import turtle
turtle.color('green')
turtle.bgcolor('black')
def branch(length, level):
    if level <= 0:
        return

    turtle.forward(length)
    turtle.left(45)
    branch(0.6*length, level-1)
    turtle.right(90)
    branch(0.6 * length, level-1)
    turtle.left(45)
    turtle.backward(length)
    return

turtle.width(3)
turtle.left(90)
branch(100, 6)
turtle.exitonclick()