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(t0), the line segment from the center of the osculating circle to X(t0), which is normal to the curve and has length given by 1/kg(t0), 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 t0, use the following buttons:

[<]: Decrease t0 by one step.
[>]: Increase t0 by one step.
[<<]: Decrease t0 until it reaches its minimum value.
[>>]: Increase t0 until it reaches its maximum value.