:root {
  --ink: #132328;
  --muted: #5b6b70;
  --paper: #ffffff;
  --bg: #f4f8f7;
  --mint: #e9f5f1;
  --line: #d8e4e2;
  --teal: #0e7a82;
  --teal-dark: #073e45;
  --gold: #f0bb58;
  --coral: #c94d5d;
  --blue: #203e63;
  font-family: "Segoe UI", "PingFang SC", "Microsoft YaHei", Arial, sans-serif;
}

* {
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
}

body {
  margin: 0;
  color: var(--ink);
  background: var(--bg);
  line-height: 1.7;
}

a {
  color: inherit;
}

button {
  font: inherit;
}

img {
  max-width: 100%;
  display: block;
}

.hero {
  min-height: 92vh;
  position: relative;
  display: grid;
  align-items: end;
  padding: 24px clamp(18px, 4vw, 56px) 72px;
  overflow: hidden;
  isolation: isolate;
}

.hero__image,
.hero__scrim {
  position: absolute;
  inset: 0;
  width: 100%;
  height: 100%;
}

.hero__image {
  object-fit: cover;
  z-index: -2;
}

.hero__scrim {
  z-index: -1;
  background:
    linear-gradient(90deg, rgba(4, 20, 25, 0.92), rgba(4, 20, 25, 0.68) 45%, rgba(4, 20, 25, 0.1)),
    linear-gradient(0deg, rgba(4, 20, 25, 0.72), transparent 45%);
}

.topnav {
  position: absolute;
  top: 18px;
  left: clamp(18px, 4vw, 56px);
  right: clamp(18px, 4vw, 56px);
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
}

.topnav a {
  min-height: 38px;
  display: inline-flex;
  align-items: center;
  padding: 0 13px;
  border: 1px solid rgba(255, 255, 255, 0.28);
  border-radius: 999px;
  color: #f4ffff;
  text-decoration: none;
  background: rgba(7, 44, 51, 0.58);
  backdrop-filter: blur(10px);
}

.hero__copy {
  max-width: 780px;
  color: white;
}

.kicker {
  margin: 0 0 12px;
  color: var(--gold);
  font-size: 14px;
  font-weight: 800;
  letter-spacing: 0.08em;
}

.hero h1 {
  max-width: 760px;
  margin: 0;
  font-size: clamp(40px, 5.8vw, 78px);
  line-height: 1.05;
  letter-spacing: 0;
}

.hero p:not(.kicker) {
  max-width: 700px;
  margin: 18px 0 0;
  color: rgba(255, 255, 255, 0.9);
  font-size: clamp(17px, 2vw, 22px);
}

.hero__actions {
  display: flex;
  flex-wrap: wrap;
  gap: 12px;
  margin-top: 26px;
}

.button {
  min-height: 46px;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  padding: 0 18px;
  border-radius: 999px;
  text-decoration: none;
  font-weight: 800;
}

.button--primary {
  color: #152328;
  background: var(--gold);
}

.button--ghost {
  color: white;
  border: 1px solid rgba(255, 255, 255, 0.42);
}

.section {
  padding: clamp(58px, 8vw, 112px) 0;
  background: var(--paper);
}

.section--mint {
  background: var(--mint);
}

.section--dark {
  color: white;
  background: #092f37;
}

.section--sources {
  background: #eef6f4;
}

.wrap {
  width: min(1180px, calc(100% - 36px));
  margin: 0 auto;
}

.section-head {
  max-width: 860px;
  margin-bottom: 30px;
}

h2 {
  margin: 0 0 16px;
  font-size: clamp(30px, 4vw, 54px);
  line-height: 1.14;
  letter-spacing: 0;
}

h3 {
  margin: 0 0 10px;
  font-size: clamp(22px, 2.3vw, 30px);
  line-height: 1.25;
}

p {
  margin: 0 0 16px;
}

.section-head p:not(.kicker),
.lesson-card__copy p,
.callout p,
.ai-copy p,
.company p,
.section--sources p,
figcaption {
  color: var(--muted);
}

.section--dark .section-head p:not(.kicker),
.section--dark .ai-copy p,
.section--dark .risk-strip p {
  color: rgba(255, 255, 255, 0.78);
}

.lesson-board {
  display: grid;
  grid-template-columns: 280px 1fr;
  gap: 18px;
  align-items: stretch;
}

.lesson-tabs,
.ai-switcher,
.frontier-cards,
.filters {
  display: grid;
  gap: 10px;
}

.lesson-tab,
.ai-option,
.frontier-card,
.filter,
.step {
  border: 1px solid var(--line);
  background: #fff;
  color: var(--ink);
  border-radius: 8px;
  cursor: pointer;
  text-align: left;
  transition: transform 0.16s ease, border-color 0.16s ease, background 0.16s ease;
}

.lesson-tab,
.ai-option,
.filter {
  min-height: 48px;
  padding: 11px 14px;
  font-weight: 800;
}

.lesson-tab:hover,
.ai-option:hover,
.frontier-card:hover,
.filter:hover,
.step:hover {
  transform: translateY(-1px);
}

.is-active.lesson-tab,
.is-active.ai-option,
.is-active.filter,
.is-active.step,
.is-active.frontier-card {
  color: white;
  border-color: var(--teal);
  background: var(--teal);
}

.lesson-card,
.callout,
.image-panel,
.risk-strip,
.company,
.wide-figure {
  border: 1px solid var(--line);
  border-radius: 8px;
  background: white;
  overflow: hidden;
  box-shadow: 0 18px 54px rgba(20, 68, 75, 0.1);
}

.lesson-card {
  display: grid;
  grid-template-columns: minmax(320px, 1fr) 0.9fr;
}

.lesson-card img,
.image-panel img,
.wide-figure img {
  width: 100%;
  height: 100%;
  object-fit: cover;
  aspect-ratio: 16 / 9;
}

.lesson-card__copy {
  padding: clamp(22px, 4vw, 42px);
  align-self: center;
}

.lesson-card__copy span {
  display: inline-flex;
  margin-bottom: 14px;
  padding: 4px 10px;
  border-radius: 999px;
  background: #fff3d7;
  color: #8a5b08;
  font-weight: 800;
  font-size: 13px;
}

.journey {
  display: grid;
  grid-template-columns: 1.1fr 0.9fr;
  gap: 18px;
  align-items: start;
}

.journey > img {
  width: 100%;
  aspect-ratio: 16 / 9;
  object-fit: cover;
  border-radius: 8px;
  border: 1px solid var(--line);
  box-shadow: 0 18px 54px rgba(20, 68, 75, 0.1);
}

.stepper {
  display: grid;
  grid-template-columns: repeat(5, 1fr);
  gap: 8px;
}

.step {
  min-height: 72px;
  padding: 10px;
  text-align: center;
  font-weight: 800;
}

.step span {
  display: grid;
  place-items: center;
  width: 28px;
  height: 28px;
  margin: 0 auto 6px;
  border-radius: 50%;
  background: rgba(15, 122, 130, 0.12);
}

.step.is-active span {
  background: rgba(255, 255, 255, 0.22);
}

.callout {
  grid-column: 2;
  padding: 24px;
}

.split,
.ai-grid,
.frontier-grid {
  display: grid;
  grid-template-columns: minmax(0, 0.9fr) minmax(340px, 1.1fr);
  gap: clamp(24px, 4vw, 54px);
  align-items: center;
}

.pill-grid {
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
  margin-top: 22px;
}

.pill-grid span {
  padding: 8px 12px;
  border-radius: 999px;
  background: #e7f3f1;
  color: var(--teal-dark);
  font-weight: 800;
}

.image-panel figcaption {
  padding: 14px 16px;
  font-size: 14px;
}

.image-panel--dark {
  background: #123d45;
  border-color: rgba(255, 255, 255, 0.16);
}

.ai-grid {
  grid-template-columns: minmax(360px, 1.1fr) minmax(300px, 0.9fr);
}

.ai-switcher {
  grid-template-columns: repeat(2, 1fr);
}

.ai-copy {
  grid-column: 1 / -1;
  padding: 24px;
  border: 1px solid rgba(255, 255, 255, 0.16);
  border-radius: 8px;
  background: rgba(255, 255, 255, 0.06);
}

.risk-strip {
  display: grid;
  grid-template-columns: 280px 1fr;
  gap: 22px;
  align-items: center;
  margin-top: 22px;
  padding: 14px;
  color: white;
  background: rgba(255, 255, 255, 0.07);
  border-color: rgba(255, 255, 255, 0.14);
}

.risk-strip img {
  width: 100%;
  aspect-ratio: 16 / 9;
  object-fit: cover;
  border-radius: 6px;
}

.frontier-grid {
  grid-template-columns: minmax(360px, 1.05fr) minmax(300px, 0.95fr);
}

.frontier-card {
  padding: 18px;
}

.frontier-card strong,
.frontier-card span {
  display: block;
}

.frontier-card span {
  margin-top: 6px;
  color: var(--muted);
}

.frontier-card.is-active span {
  color: rgba(255, 255, 255, 0.82);
}

#frontierCopy {
  margin-top: 18px;
}

.wide-figure {
  margin: 0 0 22px;
}

.wide-figure img {
  max-height: 560px;
}

.filters {
  grid-template-columns: repeat(4, max-content);
  margin-bottom: 16px;
}

.company-grid {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 14px;
}

.company {
  padding: 20px;
  min-height: 218px;
}

.company h3 {
  color: var(--teal-dark);
  font-size: 22px;
}

.company[hidden] {
  display: none;
}

.section--sources ul {
  padding-left: 20px;
}

.section--sources li {
  margin-bottom: 10px;
}

.footer {
  display: flex;
  justify-content: space-between;
  gap: 16px;
  padding: 28px clamp(18px, 4vw, 56px);
  color: white;
  background: #08272d;
}

.footer a {
  color: var(--gold);
  text-decoration: none;
  font-weight: 800;
}

@media (max-width: 980px) {
  .lesson-board,
  .lesson-card,
  .journey,
  .split,
  .ai-grid,
  .frontier-grid,
  .risk-strip {
    grid-template-columns: 1fr;
  }

  .callout {
    grid-column: auto;
  }

  .lesson-tabs {
    grid-template-columns: repeat(2, 1fr);
  }

  .company-grid {
    grid-template-columns: repeat(2, 1fr);
  }
}

@media (max-width: 680px) {
  .hero {
    min-height: 88vh;
    padding-top: 132px;
    padding-bottom: 44px;
  }

  .hero__scrim {
    background: linear-gradient(180deg, rgba(4, 20, 25, 0.66), rgba(4, 20, 25, 0.92));
  }

  .topnav a {
    min-height: 34px;
    padding: 0 9px;
    font-size: 12px;
  }

  .lesson-tabs,
  .stepper,
  .ai-switcher,
  .filters,
  .company-grid {
    grid-template-columns: 1fr;
  }

  .footer {
    flex-direction: column;
  }
}