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.
Change the value of t0 and other variables as in earlier demos.
As in earlier demos there is the "Show Color Spectrum" option. In this demo it colors everything except X(t0).