curves using a turning radius

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