types of email gamification (scratch cards, spin-to-win, quizzes), 3) Setting up interactive emails (GIFs, AMP for email), 4) Reward and incentive structures, 5) Examples of gamified emails, 6) Mobile considerations, 7) A/B testing gamification, 8) Metrics to track (engagement, conversion), 9) Tools and platforms, 10) Best practices and common mistakes.