code: function draw() {
  
    for (i=0; i<pts.length; i++) {
  
      // draw corners
      var q = mouseP.quadrant(pts[i], 2);
      var ln = cornerLine(pts[i], q, 12);
  
      form.stroke( colors["a"+(q%4+1)], 1.5);
      form.line( new Pair(ln.p1.x, ln.y).to( ln.x, ln.y) );
      form.line( new Pair(ln.x, ln.y).to( ln.x, ln.p1.y) );
  
      // draw point
      form.fill( colors.c4 ).stroke( false );
      form.point( ln.p1, 3, true);
    }
  
  }
docs: Draw the points