Just click four times anywhere on the screen, these are the control
points. A bezier curve will be drawn for you. Now you can click on any
of the four points that you have already created and drag it around. Notice
how the Bezier curve is redrawn according to the new control points. The
button is self explanatory. Have Fun!!!
P(t) = (1-t)3 P0 + 3(1-t)2 t P1
+ 3(1-t) t2 P2 + t3 P3