TetragonoS: free puzzle game app for iphone, ipad

TetragonoS is a free puzzle game app that's similar to sudoku and Latin Squares.  You are given a Latin Square: each row and each column has different numbers. You must color 4 tiles blue making sure that each blue tile gets all 4 numbers.  Basically, you can't have two blue tiles using the number 3.

I think kids will like this.