/* ==========================================================================
   Components — sidebar nav, topic header, question cards, code blocks,
   diagrams and search results.
   ========================================================================== */

/* --------------------------------------------------------------------------
   Sidebar navigation
   -------------------------------------------------------------------------- */

.nav-item {
    position: relative;
    display: flex;
    align-items: center;
    gap: 10px;
    padding: 9px 12px;
    font-size: 13.5px;
    font-weight: 500;
    color: var(--text-secondary);
    text-decoration: none;
    border-radius: var(--radius-sm);
    cursor: pointer;
    transition: background var(--transition-fast), color var(--transition-fast);
}

.nav-item:hover {
    background: var(--bg-hover);
    color: var(--text-primary);
}

.nav-item.active {
    background: var(--accent-light);
    color: var(--accent-hover);
    font-weight: 600;
}

.nav-item.active::before {
    content: '';
    position: absolute;
    left: 0;
    top: 50%;
    transform: translateY(-50%);
    width: 3px;
    height: 60%;
    background: var(--accent-color);
    border-radius: 0 3px 3px 0;
}

.nav-icon {
    flex: 0 0 auto;
    font-size: 15px;
    line-height: 1;
}

.nav-label {
    flex: 1 1 auto;
    overflow: hidden;
    text-overflow: ellipsis;
    white-space: nowrap;
}

.nav-count {
    flex: 0 0 auto;
    font-family: var(--font-mono);
    font-size: 10.5px;
    color: var(--text-muted);
}

/* Expandable groups */

.nav-item-group {
    display: flex;
    flex-direction: column;
}

.nav-item-parent {
    width: 100%;
    background: transparent;
    border: none;
    font-family: inherit;
    text-align: left;
}

.nav-chevron {
    flex: 0 0 auto;
    transition: transform var(--transition-base);
    color: var(--text-muted);
}

.nav-item-group.expanded .nav-chevron {
    transform: rotate(90deg);
}

.nav-subsections {
    display: none;
    flex-direction: column;
    gap: 1px;
    margin: 2px 0 4px 22px;
    padding-left: 10px;
    border-left: 1px solid var(--border-color);
}

.nav-item-group.expanded .nav-subsections {
    display: flex;
}

.nav-subsection {
    padding: 6px 10px;
    font-size: 12.5px;
    color: var(--text-muted);
    text-decoration: none;
    border-radius: 6px;
    cursor: pointer;
    transition: background var(--transition-fast), color var(--transition-fast);
}

.nav-subsection:hover {
    background: var(--bg-hover);
    color: var(--text-primary);
}

.nav-subsection.active {
    color: var(--accent-hover);
    font-weight: 600;
}

/* --------------------------------------------------------------------------
   Topic header
   -------------------------------------------------------------------------- */

.topic-header {
    margin-bottom: 28px;
    padding-bottom: 20px;
    border-bottom: 1px solid var(--border-color);
}

.topic-title {
    font-size: 34px;
    font-weight: 700;
    letter-spacing: -0.03em;
    line-height: 1.2;
    background: var(--gradient-accent);
    -webkit-background-clip: text;
    background-clip: text;
    -webkit-text-fill-color: transparent;
}

.topic-stats {
    display: flex;
    flex-wrap: wrap;
    gap: 16px;
    margin-top: 10px;
    font-size: 13px;
    color: var(--text-muted);
}

.topic-stat {
    display: inline-flex;
    align-items: center;
    gap: 6px;
}

/* --------------------------------------------------------------------------
   Key topics
   -------------------------------------------------------------------------- */

.key-topics-section {
    margin-bottom: 32px;
    padding: 18px 20px;
    background: var(--bg-key-topics);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-lg);
}

.key-topics-title {
    margin-bottom: 12px;
    font-size: 12px;
    font-weight: 600;
    letter-spacing: 0.08em;
    text-transform: uppercase;
    color: var(--text-secondary);
}

.key-topics-grid {
    display: flex;
    flex-wrap: wrap;
    gap: 8px;
}

.key-topic-pill {
    padding: 5px 12px;
    font-size: 12.5px;
    font-weight: 500;
    color: var(--accent-hover);
    background: var(--accent-light);
    border: 1px solid var(--border-color);
    border-radius: 999px;
    transition: background var(--transition-fast), transform var(--transition-fast);
}

.key-topic-pill:hover {
    background: var(--bg-card-hover);
    transform: translateY(-1px);
}

/* --------------------------------------------------------------------------
   Subsection dividers
   -------------------------------------------------------------------------- */

.subsection-header {
    display: flex;
    align-items: center;
    gap: 12px;
    margin: 40px 0 18px;
    scroll-margin-top: 88px;
}

.subsection-header:first-child {
    margin-top: 0;
}

.subsection-title {
    font-size: 20px;
    font-weight: 650;
    letter-spacing: -0.02em;
    color: var(--text-primary);
    white-space: nowrap;
}

.subsection-rule {
    flex: 1 1 auto;
    height: 1px;
    background: linear-gradient(90deg, var(--border-color), transparent);
}

/* --------------------------------------------------------------------------
   Question card
   -------------------------------------------------------------------------- */

.question-card {
    position: relative;
    margin-bottom: 12px;
    background: var(--bg-card);
    background-image: var(--gradient-card);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-lg);
    overflow: hidden;
    scroll-margin-top: 88px;
    transition: border-color var(--transition-base), box-shadow var(--transition-base),
                background var(--transition-base);
}

.question-card::after {
    content: '';
    position: absolute;
    inset: 0;
    background: var(--gradient-shine);
    opacity: 0;
    pointer-events: none;
    transition: opacity var(--transition-base);
}

.question-card:hover {
    border-color: var(--accent-color);
    box-shadow: var(--shadow-glow);
}

.question-card:hover::after {
    opacity: 1;
}

.question-card.expanded {
    border-color: var(--accent-color);
    background: var(--bg-card-hover);
}

.question-header {
    position: relative;
    z-index: 1;
    display: flex;
    align-items: flex-start;
    gap: 14px;
    padding: 16px 18px;
    cursor: pointer;
    user-select: none;
}

.question-number {
    flex: 0 0 auto;
    display: inline-flex;
    align-items: center;
    justify-content: center;
    width: 26px;
    height: 26px;
    margin-top: 1px;
    font-family: var(--font-mono);
    font-size: 11.5px;
    font-weight: 500;
    color: var(--accent-hover);
    background: var(--accent-light);
    border-radius: 50%;
}

.question-text {
    flex: 1 1 auto;
    font-size: 15px;
    font-weight: 550;
    line-height: 1.5;
    color: var(--text-primary);
}

.question-chevron {
    flex: 0 0 auto;
    margin-top: 4px;
    color: var(--text-muted);
    transition: transform var(--transition-base), color var(--transition-fast);
}

.question-card.expanded .question-chevron {
    transform: rotate(180deg);
    color: var(--accent-color);
}

/* Collapsible body */

.answer-body {
    position: relative;
    z-index: 1;
    max-height: 0;
    opacity: 0;
    overflow: hidden;
    transition: max-height var(--transition-slow), opacity var(--transition-base),
                padding var(--transition-base);
}

.question-card.expanded .answer-body {
    max-height: 5000px;
    opacity: 1;
    padding: 0 18px 18px 58px;
}

/* --------------------------------------------------------------------------
   Answer content
   -------------------------------------------------------------------------- */

.answer-content {
    font-size: 14.5px;
    color: var(--text-secondary);
}

.answer-content p { margin-bottom: 10px; }
.answer-content p:last-child { margin-bottom: 0; }
.answer-content strong { color: var(--text-primary); font-weight: 600; }
.answer-content ul,
.answer-content ol { margin: 0 0 12px 20px; }
.answer-content li { margin-bottom: 6px; }
.answer-content li::marker { color: var(--accent-color); }
.answer-content a { color: var(--accent-hover); text-decoration: underline; text-underline-offset: 2px; }

.answer-content code {
    padding: 2px 6px;
    font-family: var(--font-mono);
    font-size: 0.88em;
    color: var(--accent-hover);
    background: var(--bg-code-inline);
    border-radius: 5px;
}

.answer-content table {
    width: 100%;
    margin-bottom: 12px;
    border-collapse: collapse;
    font-size: 13.5px;
}

.answer-content th,
.answer-content td {
    padding: 8px 10px;
    text-align: left;
    border: 1px solid var(--border-color);
}

.answer-content th {
    color: var(--text-primary);
    background: var(--bg-glass);
    font-weight: 600;
}

/* --------------------------------------------------------------------------
   Reference links
   -------------------------------------------------------------------------- */

.reference-links {
    display: flex;
    flex-wrap: wrap;
    gap: 8px;
    margin-bottom: 14px;
}

.reference-link {
    display: inline-flex;
    align-items: center;
    gap: 6px;
    padding: 4px 11px;
    font-size: 12px;
    font-weight: 500;
    color: var(--accent-hover);
    background: var(--accent-light);
    border: 1px solid var(--border-color);
    border-radius: 999px;
    text-decoration: none;
    transition: background var(--transition-fast), border-color var(--transition-fast);
}

.reference-link:hover {
    background: var(--bg-card-hover);
    border-color: var(--accent-color);
}

/* --------------------------------------------------------------------------
   Code blocks
   -------------------------------------------------------------------------- */

.code-block {
    margin: 14px 0;
    background: var(--bg-code);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    overflow: hidden;
}

.code-block-header {
    display: flex;
    align-items: center;
    gap: 10px;
    padding: 9px 14px;
    background: var(--bg-glass);
    border-bottom: 1px solid var(--border-subtle);
    cursor: pointer;
    user-select: none;
}

.code-block-title {
    flex: 1 1 auto;
    font-size: 12.5px;
    font-weight: 600;
    color: var(--text-primary);
}

.code-block-lang {
    padding: 2px 8px;
    font-family: var(--font-mono);
    font-size: 10.5px;
    text-transform: uppercase;
    letter-spacing: 0.05em;
    color: var(--text-muted);
    background: var(--bg-hover);
    border-radius: 4px;
}

.code-block-toggle {
    color: var(--text-muted);
    transition: transform var(--transition-base);
}

.code-block.collapsed .code-block-toggle {
    transform: rotate(-90deg);
}

.code-block-body {
    max-height: 1200px;
    overflow: auto;
    transition: max-height var(--transition-base);
}

.code-block.collapsed .code-block-body {
    max-height: 0;
    overflow: hidden;
}

.code-block pre {
    margin: 0;
    padding: 14px 16px;
}

.code-block code {
    font-family: var(--font-mono);
    font-size: 12.5px;
    line-height: 1.7;
    color: var(--text-code);
    white-space: pre;
    tab-size: 4;
}

/* Syntax tokens */

.keyword    { color: var(--keyword-color); font-weight: 500; }
.string     { color: var(--string-color); }
.comment    { color: var(--comment-color); font-style: italic; }
.number     { color: var(--number-color); }
.annotation { color: var(--annotation-color); }
.tag        { color: var(--tag-color); }
.attribute  { color: var(--attribute-color); }

/* --------------------------------------------------------------------------
   Diagrams
   -------------------------------------------------------------------------- */

.diagram-container {
    margin: 16px 0;
    padding: 16px;
    background: var(--diagram-bg);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    overflow-x: auto;
}

.diagram-container:empty {
    display: none;
}

.diagram-title {
    margin-bottom: 12px;
    font-size: 12px;
    font-weight: 600;
    letter-spacing: 0.06em;
    text-transform: uppercase;
    color: var(--diagram-text);
}

.diagram-container svg {
    display: block;
    max-width: 100%;
    height: auto;
    margin: 0 auto;
}

/* --------------------------------------------------------------------------
   Search results
   -------------------------------------------------------------------------- */

.search-result-item {
    display: flex;
    flex-direction: column;
    gap: 3px;
    padding: 9px 12px;
    border-radius: var(--radius-sm);
    cursor: pointer;
    transition: background var(--transition-fast);
}

.search-result-item:hover,
.search-result-item.highlighted {
    background: var(--bg-hover);
}

.search-result-topic {
    font-size: 11px;
    font-weight: 600;
    letter-spacing: 0.04em;
    text-transform: uppercase;
    color: var(--accent-hover);
}

.search-result-question {
    font-size: 13.5px;
    line-height: 1.45;
    color: var(--text-primary);
}

.search-result-question mark {
    color: var(--accent-hover);
    background: var(--accent-light);
    border-radius: 3px;
    padding: 0 2px;
}

.search-empty {
    padding: 20px 12px;
    text-align: center;
    font-size: 13.5px;
    color: var(--text-muted);
}

/* --------------------------------------------------------------------------
   Reduced motion
   -------------------------------------------------------------------------- */

@media (prefers-reduced-motion: reduce) {
    *,
    *::before,
    *::after {
        animation-duration: 0.01ms !important;
        animation-iteration-count: 1 !important;
        transition-duration: 0.01ms !important;
        scroll-behavior: auto !important;
    }
}

/* --------------------------------------------------------------------------
   Responsive tweaks
   -------------------------------------------------------------------------- */

@media (max-width: 768px) {
    .topic-title { font-size: 26px; }
    .question-card.expanded .answer-body { padding: 0 16px 16px 16px; }
    .subsection-title { font-size: 18px; white-space: normal; }
}