protected function getOffsetClass($viewport, $value)
    {
        if ($value) {
            
            $class = [$this->offsetPrefix];
            
            $class[] = $this->grid()->getStyle('viewport', $viewport);
            
            if ($value == 'reset') {
                $class[] = 0;
            } else {
                $class[] = $value;
            }
            
            return implode('-', array_filter($class));
            
        }
    }