/* ===== 公式落地页样式 ===== */
.formula-landing {
    max-width: 900px;
    margin: 0 auto;
    padding: var(--spacing-xl) var(--spacing-lg);
}

/* 面包屑 */
.formula-breadcrumb {
    font-size: 0.85rem;
    color: var(--text-secondary);
    margin-bottom: var(--spacing-lg);
}
.formula-breadcrumb a {
    color: var(--primary-color);
    text-decoration: none;
}
.formula-breadcrumb a:hover {
    text-decoration: underline;
}
.formula-breadcrumb span.sep {
    margin: 0 6px;
    color: var(--text-tertiary);
}

/* 标题区 */
.formula-hero {
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    border-radius: var(--radius-xl);
    padding: var(--spacing-2xl) var(--spacing-xl);
    color: white;
    margin-bottom: var(--spacing-xl);
}
.formula-hero h1 {
    font-size: 1.8rem;
    font-weight: 700;
    margin: 0 0 8px;
}
.formula-hero .hero-badges {
    display: flex;
    gap: 8px;
    margin-bottom: var(--spacing-sm);
    flex-wrap: wrap;
}
.formula-hero .english-name {
    font-size: 0.95rem;
    opacity: 0.85;
    margin-bottom: var(--spacing-md);
    font-family: 'JetBrains Mono', monospace;
}
.formula-hero .formula-text {
    background: rgba(255,255,255,0.15);
    border-radius: var(--radius-md);
    padding: 12px 16px;
    font-size: 1.15rem;
    font-family: 'JetBrains Mono', monospace;
    letter-spacing: 0.5px;
    margin-top: var(--spacing-md);
}

/* 分类/难度标签 */
.hero-badge {
    display: inline-block;
    background: rgba(255,255,255,0.2);
    padding: 4px 12px;
    border-radius: 20px;
    font-size: 0.8rem;
}
.difficulty-basic { background: rgba(74,222,128,0.3); }
.difficulty-intermediate { background: rgba(250,204,21,0.3); }
.difficulty-advanced { background: rgba(248,113,113,0.3); }

/* Tab导航 */
.formula-tabs {
    display: flex;
    gap: 0;
    border-bottom: 2px solid var(--border-color);
    margin-bottom: var(--spacing-lg);
}
.formula-tab {
    padding: 12px 20px;
    cursor: pointer;
    font-size: 0.95rem;
    font-weight: 500;
    color: var(--text-secondary);
    border-bottom: 2px solid transparent;
    margin-bottom: -2px;
    transition: all 0.2s;
    user-select: none;
    display: flex;
    align-items: center;
    gap: 6px;
}
.formula-tab:hover {
    color: var(--text-primary);
}
.formula-tab.active {
    color: var(--primary-color);
    border-bottom-color: var(--primary-color);
    font-weight: 600;
}
.tab-panel { display: none; }
.tab-panel.active { display: block; }

/* 内容区卡片 */
.formula-section {
    background: var(--card-bg);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-lg);
    padding: var(--spacing-xl);
    margin-bottom: var(--spacing-lg);
}
.formula-section h2 {
    font-size: 1.2rem;
    font-weight: 600;
    margin: 0 0 var(--spacing-md);
    display: flex;
    align-items: center;
    gap: 8px;
}
.formula-section h3 {
    font-size: 1rem;
    font-weight: 600;
    margin: var(--spacing-lg) 0 var(--spacing-sm);
    color: var(--text-primary);
}
.formula-section p {
    line-height: 1.8;
    color: var(--text-primary);
}

/* 变量表格 */
.var-table {
    width: 100%;
    border-collapse: collapse;
    margin-top: var(--spacing-md);
}
.var-table th,
.var-table td {
    padding: 10px 14px;
    border: 1px solid var(--border-color);
    text-align: left;
    font-size: 0.9rem;
}
.var-table th {
    background: var(--bg-secondary);
    font-weight: 600;
    white-space: nowrap;
}

/* 计算示例 */
.example-card {
    background: #f0fdf4;
    border: 1px solid #bbf7d0;
    border-radius: var(--radius-md);
    padding: var(--spacing-md) var(--spacing-lg);
    margin-top: var(--spacing-md);
}
.example-card .example-row {
    display: flex;
    justify-content: space-between;
    padding: 6px 0;
    font-size: 0.9rem;
}
.example-card .example-result {
    font-weight: 700;
    font-size: 1.1rem;
    color: #16a34a;
    border-top: 1px solid #bbf7d0;
    padding-top: 8px;
    margin-top: 4px;
}

/* 在线计算器 */
.calculator-card {
    background: #eff6ff;
    border: 1px solid #bfdbfe;
    border-radius: var(--radius-md);
    padding: var(--spacing-lg);
    margin-top: var(--spacing-md);
}
.calc-input-group {
    display: flex;
    align-items: center;
    gap: 10px;
    margin-bottom: 10px;
}
.calc-input-group label {
    min-width: 100px;
    font-size: 0.9rem;
    font-weight: 500;
}
.calc-input-group input {
    flex: 1;
    padding: 8px 12px;
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    font-size: 0.9rem;
    max-width: 200px;
}
.calc-input-group .unit {
    font-size: 0.85rem;
    color: var(--text-secondary);
}
.calc-btn {
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    color: white;
    border: none;
    padding: 10px 24px;
    border-radius: var(--radius-md);
    cursor: pointer;
    font-size: 0.95rem;
    font-weight: 500;
    margin-top: 8px;
}
.calc-btn:hover {
    opacity: 0.9;
}
.calc-result {
    margin-top: var(--spacing-md);
    padding: 12px 16px;
    background: white;
    border-radius: var(--radius-md);
    font-size: 1.1rem;
    font-weight: 600;
    display: none;
}
.calc-result.show {
    display: block;
}

/* 应用场景 */
.application-text {
    background: #fefce8;
    border-left: 4px solid #eab308;
    padding: 12px 16px;
    border-radius: 0 var(--radius-md) var(--radius-md) 0;
    line-height: 1.8;
}

/* 提示列表 */
.tips-list, .optimization-list {
    list-style: none;
    padding: 0;
    margin: 0;
}
.tips-list li, .optimization-list li {
    position: relative;
    padding: 8px 0 8px 28px;
    line-height: 1.7;
    font-size: 0.9rem;
    border-bottom: 1px solid var(--border-light, #f1f1f1);
}
.tips-list li:last-child, .optimization-list li:last-child {
    border-bottom: none;
}
.tips-list li::before {
    content: '\1F4A1';
    position: absolute;
    left: 0;
    top: 8px;
}
.optimization-list li::before {
    content: '\2705';
    position: absolute;
    left: 0;
    top: 8px;
}

/* 变体公式 */
.variants-table {
    width: 100%;
    border-collapse: collapse;
    margin-top: var(--spacing-sm);
}
.variants-table td {
    padding: 8px 12px;
    border: 1px solid var(--border-color);
    font-size: 0.9rem;
}
.variants-table td:first-child {
    font-weight: 600;
    white-space: nowrap;
    width: 140px;
}
.variants-table td:last-child {
    font-family: 'JetBrains Mono', monospace;
    font-size: 0.85rem;
    color: var(--text-secondary);
}

/* 实战案例 */
.case-card {
    background: var(--bg-secondary);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    padding: var(--spacing-lg);
    margin-top: var(--spacing-md);
}
.case-scenario {
    font-weight: 600;
    font-size: 1rem;
    margin-bottom: var(--spacing-sm);
    color: var(--primary-color);
}
.case-data {
    display: flex;
    flex-wrap: wrap;
    gap: 12px;
    margin-bottom: var(--spacing-sm);
}
.case-data-item {
    background: white;
    border: 1px solid var(--border-color);
    border-radius: var(--radius-sm);
    padding: 4px 10px;
    font-size: 0.85rem;
}
.case-data-item strong {
    color: var(--text-secondary);
    margin-right: 4px;
}
.case-result {
    font-size: 1rem;
    font-weight: 600;
    color: #16a34a;
    margin: var(--spacing-sm) 0;
}
.case-analysis {
    font-size: 0.9rem;
    line-height: 1.8;
    color: var(--text-primary);
    background: white;
    border-radius: var(--radius-sm);
    padding: 10px 14px;
}

/* 联动区块 */
.linkage-section {
    background: var(--card-bg);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-lg);
    padding: var(--spacing-xl);
    margin-bottom: var(--spacing-lg);
}
.linkage-section h2 {
    font-size: 1.1rem;
    font-weight: 600;
    margin: 0 0 var(--spacing-md);
    display: flex;
    align-items: center;
    gap: 8px;
}
.linkage-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(220px, 1fr));
    gap: var(--spacing-sm);
}
.linkage-card {
    display: block;
    background: var(--bg-secondary);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    padding: 12px 14px;
    text-decoration: none;
    color: inherit;
    transition: box-shadow 0.2s, transform 0.2s;
}
.linkage-card:hover {
    box-shadow: 0 4px 12px rgba(0,0,0,0.08);
    transform: translateY(-2px);
}
.linkage-card .lk-name {
    font-weight: 600;
    font-size: 0.9rem;
    margin-bottom: 2px;
}
.linkage-card .lk-desc {
    font-size: 0.8rem;
    color: var(--text-secondary);
    line-height: 1.5;
}

/* 关联公式 */
.related-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(260px, 1fr));
    gap: var(--spacing-md);
    margin-top: var(--spacing-md);
}
.related-card {
    background: var(--bg-secondary);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    padding: var(--spacing-md);
    text-decoration: none;
    color: inherit;
    transition: box-shadow 0.2s, transform 0.2s;
}
.related-card:hover {
    box-shadow: 0 4px 12px rgba(0,0,0,0.1);
    transform: translateY(-2px);
}
.related-card .rc-name {
    font-weight: 600;
    font-size: 0.95rem;
    margin-bottom: 4px;
}
.related-card .rc-formula {
    font-size: 0.8rem;
    color: var(--text-secondary);
    font-family: 'JetBrains Mono', monospace;
}

/* 结构化数据不可见 */
.sr-only {
    position: absolute;
    width: 1px;
    height: 1px;
    overflow: hidden;
    clip: rect(0,0,0,0);
}