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), a point C that you may change by clicking and dragging it, the point X(t0), the segment of the tangent line to the curve X(t) at X(t0) connecting X(t0) to the closest point (shown in red) on the tangent line to C, the line segment connecting the red point to C, which is perpendicular to the tangent line, and the pedal curve traced out by the red point as t0 runs from its minimum to its maximum value. 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.