/* Shared Big Top cream theme for public indexable cover pages and About.
   Reuse on /about, /calculus/limits, /calculus/precalculus, /calculus/derivatives,
   and /calculus/integrals. Keep this file free of unit-specific copy. */

:root {
  --bt-canvas: #1a1033;
  --bt-deep-purple: #5238a8;
  --bt-cream: #fff8ec;
  --bt-carnival-red: #e63946;
  --bt-gold: #ffd166;
  --bt-teal: #457b9d;
  --bt-ink: #2b1d4a;
  --bt-meta: #6b5b7a;
  --bt-lavender: #c9b8e8;
  --bt-check: #2ec4b6;
  --bt-next: #ff6b35;
  --bt-shadow: #2b1d4a;
  --bt-display-font: 'Grandstander', cursive;
  --bt-body-font: 'Chakra Petch', sans-serif;
}

*,
*::before,
*::after {
  box-sizing: border-box;
}

html {
  color-scheme: light;
}

body.landing-body {
  margin: 0;
  min-height: 100vh;
  background-color: var(--bt-cream);
  color: var(--bt-ink);
  font-family: var(--bt-body-font);
  font-size: 1.05rem;
  line-height: 1.55;
}

.landing {
  min-height: 100vh;
  display: flex;
  flex-direction: column;
}

.landing__stripe {
  height: 10px;
  background: repeating-linear-gradient(
    135deg,
    var(--bt-gold) 0 12px,
    var(--bt-cream) 12px 24px,
    var(--bt-deep-purple) 24px 36px
  );
}

.landing__header,
.landing__footer {
  padding: 0.9rem clamp(1rem, 4vw, 2.5rem);
}

.landing__header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
  border-bottom: 1px solid var(--bt-lavender);
}

.landing__brand {
  font-family: var(--bt-display-font);
  font-weight: 700;
  font-size: 1.15rem;
  letter-spacing: 0.02em;
  color: var(--bt-ink);
  text-decoration: none;
}

.landing__brand:hover,
.landing__brand:focus-visible {
  color: var(--bt-deep-purple);
}

.landing__nav {
  display: flex;
  flex-wrap: wrap;
  gap: 0.85rem 1.15rem;
  font-weight: 600;
}

.landing__nav a {
  color: var(--bt-deep-purple);
  text-decoration: none;
}

.landing__nav a:hover,
.landing__nav a:focus-visible {
  text-decoration: underline;
  text-underline-offset: 3px;
}

.landing__main {
  flex: 1;
  width: min(760px, 100%);
  margin: 0 auto;
  padding: clamp(1.25rem, 3vw, 2.25rem) clamp(1rem, 4vw, 2.5rem) 2.75rem;
}

.landing__breadcrumbs {
  margin: 0 0 1.15rem;
  font-size: 0.92rem;
}

.landing__breadcrumbs ol {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 0.35rem 0.45rem;
  margin: 0;
  padding: 0;
  list-style: none;
}

.landing__breadcrumbs li {
  display: flex;
  align-items: center;
  gap: 0.45rem;
  color: var(--bt-meta);
  font-weight: 600;
}

.landing__breadcrumbs li:not(:last-child)::after {
  content: '/';
  color: var(--bt-lavender);
  font-weight: 500;
}

.landing__breadcrumbs a {
  color: var(--bt-deep-purple);
  text-decoration: none;
}

.landing__breadcrumbs a:hover,
.landing__breadcrumbs a:focus-visible {
  text-decoration: underline;
  text-underline-offset: 3px;
}

.landing__breadcrumbs [aria-current="page"] {
  color: var(--bt-ink);
}

.landing__main a:not(.landing__cta) {
  color: var(--bt-deep-purple);
  font-weight: 600;
  text-underline-offset: 2px;
}

.landing__hero {
  margin-bottom: 1.5rem;
}

.landing__kicker {
  margin: 0 0 0.45rem;
  font-size: 0.92rem;
  font-weight: 600;
  letter-spacing: 0.04em;
  text-transform: uppercase;
  color: var(--bt-meta);
}

.landing__title {
  font-family: var(--bt-display-font);
  font-weight: 700;
  font-size: clamp(2rem, 5vw, 3rem);
  line-height: 1.15;
  letter-spacing: 0.02em;
  margin: 0 0 0.85rem;
  text-shadow: 3px 3px 0 rgba(43, 29, 74, 0.12);
}

.landing__lead {
  margin: 0 0 1.25rem;
  font-size: clamp(1.05rem, 2.4vw, 1.2rem);
  font-weight: 500;
}

.landing__note {
  margin: 0.85rem 0 0;
  color: var(--bt-meta);
  font-size: 0.98rem;
}

.landing__cta-row {
  display: flex;
  flex-wrap: wrap;
  gap: 0.75rem;
}

.landing__cta {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  padding: 0.75rem 1.6rem;
  font-family: var(--bt-display-font);
  font-weight: 700;
  font-size: 1.05rem;
  letter-spacing: 0.03em;
  text-decoration: none;
  border-radius: 4px;
  border: 2px solid var(--bt-ink);
  box-shadow: 3px 3px 0 var(--bt-shadow);
  transition: transform 0.15s ease, box-shadow 0.15s ease;
}

.landing__cta:hover,
.landing__cta:focus-visible {
  transform: translateY(-1px);
  box-shadow: 4px 4px 0 var(--bt-shadow);
}

.landing__cta--primary {
  background-color: var(--bt-gold);
  color: var(--bt-ink);
}

.landing__cta--primary:hover,
.landing__cta--primary:focus-visible {
  background-color: #ffe08a;
  color: var(--bt-ink);
}

.landing__cta--secondary {
  background-color: transparent;
  color: var(--bt-ink);
}

.landing__cta--secondary:hover,
.landing__cta--secondary:focus-visible {
  background-color: rgba(255, 209, 102, 0.28);
  color: var(--bt-ink);
}

.landing__stats {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 0.75rem;
  margin: 0 0 1.5rem;
  padding: 0;
  list-style: none;
}

@media (min-width: 640px) {
  .landing__stats {
    grid-template-columns: repeat(4, minmax(0, 1fr));
  }
}

.landing__stat {
  padding: 0.85rem 0.9rem;
  background: rgba(255, 248, 236, 0.7);
  border-top: 2px solid var(--bt-lavender);
  border-left: 2px solid var(--bt-lavender);
  border-radius: 4px;
}

.landing__stat-value {
  display: block;
  font-family: var(--bt-display-font);
  font-weight: 700;
  font-size: 1.35rem;
  line-height: 1.2;
}

.landing__stat-label {
  display: block;
  margin-top: 0.2rem;
  color: var(--bt-meta);
  font-size: 0.88rem;
  font-weight: 600;
}

.landing__card {
  background-color: var(--bt-cream);
  border-radius: 6px;
  padding: clamp(1.25rem, 3vw, 1.75rem);
  margin-bottom: 1.25rem;
  box-shadow: 4px 4px 0 var(--bt-shadow);
  border-top: 1px solid var(--bt-lavender);
  border-left: 1px solid var(--bt-lavender);
  position: relative;
  overflow: hidden;
}

.landing__card::after {
  content: '';
  position: absolute;
  left: 0;
  right: 0;
  bottom: 0;
  height: 8px;
  background: repeating-linear-gradient(
    135deg,
    var(--bt-gold) 0 12px,
    var(--bt-cream) 12px 24px,
    var(--bt-deep-purple) 24px 36px
  );
}

.landing__section-title {
  font-family: var(--bt-display-font);
  font-weight: 700;
  font-size: clamp(1.35rem, 3.5vw, 1.75rem);
  line-height: 1.3;
  margin: 0 0 1rem;
  letter-spacing: 0.02em;
}

.landing__section-title:not(:first-child) {
  margin-top: 1.5rem;
}

.landing__card p {
  margin: 0 0 1rem;
}

.landing__card p:last-child {
  margin-bottom: 0;
}

.landing__math {
  display: block;
  margin: 1rem 0 0;
  padding: 0.85rem 1rem;
  background: rgba(201, 184, 232, 0.22);
  border-left: 4px solid var(--bt-deep-purple);
  font-size: 1rem;
}

.landing__topics {
  display: grid;
  grid-template-columns: 1fr;
  gap: 0.85rem;
  margin: 0;
  padding: 0;
  list-style: none;
}

@media (min-width: 720px) {
  .landing__topics {
    grid-template-columns: repeat(2, minmax(0, 1fr));
  }

  .landing__topics > li:last-child:nth-child(odd) {
    grid-column: 1 / -1;
  }

  .landing__topics--audience {
    grid-template-columns: repeat(3, minmax(0, 1fr));
  }

  .landing__topics--audience > li:last-child:nth-child(odd) {
    grid-column: auto;
  }
}

.landing__topic {
  height: 100%;
  padding: 1rem 1.1rem 1.15rem;
  background: rgba(255, 248, 236, 0.55);
  border-top: 2px solid rgba(201, 184, 232, 0.95);
  border-left: 2px solid rgba(201, 184, 232, 0.95);
  border-radius: 4px;
}

.landing__topic-title {
  font-family: var(--bt-display-font);
  font-weight: 700;
  font-size: 1.08rem;
  margin: 0 0 0.45rem;
}

.landing__topic-count {
  display: block;
  margin-bottom: 0.45rem;
  color: var(--bt-meta);
  font-size: 0.88rem;
  font-weight: 600;
}

.landing__topic p {
  margin: 0 0 0.75rem;
  color: var(--bt-meta);
  font-size: 0.98rem;
}

.landing__topic-link {
  font-weight: 700;
  color: var(--bt-deep-purple);
  text-underline-offset: 2px;
}

.landing__list {
  margin: 0;
  padding-left: 1.2rem;
}

.landing__list li {
  margin-bottom: 0.55rem;
}

.landing__list li:last-child {
  margin-bottom: 0;
}

.landing__faq {
  margin: 0;
}

.landing__faq-item {
  border-top: 1px solid var(--bt-lavender);
  padding: 0.65rem 0;
}

.landing__faq-item:first-child {
  border-top: 0;
  padding-top: 0;
}

.landing__faq-item summary {
  cursor: pointer;
  font-weight: 700;
  color: var(--bt-ink);
}

.landing__faq-item summary:hover,
.landing__faq-item summary:focus-visible {
  color: var(--bt-deep-purple);
}

.landing__faq-item p {
  margin: 0.65rem 0 0.15rem;
  color: var(--bt-meta);
}

.landing__related {
  display: flex;
  flex-wrap: wrap;
  gap: 0.65rem 1.15rem;
  margin: 1.15rem 0 0;
  padding: 0;
  list-style: none;
  font-weight: 600;
}

.landing__related a {
  color: var(--bt-deep-purple);
}

.landing__footer {
  border-top: 1px solid var(--bt-lavender);
  color: var(--bt-meta);
  font-size: 0.95rem;
}

.landing__footer-row {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: space-between;
  gap: 0.75rem 1.25rem;
  width: min(760px, 100%);
  margin: 0 auto;
}

.landing__footer-links {
  display: flex;
  flex-wrap: wrap;
  gap: 0.65rem 1rem;
}

.landing__footer a {
  color: var(--bt-deep-purple);
  font-weight: 600;
  text-decoration: underline;
  text-underline-offset: 2px;
}

.landing a:focus-visible,
.landing summary:focus-visible,
.landing__cta:focus-visible {
  outline: 3px solid var(--bt-check);
  outline-offset: 2px;
}