The window "Domain" displays a point C and the curve  C +  t(cos(a), sin(a)), where t runs from –1 to 1.

The window "Surface" window displays the surface X(u, v), the image of the curve from the "Domain" window on this surface, the point X(C + t0(cos(a), sin(a)), and the frenet frame, osculating, normal, and rectifying planes, and normal vector to the surface, at that point.

The vectors P, B, and N are also shown in the "P-B plane" window. The normal curvature of the curve X(C +  t(cos(a), sin(a))) at t0 is given by the curvature of X(C +  t(cos(a), sin(a))) at t0 times the dot product of P and N at t0.

It is possible to change C in the "Domain" window by clicking and dragging it, and it is possible to change a, t0, and X(u, v) in the control window.