public function render_field($args) {
    $options = get_option($this->option_name, []);
    $field_id = $args['field_id'];
    $value = $options[$field_id] ?? '';

    $plan_type = $options['plan_type'] ?? 'basic';

    $pro_fields = [
        'primary_color',
        'chat_position',
        'chat_title',
        'chat_subtitle',
    ];

    $is_pro_locked = ($plan_type !== 'pro' && in_array($field_id, $pro_fields, true));
    $disabled_attr = $is_pro_locked ? ' disabled' : '';

    switch ($field_id) {

        case 'openai_api_key':
        case 'license_key':
        case 'chat_title':
        case 'chat_subtitle':
            echo '<input type="text" class="regular-text" name="' . esc_attr($this->option_name) . '[' . esc_attr($field_id) . ']" value="' . esc_attr($value) . '"' . $disabled_attr . '>';
            break;

        case 'plan_type':
            echo '<select name="' . esc_attr($this->option_name) . '[plan_type]">';
            echo '<option value="basic"' . selected($value, 'basic', false) . '>Basic</option>';
            echo '<option value="pro"' . selected($value, 'pro', false) . '>Pro</option>';
            echo '</select>';
            break;

        case 'primary_color':
            echo '<input type="text" class="regular-text" name="' . esc_attr($this->option_name) . '[primary_color]" value="' . esc_attr($value ?: '#1d4ed8') . '" placeholder="#1d4ed8"' . $disabled_attr . '>';
            break;

        case 'welcome_message':
            echo '<textarea rows="4" cols="50" name="' . esc_attr($this->option_name) . '[welcome_message]"' . $disabled_attr . '>' . esc_textarea($value ?: 'Hi! How can I help you today?') . '</textarea>';
            break;

        case 'chat_position':
            echo '<select name="' . esc_attr($this->option_name) . '[chat_position]"' . $disabled_attr . '>';
            echo '<option value="right"' . selected($value, 'right', false) . '>Right</option>';
            echo '<option value="left"' . selected($value, 'left', false) . '>Left</option>';
            echo '</select>';
            break;
    }

    if ($is_pro_locked) {
        echo '<p style="margin:6px 0 0; color:#b45309; font-size:12px;"><strong>Pro feature.</strong> Upgrade to Pro to unlock.</p>';
    }
}<?xml version="1.0" encoding="UTF-8"?>
<?xml-stylesheet type="text/xsl" href="https://elektromotor.repair/wp-sitemap-index.xsl" ?>
<sitemapindex xmlns="http://www.sitemaps.org/schemas/sitemap/0.9"><sitemap><loc>https://elektromotor.repair/wp-sitemap-posts-page-1.xml</loc></sitemap><sitemap><loc>https://elektromotor.repair/wp-sitemap-posts-header-1.xml</loc></sitemap><sitemap><loc>https://elektromotor.repair/wp-sitemap-posts-footer-1.xml</loc></sitemap><sitemap><loc>https://elektromotor.repair/wp-sitemap-posts-megamenu-1.xml</loc></sitemap><sitemap><loc>https://elektromotor.repair/wp-sitemap-posts-fullmenu-1.xml</loc></sitemap><sitemap><loc>https://elektromotor.repair/wp-sitemap-users-1.xml</loc></sitemap></sitemapindex>