public function tree($css) {
        // Do stuff
        $this->_tokens = $this->tokenize($css);
        $results = $this->_parseTokens(array_shift($this->_tokens));

        // Add remaining items to root element
        while (count($this->_tokens)) {
            if (!$this->ignoreErrors) {
                $this->errors[] = new ParseError('Unmatched }', $this->_css, $this->_tokens[0]['index']);
            }
            $results = array_merge($results, $this->_parseTokens(array_shift($this->_tokens)));
        }

        return $results;
    }