Example drawing line 90 degree from other line

import pygame

class Line:
    def __init__(self, color, start_point, end_point):
        self.start_point = start_point
        self.end_point = end_point
        self.color = color

    def draw(self, surface):
        pygame.draw.line(surface, self.color, self.start_point, self.end_point)

    def get_line_angle_front(self, angle, color, length=0):
        vector = pygame.Vector2(self.end_point) - pygame.Vector2(self.start_point)
        vector.normalize_ip()
        vector.rotate_ip(angle)
        return self._get_line_angle(vector, self.start_point, angle, color, length)

    def get_line_angle_back(self, angle, color, length=0):
        vector = pygame.Vector2(self.start_point) - pygame.Vector2(self.end_point)
        vector.normalize_ip()
        vector.rotate_ip(angle)
        return self._get_line_angle(vector, self.end_point, angle, color, length)

    def _get_line_angle(self, vector, point, angle, color, length):
        if length < 1:
            length = pygame.Vector2(self.start_point).distance_to(pygame.Vector2(self.end_point))

        end_point = pygame.Vector2(point) + vector * length
        return Line(color, point, vec_to_int(end_point))

def vec_to_int(vector):
    return tuple(map(int, vector))

def main(caption, size, flags=0):
    pygame.display.set_caption(caption)
    surface = pygame.display.set_mode(size, flags)
    clock = pygame.time.Clock()
    rect = surface.get_rect()
    running = True
    delta = 0
    fps = 30

    line = Line("dodgerblue", rect.center, (rect.w - 100, rect.h - 100))
    lines = [line,
             line.get_line_angle_front(90, "lawngreen", 0),
             line.get_line_angle_back(90, "firebrick", 30)
             ]

    while running:
        for event in pygame.event.get():
            if event.type == pygame.QUIT:
                running = False

        surface.fill("gray10")
        for l in lines:
            l.draw(surface)

        pygame.display.flip()
        delta = clock.tick(fps) * 0.001

if __name__ == "__main__":
    pygame.init()
    main("Alter Image", (400, 300))
    pygame.quit()