Secret Code

import turtle

wp = turtle.Screen()
wp.bgcolor("black")

t = turtle.Turtle()
t.speed(10000000)

t.penup()
t.backward(450)
t.left(90)
t.forward(450)
t.right(90)

colors = ["blue", "yellow"]

t.pendown()
t.color(colors[0])

for i in range(450):
  if i <= 225:
    t.color(colors[0])
  else:
    t.color(colors[1])
  t.forward(900)
  t.right(90)
  t.forward(1)
  t.right(90)
  t.forward(900)
  t.left(90)
  t.forward(1)
  t.left(90)