Answer: Turtle Challenge #393

Here’s what the code from Turtle Challenge #393 draws. This picture was made by running the code for real.

The answers

Will the lines get longer or shorter? Longer! i goes up by 1 each time, so i * 3 makes every line 3 steps longer than the one before.

What shape does the spiral look like? It’s based on a five-pointed star, because 144 degrees is exactly 144.

How many colours will you see? 2: tomato, mediumpurple. i % 2 picks the next colour in the list each time.

How the code works

The loop runs 72 times. Each line is longer than the last, and the turtle turns 144 degrees after each one, so the lines wind outwards.

import turtle

t = turtle.Turtle()
t.speed(0)
turtle.bgcolor("black")
colours = ["tomato", "mediumpurple"]

for i in range(72):
    t.pencolor(colours[i % 2])
    t.forward(i * 3)
    t.left(144)

t.hideturtle()
turtle.done()