This pencil uses five points smoothed into a closed spline. The colors for each image are drawn from an iron palette of 32 shades. The initial positions and velocities of two points are specified in the embed markup.

The embed markup for this pencil is:

    <embed src="pencil.tcl"
      width="500" height="100"
      vspace="25" hspace="25"
      points="5" smooth="1"
      x0="320" y0="8"
      dx0="-10" dy0="2"
      x1="320" y1="12"
      dx1="10" dy1="-2"
      background="black"
      palette="palette iron 1 32">
    </embed>