This demo includes a single graphical window that displays a curve
X(t) (which you may change in the appropriate textbox in the control
window), the osculating circle to X(t) at X(t_{0}), the line
segment from
the center of the osculating circle to X(t_{0}), which is
normal to the
curve and has length given by 1/kg(t_{0}), and the evolute
curve (if the "Show evolute curve" box in the control window is
checked), which is
traced out by the center of the osculating circle. To
change t_{0}, use the following buttons:

[<]: Decrease t_{0} by one step.

[>]: Increase t_{0} by one step.

[<<]: Decrease t_{0} until it reaches its minimum
value.

[>>]: Increase t_{0} until it reaches its maximum
value.