/* 学习信息节点页（/learn/*）· 干净的文档式排版 + 打印友好 */

:root {
    --learn-bg: #f7f8fa;
    --learn-card: #ffffff;
    --learn-ink: #1f2933;
    --learn-ink-light: #5b6b7a;
    --learn-border: #e3e8ee;
    --learn-accent: #2f7d4f;
    --learn-accent-soft: #eaf5ee;
    --learn-square: #2f7d4f;
    --learn-mirror: #f0f3f6;
}

* { box-sizing: border-box; }

.learn-body {
    margin: 0;
    background: var(--learn-bg);
    color: var(--learn-ink);
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", "PingFang SC",
                 "Hiragino Sans GB", "Microsoft YaHei", sans-serif;
    line-height: 1.7;
    -webkit-font-smoothing: antialiased;
}

/* 顶部导航 */
.learn-nav {
    display: flex;
    align-items: center;
    gap: 18px;
    max-width: 880px;
    margin: 0 auto;
    padding: 16px 20px 0;
}
.learn-nav .back-link {
    color: var(--learn-ink-light);
    text-decoration: none;
    font-size: 14px;
    display: inline-flex;
    align-items: center;
    gap: 3px;
    transition: color 0.2s ease;
}
.learn-nav .back-link:hover { color: var(--learn-accent); }

/* 页面主体 */
.learn-page {
    max-width: 880px;
    margin: 0 auto;
    padding: 12px 20px 80px;
}

/* Hero */
.learn-hero {
    padding: 24px 0 8px;
    border-bottom: 1px solid var(--learn-border);
    margin-bottom: 32px;
}
.learn-genre {
    font-size: 12px;
    letter-spacing: 2px;
    color: var(--learn-accent);
    margin-bottom: 8px;
}
.learn-hero h1 {
    font-size: 34px;
    font-weight: 700;
    margin: 0 0 12px;
    letter-spacing: -0.01em;
}
.learn-lead {
    font-size: 15.5px;
    color: var(--learn-ink-light);
    margin: 0;
}
.learn-lead strong { color: var(--learn-ink); }

/* 内容分区 */
.learn-section { margin-bottom: 40px; }
.learn-section h2 {
    font-size: 21px;
    font-weight: 700;
    margin: 0 0 6px;
}
.section-head {
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: 12px;
    margin-bottom: 6px;
}
.section-head h2 { margin: 0; }
.section-note {
    font-size: 13.5px;
    color: var(--learn-ink-light);
    margin: 0 0 16px;
}
.legend-square, .legend-mirror {
    padding: 1px 6px;
    border-radius: 4px;
    font-size: 12.5px;
}
.legend-square { background: var(--learn-square); color: #fff; }
.legend-mirror { background: var(--learn-mirror); color: var(--learn-ink-light); }

/* 打印按钮 */
.print-btn {
    flex-shrink: 0;
    font: inherit;
    font-size: 13.5px;
    cursor: pointer;
    border: 1px solid var(--learn-accent);
    background: var(--learn-accent-soft);
    color: var(--learn-accent);
    border-radius: 8px;
    padding: 7px 14px;
    display: inline-flex;
    align-items: center;
    gap: 5px;
    transition: background 0.2s ease;
}
.print-btn:hover { background: #def0e5; }

/* 九九乘法表（方格表） */
.table-wrap { overflow-x: auto; }
.mult-table {
    border-collapse: collapse;
    width: 100%;
    min-width: 480px;
    background: var(--learn-card);
    border-radius: 10px;
    overflow: hidden;
    box-shadow: 0 1px 3px rgba(31, 41, 51, 0.06);
}
.mult-table th, .mult-table td {
    text-align: center;
    padding: 0;
    height: 46px;
    font-size: 15px;
    border: 1px solid var(--learn-border);
}
.mult-table thead th, .mult-table tbody th {
    background: var(--learn-accent);
    color: #fff;
    font-weight: 700;
}
.mult-table .corner { background: #246340; }
.mult-table td { color: var(--learn-ink); font-variant-numeric: tabular-nums; }
.mult-table td.is-mirror { background: var(--learn-mirror); color: var(--learn-ink-light); }
.mult-table td.is-square {
    background: var(--learn-square);
    color: #fff;
    font-weight: 700;
}

/* 乘法口诀阶梯表 */
.formula-table {
    background: var(--learn-card);
    border: 1px solid var(--learn-border);
    border-radius: 10px;
    padding: 14px 16px;
}
.formula-row {
    display: flex;
    flex-wrap: wrap;
    gap: 6px 10px;
    padding: 5px 0;
}
.formula-row + .formula-row { border-top: 1px dashed var(--learn-border); }
.formula-item {
    font-size: 14.5px;
    color: var(--learn-ink);
    background: var(--learn-accent-soft);
    border-radius: 6px;
    padding: 3px 9px;
    white-space: nowrap;
    font-variant-numeric: tabular-nums;
}

/* 记忆方法卡片 */
.tip-cards {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(220px, 1fr));
    gap: 14px;
}
.tip-card {
    background: var(--learn-card);
    border: 1px solid var(--learn-border);
    border-radius: 10px;
    padding: 18px 18px 16px;
    position: relative;
}
.tip-num {
    width: 26px;
    height: 26px;
    border-radius: 50%;
    background: var(--learn-accent);
    color: #fff;
    font-weight: 700;
    font-size: 14px;
    display: flex;
    align-items: center;
    justify-content: center;
    margin-bottom: 10px;
}
.tip-card h3 { font-size: 15.5px; margin: 0 0 6px; }
.tip-card p { font-size: 13.5px; color: var(--learn-ink-light); margin: 0; }

/* 易错点 */
.pitfall-list {
    list-style: none;
    margin: 0;
    padding: 0;
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(240px, 1fr));
    gap: 10px;
}
.pitfall-list li {
    background: var(--learn-card);
    border: 1px solid var(--learn-border);
    border-left: 3px solid #d98a2b;
    border-radius: 8px;
    padding: 10px 14px;
    font-size: 14px;
    color: var(--learn-ink-light);
}
.pitfall-list li b { color: var(--learn-ink); }

/* FAQ */
.faq-list { display: flex; flex-direction: column; gap: 8px; }
.faq-item {
    background: var(--learn-card);
    border: 1px solid var(--learn-border);
    border-radius: 8px;
    padding: 2px 16px;
}
.faq-item summary {
    cursor: pointer;
    font-weight: 600;
    font-size: 15px;
    padding: 12px 0;
    list-style: none;
}
.faq-item summary::-webkit-details-marker { display: none; }
.faq-item summary::before {
    content: '+';
    color: var(--learn-accent);
    font-weight: 700;
    margin-right: 8px;
}
.faq-item[open] summary::before { content: '\2212'; }
.faq-item p {
    margin: 0 0 14px;
    font-size: 14px;
    color: var(--learn-ink-light);
}

/* 练一练 CTA */
.learn-cta {
    background: var(--learn-accent-soft);
    border: 1px solid #cfe6d8;
    border-radius: 14px;
    padding: 28px 24px;
    text-align: center;
}
.learn-cta h2 { font-size: 20px; margin: 0 0 6px; }
.learn-cta > p {
    font-size: 14px;
    color: var(--learn-ink-light);
    margin: 0 0 18px;
}
.cta-btn {
    display: inline-flex;
    align-items: center;
    gap: 6px;
    background: var(--learn-accent);
    color: #fff;
    text-decoration: none;
    font-size: 16px;
    font-weight: 600;
    padding: 12px 28px;
    border-radius: 999px;
    transition: transform 0.2s ease, box-shadow 0.2s ease;
}
.cta-btn:hover {
    transform: translateY(-1px);
    box-shadow: 0 8px 20px -8px rgba(47, 125, 79, 0.5);
}
.related-tools {
    margin-top: 18px;
    font-size: 13.5px;
    color: var(--learn-ink-light);
}
.related-tools .related-label { margin-right: 4px; }
.related-tools a {
    color: var(--learn-accent);
    text-decoration: none;
    margin: 0 6px;
}
.related-tools a:hover { text-decoration: underline; }

@media (max-width: 600px) {
    .learn-hero h1 { font-size: 27px; }
    .learn-page { padding: 12px 14px 60px; }
    .learn-nav { padding: 14px 14px 0; }
    .mult-table th, .mult-table td { height: 40px; font-size: 14px; }
    .section-head { flex-wrap: wrap; }
}

/* 打印：只留标题 + 两张表，去掉导航/方法/易错点/FAQ/CTA */
@media print {
    .learn-body { background: #fff; }
    .learn-nav, .no-print, .print-btn { display: none !important; }
    .learn-page { max-width: none; padding: 0; }
    .learn-hero { border: none; margin-bottom: 16px; padding: 0; }
    .learn-section { margin-bottom: 20px; }
    .mult-table { box-shadow: none; min-width: 0; }
    .mult-table td.is-square { background: #ddd !important; color: #000; -webkit-print-color-adjust: exact; print-color-adjust: exact; }
    .mult-table td.is-mirror { background: #f3f3f3 !important; }
    .mult-table thead th, .mult-table tbody th { background: #eee !important; color: #000; -webkit-print-color-adjust: exact; print-color-adjust: exact; }
    .formula-item { background: #f3f3f3 !important; -webkit-print-color-adjust: exact; print-color-adjust: exact; }
}