Description: Designed for Experts – Over 85% edge pieces (438/501) create a next-level challenge, testing even seasoned puzzlers’ skills. Unique Edge Piece Design – With the majority of the pieces being edge pieces, this puzzle offers a distinctive challenge that , providing hours of thoughtful entertainment Anti-Frustration Features – Includes a sorting tray and numbered reference sheet to streamline assembly without spoiling the challenge. Therapeutic Mental Workout – Proven to improve focus and memory—ideal for stress relief or post-work relaxation. Puzzle Enthusiasts – this set is designed to offer a higher level of difficulty, making it perfect for those who appreciate a real mental workout Package:1*The river puzzle