> For the complete documentation index, see [llms.txt](https://www.lisppad.app/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://www.lisppad.app/libraries/lisppad/turtle.md).
# (lisppad turtle)
This is a library implementing a simple graphics window for displaying turtle graphics. The library supports one graphics window per LispPad session which gets initialized by invoking `init-turtle`. `init-turtle` will create a new turtle and display its drawing on a graphics window. If there is already an existing graphics window with the given title, it will be reused.
Once `init-turtle` was called, the following functions can be used to move the turtle across the plane:
* `(pen-up)`: Lifts the turtle
* `(pen-down)`: Drops the turtle
* `(pen-color color)`: Sets the current color of the turtle
* `(pen-size size)`: Sets the size of the turtle pen
* `(home)`: Moves the turtle back to the origin
* `(move x y)`: Moves the turtle to position `(x, y)`
* `(heading angle)`: Sets the angle of the turtle (in radians)
* `(turn angle)`: Turns the turtle by the given angle (in radians)
* `(left angle)`: Turn left by the given angle (in radians)
* `(right angle)`: Turn right by the given angle (in radians)
* `(forward distance)`: Moves forward by `distance` units drawing a line if the pen is down
* `(backward distance)`: Moves backward by `distance` units drawing a line if the pen is down
This library provides a simplified, interactive version of the API provided by library `(lispkit draw turtle)`.
***
**(init-turtle)** 
\
\&#xNAN;**(init-turtle scale)**\
\&#xNAN;**(init-turtle scale title)**
Initializes a new turtle and displays its drawing in a graphics window. `init-turtle` gets two optional arguments: `scale` and `title`. `scale` is a scaling factor which determines the size of the turtle drawing. `title` is a string that defines the window name of the turtle graphics. It also acts as the identify of the turtle graphics window; i.e. it won't be possible to have two sessions with the same name but a different graphics window.
**(close-turtle-window)**
Closes the turtle window and resets the turtle library.
**(turtle-drawing)**
Returns the drawing associated with the current turtle.
**(pen-up)**
Lifts the turtle from the plane. Subsequent `forward` and `backward` operations don't lead to lines being drawn. Only the current coordinates are getting updated.
**(pen-down)**
Drops the turtle onto the plane. Subsequent `forward` and `backward` operations will lead to lines being drawn.
**(pen-color *****color*****)**
Sets the drawing color of the turtle to *color*. *color* is a color object as defined by library `(lispkit draw)`.
**(pen-size *****size*****)**
Sets the pen size of the turtle to *size*. The pen size corresponds to the width of lines drawn by `forward` and `backward`.
**(home)**
Moves the turtle to its home position.
**(move *****x y*****)**
Moves the turtle to the position described by the coordinates *x* and *y*.
**(heading *****angle*****)**
Sets the heading of the turtle to *angle*. *angle* is expressed in terms of degrees.
**(turn *****angle*****)**
Adjusts the heading of the turtle by *angle* degrees.
**(right *****angle*****)**
Adjusts the heading of the turtle by *angle* degrees.
**(left *****angle*****)**
Adjusts the heading of the turtle by *-angle* degrees.
**(forward *****distance*****)**
Moves the turtle forward by *distance* units drawing a line if the pen is down.
**(backward *****distance*****)**
Moves the turtle backward by *distance* units drawing a line if the pen is down.