import turtle

depth = 3


def draw_a_line(given_turtle=None, start_x=0, start_y=0, end_x=0, end_y=0):
    if given_turtle is None:
        given_turtle = turtle.Turtle()

    given_turtle.penup()
    given_turtle.setposition(start_x, start_y)
    given_turtle.pendown()
    given_turtle.setposition(end_x, end_y)


def draw_a_triangle(given_turtle, x1, y1, x2, y2, x3, y3):
    draw_a_line(given_turtle, x1, y1, x2, y2)
    draw_a_line(given_turtle, x1, y1, x3, y3)
    draw_a_line(given_turtle, x2, y2, x3, y3)


def draw_sub_triangle(given_turtle, n, x1, y1, x2, y2, x3, y3):
    draw_a_triangle(given_turtle, x1, y1, x2, y2, x3, y3)

    if n < depth:
        n += 1

        a = (x1 + x2) / 2 + (x2 - x3) / 2
        b = (y1 + y2) / 2 + (y2 - y3) / 2
        c = (x1 + x2) / 2 + (x1 - x3) / 2
        d = (y1 + y2) / 2 + (y1 - y3) / 2
        e = (x1 + x2) / 2
        f = (y1 + y2) / 2
        draw_sub_triangle(given_turtle, n, a, b, c, d, e, f)

        a = (x3 + x2) / 2 + (x2 - x1) / 2
        b = (y3 + y2) / 2 + (y2 - y1) / 2
        c = (x3 + x2) / 2 + (x3 - x1) / 2
        d = (y3 + y2) / 2 + (y3 - y1) / 2
        e = (x3 + x2) / 2
        f = (y3 + y2) / 2
        draw_sub_triangle(given_turtle, n, a, b, c, d, e, f)

        a = (x1 + x3) / 2 + (x3 - x2) / 2
        b = (y1 + y3) / 2 + (y3 - y2) / 2
        c = (x1 + x3) / 2 + (x1 - x2) / 2
        d = (y1 + y3) / 2 + (y1 - y2) / 2
        e = (x1 + x3) / 2
        f = (y1 + y3) / 2
        draw_sub_triangle(given_turtle, n, a, b, c, d, e, f)


window = turtle.Screen()
window.bgcolor("black")
(w, h) = window.screensize()
brad = turtle.Turtle()
brad.setheading(0)
brad.shape("classic")
brad.color("white")
brad.hideturtle()
brad.speed(10)

# edge triangle
x1 = -w / 2
y1 = -h / 2
x2 = w / 2
y2 = -h / 2
x3 = 0
y3 = h / 2
draw_a_triangle(brad, x1, y1, x2, y2, x3, y3)

# start recursive
a = (x1 + x2) / 2
b = (y1 + y2) / 2
c = (x1 + x3) / 2
d = (y1 + y3) / 2
e = (x2 + x3) / 2
f = (y2 + y3) / 2
draw_sub_triangle(brad, 0, a, b, c, d, e, f)

window.exitonclick()