Turtletoy allows you to generate drawings with code, inspired by Python's Turtle graphics API. Programming turtles is done with vanilla JavaScript.

To start a new drawing, click the New turtle link and modify the example in the editor to the right.

*In short, all global code is evaluated once, then the walk function is called until it returns false.*

Let's first look at the global code of the example:

const turtle = new Turtle(); turtle.penup(); turtle.goto(-50,-20); turtle.pendown();

To draw lines, we first create a new instance of the Turtle class, then we start giving it commands. In this example, the turtle is moved to position `x`: -50, `y`: -20 on the canvas.
To prevent a line being drawn from its initial position `x`: 0, `y`: 0, `penup()`

is called first. `pendown()`

is then called
to re-enable drawing lines when moving the turtle.

Next, we define what happens every time `walk`

is called:

function walk(i) { turtle.forward(100); turtle.right(144); return i < 4; }

In this example, every call, the turtle will move forward by 100 pixels, then turn right by 144 degrees.

The `walk`

function will be called until it returns false. Argument `i` is zero the first time the function is called and will increase (+1) for each next call.
The 5^{th} call, `i` will be 4, and `i` < 4 will return false. So in this example our drawing will be complete after 5 lines.

Below is a summary of all commands available for a Turtle.

- Can I draw lines outside the walk function?
- Yes, you could choose to generate the entire drawing in global code. If you write complex turtles this can take quite some time, resulting in a canvas that will initially stay blank. To make it more responsive, it is recommended to use the walk function.
- Is the canvas updated every time the walk function is called?
- The canvas is updated after every 100 or so calls (~16ms), resulting in a — more or less — animated drawing of your turtle.
- Why can I set the pen opacity only once?
- Because we want the resulting drawing to be easy to plot with a plotter and by adding (artificial) restrictions we hope to stimulate creativity.

- forward(
`distance`) | fd(`distance`) - Move the turtle forward by the specified
`distance`, in the direction the turtle is headed. - backward(
`distance`) | bk(`distance`) | back(`distance`) - Move the turtle backward by
`distance`, opposite to the direction the turtle is headed. Do not change the turtle’s heading. - right(
`angle`) | rt(`angle`) - Turn turtle right by
`angle`units. (Units are by default degrees, but can be set via the`degrees()`

and`radians()`

functions.) - left(
`angle`) | lt(`angle`) - Turn turtle left by
`angle`units. (Units are by default degrees, but can be set via the`degrees()`

and`radians()`

functions.) - goto(
`x`,`y = undefined`) | setpos(`x`,`y = undefined`) | setposition(`x`,`y = undefined`) - If
`y`is undefined,`x`must be a pair of coordinates`[`

(e.g. as returned by`x`,`y`]`pos()`

).

Move turtle to an absolute position. If the pen is down, draw line. Do not change the turtle’s orientation. - setx(
`x`) - Set the turtle’s first coordinate to
`x`, leave second coordinate unchanged. - sety(
`y`) - Set the turtle’s second coordinate to
`y`, leave first coordinate unchanged. - setheading(
`to_angle`) | seth(`to_angle`) - Set the orientation of the turtle to
`to_angle`. - home()
- Move turtle to the origin – coordinates
`[`

– and set its heading to its start-orientation.`0`,`0`] - circle(
`radius`,`extent = undefined`,`steps = undefined`) - Draw a circle with given
`radius`. The center is`radius`units left of the turtle;`extent`– an angle – determines which part of the circle is drawn. If`extent`is not given, draw the entire circle. If`extent`is not a full circle, one endpoint of the arc is the current pen position. Draw the arc in counterclockwise direction if`radius`is positive, otherwise in clockwise direction. Finally the direction of the turtle is changed by the amount of`extent`.

As the circle is approximated by an inscribed regular polygon,`steps`determines the number of steps to use. If not given, it will be calculated automatically.

- position() | pos()
- Return the turtle’s current location
`[`

.`x`,`y`] - xcor() | x()
- Return the turtle’s
`x`coordinate. - ycor() | y()
- Return the turtle’s
`y`coordinate. - heading() | h()
- Return the turtle’s current heading.

- degrees(
`fullcircle = 360.0`) - Set angle measurement units, i.e. set number of “degrees” for a full circle. Default value is 360 degrees.
- radians()
- Set the angle measurement units to radians. Equivalent to
`degrees(`

`2`*`Math.PI`)

- pendown() | pd() | down()
- Pull the pen down – drawing when moving.
- penup() | pu() | up()
- Pull the pen up – no drawing when moving.

- clone()
- Creates a clone of the turtle.