arrowhead_curve.py

from turtle import *

def curve(depth, length, angle):
    if depth == 0:
        if angle > 0:
            pencolor('green')
        else:
            pencolor('blue')
        
        forward(length)
    else:
        curve(depth -1, length, -angle)
        right(angle)
        curve(depth -1, length, angle)
        right(angle)
        curve(depth -1, length, -angle)        

speed(0)
shape("turtle")

width(3)
curve(6, 5, 60)