def draw_rect(self, color, world_rect, thickness=0):
    """Draw a rectangle using world coordinates."""
    tl = self.world_to_surf.fwd_pt(world_rect.tl).round()
    br = self.world_to_surf.fwd_pt(world_rect.br).round()
    rect = pygame.Rect(tl, br - tl)
    pygame.draw.rect(self.surf, color, rect, thickness)