The whole story

to spiral :distance if :distance < 2 [stop] forward :distance right 91 spiral :distance - 1 end cg In the Drawing Centre, click blue and then click the turtle. Click black, the paint can and then the background. Back to the Command Centre and type spiral 190 ht ht means hide turtle.

Exercise 17 spiral uses four numbers (190, 2, 91 and 1). Experiment with different values - you'll be surprised at what you'll see.