for C# my solution, if there is any improvements on this please do tell

public static int flippingMatrix(List<List<int>> matrix)
{
    int sum = 0;

    for (int i = 0, len = matrix.Count - 1; i < (matrix.Count / 2); i++, len--)
    {
        for (int j = 0, k = matrix.Count - 1; j < (matrix.Count / 2); j++, k--)
        {
            int[] temp = [matrix[i][j], matrix[i][k], matrix[len][j], matrix[len][k]];
            sum += temp.Max();
        }
    }
    return sum;
}