/* Shared reading navigation for every OSPF lesson page. */
.ospf-series-page {
    --ospf-teal: #58d0c5;
    --ospf-teal-strong: #24afa4;
    --ospf-gold: #e5b84f;
    --primary-color: var(--ospf-teal);
    --primary-hover: #78ddd5;
    --secondary-color: var(--ospf-teal-strong);
    --accent-color: var(--ospf-gold);
    --primary-gradient: linear-gradient(135deg, var(--ospf-teal), var(--ospf-teal-strong));
    --bg-primary: #f4f7fb;
    --bg-secondary: #f8fafc;
    --bg-card: #ffffff;
    --border-color: #dbe3ee;
    background: var(--bg-primary);
}

html[data-theme='dark'] .ospf-series-page {
    --bg-primary: #0b1220;
    --bg-secondary: #182438;
    --bg-card: #111b2d;
    --border-color: #405466;
}

.ospf-series-page .welcome-section::before {
    background: linear-gradient(90deg, var(--ospf-teal), #86d5c1 72%, var(--ospf-gold)) !important;
}

.ospf-hub-page .ospf-hub .welcome-section {
    background:
        linear-gradient(rgba(88, 208, 197, .045) 1px, transparent 1px),
        linear-gradient(90deg, rgba(88, 208, 197, .045) 1px, transparent 1px),
        radial-gradient(circle at 88% 12%, rgba(36, 175, 164, .2), transparent 34rem),
        linear-gradient(135deg, #0b2530, #0c202a) !important;
    background-size: 56px 56px, 56px 56px, auto, auto !important;
    border-color: color-mix(in srgb, var(--ospf-teal) 38%, var(--border-color)) !important;
    box-shadow: none;
}

.ospf-hub-page .ospf-hub {
    box-sizing: border-box;
    padding-inline: clamp(1rem, 1.5vw, 1.5rem);
}

.ospf-hub-page .ospf-hub > .content-section {
    margin-inline: auto;
    max-width: none;
    width: 100%;
}

.ospf-hub-page .ospf-hub .welcome-section h1 {
    background: none !important;
    color: var(--text-primary) !important;
    -webkit-background-clip: border-box !important;
    background-clip: border-box !important;
    -webkit-text-fill-color: currentColor !important;
}

.ospf-hub-page .ospf-hub .welcome-section p {
    color: var(--text-secondary);
}

.ospf-hub-page .ospf-hub .menu-grid .menu-item {
    background:
        radial-gradient(circle at 100% 0, color-mix(in srgb, var(--ospf-teal) 7%, transparent), transparent 48%),
        var(--bg-card);
    border-color: var(--border-color);
}

.ospf-hub-page .ospf-hub .menu-grid .menu-item:hover,
.ospf-hub-page .ospf-hub .menu-grid .menu-item:focus-within {
    border-color: var(--ospf-teal);
    box-shadow: 0 14px 30px color-mix(in srgb, var(--ospf-teal) 11%, transparent);
    transform: translateY(-2px);
}

.ospf-hub-page .ospf-hub .menu-item a,
.ospf-hub-page .ospf-hub .menu-item a:visited,
html[data-theme="dark"] .ospf-hub-page .ospf-article-card a,
html[data-theme="dark"] .ospf-hub-page .ospf-article-card a:visited {
    color: var(--ospf-teal) !important;
}

.ospf-hub-page .ospf-hub .menu-item a:hover,
.ospf-hub-page .ospf-hub .menu-item a:focus-visible,
html[data-theme="dark"] .ospf-hub-page .ospf-article-card a:hover,
html[data-theme="dark"] .ospf-hub-page .ospf-article-card a:focus-visible {
    color: var(--ospf-gold) !important;
}

html[data-theme="light"] .ospf-hub-page .ospf-hub .welcome-section {
    background:
        linear-gradient(rgba(15, 118, 110, .045) 1px, transparent 1px),
        linear-gradient(90deg, rgba(15, 118, 110, .045) 1px, transparent 1px),
        radial-gradient(circle at 88% 12%, rgba(88, 208, 197, .18), transparent 34rem),
        linear-gradient(135deg, #f8fbfa, #edf7f5) !important;
    background-size: 56px 56px, 56px 56px, auto, auto !important;
}

.ospf-hub-page .ospf-hub > .content-section:last-child .content-card {
    margin-bottom: 0;
}

.ospf-hub-page .ospf-hub-faq {
    margin-top: 2rem;
}

.ospf-hub-page footer.netest-site-footer {
    margin-top: 1rem !important;
}

.ospf-series-page .sidebar {
    display: flex;
    flex-direction: column;
}

.ospf-series-page .rip-page-container {
    gap: clamp(1rem, 1.5vw, 1.5rem);
    padding-inline: clamp(1rem, 1.5vw, 1.5rem);
}

/* OSPF headings use the same theme-aware ink as the homepage. */
.ospf-series-page .blog-article .welcome-section h1,
.ospf-series-page .blog-article .content-card h2,
.ospf-series-page .blog-article .content-card h3,
.ospf-series-page .blog-article .content-card h4 {
    background: none !important;
    color: var(--text-primary) !important;
    -webkit-background-clip: border-box !important;
    background-clip: border-box !important;
    -webkit-text-fill-color: currentColor !important;
}

.ospf-series-page .sidebar > .content-card:has(.rip-side-menu) {
    margin-bottom: 0;
    order: 99;
}

.ospf-series-page .rip-page-container > .main-content,
.ospf-series-page .rip-page-container > .sidebar {
    padding-bottom: 0;
}

.ospf-series-page .blog-article > section:last-child {
    margin-bottom: 0;
}

.ospf-series-page .sidebar > .content-card:has(.rip-side-menu) h3 {
    align-items: center;
    display: flex;
    gap: .55rem;
}

.ospf-series-page .sidebar > .content-card:has(.rip-side-menu) h3::before {
    color: var(--primary-color);
    content: "\f5eb";
    font-family: "Font Awesome 6 Free";
    font-size: .9em;
    font-weight: 900;
}

.ospf-series-page .rip-side-menu {
    min-height: 0;
    overflow-x: hidden;
    scrollbar-color: var(--border-color) transparent;
    scrollbar-width: thin;
}

.ospf-series-page .rip-side-menu a {
    scroll-margin-block: .4rem;
}

.ospf-series-page .main-content section[id] {
    scroll-margin-top: 6.25rem;
}

.ospf-series-page .sidebar > .content-card:has(> h3 + .feature-list) .feature-list {
    display: grid;
    gap: .65rem;
    margin: 1rem 0 0;
}

.ospf-series-page .sidebar > .content-card:has(> h3 + .feature-list) .feature-list li {
    background: var(--bg-primary);
    border: 1px solid var(--border-color);
    border-radius: .7rem;
    display: block;
    line-height: 1.5;
    margin: 0 !important;
    padding: .75rem .85rem;
}

.ospf-series-page .sidebar > .content-card:has(> h3 + .feature-list) .feature-list li strong {
    color: var(--text-primary);
    display: block;
    margin-bottom: .16rem;
}

.ospf-lesson-pagination {
    display: flex;
    gap: 1rem;
    justify-content: space-between;
    margin: 1rem 0 0;
    width: 100%;
}

.ospf-series-page .rip-page-container:has(.ospf-lesson-pagination) + footer.netest-site-footer {
    margin-top: 1rem !important;
}

.ospf-series-page .ospf-faq .blog-faq-item {
    background: var(--bg-primary);
    border: 1px solid var(--border-color);
    border-radius: .7rem;
    margin-bottom: .75rem;
    overflow: hidden;
}

.ospf-series-page .ospf-faq .blog-faq-item > summary {
    align-items: center;
    cursor: pointer;
    display: flex;
    gap: 1rem;
    justify-content: space-between;
    list-style: none;
    min-height: 3.5rem;
    padding: .95rem 1.2rem;
}

.ospf-series-page .ospf-faq .blog-faq-item > summary::marker {
    content: '';
}

.ospf-series-page .ospf-faq .blog-faq-item > summary::-webkit-details-marker {
    display: none;
}

.ospf-series-page .ospf-faq .blog-faq-item > summary::after {
    border: 0;
    color: var(--primary-color);
    content: '+';
    align-items: center;
    align-self: center;
    display: inline-flex;
    flex: 0 0 1.5rem;
    font-size: 1.25rem;
    font-weight: 800;
    height: 1.5rem;
    margin: 0;
    justify-content: center;
    transform: none;
    width: 1.5rem;
}

.ospf-series-page .ospf-faq .blog-faq-item[open] > summary::after {
    content: '−';
    transform: none;
}

.ospf-series-page .ospf-faq .blog-faq-answer {
    padding: .2rem 1.2rem 1rem;
}

.ospf-lesson-pagination__card {
    background:
        radial-gradient(circle at 0 0, color-mix(in srgb, var(--primary-color) 13%, transparent), transparent 52%),
        var(--bg-card);
    border: 1px solid var(--border-color);
    border-radius: 1rem;
    color: var(--text-secondary) !important;
    display: flex;
    flex: 0 1 280px;
    flex-direction: column;
    min-height: 4.7rem;
    padding: .62rem .75rem;
    text-decoration: none !important;
    transition: border-color .2s ease, box-shadow .2s ease, transform .2s ease;
    width: min(34vw, 280px);
}

.ospf-lesson-pagination__card:hover,
.ospf-lesson-pagination__card:focus-visible {
    border-color: var(--primary-color);
    box-shadow: 0 14px 30px color-mix(in srgb, var(--primary-color) 13%, transparent);
    transform: translateY(-2px);
}

.ospf-lesson-pagination__card[data-direction="next"] {
    align-items: flex-end;
    background:
        radial-gradient(circle at 100% 0, color-mix(in srgb, var(--primary-color) 13%, transparent), transparent 52%),
        var(--bg-card);
    text-align: right;
}

.ospf-lesson-pagination__label {
    align-items: center;
    color: var(--primary-color);
    display: flex;
    font-size: .68rem;
    font-weight: 850;
    gap: .45rem;
    letter-spacing: .06em;
    margin-bottom: .3rem;
    text-transform: uppercase;
}

.ospf-lesson-pagination__card strong {
    color: var(--text-primary);
    font-size: clamp(.88rem, 1.1vw, 1rem);
    line-height: 1.3;
    margin-bottom: .35rem;
}

.ospf-lesson-pagination__card > span:last-child {
    color: var(--text-muted);
    font-size: .7rem;
    margin-top: auto;
}

@media (min-width: 1201px) {
    .ospf-series-page .rip-page-container > .sidebar {
        align-self: stretch;
        max-height: none;
        overflow: visible;
        position: static !important;
    }

    .ospf-series-page .sidebar > .content-card:has(.rip-side-menu) {
        align-self: stretch;
        display: flex;
        flex-direction: column;
        max-height: calc(100vh - 7rem);
        overflow: hidden;
        position: sticky !important;
        top: 5.75rem;
        z-index: 10;
    }

    .ospf-series-page .sidebar > .content-card:has(.rip-side-menu) .rip-side-menu {
        overflow-y: auto;
        overscroll-behavior: contain;
        padding: .25rem .4rem;
    }
}

.ospf-series-page .ospf-practice-grid {
    display: grid;
    gap: 1rem;
    margin-top: 1.35rem;
}

.ospf-series-page .ospf-practice-task {
    background: color-mix(in srgb, var(--primary-color) 5%, var(--bg-primary));
    border: 1px solid var(--border-color);
    border-left: 4px solid var(--primary-color);
    border-radius: .85rem;
    padding: 1.15rem 1.25rem;
}

.ospf-series-page .ospf-practice-task h3 {
    font-size: clamp(1.08rem, 1.7vw, 1.28rem);
    margin: 0 0 .8rem;
}

.ospf-series-page .ospf-practice-task ol {
    margin: 0;
    padding-left: 1.35rem;
}

.ospf-series-page .ospf-practice-task li {
    padding-left: .2rem;
}

.ospf-series-page .ospf-practice-result {
    background: color-mix(in srgb, var(--accent-color) 9%, var(--bg-secondary));
    border-radius: .55rem;
    margin: 1rem 0 0;
    padding: .75rem .85rem;
}

.ospf-series-page .ospf-practice-result strong {
    color: var(--text-primary);
}

/* Reusable teaching visuals and CLI panels for OSPF lessons. */
.ospf-series-page .ospf-process-visual {
    background:
        linear-gradient(rgba(88, 208, 197, .045) 1px, transparent 1px),
        linear-gradient(90deg, rgba(88, 208, 197, .045) 1px, transparent 1px),
        color-mix(in srgb, var(--primary-color) 3%, var(--bg-primary));
    background-size: 34px 34px;
    border: 1px solid var(--border-color);
    border-radius: 1rem;
    margin: 1.35rem 0 0;
    overflow: hidden;
    padding: clamp(1rem, 2vw, 1.5rem);
}

.ospf-series-page .ospf-process-track {
    align-items: stretch;
    display: grid;
    gap: .65rem;
    grid-template-columns: repeat(auto-fit, minmax(9rem, 1fr));
}

.ospf-series-page .ospf-process-track--three {
    grid-template-columns: repeat(3, minmax(0, 1fr));
}

.ospf-series-page .ospf-process-step {
    align-items: center;
    background: var(--bg-card);
    border: 1px solid var(--border-color);
    border-radius: .8rem;
    display: flex;
    flex-direction: column;
    min-height: 9rem;
    padding: 1rem .75rem;
    position: relative;
    text-align: center;
}

.ospf-series-page .ospf-process-step:not(:last-child)::after {
    align-items: center;
    background: var(--primary-color);
    border-radius: 50%;
    color: #071d22;
    content: '\f061';
    display: flex;
    font-family: 'Font Awesome 6 Free';
    font-size: .65rem;
    font-weight: 900;
    height: 1.45rem;
    justify-content: center;
    position: absolute;
    right: -.88rem;
    top: calc(50% - .72rem);
    width: 1.45rem;
    z-index: 2;
}

.ospf-series-page .ospf-process-step > span:first-child {
    color: var(--primary-color);
    font-size: .68rem;
    font-weight: 850;
}

.ospf-series-page .ospf-process-step > i {
    color: var(--primary-color);
    font-size: 1rem;
    margin-top: .35rem;
}

.ospf-series-page .ospf-process-step h3 {
    font-size: clamp(.88rem, 1.2vw, 1rem) !important;
    line-height: 1.3;
    margin: .45rem 0 .35rem !important;
}

.ospf-series-page .ospf-process-step p {
    color: var(--text-muted);
    font-size: .75rem;
    line-height: 1.5;
    margin: 0;
}

.ospf-series-page .ospf-process-number {
    align-items: center;
    background: color-mix(in srgb, var(--primary-color) 16%, var(--bg-card));
    border: 1px solid color-mix(in srgb, var(--primary-color) 45%, var(--border-color));
    border-radius: 50%;
    color: var(--primary-color);
    display: flex;
    font-size: .76rem;
    font-weight: 850;
    height: 2rem;
    justify-content: center;
    margin-bottom: .65rem;
    width: 2rem;
}

.ospf-series-page .ospf-process-step strong {
    color: var(--text-primary);
    font-size: .92rem;
    line-height: 1.3;
}

.ospf-series-page .ospf-process-step span:last-child {
    color: var(--text-muted);
    font-size: .76rem;
    line-height: 1.45;
    margin-top: .42rem;
}

.ospf-series-page .ospf-process-visual figcaption {
    color: var(--text-secondary);
    font-size: .82rem;
    line-height: 1.55;
    margin-top: 1rem;
    text-align: center;
}

.ospf-series-page .table-container {
    border: 1px solid var(--border-color);
    border-radius: .85rem;
    margin-top: 1rem;
    max-width: 100%;
    overflow-x: auto;
    width: 100%;
}

.ospf-series-page .table-container table {
    background: color-mix(in srgb, var(--primary-color) 2%, var(--bg-primary));
    border-collapse: collapse;
    min-width: 42rem;
    table-layout: auto;
    width: 100%;
}

.ospf-series-page .table-container th,
.ospf-series-page .table-container td {
    border-bottom: 1px solid var(--border-color);
    color: var(--text-secondary);
    line-height: 1.45;
    padding: .85rem 1rem;
    text-align: left;
    vertical-align: top;
}

.ospf-series-page .table-container th {
    background: color-mix(in srgb, var(--primary-color) 12%, var(--bg-card));
    color: var(--text-primary);
    font-weight: 800;
    white-space: nowrap;
}

.ospf-series-page .table-container tbody tr:last-child td { border-bottom: 0; }
.ospf-series-page .table-container td:first-child { color: var(--text-primary); }

.ospf-series-page .ospf-cli-grid {
    display: grid;
    gap: 1rem;
    grid-template-columns: repeat(2, minmax(0, 1fr));
    margin-top: 1.25rem;
}

.ospf-series-page .ospf-cli-panel {
    background: #091321;
    border: 1px solid color-mix(in srgb, var(--primary-color) 30%, #26384d);
    border-radius: .85rem;
    min-width: 0;
    overflow: hidden;
}

.ospf-series-page .ospf-cli-panel--auto {
    margin: 1.25rem 0;
}

.ospf-series-page .ospf-cli-grid > .ospf-cli-panel--auto {
    margin: 0;
}

.ospf-series-page .ospf-cli-panel h3 {
    align-items: center;
    background: #132338;
    border-bottom: 1px solid #2d4359;
    color: #f4f8fc !important;
    display: flex;
    font-size: .9rem !important;
    gap: .55rem;
    margin: 0 !important;
    padding: .75rem .9rem;
}

.ospf-series-page .ospf-cli-panel h3 i {
    color: var(--primary-color);
}

.ospf-series-page .ospf-cli-panel pre {
    background: transparent !important;
    border: 0 !important;
    border-radius: 0 !important;
    color: #cde7ee !important;
    font-size: clamp(.72rem, 1vw, .83rem) !important;
    line-height: 1.65 !important;
    margin: 0 !important;
    min-height: 8.3rem;
    overflow-x: auto;
    padding: 1rem !important;
    white-space: pre;
}

.ospf-series-page .ospf-checklist {
    display: grid;
    gap: .75rem;
    margin: 1.25rem 0 0;
    padding: 0;
}

.ospf-series-page .ospf-checklist li {
    align-items: flex-start;
    background: var(--bg-primary);
    border: 1px solid var(--border-color);
    border-radius: .7rem;
    display: flex;
    gap: .75rem;
    list-style: none;
    margin: 0;
    padding: .85rem 1rem;
}

.ospf-series-page .ospf-checklist li i {
    color: var(--primary-color);
    margin-top: .24rem;
}

.ospf-series-page .ospf-checklist li span {
    min-width: 0;
}

/* Cost-calculation lesson: formula and path-choice teaching components. */
.ospf-series-page .ospf-formula-card {
    background:
        radial-gradient(circle at 100% 0, color-mix(in srgb, var(--primary-color) 18%, transparent), transparent 48%),
        #091321;
    border: 1px solid color-mix(in srgb, var(--primary-color) 40%, #26384d);
    border-radius: 1rem;
    color: #d8e7ef;
    margin-top: 1.25rem;
    overflow: hidden;
    padding: clamp(1rem, 2.5vw, 1.6rem);
    text-align: center;
}

.ospf-series-page .ospf-formula-card > span {
    color: var(--primary-color);
    display: block;
    font-size: .72rem;
    font-weight: 850;
    letter-spacing: .08em;
    margin-bottom: .7rem;
    text-transform: uppercase;
}

.ospf-series-page .ospf-formula-expression {
    color: #f7fbff;
    font-family: ui-monospace, SFMono-Regular, Menlo, Monaco, Consolas, monospace;
    font-size: clamp(1.05rem, 2.2vw, 1.65rem);
    font-weight: 800;
    line-height: 1.4;
}

.ospf-series-page .ospf-formula-note {
    color: #aebfcd;
    font-size: .8rem;
    line-height: 1.55;
    margin: .8rem auto 0;
    max-width: 56rem;
}

.ospf-series-page .ospf-path-visual {
    background:
        linear-gradient(rgba(88, 208, 197, .04) 1px, transparent 1px),
        linear-gradient(90deg, rgba(88, 208, 197, .04) 1px, transparent 1px),
        color-mix(in srgb, var(--primary-color) 3%, var(--bg-primary));
    background-size: 32px 32px;
    border: 1px solid var(--border-color);
    border-radius: 1rem;
    margin: 1.25rem 0 0;
    padding: clamp(1rem, 2vw, 1.35rem);
}

.ospf-series-page .ospf-path-visual__legend {
    align-items: center;
    color: var(--text-muted);
    display: flex;
    flex-wrap: wrap;
    font-size: .76rem;
    gap: .75rem 1.1rem;
    justify-content: center;
    margin-bottom: 1rem;
}

.ospf-series-page .ospf-path-visual__legend span {
    align-items: center;
    display: inline-flex;
    gap: .4rem;
}

.ospf-series-page .ospf-path-visual__legend i {
    color: var(--primary-color);
}

.ospf-series-page .ospf-path-row {
    align-items: center;
    background: var(--bg-card);
    border: 1px solid var(--border-color);
    border-radius: .85rem;
    display: grid;
    gap: .65rem;
    grid-template-columns: 4.6rem minmax(5.8rem, 1fr) 4.6rem minmax(5.8rem, 1fr) 4.6rem minmax(6.2rem, auto);
    margin-top: .8rem;
    padding: .9rem;
}

.ospf-series-page .ospf-path-row.is-selected {
    border-color: var(--primary-color);
    box-shadow: inset 4px 0 0 var(--primary-color);
}

.ospf-series-page .ospf-path-router {
    align-items: center;
    background: #0d192b;
    border: 1px solid #3f5368;
    border-radius: .7rem;
    color: #f5f8fb;
    display: flex;
    flex-direction: column;
    font-size: .85rem;
    font-weight: 800;
    gap: .25rem;
    justify-content: center;
    min-height: 4.2rem;
    padding: .55rem;
}

.ospf-series-page .ospf-path-router i {
    color: var(--primary-color);
}

.ospf-series-page .ospf-path-link {
    align-items: center;
    color: var(--text-muted);
    display: flex;
    flex-direction: column;
    font-size: .7rem;
    font-weight: 700;
    gap: .38rem;
    text-align: center;
}

.ospf-series-page .ospf-path-link::after {
    background: linear-gradient(90deg, var(--primary-color), var(--accent-color));
    content: '';
    height: 3px;
    width: 100%;
}

.ospf-series-page .ospf-path-total {
    background: color-mix(in srgb, var(--accent-color) 11%, var(--bg-secondary));
    border: 1px solid color-mix(in srgb, var(--accent-color) 35%, var(--border-color));
    border-radius: .7rem;
    color: var(--text-primary);
    font-size: .76rem;
    font-weight: 750;
    line-height: 1.35;
    padding: .65rem .7rem;
    text-align: center;
}

.ospf-series-page .ospf-path-row.is-selected .ospf-path-total {
    background: color-mix(in srgb, var(--primary-color) 14%, var(--bg-secondary));
    border-color: var(--primary-color);
}

.ospf-series-page .ospf-path-result {
    color: var(--text-secondary);
    font-size: .82rem;
    line-height: 1.55;
    margin: 1rem 0 0;
    text-align: center;
}

/* Multi-area lesson: responsive backbone and ABR topology. */
.ospf-series-page .ospf-area-map {
    background:
        linear-gradient(rgba(88, 208, 197, .04) 1px, transparent 1px),
        linear-gradient(90deg, rgba(88, 208, 197, .04) 1px, transparent 1px),
        color-mix(in srgb, var(--primary-color) 3%, var(--bg-primary));
    background-size: 32px 32px;
    border: 1px solid var(--border-color);
    border-radius: 1rem;
    margin: 1.25rem 0 0;
    padding: clamp(1rem, 2vw, 1.4rem);
}

.ospf-series-page .ospf-area-map__zones {
    align-items: stretch;
    display: grid;
    gap: .8rem;
    grid-template-columns: 1fr 1.25fr 1fr;
}

.ospf-series-page .ospf-area-zone {
    background: var(--bg-card);
    border: 1px solid var(--border-color);
    border-radius: .85rem;
    min-width: 0;
    padding: .9rem;
    position: relative;
}

.ospf-series-page .ospf-area-zone.is-backbone {
    background:
        radial-gradient(circle at 50% 0, color-mix(in srgb, var(--primary-color) 13%, transparent), transparent 70%),
        var(--bg-card);
    border-color: var(--primary-color);
}

.ospf-series-page .ospf-area-zone__title {
    align-items: center;
    color: var(--text-primary);
    display: flex;
    font-size: .86rem;
    font-weight: 850;
    gap: .45rem;
    justify-content: center;
    margin-bottom: .8rem;
    text-align: center;
}

.ospf-series-page .ospf-area-zone__title i {
    color: var(--primary-color);
}

.ospf-series-page .ospf-area-zone__nodes {
    align-items: center;
    display: flex;
    gap: .45rem;
    justify-content: center;
}

.ospf-series-page .ospf-area-node {
    align-items: center;
    background: #0d192b;
    border: 1px solid #3f5368;
    border-radius: .7rem;
    color: #f5f8fb;
    display: flex;
    flex: 1 1 5rem;
    flex-direction: column;
    font-size: .76rem;
    font-weight: 800;
    gap: .25rem;
    justify-content: center;
    max-width: 7.3rem;
    min-height: 4.4rem;
    padding: .55rem .4rem;
    text-align: center;
}

.ospf-series-page .ospf-area-node i {
    color: var(--primary-color);
}

.ospf-series-page .ospf-area-node small {
    color: #9fb3c3;
    font-size: .62rem;
    font-weight: 650;
}

.ospf-series-page .ospf-area-link {
    background: linear-gradient(90deg, var(--primary-color), var(--accent-color));
    flex: 0 1 2.6rem;
    height: 3px;
    min-width: 1rem;
}

.ospf-series-page .ospf-area-zone__prefix {
    color: var(--text-muted);
    font-size: .68rem;
    line-height: 1.4;
    margin-top: .7rem;
    text-align: center;
}

.ospf-series-page .ospf-area-map figcaption {
    color: var(--text-secondary);
    font-size: .8rem;
    line-height: 1.55;
    margin-top: 1rem;
    text-align: center;
}

/* DR/BDR election topology */
.ospf-series-page .ospf-election-map {
    background: linear-gradient(145deg, rgba(83, 204, 196, .07), rgba(10, 23, 39, .5));
    border: 1px solid var(--border-color);
    border-radius: 1rem;
    margin: 1.35rem 0;
    overflow: hidden;
    padding: 1.25rem;
}

.ospf-series-page .ospf-election-lan {
    align-items: center;
    background: #0c2230;
    border: 1px solid rgba(83, 204, 196, .55);
    border-radius: .85rem;
    color: #f5f8fb;
    display: flex;
    gap: .65rem;
    justify-content: center;
    margin: 0 auto 2.1rem;
    max-width: 31rem;
    padding: .85rem 1rem;
    position: relative;
    text-align: center;
}

.ospf-series-page .ospf-election-lan::after {
    background: linear-gradient(var(--primary-color), var(--accent-color));
    bottom: -2.15rem;
    content: '';
    height: 2.15rem;
    left: calc(50% - 2px);
    position: absolute;
    width: 4px;
}

.ospf-series-page .ospf-election-lan i,
.ospf-series-page .ospf-election-lan strong { color: var(--primary-color); }
.ospf-series-page .ospf-election-lan span { color: #aec3d2; font-size: .76rem; }

.ospf-series-page .ospf-election-routers {
    border-top: 4px solid var(--primary-color);
    display: grid;
    gap: .8rem;
    grid-template-columns: repeat(4, minmax(0, 1fr));
    padding-top: 1.65rem;
}

.ospf-series-page .ospf-election-router {
    align-items: center;
    background: #0d192b;
    border: 1px solid #405469;
    border-radius: .85rem;
    color: #f5f8fb;
    display: flex;
    flex-direction: column;
    gap: .32rem;
    min-height: 9rem;
    padding: 1.35rem .65rem .8rem;
    position: relative;
    text-align: center;
}

.ospf-series-page .ospf-election-router::before {
    background: var(--primary-color);
    content: '';
    height: 1.65rem;
    left: calc(50% - 1px);
    position: absolute;
    top: -1.68rem;
    width: 2px;
}

.ospf-series-page .ospf-election-router > i { color: var(--primary-color); font-size: 1.2rem; }
.ospf-series-page .ospf-election-router > strong { font-size: 1.05rem; }
.ospf-series-page .ospf-election-router > small { color: #aec3d2; font-size: .67rem; }
.ospf-series-page .ospf-election-router > code { color: var(--primary-color); font-size: .7rem; }

.ospf-series-page .ospf-election-role {
    background: var(--primary-color);
    border-radius: 999px;
    color: #071822;
    font-size: .61rem;
    font-weight: 900;
    letter-spacing: .06em;
    padding: .22rem .5rem;
    position: absolute;
    right: .55rem;
    top: .5rem;
}

.ospf-series-page .ospf-election-router.is-bdr { border-color: #e6c75a; }
.ospf-series-page .ospf-election-router.is-bdr .ospf-election-role { background: #e6c75a; }
.ospf-series-page .ospf-election-router.is-drother .ospf-election-role { background: #6d8194; color: #fff; }
.ospf-series-page .ospf-election-router.is-ineligible { opacity: .78; }
.ospf-series-page .ospf-election-router.is-ineligible .ospf-election-role { background: #526273; color: #fff; }

.ospf-series-page .ospf-election-map figcaption {
    color: var(--text-secondary);
    font-size: .8rem;
    line-height: 1.55;
    margin-top: 1rem;
    text-align: center;
}

/* Neighbor-state lesson visuals */
.ospf-series-page .ospf-neighbor-lab {
    align-items: center;
    background: linear-gradient(145deg, rgba(83, 204, 196, .08), rgba(10, 23, 39, .5));
    border: 1px solid var(--border-color);
    border-radius: 1rem;
    display: grid;
    gap: 1rem;
    grid-template-columns: minmax(8rem, .8fr) minmax(13rem, 1.4fr) minmax(8rem, .8fr);
    margin: 1.25rem 0;
    padding: 1.25rem;
}

.ospf-series-page .ospf-neighbor-router {
    align-items: center;
    background: #0d192b;
    border: 1px solid #405469;
    border-radius: .85rem;
    color: #f5f8fb;
    display: flex;
    flex-direction: column;
    gap: .35rem;
    min-height: 8rem;
    justify-content: center;
    padding: 1rem;
    text-align: center;
}

.ospf-series-page .ospf-neighbor-router i { color: var(--primary-color); font-size: 1.35rem; }
.ospf-series-page .ospf-neighbor-router strong { font-size: 1.1rem; }
.ospf-series-page .ospf-neighbor-router span { color: #aec3d2; font-size: .72rem; }
.ospf-series-page .ospf-neighbor-router code { color: var(--primary-color); font-size: .72rem; }

.ospf-series-page .ospf-neighbor-link {
    align-items: center;
    color: var(--primary-color);
    display: grid;
    gap: .45rem;
    grid-template-columns: 1fr auto 1fr;
    text-align: center;
}

.ospf-series-page .ospf-neighbor-link::before,
.ospf-series-page .ospf-neighbor-link::after {
    background: linear-gradient(90deg, var(--primary-color), var(--accent-color));
    content: '';
    grid-row: 2;
    height: 4px;
}

.ospf-series-page .ospf-neighbor-link strong {
    background: #0c2230;
    border: 1px solid rgba(83, 204, 196, .55);
    border-radius: 999px;
    color: #f5f8fb;
    font-size: .72rem;
    grid-column: 2;
    grid-row: 2;
    padding: .55rem .75rem;
}

.ospf-series-page .ospf-neighbor-link span { font-size: .68rem; font-weight: 800; }
.ospf-series-page .ospf-neighbor-link span:first-child { grid-column: 1 / 2; }
.ospf-series-page .ospf-neighbor-link span:last-child { grid-column: 3 / 4; }

.ospf-series-page .ospf-neighbor-lab figcaption {
    color: var(--text-secondary);
    font-size: .78rem;
    grid-column: 1 / -1;
    line-height: 1.55;
    text-align: center;
}

.ospf-series-page .ospf-state-path {
    display: grid;
    gap: .7rem;
    grid-template-columns: repeat(7, minmax(0, 1fr));
    margin: 1.25rem 0;
}

.ospf-series-page .ospf-state-card {
    align-items: center;
    background: #0d192b;
    border: 1px solid #405469;
    border-radius: .8rem;
    display: flex;
    flex-direction: column;
    gap: .32rem;
    min-height: 7.6rem;
    justify-content: center;
    padding: .75rem .45rem;
    position: relative;
    text-align: center;
}

.ospf-series-page .ospf-state-card:not(:last-child)::after {
    color: var(--primary-color);
    content: '\f061';
    font-family: 'Font Awesome 6 Free';
    font-size: .65rem;
    font-weight: 900;
    position: absolute;
    right: -.7rem;
    top: calc(50% - .3rem);
    z-index: 2;
}

.ospf-series-page .ospf-state-card > span {
    color: var(--primary-color);
    font-size: .62rem;
    font-weight: 900;
    letter-spacing: .08em;
}

.ospf-series-page .ospf-state-card > strong { color: #f5f8fb; font-size: .9rem; }
.ospf-series-page .ospf-state-card > small { color: #aabccc; font-size: .62rem; line-height: 1.35; }
.ospf-series-page .ospf-state-card.is-complete { background: #123b3e; border-color: var(--primary-color); }

/* Stub-area lesson topology and design decisions */
.ospf-series-page .ospf-stub-map {
    align-items: stretch;
    background: linear-gradient(145deg, rgba(83, 204, 196, .08), rgba(10, 23, 39, .5));
    border: 1px solid var(--border-color);
    border-radius: 1rem;
    display: grid;
    gap: .8rem;
    grid-template-columns: minmax(0, 1fr) 8.5rem minmax(0, 1fr);
    margin: 1.25rem 0;
    padding: 1.1rem;
}

.ospf-series-page .ospf-stub-zone {
    background: #0d192b;
    border: 1px solid #405469;
    border-radius: .9rem;
    min-width: 0;
    padding: .85rem;
}

.ospf-series-page .ospf-stub-zone.is-backbone { border-top: 3px solid var(--primary-color); }
.ospf-series-page .ospf-stub-zone.is-edge { border-top: 3px solid #e6c75a; }

.ospf-series-page .ospf-stub-zone__label {
    color: var(--primary-color);
    display: block;
    font-size: .7rem;
    font-weight: 900;
    letter-spacing: .04em;
    margin-bottom: .8rem;
    text-align: center;
    text-transform: uppercase;
}

.ospf-series-page .ospf-stub-zone.is-edge .ospf-stub-zone__label { color: #e6c75a; }

.ospf-series-page .ospf-stub-nodes {
    align-items: center;
    display: flex;
    gap: .45rem;
    justify-content: center;
}

.ospf-series-page .ospf-stub-node {
    align-items: center;
    color: #f5f8fb;
    display: flex;
    flex: 1 1 6rem;
    flex-direction: column;
    gap: .28rem;
    min-height: 6.5rem;
    justify-content: center;
    padding: .5rem .3rem;
    text-align: center;
}

.ospf-series-page .ospf-stub-node i { color: var(--primary-color); font-size: 1.15rem; }
.ospf-series-page .ospf-stub-node strong { font-size: .78rem; }
.ospf-series-page .ospf-stub-node small { color: #aabccc; font-size: .61rem; line-height: 1.35; }
.ospf-series-page .ospf-stub-link { background: linear-gradient(90deg, var(--primary-color), var(--accent-color)); flex: 0 1 2rem; height: 3px; }

.ospf-series-page .ospf-stub-abr {
    align-items: center;
    align-self: center;
    background: #10323a;
    border: 1px solid var(--primary-color);
    border-radius: .85rem;
    color: #f5f8fb;
    display: flex;
    flex-direction: column;
    gap: .35rem;
    justify-content: center;
    min-height: 7rem;
    padding: .75rem .5rem;
    text-align: center;
}

.ospf-series-page .ospf-stub-abr i { color: var(--primary-color); font-size: 1.2rem; }
.ospf-series-page .ospf-stub-abr strong { font-size: .8rem; }
.ospf-series-page .ospf-stub-abr small { color: #aabccc; font-size: .6rem; line-height: 1.35; }

.ospf-series-page .ospf-stub-map figcaption {
    color: var(--text-secondary);
    font-size: .78rem;
    grid-column: 1 / -1;
    line-height: 1.55;
    text-align: center;
}

.ospf-series-page .ospf-stub-decisions {
    display: grid;
    gap: .8rem;
    grid-template-columns: repeat(3, minmax(0, 1fr));
    margin: 1.2rem 0;
}

.ospf-series-page .ospf-stub-decisions article {
    background: #0d192b;
    border: 1px solid #405469;
    border-radius: .85rem;
    min-height: 10rem;
    padding: 1rem;
}

.ospf-series-page .ospf-stub-decisions span {
    color: var(--primary-color);
    font-size: .64rem;
    font-weight: 900;
    letter-spacing: .06em;
    text-transform: uppercase;
}

.ospf-series-page .ospf-stub-decisions h3 {
    color: #f5f8fb;
    font-size: .93rem;
    line-height: 1.35;
    margin: .55rem 0;
}

.ospf-series-page .ospf-stub-decisions p { color: #aabccc; font-size: .73rem; line-height: 1.55; margin: 0; }

/* Route filtering lesson topology */
.ospf-series-page .ospf-filter-map {
    align-items: stretch;
    background:
        linear-gradient(rgba(88, 208, 197, .045) 1px, transparent 1px),
        linear-gradient(90deg, rgba(88, 208, 197, .045) 1px, transparent 1px),
        color-mix(in srgb, var(--primary-color) 3%, var(--bg-primary));
    background-size: 34px 34px;
    border: 1px solid var(--border-color);
    border-radius: 1rem;
    display: grid;
    gap: 1rem;
    grid-template-columns: minmax(0, 1fr) minmax(12rem, .8fr) minmax(0, 1fr);
    margin: 1.35rem 0;
    padding: 1.2rem;
}

.ospf-series-page .ospf-filter-zone {
    align-items: center;
    background: color-mix(in srgb, var(--accent-color) 7%, var(--bg-card));
    border: 1px solid color-mix(in srgb, var(--accent-color) 55%, var(--border-color));
    border-radius: .9rem;
    display: flex;
    flex-direction: column;
    gap: .85rem;
    justify-content: center;
    min-height: 12rem;
    padding: 1rem;
}

.ospf-series-page .ospf-filter-zone.is-backbone {
    background: color-mix(in srgb, var(--primary-color) 7%, var(--bg-card));
    border-color: color-mix(in srgb, var(--primary-color) 55%, var(--border-color));
}

.ospf-series-page .ospf-filter-zone__label {
    color: var(--accent-color);
    font-size: .72rem;
    font-weight: 850;
    letter-spacing: .08em;
    text-transform: uppercase;
}

.ospf-series-page .ospf-filter-zone.is-backbone .ospf-filter-zone__label { color: var(--primary-color); }

.ospf-series-page .ospf-filter-router {
    align-items: center;
    background: var(--bg-primary);
    border: 1px solid var(--border-color);
    border-radius: .8rem;
    display: flex;
    flex-direction: column;
    gap: .28rem;
    max-width: 15rem;
    padding: .85rem 1rem;
    text-align: center;
    width: 100%;
}

.ospf-series-page .ospf-filter-router > i { color: var(--primary-color); font-size: 1.2rem; }
.ospf-series-page .ospf-filter-router > strong { color: var(--text-primary); font-size: .92rem; }
.ospf-series-page .ospf-filter-router > small { color: var(--text-muted); font-size: .67rem; margin-bottom: .2rem; }
.ospf-series-page .ospf-filter-router > code { color: var(--primary-color); font-size: .68rem; }

.ospf-series-page .ospf-filter-boundary {
    align-items: center;
    display: flex;
    flex-direction: column;
    gap: .65rem;
    justify-content: center;
    min-width: 0;
    position: relative;
    text-align: center;
}

.ospf-series-page .ospf-filter-boundary::before {
    background: linear-gradient(90deg, var(--accent-color), var(--primary-color));
    content: '';
    height: 4px;
    left: -1rem;
    position: absolute;
    right: -1rem;
    top: 50%;
}

.ospf-series-page .ospf-filter-boundary > * { position: relative; z-index: 1; }
.ospf-series-page .ospf-filter-boundary > span {
    background: var(--bg-primary);
    border: 1px solid var(--border-color);
    border-radius: 999px;
    color: var(--primary-color);
    font-size: .66rem;
    font-weight: 850;
    padding: .35rem .65rem;
    text-transform: uppercase;
}
.ospf-series-page .ospf-filter-boundary > small {
    background: var(--bg-primary);
    border-radius: .45rem;
    color: var(--text-muted);
    font-size: .65rem;
    line-height: 1.5;
    padding: .3rem .55rem;
}
.ospf-series-page .ospf-filter-boundary .ospf-filter-router.is-abr {
    background: color-mix(in srgb, var(--primary-color) 10%, var(--bg-card));
    border-color: var(--primary-color);
    box-shadow: 0 10px 24px color-mix(in srgb, var(--primary-color) 12%, transparent);
}

.ospf-series-page .ospf-filter-map figcaption {
    color: var(--text-muted);
    font-size: .72rem;
    grid-column: 1 / -1;
    line-height: 1.55;
    text-align: center;
}

/* Virtual-link lesson topology */
.ospf-series-page .ospf-virtual-map {
    background:
        linear-gradient(rgba(88, 208, 197, .045) 1px, transparent 1px),
        linear-gradient(90deg, rgba(88, 208, 197, .045) 1px, transparent 1px),
        color-mix(in srgb, var(--primary-color) 3%, var(--bg-primary));
    background-size: 34px 34px;
    border: 1px solid var(--border-color);
    border-radius: 1rem;
    display: grid;
    gap: .85rem;
    grid-template-columns: minmax(0, 1fr) minmax(12rem, .85fr) minmax(0, 1fr);
    margin: 1.35rem 0;
    padding: 1.2rem;
}

.ospf-series-page .ospf-virtual-zone {
    align-items: center;
    border: 1px solid var(--border-color);
    border-radius: .9rem;
    display: flex;
    gap: .65rem;
    justify-content: center;
    min-height: 12rem;
    padding: 1rem;
    position: relative;
}

.ospf-series-page .ospf-virtual-zone.is-backbone {
    background: color-mix(in srgb, var(--primary-color) 7%, var(--bg-card));
    border-color: color-mix(in srgb, var(--primary-color) 55%, var(--border-color));
}

.ospf-series-page .ospf-virtual-zone.is-transit {
    background: color-mix(in srgb, var(--accent-color) 7%, var(--bg-card));
    border-color: color-mix(in srgb, var(--accent-color) 55%, var(--border-color));
    flex-direction: column;
    text-align: center;
}

.ospf-series-page .ospf-virtual-zone > span {
    color: var(--primary-color);
    font-size: .66rem;
    font-weight: 900;
    left: 50%;
    letter-spacing: .07em;
    position: absolute;
    text-transform: uppercase;
    top: .65rem;
    transform: translateX(-50%);
    white-space: nowrap;
}

.ospf-series-page .ospf-virtual-zone.is-transit > span { color: var(--accent-color); }

.ospf-series-page .ospf-virtual-node {
    align-items: center;
    background: var(--bg-primary);
    border: 1px solid var(--border-color);
    border-radius: .75rem;
    display: flex;
    flex: 1 1 0;
    flex-direction: column;
    gap: .25rem;
    justify-content: center;
    min-height: 7rem;
    min-width: 0;
    padding: .75rem .45rem;
    text-align: center;
}

.ospf-series-page .ospf-virtual-node.is-endpoint { border-color: var(--primary-color); }
.ospf-series-page .ospf-virtual-node > i { color: var(--primary-color); font-size: 1.15rem; }
.ospf-series-page .ospf-virtual-node > strong { color: var(--text-primary); font-size: .78rem; }
.ospf-series-page .ospf-virtual-node > small { color: var(--text-muted); font-size: .61rem; }
.ospf-series-page .ospf-virtual-node > code { color: var(--primary-color); font-size: .62rem; }

.ospf-series-page .ospf-virtual-tunnel {
    align-items: center;
    background: var(--bg-primary);
    border: 2px dashed var(--primary-color);
    border-radius: 999px;
    display: flex;
    flex-direction: column;
    gap: .16rem;
    padding: .75rem 1rem;
    position: relative;
    width: min(100%, 13rem);
}

.ospf-series-page .ospf-virtual-tunnel::before,
.ospf-series-page .ospf-virtual-tunnel::after {
    background: var(--primary-color);
    content: '';
    height: 3px;
    position: absolute;
    top: 50%;
    width: .9rem;
}

.ospf-series-page .ospf-virtual-tunnel::before { left: -.9rem; }
.ospf-series-page .ospf-virtual-tunnel::after { right: -.9rem; }
.ospf-series-page .ospf-virtual-tunnel > small { color: var(--text-muted); font-size: .57rem; }
.ospf-series-page .ospf-virtual-tunnel > strong { color: var(--text-primary); font-size: .78rem; }
.ospf-series-page .ospf-virtual-tunnel > i { color: var(--primary-color); }
.ospf-series-page .ospf-virtual-zone.is-transit > small { color: var(--text-muted); font-size: .62rem; line-height: 1.45; }

.ospf-series-page .ospf-virtual-map figcaption {
    color: var(--text-muted);
    font-size: .72rem;
    grid-column: 1 / -1;
    line-height: 1.55;
    text-align: center;
}

/* Troubleshooting lesson baseline and diagnostic flow */
.ospf-series-page .ospf-trouble-map {
    align-items: center;
    background:
        linear-gradient(rgba(88, 208, 197, .045) 1px, transparent 1px),
        linear-gradient(90deg, rgba(88, 208, 197, .045) 1px, transparent 1px),
        color-mix(in srgb, var(--primary-color) 3%, var(--bg-primary));
    background-size: 34px 34px;
    border: 1px solid var(--border-color);
    border-radius: 1rem;
    display: grid;
    gap: .55rem;
    grid-template-columns: minmax(7rem, .8fr) minmax(6rem, .65fr) minmax(7rem, .8fr) minmax(6rem, .65fr) minmax(7rem, .8fr);
    margin: 1.35rem 0;
    padding: 1.2rem;
}

.ospf-series-page .ospf-trouble-router {
    align-items: center;
    background: var(--bg-card);
    border: 1px solid var(--border-color);
    border-radius: .85rem;
    display: flex;
    flex-direction: column;
    gap: .28rem;
    justify-content: center;
    min-height: 8.5rem;
    padding: .85rem .55rem;
    text-align: center;
}

.ospf-series-page .ospf-trouble-router.is-core {
    background: color-mix(in srgb, var(--primary-color) 9%, var(--bg-card));
    border-color: var(--primary-color);
    box-shadow: 0 10px 24px color-mix(in srgb, var(--primary-color) 12%, transparent);
}

.ospf-series-page .ospf-trouble-router > i { color: var(--primary-color); font-size: 1.2rem; }
.ospf-series-page .ospf-trouble-router > strong { color: var(--text-primary); font-size: .9rem; }
.ospf-series-page .ospf-trouble-router > code { color: var(--primary-color); font-size: .64rem; }
.ospf-series-page .ospf-trouble-router > small { color: var(--text-muted); font-size: .64rem; }

.ospf-series-page .ospf-trouble-link {
    align-items: center;
    display: flex;
    flex-direction: column;
    gap: .25rem;
    justify-content: center;
    min-height: 5rem;
    position: relative;
    text-align: center;
}

.ospf-series-page .ospf-trouble-link::before {
    background: linear-gradient(90deg, var(--primary-color), var(--accent-color));
    content: '';
    height: 4px;
    left: -.55rem;
    position: absolute;
    right: -.55rem;
    top: 50%;
}

.ospf-series-page .ospf-trouble-link > * {
    background: var(--bg-primary);
    padding: .1rem .35rem;
    position: relative;
    z-index: 1;
}
.ospf-series-page .ospf-trouble-link > span { color: var(--text-muted); font-size: .58rem; }
.ospf-series-page .ospf-trouble-link > strong { color: var(--primary-color); font-size: .72rem; }
.ospf-series-page .ospf-trouble-link > small { color: var(--accent-color); font-size: .6rem; font-weight: 800; }

.ospf-series-page .ospf-trouble-map figcaption {
    color: var(--text-muted);
    font-size: .72rem;
    grid-column: 1 / -1;
    line-height: 1.55;
    text-align: center;
}

.ospf-series-page .ospf-process-track.ospf-trouble-track {
    grid-template-columns: repeat(5, minmax(0, 1fr));
}

.ospf-series-page .ospf-trouble-track .ospf-process-step { min-height: 12rem; padding-inline: .65rem; }
.ospf-series-page .ospf-trouble-track .ospf-process-step h3 { font-size: .82rem; }
.ospf-series-page .ospf-trouble-track .ospf-process-step p { font-size: .66rem; }

/* OSPFv3 IPv6 lesson topology */
.ospf-series-page .ospfv3-map {
    align-items: center;
    background: linear-gradient(145deg, rgba(83, 204, 196, .08), rgba(10, 23, 39, .5));
    border: 1px solid var(--border-color);
    border-radius: 1rem;
    display: grid;
    gap: 1rem;
    grid-template-columns: minmax(9rem, .85fr) minmax(13rem, 1.3fr) minmax(9rem, .85fr);
    margin: 1.25rem 0;
    padding: 1.2rem;
}

.ospf-series-page .ospfv3-router {
    align-items: center;
    background: #0d192b;
    border: 1px solid #405469;
    border-radius: .9rem;
    color: #f5f8fb;
    display: flex;
    flex-direction: column;
    gap: .32rem;
    justify-content: center;
    min-height: 9.25rem;
    padding: 1rem .65rem;
    text-align: center;
}

.ospf-series-page .ospfv3-router > span {
    color: #aabccc;
    font-size: .62rem;
    font-weight: 750;
}

.ospf-series-page .ospfv3-router > i { color: var(--primary-color); font-size: 1.35rem; }
.ospf-series-page .ospfv3-router > strong { font-size: 1.05rem; }
.ospf-series-page .ospfv3-router > code { color: var(--primary-color); font-size: .67rem; }
.ospf-series-page .ospfv3-router > small { color: #e6c75a; font-size: .64rem; }

.ospf-series-page .ospfv3-link {
    align-items: center;
    display: flex;
    flex-direction: column;
    gap: .38rem;
    position: relative;
    text-align: center;
}

.ospf-series-page .ospfv3-link::before {
    background: linear-gradient(90deg, var(--primary-color), #e6c75a, var(--primary-color));
    content: '';
    height: 4px;
    left: 0;
    position: absolute;
    right: 0;
    top: calc(50% - 2px);
}

.ospf-series-page .ospfv3-link > * {
    background: #0c2230;
    padding: .08rem .45rem;
    position: relative;
    z-index: 1;
}

.ospf-series-page .ospfv3-link > span { color: var(--primary-color); font-size: .64rem; font-weight: 850; }
.ospf-series-page .ospfv3-link > strong { border: 1px solid rgba(83, 204, 196, .55); border-radius: 999px; color: #f5f8fb; font-size: .77rem; padding: .48rem .72rem; }
.ospf-series-page .ospfv3-link > small { color: #aabccc; font-size: .61rem; }

.ospf-series-page .ospfv3-map figcaption {
    color: var(--text-secondary);
    font-size: .78rem;
    grid-column: 1 / -1;
    line-height: 1.55;
    text-align: center;
}

@media (max-width: 1200px) {
    /* The base layout moves every sidebar above the article on narrow screens.
       Lesson pages should always open on the lesson itself; supporting cards
       and the on-page menu belong after the article when the grid collapses. */
    .ospf-series-page .rip-page-container > .main-content {
        order: 1;
    }

    .ospf-series-page .rip-page-container > .sidebar {
        order: 2;
    }

    .ospf-series-page .sidebar > .content-card:has(.rip-side-menu) {
        max-height: none;
        position: static !important;
    }

    .ospf-series-page .rip-side-menu {
        overflow: visible;
    }
}

@media (max-width: 640px) {
    .ospf-lesson-pagination { flex-direction: column; }
    .ospf-lesson-pagination__card { flex-basis: auto; min-height: 5.25rem; width: 100%; }
}

@media (max-width: 900px) {
    .ospf-series-page .ospf-process-track { grid-template-columns: 1fr; }
    .ospf-series-page .ospf-process-track--three { grid-template-columns: 1fr; }
    .ospf-series-page .ospf-process-step { min-height: 0; }
    .ospf-series-page .ospf-process-step:not(:last-child)::after {
        bottom: -.88rem;
        content: '\f063';
        left: calc(50% - .72rem);
        right: auto;
        top: auto;
    }
    .ospf-series-page .ospf-cli-grid { grid-template-columns: 1fr; }
    .ospf-series-page .ospf-path-row {
        grid-template-columns: 1fr;
        text-align: center;
    }
    .ospf-series-page .ospf-path-link::after {
        height: 2.5rem;
        width: 3px;
    }
    .ospf-series-page .ospf-path-total { justify-self: stretch; }
    .ospf-series-page .ospf-area-map__zones { grid-template-columns: 1fr; }
    .ospf-series-page .ospf-area-zone__nodes { min-height: 5rem; }
    .ospf-series-page .ospf-election-routers { grid-template-columns: repeat(2, minmax(0, 1fr)); }
    .ospf-series-page .ospf-election-router:nth-child(n+3)::before { display: none; }
    .ospf-series-page .ospf-neighbor-lab { grid-template-columns: 1fr; }
    .ospf-series-page .ospf-neighbor-link { min-height: 5rem; transform: rotate(90deg); }
    .ospf-series-page .ospf-state-path { grid-template-columns: repeat(2, minmax(0, 1fr)); }
    .ospf-series-page .ospf-state-card:not(:last-child)::after { display: none; }
    .ospf-series-page .ospf-stub-map { grid-template-columns: 1fr; }
    .ospf-series-page .ospf-filter-map { grid-template-columns: 1fr; }
    .ospf-series-page .ospf-filter-boundary { min-height: 8rem; }
    .ospf-series-page .ospf-filter-boundary::before { bottom: 0; height: auto; left: calc(50% - 2px); right: auto; top: 0; width: 4px; }
    .ospf-series-page .ospf-virtual-map { grid-template-columns: 1fr; }
    .ospf-series-page .ospf-virtual-zone { min-height: 10rem; }
    .ospf-series-page .ospf-virtual-zone.is-transit { min-height: 8rem; }
    .ospf-series-page .ospf-virtual-tunnel::before,
    .ospf-series-page .ospf-virtual-tunnel::after { display: none; }
    .ospf-series-page .ospf-trouble-map { grid-template-columns: 1fr; }
    .ospf-series-page .ospf-trouble-router { min-height: 7rem; }
    .ospf-series-page .ospf-trouble-link { min-height: 4rem; }
    .ospf-series-page .ospf-trouble-link::before { bottom: -.55rem; height: auto; left: calc(50% - 2px); right: auto; top: -.55rem; width: 4px; }
    .ospf-series-page .ospf-process-track.ospf-trouble-track { grid-template-columns: 1fr; }
    .ospf-series-page .ospf-trouble-track .ospf-process-step { min-height: 0; }
    .ospf-series-page .ospf-stub-abr { justify-self: center; min-height: 6rem; width: min(100%, 16rem); }
    .ospf-series-page .ospf-stub-decisions { grid-template-columns: 1fr; }
    .ospf-series-page .ospf-stub-decisions article { min-height: 0; }
    .ospf-series-page .ospfv3-map { grid-template-columns: 1fr; }
    .ospf-series-page .ospfv3-link { min-height: 6rem; justify-content: center; }
    .ospf-series-page .ospfv3-link::before { bottom: 0; height: auto; left: calc(50% - 2px); right: auto; top: 0; width: 4px; }
}

@media (max-width: 560px) {
    .ospf-series-page .ospf-election-map { padding: .85rem; }
    .ospf-series-page .ospf-election-lan { align-items: flex-start; flex-direction: column; }
    .ospf-series-page .ospf-election-lan::after { display: none; }
    .ospf-series-page .ospf-election-routers { border-top: 0; grid-template-columns: 1fr; padding-top: 0; }
    .ospf-series-page .ospf-election-router::before { display: none; }
    .ospf-series-page .ospf-neighbor-lab { padding: .85rem; }
    .ospf-series-page .ospf-state-path { grid-template-columns: 1fr; }
    .ospf-series-page .ospf-state-card { min-height: 5.5rem; }
    .ospf-series-page .ospf-stub-map { padding: .8rem; }
    .ospf-series-page .ospf-stub-nodes { flex-direction: column; }
    .ospf-series-page .ospf-stub-node { min-height: 4.8rem; width: 100%; }
    .ospf-series-page .ospf-stub-link { flex-basis: 1.4rem; height: 1.4rem; width: 3px; }
    .ospf-series-page .ospfv3-map { padding: .8rem; }
    .ospf-series-page .ospfv3-router { min-height: 7.5rem; }
}

@media (min-width: 769px) {
    .ospf-series-page .header .labs-mega-menu .mega-menu-content:has(.mega-menu-section[data-mega-panel="labs-ospf"].active) {
        overflow-y: auto !important;
        overscroll-behavior: contain;
        scrollbar-color: var(--primary-color) transparent;
        scrollbar-gutter: stable;
        scrollbar-width: thin;
        touch-action: pan-y;
    }

    .ospf-series-page .header .labs-mega-menu .mega-menu-content:has(.mega-menu-section[data-mega-panel="labs-ospf"].active)::-webkit-scrollbar {
        width: .55rem;
    }

    .ospf-series-page .header .labs-mega-menu .mega-menu-content:has(.mega-menu-section[data-mega-panel="labs-ospf"].active)::-webkit-scrollbar-thumb {
        background: var(--primary-color);
        border-radius: 999px;
    }
}
.series-related-learning > p {
    color: var(--text-muted);
    margin-bottom: 1.25rem;
}

.ospf-series-page .lesson-outline-card .toc-list {
    column-gap: 3rem;
    display: grid;
    grid-template-columns: repeat(2, minmax(0, 1fr));
    margin: 0;
    padding-left: 1.3rem;
}

.main-content > .lesson-outline-card .toc-list {
    column-gap: 3rem;
    display: grid;
    grid-template-columns: repeat(2, minmax(0, 1fr));
    margin: 0;
    padding-left: 1.3rem;
}

.ospf-series-page .lesson-outline-card .toc-list li {
    margin: 0;
    padding: .28rem 0;
}

@media (max-width: 760px) {
    .ospf-series-page .lesson-outline-card .toc-list { display: block; }
    .main-content > .lesson-outline-card .toc-list { display: block; }
}

.series-related-grid {
    display: grid;
    gap: 1rem;
    grid-template-columns: repeat(3, minmax(0, 1fr));
}

.series-related-grid > a {
    background: color-mix(in srgb, var(--card-bg, #142238) 88%, var(--primary-color) 12%);
    border: 1px solid var(--border-color);
    border-radius: 16px;
    color: var(--text-color);
    display: flex;
    flex-direction: column;
    min-height: 180px;
    padding: 1.15rem;
    text-decoration: none;
    transition: border-color .2s ease, transform .2s ease;
}

.series-related-grid > a:hover {
    border-color: var(--primary-color);
    transform: translateY(-2px);
}

.series-related-grid strong {
    color: var(--heading-color, var(--text-color));
    font-size: 1rem;
    line-height: 1.35;
}

.series-related-grid span {
    color: var(--text-muted);
    font-size: .82rem;
    line-height: 1.6;
    margin-top: .65rem;
}

.series-related-grid em {
    color: var(--primary-color);
    font-size: .78rem;
    font-style: normal;
    font-weight: 800;
    margin-top: auto;
    padding-top: 1rem;
}

@media (max-width: 760px) {
    .series-related-grid { grid-template-columns: 1fr; }
    .series-related-grid > a { min-height: 0; }
}