Lets you know about En-Queen, it originates from 8-Queen Problem, proposed in 1848 by Chess player.
En-Queen like a mystified iPhone application.It comprises of various levels.You should unlock each level by walk away from its previous level .Each level associated with NxN chess board, you should place N Queens such that no two Queens fire each other, i.e, In each level solution requires that no two Queens share same row, column, or diagonal.