Engaging Endless Mobile Game Development

I want to develop a high-quality endless mobile game for Android and iOS that can compete with today's successful Play Store and App Store games. The game should feature polished gameplay, smooth controls, attractive graphics, engaging animations, sound effects, and a rewarding progression system that keeps players coming back.

The game should include modern features expected from successful endless games, such as:

1. Endless procedurally generated gameplay with increasing difficulty
2. Multiple unlockable characters, skins, or abilities
3. Daily rewards and login streaks
4. Missions, achievements, and progression system
5. Leaderboards and high-score tracking
6. In-game currency and upgrade system
7. Rewarded ads and optional in-app purchases
8. Save game progress using cloud/local storage
9. Responsive UI optimized for different screen sizes
10. Performance optimized for both Android and iOS devices
11. Clean, scalable code with proper architecture and documentation

Please share similar games you have developed previously, the game engine you plan to use (Unity, Godot, etc.), your estimated timeline, and recommendations for additional features that can improve player retention and monetization.