body {
            margin: 0;
            padding: 40px;
            background-color: #f5f5f5;
            font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
        }
        .form-container {
            max-width: 800px;
            margin: 0 auto;
        }
        .recipient {
            color: #1677ff;
            font-size: 16px;
            margin-bottom: 16px;
        }
        .instructions {
            color: #666;
            font-size: 14px;
            margin-bottom: 12px;
        }
        .requirements-input {
            width: 100%;
            height: 180px;
            border: 1px solid #d9d9d9;
            border-radius: 4px;
            padding: 12px;
            font-size: 14px;
            resize: vertical;
            margin-bottom: 16px;
            box-sizing: border-box;
        }
        .requirements-input::placeholder {
            color: #bfbfbf;
        }
        .attachment-link {
            color: #fa8c16;
            font-size: 14px;
            text-decoration: none;
            margin-bottom: 24px;
            display: inline-block;
            cursor: pointer;
        }
        .attachment-link::before {
            content: "📎 ";
        }
        /* 隐藏原生文件选择框，仅通过链接触发 */
        #file-upload {
            display: none;
        }
        .send-btn {
            background-color: #1677ff;
            color: white;
            border: none;
            border-radius: 4px;
            padding: 10px 24px;
            font-size: 14px;
            cursor: pointer;
            transition: background-color 0.3s;
        }
        .send-btn:hover {
            background-color: #40a9ff;
        }
        .hint-text {
            color: #999;
            font-size: 12px;
            margin-top: 8px;
        }