code: function linkPerpendicularYToLinkTarget(longerLink, shorterLink) {
    // get the angle for the longer link
    var angle = linkAngle(longerLink);
  
    // get the adjacent length to the other link's x position
    var heightFromY1ToPependicular = linkXLength(shorterLink) / Math.tan(angle);
  
    // add or subtract from longer link's original y1, depending on the slope
    var yPerpendicular = incline(longerLink) == 'up' ? longerLink.y1 - heightFromY1ToPependicular : longerLink.y1 + heightFromY1ToPependicular;
  
    return yPerpendicular;
  }
docs: Return the Y coordinate on the longerLink path * which is perpendicular shorterLink's source. * approx, based on a straight line from target to source, when in fact the path is a bezier