This Circle guide will allow you to draw perfectly round circles.
Start by drawing a virtual circle (in blue by default) in your drawing area.

As long as you are not releasing the cursor, you can give the guide the size you want. The small square indicates the position of the cursor. You will notice that the cursor is the center of the circle.

Once satisfied, release the cursor. The Circle guide is created. You then have access to all of its options in the Guidelines panel.

As for the Line angle and Segment guides, the first options (Eye, Snap, Transparency, Margin ) have the same functions and parameters. With the Assist tool, you can draw perfectly round circles, remotely of parallel to the virtual circle you have created.

A smaller virtual curved line will appear at the position of the cursor.

You will not be able to deviate from this Assist guide.

With this Circle guide, you have three types of coordinates :
- Center X and Center Y are the position of the Circle guide. It is possible to change these parameters with the mini-elevators on the right or with the numeric fields.
- The Ray will allow you to shrink or extend the Circle guide.

You can also use the Edit function. You will then have access once again to the small blue squares to manually modify the Circle guide.