/* ============================================
   Andrew Ng ML Course — Landing Page Styles
   Adapted from Frame Innovation study guide
   ============================================ */

/* ── Hero Section ──────────────────────────── */
.hero {
  background: linear-gradient(135deg, #1e3a5f 0%, #0d9488 100%);
  color: #fff;
  text-align: center;
  padding: 80px 24px;
}

.hero__title {
  font-family: Georgia, 'PT Serif', serif;
  font-size: 3rem;
  font-weight: 700;
  line-height: 1.15;
  margin-bottom: 16px;
  color: #fff;
}

.hero__subtitle {
  font-size: 1.35rem;
  font-weight: 400;
  line-height: 1.5;
  margin-bottom: 12px;
  opacity: 0.95;
}

.hero__label {
  font-size: 0.9rem;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  opacity: 0.7;
  margin-bottom: 12px;
}

.hero__author {
  font-size: 1.1rem;
  opacity: 0.85;
  margin-bottom: 8px;
}

.hero__meta {
  font-size: 0.95rem;
  opacity: 0.7;
  margin-bottom: 28px;
}

.hero__actions {
  display: flex;
  flex-direction: row;
  justify-content: center;
  align-items: center;
  gap: 16px;
  flex-wrap: wrap;
}

/* ── Buttons ───────────────────────────────── */
.btn {
  display: inline-block;
  padding: 14px 32px;
  border-radius: 8px;
  font-weight: 600;
  font-size: 1rem;
  text-decoration: none;
  cursor: pointer;
  border: 2px solid transparent;
  transition: all var(--transition-normal);
}

.btn:hover {
  text-decoration: none;
}

.btn--primary {
  background: #fff;
  color: #1e3a5f;
  box-shadow: var(--shadow-md);
}

.btn--primary:hover {
  background: #f0f4ff;
  box-shadow: var(--shadow-lg);
  transform: translateY(-1px);
}

.btn--secondary {
  background: transparent;
  color: #fff;
  border-color: #fff;
}

.btn--secondary:hover {
  background: rgba(255, 255, 255, 0.12);
}

/* ── Sections ──────────────────────────────── */
.section {
  padding: 64px 24px;
  max-width: 1200px;
  margin: 0 auto;
}

.section--alt {
  background: var(--gray-100);
  max-width: 100%;
  padding: 64px 24px;
}

.section--alt > * {
  max-width: 1200px;
  margin-left: auto;
  margin-right: auto;
}

.section__title,
.section__heading {
  font-family: Georgia, 'PT Serif', serif;
  font-size: 2rem;
  font-weight: 700;
  text-align: center;
  margin-bottom: 12px;
  color: var(--gray-900);
  position: relative;
  padding-bottom: 16px;
}

.section__title::after,
.section__heading::after {
  content: '';
  display: block;
  width: 48px;
  height: 3px;
  background: linear-gradient(90deg, var(--color-primary), var(--color-secondary));
  border-radius: 2px;
  margin: 12px auto 0;
}

.section__subtitle,
.section__description {
  text-align: center;
  color: var(--gray-500);
  font-size: 1.05rem;
  max-width: 640px;
  margin: 0 auto 40px;
  line-height: 1.6;
}

/* ── Grid Layout ───────────────────────────── */
.grid,
.weeks-grid,
.extras-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(320px, 1fr));
  gap: 24px;
}

/* ── Week Cards ────────────────────────────── */
.week-card {
  background: #fff;
  border-radius: 10px;
  box-shadow: var(--shadow-sm);
  border-left: 4px solid var(--gray-300);
  padding: 24px;
  transition: transform var(--transition-normal), box-shadow var(--transition-normal);
}

.week-card:hover {
  transform: translateY(-4px);
  box-shadow: var(--shadow-lg);
}

/* Week card border color variants */
.week-card--1 { border-left-color: #3b82f6; }
.week-card--2 { border-left-color: #f59e0b; }
.week-card--3 { border-left-color: #10b981; }
.week-card--4 { border-left-color: #8b5cf6; }
.week-card--5 { border-left-color: #ef4444; }
.week-card--6 { border-left-color: #06b6d4; }
.week-card--7 { border-left-color: #f97316; }
.week-card--8 { border-left-color: #ec4899; }
.week-card--10 { border-left-color: #6366f1; }
.week-card--11 { border-left-color: #14b8a6; }

.week-card__number {
  font-size: 0.8rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  color: var(--gray-500);
  margin-bottom: 6px;
}

.week-card__title {
  font-family: Georgia, 'PT Serif', serif;
  font-size: 1.2rem;
  font-weight: 700;
  color: var(--gray-900);
  margin-bottom: 8px;
  line-height: 1.3;
}

.week-card__desc {
  font-size: 0.92rem;
  color: var(--gray-500);
  line-height: 1.55;
  margin-bottom: 16px;
}

.week-card__materials {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
}

/* ── Material Groups ──────────────────────── */
.material-group {
  width: 100%;
  margin-bottom: 8px;
}

.material-group__label {
  display: block;
  font-size: 0.78rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.04em;
  color: var(--gray-400);
  margin-bottom: 6px;
}

.material-group__links {
  display: flex;
  flex-wrap: wrap;
  gap: 6px;
}

/* ── Material Links ────────────────────────── */
.material-link {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  padding: 6px 12px;
  border-radius: 6px;
  font-size: 0.85rem;
  background: var(--gray-100);
  color: var(--gray-700);
  text-decoration: none;
  transition: background var(--transition-fast), color var(--transition-fast);
}

.material-link:hover {
  background: #e0e7ff;
  color: var(--color-primary);
  text-decoration: none;
}

.material-link__icon {
  font-size: 1rem;
  line-height: 1;
}

/* ── Extra Cards ───────────────────────────── */
.extra-card {
  background: #fff;
  border-radius: 10px;
  box-shadow: var(--shadow-sm);
  border-top: 4px solid var(--gray-300);
  padding: 24px;
  transition: transform var(--transition-normal), box-shadow var(--transition-normal);
}

.extra-card:hover {
  transform: translateY(-4px);
  box-shadow: var(--shadow-lg);
  text-decoration: none;
}

.extra-card__icon {
  display: block;
  font-size: 2rem;
  margin-bottom: 12px;
  line-height: 1;
}

.extra-card__title {
  font-family: Georgia, 'PT Serif', serif;
  font-size: 1.1rem;
  font-weight: 700;
  color: var(--gray-900);
  margin-bottom: 8px;
  line-height: 1.3;
}

.extra-card__desc {
  font-size: 0.9rem;
  color: var(--gray-500);
  line-height: 1.5;
  margin-bottom: 0;
}

/* Extra card border color variants */
.extra-card--blue   { border-top-color: #3b82f6; }
.extra-card--green  { border-top-color: #10b981; }
.extra-card--purple { border-top-color: #8b5cf6; }
.extra-card--amber  { border-top-color: #f59e0b; }

/* ── Footer ────────────────────────────────── */
.footer {
  text-align: center;
  padding: 32px 24px;
  color: var(--gray-500);
  font-size: 0.9rem;
  border-top: 1px solid var(--gray-200);
  margin-top: 48px;
}

.footer a {
  color: var(--gray-600);
}

.footer a:hover {
  color: var(--color-primary);
}

/* ── Responsive ────────────────────────────── */
@media (max-width: 640px) {
  .hero {
    padding: 48px 16px;
  }

  .hero__title {
    font-size: 2rem;
  }

  .hero__subtitle {
    font-size: 1.1rem;
  }

  .hero__author {
    font-size: 1rem;
  }

  .hero__actions {
    flex-direction: column;
    gap: 12px;
  }

  .btn {
    width: 100%;
    text-align: center;
  }

  .section {
    padding: 40px 16px;
  }

  .section__title,
  .section__heading {
    font-size: 1.6rem;
  }

  .grid,
  .weeks-grid,
  .extras-grid {
    grid-template-columns: 1fr;
    gap: 16px;
  }
}