The turtle

The shapes of the last chapter appear where you tell them to. There is another way to draw: the turtle. It crawls over the canvas and leaves a trail behind it.

The turtle starts in the middle of the canvas, looking right, with its pen down.

Forward and turn

forward moves the turtle the way it is looking, and right and left turn it by a number of degrees.

color("blue")
forward(150)
right(90)
forward(150)

A square in a loop

Four identical steps are a job for a loop.

repeat 4 times:
    forward(120)
    right(90)

A full turn is 360 degrees. Divide 360 by the number of corners and you get the turn you need.

Filling

begin_fill tells the turtle to remember its path, and end_fill paints the shape it walked around.

color("yellow")
begin_fill()
repeat 5 times:
    forward(200)
    right(144)
end_fill()

Pen up

pen_up lets the turtle move somewhere else without leaving a trail, and pen_down starts drawing again.

pen_up()
back(150)
pen_down()
color("green")
repeat 3 times:
    forward(150)
    left(120)

A spiral

Make the step a little longer each time and the line curls up.

step_length = 5
repeat 40 times:
    forward(step_length)
    right(20)
    step_length = step_length + 3

Try it yourself

1. Draw a triangle with a function that takes the length of a side.

Show the answer

function triangle(side):
    repeat 3 times:
        forward(side)
        right(120)

color("red")
triangle(150)

Open in Studio

2. Draw a star of eight rays coming out of one point.

Show the answer

color("pink")
repeat 8 times:
    forward(80)
    back(80)
    right(45)

Open in Studio