Answer: Turtle Challenge #161

Here’s what the code from Turtle Challenge #161 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 * 2 makes every line 2 steps longer than the one before.

What shape does the spiral look like? It’s based on a hexagon, because 61 degrees is close to 60. Because 61 is just a little more than 60, every corner is slightly off, so the spiral slowly twists round like a whirlpool.

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

How the code works

The loop runs 80 times. Each line is longer than the last, and the turtle turns 61 degrees after each one, so the lines wind outwards.

import turtle

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

for i in range(80):
    t.pencolor(colours[i % 2])
    t.forward(i * 2)
    t.left(61)

t.hideturtle()
turtle.done()