.settings-panel { background: var(--card-bg); flex: 1; padding: 25px; border-radius: var(--radius); box-shadow: 0 4px 12px rgba(0,0,0,0.08); border: 1px solid var(--border-color); }
       
        .control-group { margin-bottom: 15px; }
        .control-group label { display: block; margin-bottom: 6px; font-weight: 600; font-size: 0.85rem; color: var(--text-main); }
        .text-input { width: 100%; padding: 10px; border: 1px solid var(--border-color); border-radius: 8px; font-size: 0.9rem; background: #fafafa; }
        .text-input:focus { outline: 2px solid var(--primary-color); background: #fff; }

        .action-btn { width: 100%; background-color: var(--primary-color); color: white; border: none; border-radius: 8px; padding: 12px; font-size: 1rem; font-weight: 600; cursor: pointer; transition: background-color 0.2s; margin-top: 10px; }
        .action-btn:hover { background-color: var(--primary-hover); }
        
        .preview-panel { background: #fff; flex: 1; padding: 25px; border-radius: var(--radius); box-shadow: 0 4px 12px rgba(0,0,0,0.08); border: 1px solid var(--border-color); display: flex; flex-direction: column; justify-content: center; align-items: center; text-align: center; }
        
        .validation-box { width: 100%; padding: 15px; border-radius: 8px; font-weight: 600; font-size: 1rem; margin-top: 10px; display: none; }
        .validation-box.valid { background: #e8f8f5; border: 1px solid #27ae60; color: #27ae60; }
        .validation-box.invalid { background: #fdebd0; border: 1px solid #e74c3c; color: #c0392b; }

        .details-list { text-align: left; width: 100%; margin-top: 15px; font-size: 0.85rem; color: var(--text-muted); display: none; }
        .details-list ul { padding-left: 20px; }
        .details-list li { margin-bottom: 4px; }

        .instruction { color: var(--text-muted); font-size: 0.85rem; }

        @media (max-width: 768px) { .main-container { flex-direction: column; } }