code: function repel( pt, i ) {
    if ( pt.distance(mouse) < threshold ) { // smaller than threshold distance, push it out
      var dir = pt.$subtract(mouse).normalize();
      pt.set( dir.multiply(threshold).add( mouse ).min( space.size ).max(0, 0) );
    } else { // bigger than threshold distance, pull it in
      var orig = origs[i];
      pt.set ( orig.$add( pt.$subtract(orig).multiply(0.98) ) );
    }
  }
docs: Repel the control points when mouse is near i