from turtle import *
from superturtle.movement import fly

def centered_circle(radius):
    """Draws a circle, centered on the turtle's current position.
    The built-in circle function annoyingly draws a circle whose center
    is one radius left of the turtle.
    """
    right(90)
    penup()
    forward(radius)
    pendown()
    left(90)
    circle(radius)
    left(90)
    penup()
    forward(radius)
    pendown()
    right(90)

def write_label(point, label, align=None, font=None):
    fly(point.x, point.y)
    write(label, align=align, font=font)

def line_end_arrow():
    "Draws an arrow"
    left(20)
    back(20)
    forward(20)
    right(40)
    back(20)
    forward(20)
    left(20)