Most of the Curves are merged into a unique parametric model, which can be used to blend a circle into an ellipse into an arc or into a rounded rect, or a mix of all of them. You shall try the parameters to discover what you can create here. When you create one of this curves, it will be shaped into one of this possible presets:
On each curve, you can take one of this actions:
N: number of edges (sides) used on the Curve
Center: use this to edit the center of the curve.
Orientation: rotate the curve.
Bounds-size: overall size of the curve. For instance, it controls the radius of a circle or the axis of an ellipse.
Bounds-stretch: stretch the shape in one direction. For instance this can be used to transform a circle in an ellipse.
Angles-0: first angle on which an arc is defined. This can be used, for instance, to transform a circle into an arc. Default value is 0.
Angles-1: second angle on which an arc is defined. This can be used, for instance, to transform a circle into an arc. Default value is 6.283185 (sorry for radians!).
Raps-hRap: first value used to blend a circle into a Round Rect. Try it!
Raps-wRap: second value used to blend a circle into a Round Rect. Try it!
Raps-starRap: add an oscillation to the shape of the curve, allows the generation of star-shaped curves (use N to define the amount of tips of the star)