:root {
  --ink: #172126;
  --muted: #62706f;
  --paper: #fbfbf7;
  --line: #dce3dd;
  --green: #245a50;
  --green-soft: #dcebe3;
  --coral: #d85d4f;
  --gold: #c89731;
  --blue: #294c7a;
  --white: #ffffff;
  --shadow: 0 18px 48px rgba(23, 33, 38, 0.14);
}

* {
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
}

body {
  margin: 0;
  color: var(--ink);
  background: var(--paper);
  font-family:
    Inter, ui-sans-serif, system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI",
    "Microsoft YaHei", sans-serif;
}

a {
  color: inherit;
  text-decoration: none;
}

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

.topbar {
  position: sticky;
  top: 0;
  z-index: 20;
  display: flex;
  align-items: center;
  justify-content: space-between;
  min-height: 68px;
  padding: 0 5vw;
  background: rgba(251, 251, 247, 0.88);
  border-bottom: 1px solid rgba(220, 227, 221, 0.72);
  backdrop-filter: blur(18px);
}

.brand,
.nav-links,
.hero-actions,
.filters,
.course-top,
.resource-list a,
.footer {
  display: flex;
  align-items: center;
}

.brand {
  gap: 10px;
  font-weight: 800;
}

.brand-mark {
  display: grid;
  place-items: center;
  width: 36px;
  height: 36px;
  border-radius: 7px;
  color: var(--white);
  background: var(--green);
  letter-spacing: 0;
}

.nav-links {
  gap: clamp(16px, 3vw, 34px);
  color: var(--muted);
  font-size: 0.95rem;
}

.nav-links a:hover {
  color: var(--green);
}

.nav-action,
.primary-button,
.secondary-button {
  min-height: 44px;
  padding: 0 18px;
  border-radius: 7px;
  font-weight: 750;
}

.nav-action,
.primary-button {
  display: inline-flex;
  align-items: center;
  background: var(--coral);
  color: var(--white);
}

.secondary-button {
  display: inline-flex;
  align-items: center;
  border: 1px solid rgba(255, 255, 255, 0.68);
  color: var(--white);
  background: rgba(255, 255, 255, 0.13);
}

.hero {
  position: relative;
  min-height: calc(100vh - 68px);
  display: grid;
  align-items: center;
  overflow: hidden;
  background: #172126 url("assets/ap-study-hero.png") center / cover no-repeat;
}

.hero img,
.hero-shade {
  position: absolute;
  inset: 0;
  width: 100%;
  height: 100%;
}

.hero img {
  z-index: 0;
  object-fit: cover;
}

.hero-shade {
  z-index: 1;
  background:
    linear-gradient(90deg, rgba(18, 28, 31, 0.82), rgba(18, 28, 31, 0.45), rgba(18, 28, 31, 0.18)),
    linear-gradient(0deg, rgba(18, 28, 31, 0.45), transparent 34%);
}

.hero-content {
  position: relative;
  z-index: 2;
  width: min(760px, 90vw);
  padding: 10vh 0 14vh;
  margin-left: 5vw;
  color: var(--white);
}

.eyebrow {
  margin: 0 0 12px;
  color: var(--coral);
  font-size: 0.78rem;
  font-weight: 850;
  letter-spacing: 0.08em;
  text-transform: uppercase;
}

.hero .eyebrow {
  color: #ffb37a;
}

h1,
h2,
h3,
p {
  margin-top: 0;
}

h1 {
  max-width: 760px;
  margin-bottom: 22px;
  font-size: clamp(2.65rem, 5vw, 4.9rem);
  line-height: 1.08;
  letter-spacing: 0;
}

h1 span {
  display: block;
}

.hero-copy {
  max-width: 620px;
  color: rgba(255, 255, 255, 0.88);
  font-size: clamp(1rem, 2vw, 1.25rem);
  line-height: 1.8;
}

.hero-actions {
  flex-wrap: wrap;
  gap: 12px;
  margin-top: 32px;
}

.metrics {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 1px;
  background: var(--line);
  border-bottom: 1px solid var(--line);
}

.metrics div {
  min-height: 132px;
  padding: 28px 5vw;
  background: var(--white);
}

.metrics span {
  color: var(--green);
  font-size: clamp(1.8rem, 3vw, 3rem);
  font-weight: 900;
}

.metrics p {
  max-width: 320px;
  margin: 8px 0 0;
  color: var(--muted);
  line-height: 1.6;
}

.section {
  padding: clamp(64px, 9vw, 118px) 5vw;
}

.section-heading {
  max-width: 980px;
  margin: 0 auto 34px;
}

.section h2 {
  margin-bottom: 14px;
  font-size: clamp(2rem, 4vw, 4rem);
  line-height: 1.08;
}

.section-copy p:not(.eyebrow) {
  color: var(--muted);
  font-size: 1.06rem;
  line-height: 1.85;
}

.intro-grid,
.resource-grid {
  display: grid;
  grid-template-columns: minmax(0, 0.9fr) minmax(320px, 1.1fr);
  gap: clamp(28px, 5vw, 78px);
  align-items: center;
}

.decision-list,
.resource-list {
  display: grid;
  gap: 14px;
}

.decision-list div,
.course-card,
.plan-detail,
.timeline div {
  border: 1px solid var(--line);
  border-radius: 8px;
  background: var(--white);
  box-shadow: 0 1px 0 rgba(23, 33, 38, 0.04);
}

.decision-list div {
  display: grid;
  grid-template-columns: 34px 130px 1fr;
  gap: 16px;
  align-items: center;
  min-height: 92px;
  padding: 20px;
}

.decision-list svg,
.resource-list svg,
.course-top svg {
  width: 24px;
  height: 24px;
  color: var(--green);
}

.decision-list span {
  color: var(--muted);
  line-height: 1.6;
}

.band {
  background: #eef4ef;
  border-block: 1px solid var(--line);
}

.filters {
  width: min(980px, 100%);
  margin: 0 auto 24px;
  gap: 10px;
  flex-wrap: wrap;
}

.filter {
  min-height: 40px;
  padding: 0 16px;
  border: 1px solid var(--line);
  border-radius: 999px;
  color: var(--muted);
  background: var(--white);
  cursor: pointer;
  font: inherit;
  font-weight: 700;
}

.filter.active {
  color: var(--white);
  border-color: var(--green);
  background: var(--green);
}

.course-grid {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: 18px;
  width: min(1180px, 100%);
  margin: 0 auto;
}

.course-card {
  min-height: 304px;
  padding: 24px;
  transition:
    transform 160ms ease,
    box-shadow 160ms ease,
    opacity 160ms ease;
}

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

.course-card.hidden {
  display: none;
}

.course-top {
  justify-content: space-between;
  margin-bottom: 24px;
}

.course-top span {
  color: var(--blue);
  font-size: 0.82rem;
  font-weight: 800;
}

.course-card h3 {
  margin-bottom: 10px;
  font-size: 1.35rem;
}

.course-card p,
.course-card li {
  color: var(--muted);
  line-height: 1.65;
}

.course-card ul {
  padding-left: 18px;
  margin: 16px 0 0;
}

.plan-layout {
  display: grid;
  grid-template-columns: 340px minmax(0, 1fr);
  gap: 18px;
  width: min(980px, 100%);
  margin: 0 auto;
}

.week-list {
  display: grid;
  gap: 10px;
}

.week {
  display: grid;
  grid-template-columns: 72px 1fr;
  align-items: center;
  min-height: 72px;
  border: 1px solid var(--line);
  border-radius: 8px;
  background: var(--white);
  color: var(--ink);
  cursor: pointer;
  font: inherit;
  text-align: left;
}

.week span {
  color: var(--coral);
  font-weight: 850;
  text-align: center;
}

.week.active {
  border-color: var(--green);
  background: var(--green);
  color: var(--white);
}

.week.active span {
  color: #f4d06f;
}

.plan-detail {
  min-height: 318px;
  padding: clamp(24px, 4vw, 44px);
}

.plan-detail h3 {
  font-size: clamp(1.7rem, 3vw, 3rem);
}

.plan-detail p {
  color: var(--muted);
  line-height: 1.8;
}

.checklist {
  display: grid;
  gap: 12px;
  margin-top: 28px;
}

.checklist label {
  display: flex;
  gap: 12px;
  align-items: flex-start;
  padding: 14px;
  border-radius: 7px;
  background: #f5f8f5;
  line-height: 1.5;
}

.checklist input {
  width: 18px;
  height: 18px;
  margin-top: 2px;
  accent-color: var(--green);
}

.resource-list a {
  min-height: 74px;
  gap: 16px;
  padding: 18px 20px;
  border: 1px solid var(--line);
  border-radius: 8px;
  background: var(--white);
  font-weight: 760;
}

.resource-list a:hover {
  border-color: var(--green);
  box-shadow: var(--shadow);
}

.timeline {
  display: grid;
  grid-template-columns: repeat(4, minmax(0, 1fr));
  gap: 16px;
  width: min(1180px, 100%);
  margin: 0 auto;
}

.timeline div {
  min-height: 232px;
  padding: 24px;
}

.timeline span {
  display: inline-flex;
  margin-bottom: 22px;
  color: var(--gold);
  font-weight: 900;
}

.timeline h3 {
  font-size: 1.3rem;
}

.timeline p {
  color: var(--muted);
  line-height: 1.7;
}

.footer {
  justify-content: space-between;
  gap: 20px;
  min-height: 88px;
  padding: 0 5vw;
  color: var(--muted);
  background: var(--ink);
}

.footer a {
  color: var(--white);
  font-weight: 800;
}

@media (max-width: 920px) {
  .nav-links {
    display: none;
  }

  .metrics,
  .intro-grid,
  .resource-grid,
  .plan-layout,
  .timeline {
    grid-template-columns: 1fr;
  }

  .course-grid {
    grid-template-columns: repeat(2, minmax(0, 1fr));
  }

  .decision-list div {
    grid-template-columns: 34px 1fr;
  }

  .decision-list span {
    grid-column: 2;
  }
}

@media (max-width: 640px) {
  .topbar {
    min-height: 62px;
    padding: 0 18px;
  }

  .nav-action {
    display: none;
  }

  .hero {
    min-height: 720px;
  }

  .hero-content {
    width: auto;
    margin: 0;
    padding: 90px 22px 96px;
  }

  h1 {
    font-size: clamp(2.2rem, 9vw, 2.7rem);
  }

  .hero-shade {
    background: linear-gradient(0deg, rgba(18, 28, 31, 0.84), rgba(18, 28, 31, 0.38));
  }

  .section,
  .metrics div {
    padding-inline: 22px;
  }

  .course-grid {
    grid-template-columns: 1fr;
  }

  .week {
    grid-template-columns: 66px 1fr;
  }

  .footer {
    align-items: flex-start;
    flex-direction: column;
    justify-content: center;
    padding-block: 22px;
  }
}