Bezier curve tool with curvature monotonicity regions
Click then drag to draw a curve.
Press ENTER or cntrl+click to end the curve.
Drag to move a control ponit with its two associated points.
Press Alt (or Option for Mac) and move a control point to make the curve G^0.
Select a control point and press Delete to delete three consecutive points. Click again to deselect.
Use arrow keys to translate and +/- to scale.
The purple region indicates that that the curvature will be monotonically varying for the left(previous) curve.
The cyan region indicates the region for the right(next) curve.