In this mathematical game you and your opponent fill cells of 3x3 matrix with numbers from one to nine. Each number can be used only once. Player labeled with (+) sign tries to set values so the determinant of fully filled matrix is positive. His opponent (-) tries to get negative determinant.
Player uses Rule of Sarrus (http://en.wikipedia.org/wiki/Rule_of_Sarrus) to achieve victory. So this game turns to be kind of sudoku-style.
Remember that each new number in matrix adds both to negative and positive parts of determinant. Choose values and cells the way part you play for increases more.