/* Mastering Mandarin — AEO pilot landing page
   Reference-book aesthetic: ink navy + parchment + brass accent. */

:root{
  --ink: #1b2233;
  --ink-soft: #333c52;
  --navy: #16213e;
  --navy-deep: #0f1729;
  --parchment: #faf7f0;
  --paper: #ffffff;
  --line: #e2ddd0;
  --brass: #a9772f;
  --brass-deep: #8a5f22;
  --jade: #2f5d50;
  --max-w: 1120px;
  --radius: 4px;
}

*{ box-sizing: border-box; }
html{ scroll-behavior: smooth; }

body{
  margin: 0;
  background: var(--parchment);
  color: var(--ink);
  font-family: "Source Sans 3", "Segoe UI", Helvetica, Arial, sans-serif;
  font-size: 17px;
  line-height: 1.6;
  -webkit-font-smoothing: antialiased;
}

h1, h2, h3, .display{
  font-family: "Source Serif 4", Georgia, "Times New Roman", serif;
  color: var(--navy-deep);
  line-height: 1.15;
  margin: 0;
}

a{ color: inherit; }

.wrap{
  max-width: var(--max-w);
  margin: 0 auto;
  padding: 0 28px;
}

/* ---------- top bar ---------- */
.topbar{
  background: var(--navy-deep);
  color: #cfd6e6;
  font-size: 0.85rem;
  letter-spacing: .03em;
}
.topbar .wrap{
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding-top: 12px;
  padding-bottom: 12px;
}
.topbar .brand{
  font-family: "Source Serif 4", Georgia, serif;
  font-weight: 600;
  color: #f4efe3;
  font-size: 1rem;
  letter-spacing: .04em;
}
.topbar .brand span{ color: var(--brass); }

/* ---------- hero ---------- */
.hero{
  background: linear-gradient(180deg, var(--navy) 0%, var(--navy-deep) 100%);
  color: #eef0f6;
  padding: 64px 0 56px;
}
.hero .wrap{
  display: grid;
  grid-template-columns: 1.15fr 0.85fr;
  gap: 56px;
  align-items: center;
}
.eyebrow{
  display: inline-block;
  font-size: 0.78rem;
  font-weight: 700;
  letter-spacing: .12em;
  text-transform: uppercase;
  color: #d9c08c;
  background: rgba(169,119,47,0.15);
  border: 1px solid rgba(169,119,47,0.5);
  padding: 6px 14px;
  border-radius: 999px;
  margin-bottom: 22px;
}
.hero h1{
  color: #ffffff;
  font-size: clamp(2rem, 4vw, 2.85rem);
  font-weight: 600;
  margin-bottom: 20px;
}
.hero .lede{
  font-size: 1.15rem;
  color: #c9cfdd;
  max-width: 56ch;
  margin-bottom: 28px;
}
.hero .lede strong{ color: #f4efe3; font-weight: 600; }

.cta-row{
  display: flex;
  gap: 14px;
  flex-wrap: wrap;
  margin-bottom: 10px;
}
.btn{
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 13px 22px;
  border-radius: var(--radius);
  font-weight: 600;
  font-size: 0.95rem;
  text-decoration: none;
  border: 1px solid transparent;
  transition: transform .12s ease, background .15s ease;
}
.btn:hover{ transform: translateY(-1px); }
.btn-primary{
  background: var(--brass);
  color: #1b1400;
}
.btn-primary:hover{ background: #bf8637; }
.btn-outline{
  background: transparent;
  border-color: rgba(238,240,246,0.4);
  color: #eef0f6;
}
.btn-outline:hover{ background: rgba(238,240,246,0.08); }
.hero-note{
  font-size: 0.85rem;
  color: #9aa2b8;
}

.hero-cover{
  display: flex;
  justify-content: center;
}
.hero-cover img{
  width: 100%;
  max-width: 300px;
  height: auto;
  box-shadow: 0 22px 44px rgba(0,0,0,0.45), 0 2px 0 rgba(255,255,255,0.04) inset;
  border-radius: 2px;
}

/* ---------- quick facts strip ---------- */
.facts{
  background: var(--paper);
  border-bottom: 1px solid var(--line);
}
.facts .wrap{
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 0;
  padding-top: 26px;
  padding-bottom: 26px;
}
.fact{
  padding: 0 22px;
  border-left: 1px solid var(--line);
}
.fact:first-child{ border-left: none; padding-left: 0; }
.fact .k{
  font-size: 0.72rem;
  letter-spacing: .08em;
  text-transform: uppercase;
  color: var(--brass-deep);
  font-weight: 700;
  margin-bottom: 6px;
}
.fact .v{
  font-family: "Source Serif 4", Georgia, serif;
  font-size: 1.2rem;
  color: var(--navy-deep);
  font-weight: 600;
}
.fact .v small{
  display: block;
  font-family: "Source Sans 3", sans-serif;
  font-size: 0.78rem;
  color: var(--ink-soft);
  font-weight: 400;
  margin-top: 3px;
}

/* ---------- sections ---------- */
section{ padding: 68px 0; }
.section-head{
  max-width: 68ch;
  margin-bottom: 38px;
}
.section-head .tag{
  font-size: 0.75rem;
  font-weight: 700;
  letter-spacing: .1em;
  text-transform: uppercase;
  color: var(--brass-deep);
  margin-bottom: 10px;
  display: block;
}
.section-head h2{
  font-size: clamp(1.5rem, 2.6vw, 2rem);
  font-weight: 600;
}
.section-head p{ color: var(--ink-soft); margin-top: 12px; font-size: 1.02rem; }

.not-for{
  background: #fbf2e4;
  border: 1px solid #e7cf9f;
  border-radius: var(--radius);
  padding: 18px 22px;
  margin-top: 22px;
  font-size: 0.96rem;
  color: #5c4315;
}
.not-for strong{ color: #3f2d0c; }

/* ---------- FAQ / extractability ---------- */
.faq{ background: var(--paper); }
.faq-grid{
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 28px;
}
.faq-item{
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 26px 28px;
  background: var(--parchment);
}
.faq-item h3{
  font-size: 1.12rem;
  font-weight: 600;
  margin-bottom: 10px;
  color: var(--navy-deep);
}
.faq-item p{ margin: 0 0 10px; color: var(--ink-soft); }
.faq-item p:last-child{ margin-bottom: 0; }
.faq-item ul{ margin: 8px 0 0; padding-left: 20px; color: var(--ink-soft); }
.faq-item li{ margin-bottom: 6px; }

/* ---------- differentiators ---------- */
.diff{ background: var(--parchment); }
.diff-grid{
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 26px;
}
.diff-card{
  background: var(--paper);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 26px 24px;
}
.diff-card .num{
  font-family: "Source Serif 4", Georgia, serif;
  font-size: 0.85rem;
  font-weight: 700;
  color: var(--brass);
  letter-spacing: .06em;
  text-transform: uppercase;
  margin-bottom: 10px;
  display: block;
}
.diff-card h3{
  font-size: 1.08rem;
  margin-bottom: 8px;
}
.diff-card p{ color: var(--ink-soft); margin: 0; font-size: 0.96rem; }

.baseline-box{
  margin-top: 34px;
  background: var(--navy-deep);
  color: #dfe3ee;
  border-radius: 6px;
  padding: 30px 32px;
}
.baseline-box .tag{
  color: #d9c08c;
  font-size: 0.72rem;
  font-weight: 700;
  letter-spacing: .1em;
  text-transform: uppercase;
  display: block;
  margin-bottom: 12px;
}
.baseline-box p{ margin: 0 0 12px; color: #c9cfdd; }
.baseline-box p:last-child{ margin-bottom: 0; }
.baseline-box .q{
  font-style: italic;
  color: #f4efe3;
  border-left: 3px solid var(--brass);
  padding-left: 16px;
  margin: 16px 0;
}

/* ---------- buy ---------- */
.buy{ background: var(--navy-deep); color: #eef0f6; }
.buy .section-head h2{ color: #ffffff; }
.buy .section-head p{ color: #c9cfdd; }
.buy-grid{
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 22px;
}
.buy-card{
  background: rgba(255,255,255,0.04);
  border: 1px solid rgba(255,255,255,0.14);
  border-radius: 6px;
  padding: 26px 24px;
  display: flex;
  flex-direction: column;
}
.buy-card h3{
  color: #ffffff;
  font-size: 1.1rem;
  margin-bottom: 4px;
}
.buy-card .fmt-note{
  font-size: 0.82rem;
  color: #9aa2b8;
  margin-bottom: 14px;
}
.buy-card .price{
  font-family: "Source Serif 4", Georgia, serif;
  font-size: 1.7rem;
  font-weight: 600;
  color: #f4efe3;
  margin-bottom: 4px;
}
.buy-card .asin{
  font-size: 0.76rem;
  color: #7d859c;
  margin-bottom: 18px;
  font-family: "SFMono-Regular", Menlo, monospace;
}
.buy-card .btn{ margin-top: auto; justify-content: center; }

/* ---------- footer ---------- */
footer{
  background: var(--navy-deep);
  border-top: 1px solid rgba(255,255,255,0.08);
  color: #8b93aa;
  font-size: 0.85rem;
  padding: 28px 0;
}
footer .wrap{
  display: flex;
  justify-content: space-between;
  flex-wrap: wrap;
  gap: 10px;
}
footer a{ color: #b7bdd0; text-decoration: none; }

/* ---------- responsive ---------- */
@media (max-width: 880px){
  .hero .wrap{ grid-template-columns: 1fr; }
  .hero-cover{ order: -1; }
  .hero-cover img{ max-width: 220px; }
  .facts .wrap{ grid-template-columns: repeat(2, 1fr); row-gap: 20px; }
  .fact{ border-left: none; padding-left: 0; }
  .faq-grid{ grid-template-columns: 1fr; }
  .diff-grid{ grid-template-columns: 1fr; }
  .buy-grid{ grid-template-columns: 1fr; }
}