, 2500 Challenges from Beginner to Master, 1v1 Battle via Bluetooth, Switch Between 6x6 and 4x4 Grid, Sudoku in Six Colors, Builds Critical Thinking, Improves Early Math, Problem-Solving Skills, Perfect for Road Trips and Travel, Made from high-quality, BPA-Free, non-toxic ABS plastic�durable, safe, and built for years of learning through play.Need 2 AA batteries but not-included in the package. Smart Sudoku is designed for children aged 4 and up. The puzzles scale in difficulty so your child continues to be challenged as they grow.