drag any point to move it (and, consequently, change curve shape)
double click any control point to remove it (and decrease curve order by one)
click adder markers on the guides to add a new, randomly positioned control point in between the points connected by the line the adder is on (and increase the curve order); when the adder markers have disappeared, you cannot add more control points
if you allow oscillation, then the points oscillate until you move the mouse cursor or tap anywhere