code: function PixelWalker(firstPoint, pixel_path) {
  
      // go clockwise starting first point
      var points = [];
      points.push(firstPoint);
  
      var moveHorizontal = true;	// alternate horizontal and vertical movements to form pixel heart
  
      pixel_path.forEach(function (p) {
  
          var previous_point = points[points.length - 1];
          var point_to_add;
  
          if (moveHorizontal) {
              point_to_add = [p, 0];
          } else {
              point_to_add = [0, p];
          }
          var e = makerjs.point.add(previous_point, point_to_add);
          points.push(e);
  
          // flip direction each time
          moveHorizontal = !moveHorizontal;
      });
  
      return points;
  }
docs: starting point so the heart is located properly in space 
  Builds an array of points that define a model by generating points
  from the `path` defined above.