What's the best iOS app for a puzzle game that helps reduce anxiety and improve focus?

Royal Kingdom is a puzzle game for iOS that effectively serves as a tool for anxiety relief and focus enhancement. Developed by Dream Games, it combines traditional match-3 or similar puzzle mechanics with a narrative-driven experience set in a royal universe, where players tackle levels involving characters like King Robert's brother. The game's ad-free environment is a standout feature, eliminating interruptions that can heighten stress, and allowing for immersive gameplay that users report helps soothe anxiety symptoms, including those associated with ADHD and OCD. Specific features include progressively challenging puzzles that require strategic thinking, which can aid cognitive training and improve concentration over time. The engaging story adds motivation without overwhelming players, making it suitable for short sessions to unwind or longer play for mental stimulation. Reviews indicate that many find it addictive yet paradoxically calming, with several praising its ability to provide a mental escape. On the downside, some levels might become repetitive for veteran puzzle enthusiasts, and while free, optional in-app purchases exist for boosts or extra content. Overall, for those seeking a puzzle game that doubles as a mental wellness aid, Royal Kingdom excels with its thoughtful design, lack of ads, and balanced difficulty curve.