/* ==========================================================================
   FatDig University (FDU) — shared styles for the hub + every article.
   Uses the same design tokens as the rest of the site (--fd-blue etc.).
   ========================================================================== */

.fdu-body {
    background: var(--fd-bg, #f5f5f5);
    color: var(--fd-ink, #1a2233);
    font-family: 'Roboto Slab', Georgia, serif;
    margin: 0;
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
    line-height: 1.6;
}

.fdu-mono {
    font-family: 'JetBrains Mono', ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;
}

/* ---------- Top bar ---------------------------------------------------- */
.fdu-topbar {
    background: #fff;
    border-bottom: 1px solid var(--fd-line, #e3e8f0);
    padding: 0.85rem 1.5rem;
    position: sticky;
    top: 0;
    z-index: 50;
    backdrop-filter: saturate(180%) blur(8px);
    background: rgba(255, 255, 255, 0.96);
}
.fdu-topbar__inner {
    max-width: 1200px;
    margin: 0 auto;
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: 1.5rem;
}
.fdu-topbar__brand {
    display: flex;
    align-items: center;
    gap: 0.75rem;
    text-decoration: none !important;
}
.fdu-topbar__tag {
    font-family: 'Open Sans', sans-serif;
    font-weight: 700;
    font-size: 0.7rem;
    letter-spacing: 0.13em;
    text-transform: uppercase;
    color: var(--fd-ink-soft, #51607a);
    padding: 3px 8px;
    border: 1px solid var(--fd-line, #e3e8f0);
    border-radius: 999px;
    white-space: nowrap;
}
.fdu-topbar__nav {
    display: flex;
    gap: 1.25rem;
    font-family: 'Open Sans', sans-serif;
    font-weight: 600;
    font-size: 0.9rem;
}
.fdu-topbar__nav a {
    color: var(--fd-ink-soft, #51607a) !important;
    text-decoration: none !important;
    transition: color .15s ease;
}
.fdu-topbar__nav a:hover { color: var(--fd-blue, #3169bb) !important; }

@media (max-width: 600px) {
    .fdu-topbar__nav { display: none; }
}

/* ---------- HUB page --------------------------------------------------- */
.fdu-hub {
    max-width: 1200px;
    margin: 0 auto;
    padding: 3rem 1.5rem 4rem;
}

.fdu-hero {
    display: grid;
    grid-template-columns: 1fr;
    gap: 2rem;
    align-items: center;
    padding: 3rem 0;
    border-bottom: 1px solid var(--fd-line);
    margin-bottom: 3rem;
}
@media (min-width: 900px) {
    .fdu-hero { grid-template-columns: 1.4fr 1fr; gap: 3rem; }
}
.fdu-hero__title {
    font-family: 'Open Sans', sans-serif;
    font-weight: 800;
    font-size: clamp(2.2rem, 4.5vw, 3.4rem);
    color: var(--fd-ink);
    line-height: 1.1;
    margin: 0 0 1rem;
    letter-spacing: -0.015em;
}
.fdu-hero__lead {
    font-size: 1.15rem;
    color: var(--fd-ink-soft);
    line-height: 1.55;
    margin: 0 0 1.5rem;
}
.fdu-hero__graphic {
    display: flex;
    justify-content: center;
    align-items: center;
}
.fdu-hero__graphic svg { width: 100%; max-width: 380px; height: auto; }
.fdu-hero__eyebrow {
    display: inline-block;
    font-family: 'Open Sans', sans-serif;
    font-weight: 700;
    font-size: 0.78rem;
    letter-spacing: 0.16em;
    text-transform: uppercase;
    color: var(--fd-blue);
    margin-bottom: 0.75rem;
}
.fdu-stats {
    display: flex;
    flex-wrap: wrap;
    gap: 2rem;
    margin-top: 1rem;
}
.fdu-stat__num {
    display: block;
    font-family: 'Open Sans', sans-serif;
    font-weight: 800;
    font-size: 2rem;
    color: var(--fd-blue);
    line-height: 1;
}
.fdu-stat__label {
    font-family: 'Open Sans', sans-serif;
    font-size: 0.75rem;
    color: var(--fd-ink-soft);
    text-transform: uppercase;
    letter-spacing: 0.12em;
    margin-top: 0.25rem;
}

/* Hub section heading */
.fdu-section {
    margin: 3rem 0;
}
.fdu-section__head {
    text-align: center;
    max-width: 700px;
    margin: 0 auto 2.5rem;
}
.fdu-section__eyebrow {
    display: inline-block;
    font-family: 'Open Sans', sans-serif;
    font-weight: 700;
    font-size: 0.75rem;
    letter-spacing: 0.16em;
    text-transform: uppercase;
    color: var(--fd-blue);
    margin-bottom: 0.5rem;
}
.fdu-section__title {
    font-family: 'Open Sans', sans-serif;
    font-weight: 800;
    font-size: clamp(1.6rem, 3vw, 2.1rem);
    color: var(--fd-ink);
    margin: 0 0 0.75rem;
    line-height: 1.2;
}
.fdu-section__lead {
    color: var(--fd-ink-soft);
    font-size: 1.05rem;
    margin: 0;
}

/* Topic-area grid on hub */
.fdu-topics {
    display: grid;
    grid-template-columns: 1fr;
    gap: 1.25rem;
}
@media (min-width: 700px) { .fdu-topics { grid-template-columns: 1fr 1fr; } }
.fdu-topic {
    background: #fff;
    border: 1px solid var(--fd-line);
    border-radius: 14px;
    padding: 1.75rem;
    display: flex;
    gap: 1.25rem;
}
.fdu-topic__icon {
    flex: 0 0 56px;
    width: 56px;
    height: 56px;
    background: var(--fd-blue-50, #eaf1fb);
    border-radius: 12px;
    display: flex;
    align-items: center;
    justify-content: center;
}
.fdu-topic__icon svg { width: 32px; height: 32px; }
.fdu-topic__title {
    font-family: 'Open Sans', sans-serif;
    font-weight: 700;
    font-size: 1.15rem;
    color: var(--fd-ink);
    margin: 0 0 0.4rem;
}
.fdu-topic__body {
    color: var(--fd-ink-soft);
    font-size: 0.95rem;
    line-height: 1.55;
    margin: 0 0 0.75rem;
}
.fdu-topic__articles {
    list-style: none;
    padding: 0;
    margin: 0;
    font-size: 0.9rem;
}
.fdu-topic__articles li { margin: 0.25rem 0; }
.fdu-topic__articles a {
    color: var(--fd-blue) !important;
    text-decoration: none !important;
}
.fdu-topic__articles a:hover { text-decoration: underline !important; }
.fdu-topic__articles .soon {
    font-family: 'Open Sans', sans-serif;
    font-weight: 600;
    font-size: 0.65rem;
    letter-spacing: 0.1em;
    text-transform: uppercase;
    color: var(--fd-ink-soft);
    background: var(--fd-line);
    padding: 1px 7px;
    border-radius: 999px;
    margin-left: 0.5rem;
}

/* Featured article grid (4-up) */
.fdu-featured {
    display: grid;
    grid-template-columns: 1fr;
    gap: 1.25rem;
}
@media (min-width: 600px) { .fdu-featured { grid-template-columns: 1fr 1fr; } }
@media (min-width: 992px) { .fdu-featured { grid-template-columns: repeat(4, 1fr); } }
.fdu-card {
    background: #fff;
    border: 1px solid var(--fd-line);
    border-radius: 14px;
    padding: 1.5rem 1.25rem 1.25rem;
    display: flex;
    flex-direction: column;
    text-decoration: none !important;
    color: inherit !important;
    transition: transform .18s ease, box-shadow .18s ease, border-color .18s ease;
}
.fdu-card:hover {
    transform: translateY(-3px);
    box-shadow: 0 10px 24px -12px rgba(49, 105, 187, 0.25);
    border-color: var(--fd-blue);
}
.fdu-card__icon {
    width: 44px;
    height: 44px;
    background: var(--fd-blue-50);
    border-radius: 10px;
    display: flex;
    align-items: center;
    justify-content: center;
    margin-bottom: 1rem;
}
.fdu-card__icon svg { width: 28px; height: 28px; }
.fdu-card__category {
    font-family: 'Open Sans', sans-serif;
    font-weight: 700;
    font-size: 0.62rem;
    letter-spacing: 0.14em;
    text-transform: uppercase;
    color: var(--fd-blue);
    margin-bottom: 0.4rem;
}
.fdu-card__title {
    font-family: 'Open Sans', sans-serif;
    font-weight: 700;
    font-size: 1rem;
    color: var(--fd-ink);
    line-height: 1.3;
    margin: 0 0 0.5rem;
}
.fdu-card__body {
    font-size: 0.88rem;
    color: var(--fd-ink-soft);
    line-height: 1.5;
    margin: 0 0 0.85rem;
    flex: 1;
}
.fdu-card__meta {
    font-family: 'Open Sans', sans-serif;
    font-size: 0.72rem;
    color: var(--fd-ink-soft);
    border-top: 1px solid var(--fd-line);
    padding-top: 0.5rem;
    display: flex;
    justify-content: space-between;
}

/* Banner: "Why FDU exists" */
.fdu-banner {
    background: linear-gradient(135deg, var(--fd-blue, #3169bb) 0%, var(--fd-blue-dark, #234c8a) 100%);
    color: #fff;
    border-radius: 16px;
    padding: 2.5rem 2rem;
    display: grid;
    gap: 1.5rem;
    align-items: center;
    margin: 3rem 0;
    grid-template-columns: 1fr;
}
@media (min-width: 800px) { .fdu-banner { grid-template-columns: 1fr auto; gap: 2.5rem; } }
.fdu-banner__title {
    font-family: 'Open Sans', sans-serif;
    font-weight: 800;
    font-size: clamp(1.4rem, 2.3vw, 1.9rem);
    color: #fff;
    margin: 0 0 0.5rem;
}
.fdu-banner__body {
    color: rgba(255, 255, 255, 0.88);
    margin: 0;
    font-size: 1rem;
    line-height: 1.55;
    max-width: 60ch;
}
.fdu-banner__btn {
    display: inline-flex;
    align-items: center;
    background: #fff;
    color: var(--fd-blue) !important;
    font-family: 'Open Sans', sans-serif;
    font-weight: 700;
    padding: 0.85rem 1.5rem;
    border-radius: 999px;
    text-decoration: none !important;
    white-space: nowrap;
    transition: transform .18s ease, box-shadow .18s ease;
}
.fdu-banner__btn:hover {
    transform: translateY(-2px);
    box-shadow: 0 14px 28px -10px rgba(0, 0, 0, 0.35);
}

/* ---------- ARTICLE pages --------------------------------------------- */
.fdu-article {
    max-width: 760px;
    margin: 0 auto;
    padding: 2.5rem 1.5rem 4rem;
}
.fdu-article__breadcrumb {
    font-family: 'Open Sans', sans-serif;
    font-size: 0.8rem;
    color: var(--fd-ink-soft);
    margin-bottom: 1rem;
}
.fdu-article__breadcrumb a {
    color: var(--fd-blue) !important;
    text-decoration: none !important;
}
.fdu-article__breadcrumb a:hover { text-decoration: underline !important; }
.fdu-article__category {
    display: inline-block;
    font-family: 'Open Sans', sans-serif;
    font-weight: 700;
    font-size: 0.72rem;
    letter-spacing: 0.14em;
    text-transform: uppercase;
    color: var(--fd-blue);
    background: var(--fd-blue-50);
    padding: 4px 12px;
    border-radius: 999px;
    margin-bottom: 1rem;
}
.fdu-article__title {
    font-family: 'Open Sans', sans-serif;
    font-weight: 800;
    font-size: clamp(2rem, 4vw, 3rem);
    color: var(--fd-ink);
    line-height: 1.1;
    margin: 0 0 1rem;
    letter-spacing: -0.015em;
}
.fdu-article__lead {
    font-family: 'Roboto Slab', serif;
    font-size: 1.2rem;
    color: var(--fd-ink-soft);
    line-height: 1.55;
    margin: 0 0 1rem;
}
.fdu-article__meta {
    font-family: 'Open Sans', sans-serif;
    font-size: 0.85rem;
    color: var(--fd-ink-soft);
    margin: 0 0 2rem;
    padding-bottom: 1.5rem;
    border-bottom: 1px solid var(--fd-line);
    display: flex;
    gap: 1.5rem;
    flex-wrap: wrap;
}
.fdu-article__meta strong { color: var(--fd-ink); }

/* Summary box at top */
.fdu-tldr {
    background: var(--fd-blue-50);
    border-left: 4px solid var(--fd-blue);
    border-radius: 8px;
    padding: 1.25rem 1.5rem;
    margin: 1.5rem 0 2.5rem;
}
.fdu-tldr__label {
    font-family: 'Open Sans', sans-serif;
    font-weight: 800;
    font-size: 0.75rem;
    text-transform: uppercase;
    letter-spacing: 0.14em;
    color: var(--fd-blue);
    margin-bottom: 0.5rem;
}
.fdu-tldr__body {
    color: var(--fd-ink);
    margin: 0;
    font-size: 1.02rem;
    line-height: 1.55;
}

/* Article body typography */
.fdu-article h2 {
    font-family: 'Open Sans', sans-serif;
    font-weight: 700;
    font-size: 1.55rem;
    color: var(--fd-ink);
    margin: 3rem 0 1rem;
    line-height: 1.25;
    letter-spacing: -0.005em;
}
.fdu-article h3 {
    font-family: 'Open Sans', sans-serif;
    font-weight: 700;
    font-size: 1.2rem;
    color: var(--fd-ink);
    margin: 2rem 0 0.75rem;
    line-height: 1.3;
}
.fdu-article p {
    color: var(--fd-ink);
    font-size: 1.05rem;
    line-height: 1.7;
    margin: 0 0 1.25rem;
}
.fdu-article ul,
.fdu-article ol {
    color: var(--fd-ink);
    font-size: 1.02rem;
    line-height: 1.65;
    padding-left: 1.4rem;
    margin: 0 0 1.5rem;
}
.fdu-article li { margin-bottom: 0.5rem; }
.fdu-article a {
    color: var(--fd-blue) !important;
    text-decoration: underline;
    text-decoration-color: rgba(49, 105, 187, 0.3);
    text-underline-offset: 3px;
    transition: text-decoration-color .15s ease;
}
.fdu-article a:hover { text-decoration-color: var(--fd-blue); }

.fdu-article code {
    font-family: 'JetBrains Mono', ui-monospace, monospace;
    font-size: 0.88em;
    background: var(--fd-blue-50);
    color: var(--fd-blue-dark);
    padding: 1px 7px;
    border-radius: 5px;
    word-break: break-word;
}
.fdu-article pre {
    font-family: 'JetBrains Mono', ui-monospace, monospace;
    font-size: 0.85rem;
    line-height: 1.55;
    background: #fafbfc;
    border: 1px solid var(--fd-line);
    border-radius: 10px;
    padding: 1rem 1.2rem;
    margin: 1rem 0 1.5rem;
    overflow-x: auto;
    white-space: pre;
    color: var(--fd-ink);
}
.fdu-article pre code {
    background: transparent;
    color: inherit;
    padding: 0;
    font-size: 1em;
}

/* Callout boxes */
.fdu-callout,
.fdu-warning,
.fdu-tryit {
    border-radius: 10px;
    padding: 1.1rem 1.3rem;
    margin: 1.5rem 0;
    display: flex;
    gap: 0.85rem;
    align-items: flex-start;
}
.fdu-callout {
    background: #f0f7ff;
    border-left: 4px solid var(--fd-blue);
}
.fdu-warning {
    background: #fef3c7;
    border-left: 4px solid #d97706;
}
.fdu-tryit {
    background: #dcfce7;
    border-left: 4px solid #16a34a;
}
.fdu-callout__icon,
.fdu-warning__icon,
.fdu-tryit__icon {
    flex-shrink: 0;
    width: 22px;
    height: 22px;
    margin-top: 2px;
}
.fdu-callout__body,
.fdu-warning__body,
.fdu-tryit__body {
    font-size: 0.96rem;
    line-height: 1.55;
    color: var(--fd-ink);
    margin: 0;
}
.fdu-callout__body strong,
.fdu-warning__body strong,
.fdu-tryit__body strong {
    color: var(--fd-ink);
}
.fdu-tryit__body a {
    font-weight: 700;
}

/* Inline diagrams */
.fdu-diagram {
    margin: 2rem 0;
    text-align: center;
    background: #fafbfc;
    border: 1px solid var(--fd-line);
    border-radius: 12px;
    padding: 1.5rem;
}
.fdu-diagram svg {
    max-width: 100%;
    height: auto;
}
.fdu-diagram__caption {
    font-family: 'Open Sans', sans-serif;
    font-size: 0.82rem;
    color: var(--fd-ink-soft);
    margin: 0.85rem 0 0;
}

/* Annotated table */
.fdu-table {
    width: 100%;
    border-collapse: collapse;
    margin: 1.5rem 0;
    font-size: 0.95rem;
}
.fdu-table th {
    text-align: left;
    background: #fafbfc;
    font-family: 'Open Sans', sans-serif;
    font-weight: 700;
    font-size: 0.78rem;
    color: var(--fd-ink-soft);
    text-transform: uppercase;
    letter-spacing: 0.1em;
    padding: 0.75rem 1rem;
    border-bottom: 1px solid var(--fd-line);
}
.fdu-table td {
    padding: 0.85rem 1rem;
    border-bottom: 1px solid var(--fd-line);
    vertical-align: top;
    color: var(--fd-ink);
}
.fdu-table tr:last-child td { border-bottom: none; }
.fdu-table code {
    background: var(--fd-blue-50);
    color: var(--fd-blue-dark);
    font-size: 0.82rem;
    padding: 1px 6px;
    border-radius: 4px;
    white-space: nowrap;
}

/* Footer / next article navigation */
.fdu-article__footer {
    margin-top: 4rem;
    padding-top: 2rem;
    border-top: 1px solid var(--fd-line);
}
.fdu-next {
    background: #fff;
    border: 1px solid var(--fd-line);
    border-radius: 14px;
    padding: 1.5rem;
    display: flex;
    justify-content: space-between;
    align-items: center;
    gap: 1.5rem;
    text-decoration: none !important;
    color: inherit !important;
    transition: transform .18s ease, box-shadow .18s ease, border-color .18s ease;
}
.fdu-next:hover {
    transform: translateY(-2px);
    box-shadow: 0 10px 24px -12px rgba(49, 105, 187, 0.25);
    border-color: var(--fd-blue);
}
.fdu-next__label {
    font-family: 'Open Sans', sans-serif;
    font-size: 0.72rem;
    letter-spacing: 0.14em;
    text-transform: uppercase;
    color: var(--fd-ink-soft);
    margin: 0 0 0.3rem;
    font-weight: 700;
}
.fdu-next__title {
    font-family: 'Open Sans', sans-serif;
    font-weight: 700;
    font-size: 1.05rem;
    color: var(--fd-ink);
    margin: 0;
}
.fdu-next__arrow {
    font-size: 1.5rem;
    color: var(--fd-blue);
    font-weight: 700;
}

/* Site footer */
.fdu-footer {
    border-top: 1px solid var(--fd-line);
    padding: 1.25rem 0;
    text-align: center;
    color: var(--fd-ink-soft);
    background: #fff;
    font-family: 'Open Sans', sans-serif;
    font-size: 0.85rem;
}
.fdu-footer a {
    color: var(--fd-blue) !important;
    text-decoration: none !important;
}
.fdu-footer a:hover { text-decoration: underline !important; }