docs: function Millipede(size, options) {
      options = options || {};
  
      this.size = size;
      this.reverse = options.reverse;
      this.horizontal = options.horizontal;
  
      this.position = options.position || 0;
      this.top = options.top || 0;
      this.left = options.left || 0;
  
      this.validate();
  }