Blits a surface on the screen at pos

        :param surface: Surface to blit
        :param pos: Top left corner to start blitting
        :type surface: Surface
        :type pos: tuple

def blit(self, surface, pos=(0, 0)):
        """
        Blits a surface on the screen at pos

        :param surface: Surface to blit
        :param pos: Top left corner to start blitting
        :type surface: Surface
        :type pos: tuple
        """
        for x in range(surface.width):
            for y in range(surface.height):
                point = (x + pos[0], y + pos[1])
                if self.point_on_screen(point):
                    self.matrix[point[0]][point[1]] = surface.matrix[x][y]