/* 前置知识页：左侧目录 + 右侧正文 */

.preliminary-section {
    padding: 100px 0 60px;
    min-height: calc(100vh - 120px);
    background: var(--bg-light);
}

.preliminary-layout {
    display: grid;
    grid-template-columns: minmax(220px, 280px) minmax(0, 1fr);
    gap: 2rem;
    align-items: start;
    max-width: 1800px;
    margin: 0 auto;
}

.preliminary-back {
    margin-bottom: 1.25rem;
}

.preliminary-back .btn-back {
    display: inline-flex;
    align-items: center;
    gap: 8px;
    padding: 10px 20px;
    background: linear-gradient(135deg, #2d5016 0%, #4a7c2a 100%);
    color: white;
    text-decoration: none;
    border-radius: 8px;
    font-size: 14px;
    transition: all 0.3s ease;
    box-shadow: 0 2px 10px rgba(45, 80, 22, 0.3);
}

.preliminary-back .btn-back:hover {
    transform: translateY(-2px);
    box-shadow: 0 4px 15px rgba(45, 80, 22, 0.4);
}

.preliminary-page-title {
    font-size: 1.75rem;
    color: var(--text-color);
    margin-bottom: 0.35rem;
    display: flex;
    align-items: center;
    gap: 0.5rem;
}

.preliminary-page-title i {
    color: var(--primary-color);
}

.preliminary-page-desc {
    font-size: 0.9rem;
    color: var(--text-light);
    margin-bottom: 1.5rem;
}

/* 左侧目录 */
.preliminary-toc-wrap {
    position: sticky;
    top: 88px;
    max-height: calc(100vh - 100px);
    overflow-y: auto;
    padding: 1rem 1rem 1rem 0;
    border-right: 1px solid var(--border-color);
}

.preliminary-toc-title {
    font-size: 0.75rem;
    text-transform: uppercase;
    letter-spacing: 0.06em;
    color: var(--text-light);
    margin-bottom: 0.75rem;
    font-weight: 600;
}

.preliminary-toc {
    list-style: none;
    margin: 0;
    padding: 0;
}

.preliminary-toc li {
    margin: 0;
}

.preliminary-toc a {
    display: block;
    padding: 0.35rem 0.5rem 0.35rem 0;
    font-size: 0.8rem;
    line-height: 1.35;
    color: #9ca3af;
    text-decoration: none;
    border-radius: 4px;
    transition: var(--transition);
}

.preliminary-toc a:hover {
    color: var(--secondary-color);
    background: rgba(74, 124, 42, 0.06);
}

.preliminary-toc a.active {
    color: var(--primary-color);
    font-weight: 500;
}

.preliminary-toc .toc-num {
    font-weight: 600;
    color: var(--text-light);
    margin-right: 0.2em;
}

.preliminary-toc a.active .toc-num {
    color: var(--primary-color);
}

.preliminary-toc .toc-depth-1 { padding-left: 0; }
.preliminary-toc .toc-depth-2 { padding-left: 0.75rem; }
.preliminary-toc .toc-depth-3 { padding-left: 1.5rem; }
.preliminary-toc .toc-depth-4 { padding-left: 2.25rem; }
.preliminary-toc .toc-depth-5 { padding-left: 3rem; }
.preliminary-toc .toc-depth-6 { padding-left: 3.75rem; }

/* 右侧正文 */
.preliminary-main {
    min-width: 0;
    background: var(--bg-color);
    border-radius: 12px;
    padding: 1.75rem 2rem 2.5rem;
    box-shadow: var(--shadow);
}

.preliminary-md {
    font-size: 0.95rem;
    line-height: 1.7;
    color: var(--text-color);
}

.preliminary-md h1,
.preliminary-md h2,
.preliminary-md h3,
.preliminary-md h4,
.preliminary-md h5,
.preliminary-md h6 {
    scroll-margin-top: 96px;
    margin-top: 1.5rem;
    margin-bottom: 0.75rem;
    color: var(--text-color);
    font-weight: 600;
}

.preliminary-md h1 { font-size: 1.5rem; }
.preliminary-md h2 { font-size: 1.35rem; }
.preliminary-md h3 { font-size: 1.2rem; }
.preliminary-md h4 { font-size: 1.1rem; }

.preliminary-md .heading-number {
    display: inline-block;
    margin-right: 0.35em;
    font-weight: 700;
    color: var(--text-light);
    font-variant-numeric: tabular-nums;
}

.preliminary-md p { margin-bottom: 0.85rem; }
.preliminary-md ul, .preliminary-md ol { margin: 0.5rem 0 1rem 1.25rem; }
.preliminary-md li { margin-bottom: 0.35rem; }

.preliminary-md table {
    width: 100%;
    border-collapse: collapse;
    font-size: 0.85rem;
    margin: 1rem 0;
    overflow-x: auto;
    display: block;
}

.preliminary-md th,
.preliminary-md td {
    border: 1px solid var(--border-color);
    padding: 0.5rem 0.65rem;
    text-align: left;
}

.preliminary-md img {
    max-width: 100%;
    height: auto;
    border-radius: 8px;
    margin: 0.75rem 0;
}

.preliminary-md pre {
    background: #f3f4f6;
    padding: 1rem;
    border-radius: 8px;
    overflow-x: auto;
    font-size: 0.85rem;
    margin: 1rem 0;
}

.preliminary-md code {
    background: #f3f4f6;
    padding: 0.15rem 0.4rem;
    border-radius: 4px;
    font-size: 0.88em;
}

.preliminary-md blockquote {
    border-left: 4px solid var(--secondary-color);
    margin: 1rem 0;
    padding-left: 1rem;
    color: var(--text-light);
}

.preliminary-empty-toc {
    font-size: 0.8rem;
    color: var(--text-light);
}

@media (max-width: 900px) {
    .preliminary-layout {
        grid-template-columns: 1fr;
    }

    .preliminary-toc-wrap {
        position: relative;
        top: 0;
        max-height: none;
        border-right: none;
        border-bottom: 1px solid var(--border-color);
        padding: 0 0 1rem 0;
    }

    .preliminary-toc {
        display: flex;
        flex-wrap: wrap;
        gap: 0.35rem;
    }

    .preliminary-toc li {
        display: inline-block;
    }

    .preliminary-toc a {
        padding: 0.35rem 0.65rem;
        background: #f3f4f6;
        border-radius: 6px;
        font-size: 0.75rem;
    }

    .preliminary-toc .toc-depth-2,
    .preliminary-toc .toc-depth-3,
    .preliminary-toc .toc-depth-4,
    .preliminary-toc .toc-depth-5,
    .preliminary-toc .toc-depth-6 {
        padding-left: 0.65rem;
    }
}