def transform_vector(vector, matrix):
    """Transform a vector by a matrix. This is similar to transform_point,
    except that translation isn't honored. Think of a vector as displacement in
    space, and a point as, well, a point in space.

    :param list vector: 2-item list
    :param list matrix: 6-item list representing transformation matrix
    :returns list: 2-item transformed point
    """
    x, y = vector
    a, b, c, d, _, _ = matrix
    new_x = x * a + y * c
    new_y = x * b + y * d
    return [new_x, new_y]