Learning goals

Explain how a positive or negative radius changes the direction of a circle.

Use an extent to draw part of a circle.

Which way does the circle go?

A positive radius draws the circle counterclockwise: the turtle turns to the left, so the circle appears above the turtle. A negative radius draws the circle clockwise: the turtle turns to the right, so the circle appears below the turtle.

otto.circle(50)
otto.circle(-50)

This draws two circles that touch each other at the starting position: one above and one below.

Drawing part of a circle

You can add a second number, the extent. This is the angle in degrees of the part of the circle that you want to draw. A full circle is 360 degrees, so circle(50) is the same as circle(50, 360).

otto.circle(50, 180)

This draws a half circle. With an extent of 90 you draw a quarter of a circle, which is useful for rounded corners.

Summary

Command	What it does
`circle(radius)`	Draws a circle counterclockwise. The center is to the left.
`circle(-radius)`	Draws a circle clockwise. The center is to the right.
`circle(radius, extent)`	Draws only part of a circle. The `extent` is the angle in degrees.