/* ============================================================
   DESIGN TOKENS
   ============================================================ */
:root {
  /* Backgrounds */
  --bg:          #F8FAFC;
  --surface:     #FFFFFF;
  --surface-2:   #F1F5F9;
  --surface-3:   #E2E8F0;

  /* Text */
  --text:        #0F172A;
  --text-2:      #334155;
  --muted:       #64748B;

  /* Borders */
  --border:      #E2E8F0;
  --border-2:    #94A3B8;

  /* Accent — Primary */
  --violet:      #1E3A8A;
  --violet-mid:  #1D4ED8;
  --violet-pale: #EFF6FF;
  --violet-tag:  #BFDBFE;

  /* Accent — Teal (secondary) */
  --teal:        #0F766E;
  --teal-pale:   #ECFDF5;
  --teal-tag:    #A7F3D0;

  /* Accent — Blue (tertiary) */
  --blue:        #2563EB;
  --blue-pale:   #F0F9FF;
  --blue-tag:    #BFDBFE;

  /* Accent — Amber */
  --amber:       #92400E;
  --amber-pale:  #FFFBEB;
  --amber-tag:   #FDE68A;

  /* Shadows */
  --shadow-sm:   0 1px 2px rgba(15,23,42,0.04);
  --shadow-md:   0 10px 24px rgba(15,23,42,0.08);
  --shadow-lg:   0 18px 42px rgba(15,23,42,0.10);
  --shadow-hover:0 16px 36px rgba(15,23,42,0.12);

  /* Shape */
  --radius:      10px;
  --radius-sm:   8px;
  --radius-xs:   4px;

  /* Typography */
  --font: "Inter", ui-sans-serif, system-ui, -apple-system, "Segoe UI", Roboto, sans-serif;
  --font-mono: "JetBrains Mono", "Fira Code", ui-monospace, monospace;

  /* Layout */
  --max-w: 1160px;
}

/* ============================================================
   RESET & BASE
   ============================================================ */
*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }
html { scroll-behavior: smooth; }
body {
  font-family: var(--font);
  font-size: 15px;
  line-height: 1.65;
  background: var(--bg);
  color: var(--text);
  -webkit-font-smoothing: antialiased;
  min-height: 100vh;
  display: flex;
  flex-direction: column;
}
img { max-width: 100%; display: block; }
a { color: var(--violet-mid); text-decoration: none; transition: color 0.15s; }
a:hover { color: var(--violet); text-decoration: underline; }
strong { color: var(--text); }

/* ============================================================
   LAYOUT UTILITIES
   ============================================================ */
.container {
  width: min(var(--max-w), calc(100% - 40px));
  margin: 0 auto;
}
.main { flex: 1; padding-bottom: 56px; }

/* ============================================================
   TOPBAR
   ============================================================ */
.topbar {
  position: sticky;
  top: 0;
  z-index: 100;
  background: rgba(255,255,255,0.94);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  border-bottom: 1px solid var(--border);
}
.topbar__inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 12px 0;
  gap: 16px;
}
.brand {
  font-weight: 700;
  font-size: 14px;
  letter-spacing: 0;
  color: var(--text);
  display: flex;
  align-items: center;
  gap: 8px;
  white-space: nowrap;
}
.brand:hover { color: var(--violet-mid); text-decoration: none; }
.brand-dot {
  width: 9px; height: 9px; border-radius: 2px;
  background: var(--violet);
  box-shadow: none;
  flex-shrink: 0;
}
.nav {
  display: flex;
  align-items: center;
  gap: 4px;
  flex-wrap: wrap;
}
.nav a {
  padding: 6px 10px;
  border-radius: var(--radius-xs);
  font-size: 13px;
  font-weight: 500;
  color: var(--text-2);
  transition: background 0.15s, color 0.15s;
}
.nav a:hover { background: var(--surface-2); color: var(--text); text-decoration: none; }
.nav a.active { background: var(--text); color: #fff; font-weight: 700; }

/* ============================================================
   BREADCRUMB
   ============================================================ */
.breadcrumb {
  display: flex;
  align-items: center;
  gap: 6px;
  font-size: 13px;
  color: var(--muted);
  padding: 12px 0 0;
  flex-wrap: wrap;
}
.breadcrumb a { color: var(--muted); font-weight: 500; }
.breadcrumb a:hover { color: var(--violet-mid); text-decoration: none; }
.breadcrumb span { color: var(--border-2); }

/* ============================================================
   HERO
   ============================================================ */
.hero {
  padding: 46px 0 34px;
}
.hero--run {
  padding: 36px 0 32px;
  border-bottom: 1px solid var(--border);
  margin-bottom: 32px;
}
.hero__eyebrow {
  font-size: 12px;
  font-weight: 600;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--muted);
  margin-bottom: 12px;
}
.hero__title {
  font-size: 42px;
  font-weight: 800;
  line-height: 1.08;
  letter-spacing: 0;
  color: var(--text);
  margin-bottom: 14px;
}
.hero__title em {
  font-style: normal;
  color: var(--blue);
}
.hero__subtitle {
  font-size: 16px;
  color: var(--text-2);
  max-width: 64ch;
  line-height: 1.7;
  margin-bottom: 22px;
}
.hero__bg {
  position: relative;
}
.hero__bg::before {
  content: none;
}

/* ============================================================
   BADGES / TAGS
   ============================================================ */
.badges { display: flex; flex-wrap: wrap; gap: 8px; margin-bottom: 16px; }
.badge {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  padding: 5px 10px;
  border-radius: 999px;
  font-size: 12px;
  font-weight: 700;
  letter-spacing: 0.01em;
  border: 1px solid transparent;
}
.badge--violet  { background: var(--violet-pale); color: var(--violet-mid); border-color: var(--violet-tag); }
.badge--teal    { background: var(--teal-pale); color: var(--teal); border-color: var(--teal-tag); }
.badge--blue    { background: var(--blue-pale); color: var(--blue); border-color: var(--blue-tag); }
.badge--amber   { background: var(--amber-pale); color: var(--amber); border-color: var(--amber-tag); }
.badge--muted   { background: var(--surface-2); color: var(--muted); border-color: var(--border); }

.tag {
  display: inline-flex;
  align-items: center;
  padding: 2px 8px;
  border-radius: var(--radius-xs);
  font-size: 11px;
  font-weight: 700;
  letter-spacing: 0.03em;
  text-transform: uppercase;
}
.tag--violet  { background: var(--violet-pale); color: var(--violet-mid); }
.tag--teal    { background: var(--teal-pale); color: var(--teal); }
.tag--blue    { background: var(--blue-pale); color: var(--blue); }
.tag--amber   { background: var(--amber-pale); color: var(--amber); }
.tag--muted   { background: var(--surface-2); color: var(--muted); }

.dot {
  width: 7px; height: 7px; border-radius: 50%;
  flex-shrink: 0;
}
.dot--violet { background: var(--violet-mid); }
.dot--teal   { background: var(--teal); }
.dot--blue   { background: var(--blue); }
.dot--muted  { background: var(--muted); }

/* ============================================================
   STATS ROW
   ============================================================ */
.stats {
  display: flex;
  flex-wrap: wrap;
  gap: 0;
  border: 1px solid var(--border);
  border-radius: var(--radius);
  background: var(--surface);
  overflow: hidden;
  box-shadow: none;
  margin-bottom: 40px;
}
.stat {
  flex: 1;
  min-width: 120px;
  padding: 18px 22px;
  border-right: 1px solid var(--border);
  text-align: center;
}
.stat:last-child { border-right: none; }
.stat__num {
  font-size: 28px;
  font-weight: 800;
  letter-spacing: -1px;
  color: var(--text);
  line-height: 1;
  margin-bottom: 4px;
}
.stat__label {
  font-size: 12px;
  font-weight: 600;
  color: var(--muted);
  text-transform: uppercase;
  letter-spacing: 0.06em;
}

.course-strip {
  background: #F8FBFF;
  color: var(--text);
  border: 1px solid var(--blue-tag);
  border-radius: var(--radius);
  padding: 18px 20px;
  margin: -18px 0 36px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 18px;
}
.course-strip .card__number { color: var(--blue); margin-bottom: 4px; }
.course-strip__title {
  font-size: 18px;
  font-weight: 800;
  letter-spacing: 0;
}
.course-strip__desc {
  color: var(--text-2);
  font-size: 13.5px;
  margin-top: 2px;
}
.course-strip .btn--primary {
  background: var(--text);
  color: #fff;
  border-color: var(--text);
}
.course-strip .btn--primary:hover {
  background: #020617;
  color: #fff;
}

.unit-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(260px, 1fr));
  gap: 14px;
  margin-bottom: 42px;
}
.unit-card {
  background: var(--surface);
  border: 1px solid var(--border);
  border-left: 4px solid var(--border-2);
  border-radius: var(--radius);
  padding: 18px 18px 16px;
}
.unit-card__title {
  font-size: 15px;
  font-weight: 800;
  color: var(--text);
  margin-bottom: 5px;
}
.unit-card__meta {
  font-size: 13px;
  color: var(--text-2);
  line-height: 1.5;
  min-height: 58px;
}
.unit-card__actions {
  display: flex;
  flex-wrap: wrap;
  gap: 7px;
  margin-top: 14px;
}

/* ============================================================
   GRID & CARDS
   ============================================================ */
.grid {
  display: grid;
  gap: 18px;
}
.grid--3 { grid-template-columns: repeat(3, 1fr); }
.grid--2 { grid-template-columns: repeat(2, 1fr); }
.grid--4 { grid-template-columns: repeat(4, 1fr); }
.grid--auto { grid-template-columns: repeat(auto-fill, minmax(300px, 1fr)); }

.card {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 22px 24px;
  box-shadow: none;
  transition: box-shadow 0.2s, border-color 0.2s, background 0.2s;
}
.card:hover {
  box-shadow: var(--shadow-sm);
  border-color: var(--border-2);
}
.card--link { cursor: pointer; }
.card--link a.card-link {
  display: block;
  color: inherit;
  text-decoration: none;
}
.card__icon {
  width: 44px; height: 44px;
  border-radius: var(--radius-sm);
  background: var(--surface-2);
  display: flex; align-items: center; justify-content: center;
  margin-bottom: 16px;
  font-size: 12px;
  font-weight: 800;
  color: var(--violet-mid);
  letter-spacing: 0.04em;
  text-transform: uppercase;
}
.card__icon--teal { background: var(--teal-pale); color: var(--teal); }
.card__icon--blue { background: var(--blue-pale); color: var(--blue); }
.card__icon--amber { background: var(--amber-pale); color: var(--amber); }
.card__number {
  font-size: 11px;
  font-weight: 700;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--muted);
  margin-bottom: 6px;
}
.card__title {
  font-size: 16px;
  font-weight: 700;
  color: var(--text);
  letter-spacing: -0.3px;
  margin-bottom: 6px;
}
.card__desc {
  font-size: 13.5px;
  color: var(--text-2);
  line-height: 1.6;
  margin-bottom: 14px;
}
.card__tags { display: flex; flex-wrap: wrap; gap: 6px; margin-top: 12px; }
.card__footer {
  margin-top: 16px;
  padding-top: 14px;
  border-top: 1px solid var(--border);
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 8px;
}
.card__links { display: flex; flex-wrap: wrap; gap: 8px; }
.card h3 {
  font-size: 15px;
  font-weight: 700;
  color: var(--text);
  letter-spacing: -0.2px;
  margin-bottom: 12px;
}
.card ul { list-style: none; padding: 0; margin: 0; }
.card li { padding: 5px 0; border-bottom: 1px solid var(--border); }
.card li:last-child { border-bottom: none; }
.card li a {
  font-size: 14px;
  font-weight: 500;
  color: var(--text-2);
  display: flex;
  align-items: center;
  gap: 8px;
}
.card li a:hover { color: var(--violet-mid); text-decoration: none; }

/* Featured card (large) */
.card--featured {
  background: var(--surface);
  border-color: var(--border-2);
}

/* Run card (on homepage) */
.run-card {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 28px 28px 22px;
  box-shadow: none;
  display: flex;
  flex-direction: column;
  gap: 0;
  transition: box-shadow 0.2s, border-color 0.2s;
  text-decoration: none;
  color: inherit;
}
.run-card:hover {
  box-shadow: var(--shadow-md);
  border-color: var(--border-2);
  text-decoration: none;
}
.run-card__meta {
  display: flex;
  justify-content: space-between;
  align-items: flex-start;
  margin-bottom: 14px;
}
.run-card__title {
  font-size: 20px;
  font-weight: 800;
  color: var(--text);
  letter-spacing: -0.4px;
  margin-bottom: 6px;
}
.run-card__desc {
  font-size: 14px;
  color: var(--text-2);
  line-height: 1.6;
  margin-bottom: 18px;
}
.run-card__footer {
  margin-top: auto;
  display: flex;
  align-items: center;
  justify-content: space-between;
  font-size: 13px;
  color: var(--muted);
}
.run-card__arrow {
  color: var(--violet-mid);
  font-size: 18px;
  transition: transform 0.2s;
}
.run-card:hover .run-card__arrow { transform: translateX(4px); }

/* ============================================================
   SECTION HEADERS
   ============================================================ */
.section-header {
  margin-bottom: 20px;
  display: flex;
  align-items: baseline;
  gap: 12px;
}
.section-header h2 {
  font-size: 20px;
  font-weight: 800;
  letter-spacing: -0.4px;
  color: var(--text);
}
.section-header .section-count {
  font-size: 13px;
  font-weight: 600;
  color: var(--muted);
}

.section-divider {
  height: 1px;
  background: var(--border);
  margin: 40px 0;
}

/* ============================================================
   SLIDE ROWS (tabla de clases)
   ============================================================ */
.slides-list {
  display: flex;
  flex-direction: column;
  gap: 14px;
}
.slide-row {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 20px 24px;
  display: grid;
  grid-template-columns: 56px 1fr auto;
  gap: 20px;
  align-items: start;
  box-shadow: none;
  transition: box-shadow 0.2s, border-color 0.2s;
}
.slide-row:hover {
  box-shadow: var(--shadow-sm);
  border-color: var(--border-2);
}
.slide-row__num {
  width: 48px; height: 48px;
  background: var(--violet-pale);
  border-radius: var(--radius-sm);
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 15px;
  font-weight: 800;
  color: var(--violet-mid);
  flex-shrink: 0;
}
.slide-row__body {}
.slide-row__title {
  font-size: 16px;
  font-weight: 700;
  color: var(--text);
  letter-spacing: -0.2px;
  margin-bottom: 4px;
}
.slide-row__desc {
  font-size: 13.5px;
  color: var(--text-2);
  line-height: 1.55;
  margin-bottom: 10px;
}
.slide-row__actions {
  display: flex;
  flex-direction: column;
  gap: 8px;
  align-items: flex-end;
  flex-shrink: 0;
}

.resource-section {
  margin-top: 32px;
}
.resource-section__header {
  display: flex;
  align-items: flex-end;
  justify-content: space-between;
  gap: 16px;
  margin-bottom: 14px;
}
.resource-section__title {
  font-size: 18px;
  font-weight: 800;
  color: var(--text);
}
.resource-section__meta {
  font-size: 13px;
  color: var(--muted);
}
.material-grid {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 14px;
}
.pdf-grid {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 18px;
}
.pdf-card {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  box-shadow: none;
  overflow: hidden;
}
.pdf-card__header {
  min-height: 132px;
  padding: 20px 20px 14px;
  display: flex;
  align-items: flex-start;
  justify-content: space-between;
  gap: 16px;
  border-bottom: 1px solid var(--border);
}
.pdf-card__title {
  font-size: 17px;
  font-weight: 800;
  color: var(--text);
  line-height: 1.25;
  margin: 4px 0 7px;
}
.pdf-card__desc {
  font-size: 13.5px;
  color: var(--text-2);
  line-height: 1.55;
  max-width: 58ch;
}
.pdf-frame {
  height: 420px;
  background: #F8FAFC;
  border-bottom: 1px solid var(--border);
}
.pdf-frame iframe {
  width: 100%;
  height: 100%;
  border: 0;
  display: block;
}
.pdf-card__actions {
  padding: 12px 14px;
  display: flex;
  justify-content: flex-end;
  flex-wrap: wrap;
  gap: 8px;
}
.material-card {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 18px 20px;
  box-shadow: none;
}
.material-card__top {
  display: flex;
  align-items: flex-start;
  justify-content: space-between;
  gap: 12px;
  margin-bottom: 8px;
}
.material-card__title {
  font-size: 15px;
  font-weight: 800;
  color: var(--text);
}
.material-card__desc {
  font-size: 13.5px;
  color: var(--text-2);
  line-height: 1.55;
  margin-bottom: 14px;
}
.material-card__actions {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
}

/* ============================================================
   BUTTONS / LINKS
   ============================================================ */
.btn {
  display: inline-flex;
  align-items: center;
  gap: 7px;
  padding: 8px 16px;
  border-radius: var(--radius-sm);
  font-size: 13px;
  font-weight: 600;
  transition: background 0.15s, color 0.15s, border-color 0.15s, box-shadow 0.15s;
  white-space: nowrap;
  text-decoration: none;
  cursor: pointer;
  border: 1px solid transparent;
}
.btn:hover { text-decoration: none; }
.btn--primary {
  background: var(--text);
  color: #fff;
  box-shadow: none;
}
.btn--primary:hover {
  background: #020617;
  color: #fff;
  box-shadow: none;
}
.btn--outline {
  background: var(--surface);
  color: var(--text);
  border: 1px solid var(--border-2);
}
.btn--outline:hover {
  background: var(--surface-2);
  color: var(--text);
}
.btn--ghost {
  background: transparent;
  color: var(--text-2);
  border: 1px solid var(--border);
}
.btn--ghost:hover { background: var(--surface-2); color: var(--text); }
.btn--disabled {
  background: var(--surface-2);
  color: var(--muted);
  border: 1px solid var(--border);
  cursor: default;
  pointer-events: none;
}
.btn--sm { padding: 5px 11px; font-size: 12px; }
.btn--violet { background: var(--violet-mid); color: #fff; box-shadow: none; }
.btn--violet:hover { background: var(--violet); color: #fff; }
.btn--blue { background: var(--blue); color: #fff; box-shadow: none; }
.btn--blue:hover { background: #1d4ed8; color: #fff; }
.btn--teal { background: var(--teal); color: #fff; box-shadow: none; }
.btn--teal:hover { background: #115e59; color: #fff; }

/* ============================================================
   LAB CARDS (detailed)
   ============================================================ */
.lab-card {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 22px 24px;
  box-shadow: none;
  transition: box-shadow 0.2s, border-color 0.2s;
  display: flex;
  flex-direction: column;
  gap: 0;
}
.lab-card:hover {
  box-shadow: var(--shadow-sm);
  border-color: var(--border-2);
}
.lab-card__header {
  display: flex;
  align-items: flex-start;
  gap: 14px;
  margin-bottom: 12px;
}
.lab-card__num {
  width: 40px; height: 40px;
  border-radius: var(--radius-sm);
  background: var(--blue-pale);
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 13px;
  font-weight: 800;
  color: var(--blue);
  flex-shrink: 0;
}
.lab-card__meta { flex: 1; }
.lab-card__title {
  font-size: 15px;
  font-weight: 700;
  color: var(--text);
  letter-spacing: -0.2px;
  margin-bottom: 3px;
}
.lab-card__subtitle {
  font-size: 12px;
  color: var(--muted);
  font-weight: 500;
}
.lab-card__desc {
  font-size: 13.5px;
  color: var(--text-2);
  line-height: 1.6;
  margin-bottom: 14px;
  flex: 1;
}
.lab-card__footer {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 8px;
  padding-top: 12px;
  border-top: 1px solid var(--border);
}

/* ============================================================
   RECURSO CARDS
   ============================================================ */
.recurso-card {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 28px;
  box-shadow: none;
  transition: box-shadow 0.2s, border-color 0.2s;
  display: flex;
  flex-direction: column;
  gap: 16px;
}
.recurso-card:hover {
  box-shadow: var(--shadow-sm);
  border-color: var(--border-2);
}
.recurso-card__icon {
  width: 52px; height: 52px;
  border-radius: var(--radius);
  background: var(--surface-2);
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 13px;
  font-weight: 800;
  color: var(--violet-mid);
  letter-spacing: 0.04em;
  text-transform: uppercase;
  border: 1px solid var(--border);
}
.recurso-card__title {
  font-size: 18px;
  font-weight: 700;
  color: var(--text);
  letter-spacing: -0.3px;
  margin-bottom: 6px;
}
.recurso-card__desc {
  font-size: 14px;
  color: var(--text-2);
  line-height: 1.65;
}
.recurso-card__links { display: flex; flex-wrap: wrap; gap: 10px; }

/* ============================================================
   EMBEDDED TOOLS
   ============================================================ */
.tool-bar {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 14px 0;
  gap: 12px;
  flex-wrap: wrap;
}
.tool-bar__left {
  display: flex;
  align-items: center;
  gap: 10px;
  flex-wrap: wrap;
}
.tool-bar__title {
  margin: 0;
  font-size: 15px;
  font-weight: 800;
  color: var(--text);
}
.tool-frame {
  width: 100%;
  border: 1px solid var(--border);
  border-radius: var(--radius);
  overflow: hidden;
  background: var(--surface);
  height: calc(100vh - 178px);
  min-height: 560px;
}
.tool-frame iframe {
  width: 100%;
  height: 100%;
  border: 0;
  display: block;
}

/* ============================================================
   LITERATURE LIST
   ============================================================ */
.lit-item {
  display: flex;
  gap: 14px;
  padding: 14px 0;
  border-bottom: 1px solid var(--border);
  align-items: flex-start;
}
.lit-item:last-child { border-bottom: none; }
.lit-item__num {
  font-size: 11px;
  font-weight: 700;
  color: var(--muted);
  min-width: 20px;
  padding-top: 2px;
}
.lit-item__body {}
.lit-item__title { font-size: 14px; font-weight: 600; color: var(--text); margin-bottom: 2px; }
.lit-item__authors { font-size: 12.5px; color: var(--muted); }

/* ============================================================
   ABOUT SECTION (homepage)
   ============================================================ */
.about-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 24px;
  margin-top: 16px;
}
.about-item {
  display: flex;
  gap: 14px;
  align-items: flex-start;
}
.about-item__icon {
  width: 40px; height: 40px;
  border-radius: var(--radius-sm);
  background: var(--violet-pale);
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 12px;
  font-weight: 800;
  color: var(--violet-mid);
  letter-spacing: 0.04em;
  text-transform: uppercase;
  flex-shrink: 0;
}
.about-item__title { font-size: 14px; font-weight: 700; color: var(--text); margin-bottom: 4px; }
.about-item__desc { font-size: 13px; color: var(--text-2); line-height: 1.55; }

/* ============================================================
   FOOTER
   ============================================================ */
.footer {
  border-top: 1px solid var(--border);
  background: var(--surface);
  margin-top: auto;
}
.footer__inner {
  padding: 18px 0;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 16px;
  flex-wrap: wrap;
}
.footer__left { font-size: 13px; color: var(--muted); }
.footer__right {
  display: flex;
  gap: 16px;
  font-size: 13px;
  align-items: center;
  flex-wrap: wrap;
  color: var(--muted);
}
.footer__right a { color: var(--muted); font-weight: 500; }
.footer__right a:hover { color: var(--violet-mid); text-decoration: none; }
.footer__link {
  color: var(--text-2);
  font-weight: 700;
  border-bottom: 1px solid transparent;
}
.footer__link:hover {
  color: var(--violet-mid);
  border-bottom-color: var(--violet-tag);
  text-decoration: none;
}

/* ============================================================
   RESPONSIVE
   ============================================================ */
@media (max-width: 900px) {
  .grid--3  { grid-template-columns: 1fr; }
  .grid--2  { grid-template-columns: 1fr; }
  .grid--4  { grid-template-columns: repeat(2, 1fr); }
  .about-grid { grid-template-columns: 1fr; }
  .slide-row { grid-template-columns: 48px 1fr; }
  .slide-row__actions { flex-direction: row; align-items: center; grid-column: 1 / -1; }
  .pdf-grid { grid-template-columns: 1fr; }
  .material-grid { grid-template-columns: 1fr; }
  .course-strip { align-items: flex-start; flex-direction: column; margin-top: -12px; }
  .stats { flex-wrap: wrap; }
  .stat { min-width: 50%; border-right: none; border-bottom: 1px solid var(--border); }
  .stat:last-child, .stat:nth-last-child(2) { border-bottom: none; }
}
@media (max-width: 600px) {
  .grid--4 { grid-template-columns: 1fr; }
  .hero__title { font-size: 30px; }
  .topbar__inner { flex-wrap: wrap; }
  .nav { gap: 2px; }
  .nav a { padding: 5px 8px; font-size: 13px; }
  .container { width: calc(100% - 28px); }
  .resource-section__header { align-items: flex-start; flex-direction: column; }
  .slide-row { grid-template-columns: 1fr; }
  .slide-row__num { width: 40px; height: 40px; }
  .pdf-card__header { min-height: 0; flex-direction: column; }
  .pdf-frame { height: 360px; }
}

/* ============================================================
   UTILITIES
   ============================================================ */
.mt-0 { margin-top: 0; }
.mt-8 { margin-top: 8px; }
.mt-16 { margin-top: 16px; }
.mt-24 { margin-top: 24px; }
.mt-32 { margin-top: 32px; }
.mt-40 { margin-top: 40px; }
.mb-0 { margin-bottom: 0; }
.mb-8 { margin-bottom: 8px; }
.mb-16 { margin-bottom: 16px; }
.mb-24 { margin-bottom: 24px; }
.mb-32 { margin-bottom: 32px; }
.text-muted { color: var(--muted); }
.text-sm { font-size: 13px; }
.font-mono { font-family: var(--font-mono); }
.sr-only { position: absolute; width: 1px; height: 1px; padding: 0; overflow: hidden; clip: rect(0,0,0,0); white-space: nowrap; border: 0; }