:root {
            --bg: #f2f2f2;
            --container-bg: #ffffff;
            --text: #333333;
            --text-light: #555555;
            --text-muted: #777777;
            --border: #d0d0d0;
            --border-light: #e6e6e6;
            --primary: #3b6fb6;
            --primary-dark: #2d5a96;
            --primary-light: #e8f0fa;
            --accent-green: #4a9c5d;
            --accent-green-bg: #edf7f0;
            --accent-orange: #d4833a;
            --accent-orange-bg: #fef7f1;
            --accent-red: #c0392b;
            --accent-red-bg: #fdf2f2;
            --accent-blue: #3b7db6;
            --accent-blue-bg: #eef5fa;
            --shadow-sm: 0 1px 3px rgba(0, 0, 0, 0.08);
            --radius: 4px;
            --radius-sm: 3px;
            --font-stack: -apple-system, BlinkMacSystemFont, "Segoe UI", "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", "Helvetica Neue", Arial, sans-serif;
        }

        * {
            margin: 0;
            padding: 0;
            box-sizing: border-box;
        }
        html {
            font-size: 15px;
            scroll-behavior: smooth;
        }
        body {
            font-family: var(--font-stack);
            background: var(--bg);
            color: var(--text);
            line-height: 1.6;
            min-height: 100vh;
            display: flex;
            flex-direction: column;
        }

        /* Header */
        .site-header {
            background: #fafafa;
            border-bottom: 1px solid var(--border);
            flex-shrink: 0;
            position: sticky;
            top: 0;
            z-index: 100;
            box-shadow: var(--shadow-sm);
            width: 100%;
        }
        .header-inner {
            max-width: 1060px;
            margin: 0 auto;
            padding: 0 16px;
            height: 54px;
            display: flex;
            align-items: center;
            justify-content: space-between;
        }
        .logo {
            font-size: 1.25rem;
            font-weight: 700;
            color: var(--primary-dark);
            text-decoration: none;
            letter-spacing: 0.3px;
            white-space: nowrap;
        }
        .logo span {
            color: var(--accent-green);
        }
        .top-nav {
            display: flex;
            gap: 20px;
            list-style: none;
            align-items: center;
            font-size: 0.9rem;
        }
        .top-nav a {
            color: var(--text-light);
            text-decoration: none;
            transition: color 0.15s;
            white-space: nowrap;
        }
        .top-nav a:hover {
            color: var(--primary);
        }
        .top-nav a.active {
            color: var(--primary);
            font-weight: 600;
        }

        /* 主容器 */
        .main-container {
            max-width: 1060px;
            margin: 0 auto;
            padding: 24px 16px 28px;
            flex: 1;
            width: 100%;
        }

        /* 功能区 */
        .calculator-section {
            background: var(--container-bg);
            border: 1px solid var(--border);
            border-radius: var(--radius);
            box-shadow: var(--shadow-sm);
            margin-bottom: 22px;
            overflow: hidden;
        }
        .section-header {
            background: #fafbfc;
            border-bottom: 1px solid var(--border-light);
            padding: 14px 20px;
        }
        .section-header h1 {
            font-size: 1.35rem;
            font-weight: 700;
            color: #222;
            margin: 0;
            letter-spacing: 0.2px;
        }
        .subtitle {
            font-size: 0.85rem;
            color: var(--text-muted);
            margin-top: 3px;
        }
        .calc-body {
            display: flex;
            flex-direction: row;
            min-height: 380px;
        }

        /* 左侧表单 */
        .calc-form-panel {
            flex: 0 0 52%;
            padding: 18px 20px 16px;
            border-right: 1px solid var(--border-light);
            background: #fdfdfd;
        }
        .form-row {
            display: flex;
            align-items: center;
            margin-bottom: 13px;
            gap: 10px;
            flex-wrap: wrap;
        }
        .form-row label {
            flex: 0 0 90px;
            font-weight: 600;
            font-size: 0.9rem;
            color: var(--text-light);
            text-align: right;
            white-space: nowrap;
        }
        .input-group {
            flex: 1;
            display: flex;
            align-items: center;
            gap: 8px;
            min-width: 160px;
        }
        input[type="number"] {
            width: 100%;
            max-width: 160px;
            padding: 8px 10px;
            border: 1px solid var(--border);
            border-radius: var(--radius-sm);
            font-size: 0.95rem;
            font-family: var(--font-stack);
            color: var(--text);
            background: #fff;
            transition: border-color 0.15s;
            text-align: center;
        }
        input[type="number"]:focus {
            outline: none;
            border-color: var(--primary);
            box-shadow: 0 0 0 2px rgba(59, 111, 182, 0.1);
        }
        .unit-label {
            font-size: 0.85rem;
            color: var(--text-muted);
            white-space: nowrap;
            min-width: 28px;
        }
        select {
            width: 100%;
            max-width: 280px;
            padding: 8px 10px;
            border: 1px solid var(--border);
            border-radius: var(--radius-sm);
            font-size: 0.9rem;
            font-family: var(--font-stack);
            color: var(--text);
            background: #fff;
            cursor: pointer;
            transition: border-color 0.15s;
        }
        select:focus {
            outline: none;
            border-color: var(--primary);
            box-shadow: 0 0 0 2px rgba(59, 111, 182, 0.1);
        }
        .radio-group {
            display: flex;
            gap: 16px;
            align-items: center;
        }
        .radio-group label {
            font-weight: 400 !important;
            flex: 0 0 auto !important;
            text-align: left !important;
            cursor: pointer;
            display: flex;
            align-items: center;
            gap: 5px;
            font-size: 0.9rem;
            color: var(--text) !important;
        }
        .radio-group input[type="radio"] {
            accent-color: var(--primary);
            width: 16px;
            height: 16px;
            cursor: pointer;
        }
        .btn-row {
            margin-top: 6px;
            padding-left: 100px;
            display: flex;
            gap: 10px;
            align-items: center;
        }
        .btn-calc {
            padding: 9px 22px;
            background: var(--primary);
            color: #fff;
            border: none;
            border-radius: var(--radius-sm);
            font-size: 0.95rem;
            font-weight: 600;
            cursor: pointer;
            letter-spacing: 0.3px;
            transition: background 0.15s;
        }
        .btn-calc:hover {
            background: var(--primary-dark);
        }
        .btn-reset {
            padding: 9px 18px;
            background: #fff;
            color: var(--text-light);
            border: 1px solid var(--border);
            border-radius: var(--radius-sm);
            font-size: 0.9rem;
            cursor: pointer;
            transition: all 0.15s;
        }
        .btn-reset:hover {
            background: #f5f5f5;
            border-color: #bbb;
        }
        .auto-calc-hint {
            font-size: 0.75rem;
            color: #999;
            margin-left: 4px;
            font-style: italic;
        }

        /* 右侧结果 */
        .calc-result-panel {
            flex: 0 0 48%;
            padding: 18px 20px 16px;
            background: #fff;
            display: flex;
            flex-direction: column;
            gap: 12px;
        }
        .result-card {
            background: #fafbfc;
            border: 1px solid var(--border-light);
            border-radius: var(--radius-sm);
            padding: 14px 16px;
        }
        .primary-result {
            background: var(--primary-light);
            border-color: #d0dff0;
            text-align: center;
        }
        .big-number {
            font-size: 2.8rem;
            font-weight: 700;
            color: var(--primary-dark);
            line-height: 1.1;
            letter-spacing: -0.5px;
        }
        .big-unit {
            font-size: 1rem;
            color: var(--primary);
            font-weight: 500;
        }
        .card-label {
            font-size: 0.85rem;
            color: var(--text-muted);
            margin-bottom: 2px;
        }
        .result-row {
            display: flex;
            gap: 10px;
            flex-wrap: wrap;
        }
        .result-row .result-card {
            flex: 1;
            min-width: 100px;
            text-align: center;
        }
        .val {
            font-size: 1.5rem;
            font-weight: 700;
            color: #222;
        }
        .val.small {
            font-size: 1.2rem;
        }
        .lbl {
            font-size: 0.78rem;
            color: var(--text-muted);
            margin-bottom: 3px;
        }
        .tag {
            display: inline-block;
            padding: 3px 10px;
            border-radius: 12px;
            font-size: 0.78rem;
            font-weight: 600;
            letter-spacing: 0.3px;
            margin-top: 4px;
        }
        .tag-normal { background: var(--accent-green-bg); color: var(--accent-green); }
        .tag-warning { background: var(--accent-orange-bg); color: var(--accent-orange); }
        .tag-danger { background: var(--accent-red-bg); color: var(--accent-red); }
        .tag-info { background: var(--accent-blue-bg); color: var(--accent-blue); }
        .suggestion-row {
            display: flex;
            gap: 10px;
            flex-wrap: wrap;
        }
        .suggestion-row .result-card {
            flex: 1;
            min-width: 110px;
            text-align: center;
            border-left: 3px solid transparent;
        }
        .suggestion-row .lose { border-left-color: var(--accent-orange); }
        .suggestion-row .gain { border-left-color: var(--accent-green); }
        .sug-val {
            font-size: 1.3rem;
            font-weight: 700;
            color: #333;
        }
        .sug-lbl {
            font-size: 0.75rem;
            color: var(--text-muted);
        }

        /* 知识介绍区 */
        .content-section {
            background: var(--container-bg);
            border: 1px solid var(--border);
            border-radius: var(--radius);
            box-shadow: var(--shadow-sm);
            padding: 24px 26px;
            margin-bottom: 22px;
        }
        .content-section h2 {
            font-size: 1.25rem;
            font-weight: 700;
            color: #222;
            margin-bottom: 14px;
            padding-bottom: 10px;
            border-bottom: 2px solid var(--border-light);
            letter-spacing: 0.2px;
        }
        .content-section h3 {
            font-size: 1.05rem;
            font-weight: 600;
            color: #333;
            margin: 16px 0 8px;
        }
        .content-section p {
            font-size: 0.92rem;
            color: var(--text-light);
            margin-bottom: 10px;
            text-align: justify;
        }
        .content-section ul,
        .content-section ol {
            margin: 6px 0 12px 20px;
            font-size: 0.9rem;
            color: var(--text-light);
        }
        .content-section li { margin-bottom: 5px; }
        .info-grid {
            display: grid;
            grid-template-columns: 1fr 1fr;
            gap: 16px;
            margin-top: 10px;
        }
        .info-card {
            background: #fafbfc;
            border: 1px solid var(--border-light);
            border-radius: var(--radius-sm);
            padding: 14px 16px;
        }
        .info-card h4 {
            font-size: 0.95rem;
            font-weight: 600;
            margin-bottom: 6px;
            color: #333;
        }
        .info-card p {
            font-size: 0.85rem;
            margin-bottom: 0;
        }

        /* FAQ 区域 (使用 details/summary) */
        .faq-section {
            background: var(--container-bg);
            border: 1px solid var(--border);
            border-radius: var(--radius);
            box-shadow: var(--shadow-sm);
            padding: 24px 26px;
            margin-bottom: 22px;
        }
        .faq-section h2 {
            font-size: 1.25rem;
            font-weight: 700;
            color: #222;
            margin-bottom: 16px;
            padding-bottom: 10px;
            border-bottom: 2px solid var(--border-light);
            letter-spacing: 0.2px;
        }
        .faq-list details {
            border-bottom: 1px solid var(--border-light);
            padding: 13px 0;
        }
        .faq-list details:last-child {
            border-bottom: none;
        }
        .faq-list summary {
            font-weight: 600;
            font-size: 0.95rem;
            color: #333;
            display: flex;
            justify-content: space-between;
            align-items: center;
            gap: 10px;
            cursor: pointer;
            user-select: none;
            list-style: none; /* 隐藏默认箭头 */
            outline: none;
        }
        .faq-list summary::-webkit-details-marker {
            display: none;
        }
        .faq-list summary::after {
            content: "▼";
            font-size: 0.7rem;
            color: #999;
            transition: transform 0.2s;
            flex-shrink: 0;
        }
        .faq-list details[open] summary::after {
            transform: rotate(180deg);
            color: var(--primary);
        }
        .faq-list details:hover summary {
            color: var(--primary);
        }
        .faq-answer {
            font-size: 0.88rem;
            color: var(--text-light);
            margin-top: 8px;
            line-height: 1.7;
            text-align: justify;
        }

        /* Footer */
        .site-footer {
            background: #f5f5f5;
            border-top: 1px solid var(--border);
            padding: 18px 20px;
            text-align: center;
            font-size: 0.82rem;
            color: var(--text-muted);
            flex-shrink: 0;
        }
        .site-footer a {
            color: var(--text-muted);
            text-decoration: none;
            margin: 0 8px;
        }
        .site-footer a:hover {
            color: var(--primary);
            text-decoration: underline;
        }
        .disclaimer {
            margin-top: 8px;
            font-size: 0.75rem;
            color: #aaa;
            max-width: 700px;
            margin-left: auto;
            margin-right: auto;
            line-height: 1.5;
        }

        /* 响应式 */
        @media (max-width: 860px) {
            .calc-body { flex-direction: column; }
            .calc-form-panel {
                flex: 0 0 auto;
                border-right: none;
                border-bottom: 1px solid var(--border-light);
                padding: 16px 14px;
            }
            .calc-result-panel { flex: 0 0 auto; padding: 16px 14px; }
            .form-row { flex-direction: column; align-items: stretch; gap: 4px; }
            .form-row label { text-align: left; flex: 0 0 auto; }
            .input-group { min-width: 100%; }
            input[type="number"] { max-width: 100%; }
            select { max-width: 100%; }
            .btn-row { padding-left: 0; justify-content: flex-start; flex-wrap: wrap; }
            .top-nav { gap: 10px; font-size: 0.8rem; }
            .logo { font-size: 1.1rem; }
            .result-row, .suggestion-row { flex-direction: column; }
            .big-number { font-size: 2.2rem; }
            .info-grid { grid-template-columns: 1fr; }
        }
        @media (max-width: 480px) {
            .header-inner { height: 44px; padding: 0 10px; }
            .logo { font-size: 0.95rem; }
            .top-nav { gap: 6px; font-size: 0.7rem; }
            .section-header h1 { font-size: 1.15rem; }
            .calc-form-panel { padding: 12px 10px; }
            .calc-result-panel { padding: 12px 10px; gap: 8px; }
            .result-card { padding: 10px 12px; }
            .content-section, .faq-section { padding: 16px 14px; }
        }