Curves can be drawn by giving a second argument to `rt`

and `lt`

.

The optional second argument for `rt`

and `lt`

is a *turning radius*.
The turn is made while tracing out part of a circle of that radius.

`rt 180, 50`

If you provide a radius of 0, the turtle will just pivot in place as with a normal turn.

A complete circle can be drawn by turning 360 degrees (or more).

`lt 360, 25`

To draw a circle, the turtle must start on the edge of the circle. For example, if we wish to draw a circle around a dot, we must move the circle to the edge of the dot to begin:

dot yellow, 100 fd 50 rt 90 pen violet, 3 rt 360, 50