Details

Click an arc to delete it. Click an empty space to add an arc. The radius of the added arc is given by the distance of the click from the center line. Drag an arc to change which connection points it spans.

With the "show points" box checked, click a connection point to delete it. Drag a connection point to change its position. Click an empty space on the center line to add a connection point. Clicking the "re-space points" button will space the connection points evenly between the outermost points.

Clicking the "undo" button undoes the last drag, add, delete, or re-space points operation.