def rotate_90_counter_clockwise(matrix):
    """
    The function rotates any square matrix by 90° counter clock-wise.
    """
    for row in matrix:
        row.reverse()

    n = len(matrix)
    for row in range(n):
        for col in range(row, n):
            matrix[row][col], matrix[col][row] = matrix[col][row], matrix[row][col]
    return matrix