@import url('https://fonts.googleapis.com/css2?family=Noto+Sans+SC:wght@400;500;600;700&family=Noto+Serif+SC:wght@400;500;600;700;900&display=swap');

:root {
  --ink: #272b27;
  --muted: #69675e;
  --paper: #f7f1e4;
  --card: #fbf7ee;
  --rule: #c8bda8;
  --vermilion: #a94737;
  --jade: #526e69;
  --serif: "Noto Serif SC", "Songti SC", "STSong", serif;
  --sans: "Noto Sans SC", "PingFang SC", sans-serif;
}

* { box-sizing: border-box; }
html { scroll-behavior: smooth; }
body {
  min-width: 320px;
  margin: 0;
  color: var(--ink);
  background: #ded8c9;
  background-image: radial-gradient(circle at 8% 16%, rgba(255,255,255,.5), transparent 35%),
                    radial-gradient(circle at 88% 90%, rgba(124,116,92,.15), transparent 37%);
  font-family: var(--sans);
}
a { color: inherit; }
a:focus-visible { outline: 3px solid var(--vermilion); outline-offset: 4px; }
h1, h2, h3, p, figure { margin: 0; }
img { display: block; max-width: 100%; }

.page {
  width: min(1440px, calc(100% - 44px));
  margin: 22px auto;
  overflow: hidden;
  border: 1px solid #b8ad99;
  background: var(--paper);
  box-shadow: 0 22px 70px rgba(43, 38, 28, .12);
}
.topbar {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 16px;
  min-height: 68px;
  padding: 12px clamp(22px, 4vw, 64px);
  border-bottom: 1px solid var(--rule);
  background: rgba(250,247,239,.94);
}
.brand {
  display: inline-flex;
  align-items: center;
  gap: 12px;
  font-family: var(--serif);
  font-size: 18px;
  font-weight: 900;
  letter-spacing: .08em;
  text-decoration: none;
}
.brand:hover { color: var(--vermilion); }
.brand-mark {
  display: grid;
  place-items: center;
  width: 33px;
  height: 33px;
  border: 1px solid #8d3229;
  background: var(--vermilion);
  color: #fff8e9;
  font-family: var(--serif);
  font-size: 21px;
  line-height: 1;
}
.top-note {
  color: #6b675d;
  font-family: var(--serif);
  font-size: 12px;
  letter-spacing: .18em;
}

.hero {
  position: relative;
  display: flex;
  align-items: center;
  min-height: clamp(460px, 44vw, 620px);
  overflow: hidden;
  isolation: isolate;
  border-bottom: 1px solid #b8ad99;
  background: #e8dfcb;
}
.hero-art {
  position: absolute;
  inset: 0;
  z-index: -2;
  width: 100%;
  height: 100%;
  object-fit: cover;
  object-position: center;
}
.hero::before {
  position: absolute;
  inset: 0;
  z-index: -1;
  content: "";
  background: linear-gradient(90deg, rgba(247,241,228,.92) 0%, rgba(247,241,228,.71) 28%, rgba(247,241,228,.07) 54%, transparent 78%);
}
.hero-copy {
  width: min(52%, 635px);
  padding: 50px 0 66px clamp(34px, 6.2vw, 92px);
}
.eyebrow {
  display: inline-flex;
  align-items: center;
  gap: 11px;
  margin-bottom: 22px;
  color: #665c4c;
  font-family: var(--serif);
  font-size: 13px;
  font-weight: 700;
  letter-spacing: .16em;
}
.eyebrow::before {
  width: 30px;
  height: 1px;
  background: var(--vermilion);
  content: "";
}
h1 {
  font-family: var(--serif);
  font-size: clamp(58px, 6.4vw, 94px);
  font-weight: 900;
  line-height: 1.19;
  letter-spacing: .05em;
  text-shadow: 0 2px 16px rgba(247,241,228,.45);
}
h1 em { color: var(--vermilion); font-style: normal; }
.hero-lead {
  max-width: 530px;
  margin-top: 24px;
  color: #474741;
  font-family: var(--serif);
  font-size: clamp(15px, 1.38vw, 19px);
  font-weight: 600;
  line-height: 1.9;
  letter-spacing: .03em;
}
.hero-link {
  display: inline-flex;
  align-items: center;
  gap: 16px;
  margin-top: 28px;
  padding: 13px 20px 14px;
  border: 1px solid #7f3a2f;
  background: var(--vermilion);
  color: #fff7e8;
  font-family: var(--serif);
  font-size: 15px;
  font-weight: 700;
  letter-spacing: .12em;
  text-decoration: none;
  transition: transform .2s, background .2s;
}
.hero-link:hover { transform: translateY(-3px); background: #853a2e; }
.hero-link span { font-family: var(--sans); font-size: 18px; line-height: 1; }
.hero-seal {
  position: absolute;
  right: clamp(18px, 3vw, 48px);
  bottom: 24px;
  display: grid;
  place-items: center;
  width: 54px;
  height: 54px;
  border: 2px solid #a64b3c;
  color: #a64b3c;
  font-family: var(--serif);
  font-size: 17px;
  font-weight: 900;
  line-height: 1.05;
  text-align: center;
  transform: rotate(8deg);
}

main { padding: 0; }
.main-content { padding: 0 clamp(24px, 5.2vw, 76px) 84px; }
.lesson-search {
  display: grid;
  grid-template-columns: minmax(230px, .8fr) minmax(0, 1.2fr);
  gap: 12px clamp(26px, 4vw, 60px);
  margin-top: 48px;
  padding: clamp(24px, 3vw, 38px);
  border: 1px solid #ad9d80;
  border-top: 4px solid var(--jade);
  background: #f0eadb;
  box-shadow: 5px 6px 0 rgba(82, 110, 105, .12);
}
.lesson-search-eyebrow {
  color: var(--vermilion);
  font-family: var(--serif);
  font-size: 12px;
  font-weight: 700;
  letter-spacing: .16em;
}
.lesson-search-intro h2 {
  margin: 10px 0 8px;
  font-family: var(--serif);
  font-size: clamp(27px, 2.7vw, 39px);
  font-weight: 900;
  line-height: 1.25;
}
.lesson-search-intro p {
  max-width: 390px;
  color: #5d5a51;
  font-size: 14px;
  line-height: 1.75;
}
.lesson-search-form { align-self: center; min-width: 0; }
.lesson-search-form label {
  display: block;
  margin-bottom: 10px;
  color: #4a584f;
  font-family: var(--serif);
  font-size: 14px;
  font-weight: 700;
}
.lesson-search-controls { display: grid; grid-template-columns: minmax(0, 1fr) auto; gap: 9px; }
.lesson-search-controls input {
  width: 100%;
  min-width: 0;
  min-height: 55px;
  padding: 12px 16px;
  border: 1px solid #918775;
  border-radius: 0;
  outline: none;
  background: #fffdf7;
  color: var(--ink);
  font: 16px/1.4 var(--sans);
}
.lesson-search-controls input:focus-visible { border-color: var(--jade); outline: 2px solid var(--jade); outline-offset: 2px; }
.lesson-search-controls input::placeholder { color: #888578; }
.lesson-search-controls button {
  min-height: 55px;
  padding: 11px 20px;
  border: 1px solid #3d5a54;
  background: var(--jade);
  color: #fffaf0;
  font-family: var(--serif);
  font-size: 15px;
  font-weight: 700;
  cursor: pointer;
}
.lesson-search-controls button:hover { background: #3d5a54; }
.lesson-search-controls button:focus-visible { outline: 3px solid var(--vermilion); outline-offset: 3px; }
.lesson-search-controls button span { margin-left: 8px; font-family: var(--sans); }
.lesson-search-hint { margin-top: 10px; color: #6d6b60; font-size: 12px; line-height: 1.6; }
.lesson-search-status {
  grid-column: 1 / -1;
  color: #4d625b;
  font-size: 13px;
  font-weight: 700;
  line-height: 1.6;
}
.lesson-search-status:empty { display: none; }
.lesson-search-results {
  grid-column: 1 / -1;
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 10px;
  margin: 0;
  padding: 14px 0 0;
  border-top: 1px solid #c8bda8;
  list-style: none;
}
.lesson-search-results[hidden] { display: none; }
.lesson-search-results li { min-width: 0; }
.lesson-search-result {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 16px;
  min-height: 84px;
  padding: 14px 16px;
  border: 1px solid #c9bda8;
  background: #fbf7ee;
  text-decoration: none;
  transition: border-color .2s, background .2s;
}
.lesson-search-result:hover { border-color: var(--vermilion); background: #fffdf7; }
.lesson-search-result strong { display: block; font: 800 18px/1.4 var(--serif); }
.lesson-search-result small { display: block; margin-top: 6px; color: #6b695f; font: 12px/1.5 var(--sans); }
.lesson-search-result .result-arrow { flex: none; color: var(--vermilion); font: 700 21px/1 var(--sans); }
.grade-entries {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 18px;
  margin-top: 48px;
  scroll-margin-top: 22px;
}
.start {
  position: relative;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 20px;
  min-height: 170px;
  padding: 25px clamp(24px, 3vw, 42px);
  overflow: hidden;
  border: 1px solid #b8ad99;
  background: #ede7d7;
}
.start::before {
  content: attr(data-mark);
  position: absolute;
  right: 10px;
  bottom: -50px;
  color: rgba(82,110,105,.12);
  font-family: var(--serif);
  font-size: 182px;
  font-weight: 900;
  line-height: 1;
}
.start:nth-child(4n + 2),
.start:nth-child(4n + 3) { background: #e3e8e1; }
.start > * { position: relative; z-index: 1; }
.start p {
  margin-bottom: 12px;
  color: var(--vermilion);
  font-family: var(--serif);
  font-size: 13px;
  font-weight: 700;
  letter-spacing: .14em;
}
.start h2 {
  font-family: var(--serif);
  font-size: clamp(27px, 2.6vw, 39px);
  font-weight: 900;
  letter-spacing: .03em;
  line-height: 1.3;
}
.start-button {
  flex: 0 0 auto;
  min-width: 112px;
  padding: 12px 16px;
  border: 1px solid #6a6255;
  background: rgba(251,247,238,.9);
  font-family: var(--serif);
  font-size: 13px;
  font-weight: 700;
  letter-spacing: .06em;
  text-align: center;
  text-decoration: none;
  transition: transform .2s, border-color .2s, color .2s;
}
.start-button:hover { transform: translateY(-3px); border-color: var(--vermilion); color: var(--vermilion); }

.section-rule {
  width: 76px;
  height: 3px;
  margin: 88px 0 23px;
  background: var(--vermilion);
}
.map-heading h2 {
  font-family: var(--serif);
  font-size: clamp(30px, 3.3vw, 49px);
  font-weight: 900;
  line-height: 1.35;
  letter-spacing: .025em;
}
.principle {
  max-width: 920px;
  margin: 14px 0 40px;
  color: #5d5a51;
  font-size: 15px;
  line-height: 1.9;
}
.key-map { display: grid; gap: 28px; }
.key-pair {
  display: grid;
  grid-template-columns: minmax(245px, 33%) minmax(0, 1fr);
  grid-template-rows: auto 1fr;
  gap: 0 clamp(24px, 3vw, 42px);
  min-width: 0;
  padding: 21px;
  border: 1px solid var(--rule);
  background: #eee9dc;
}
.key-pair:nth-child(2) { background: #e9eae1; }
.key-pair:nth-child(3) { background: #eee8df; }
.chapter-art {
  grid-column: 1;
  grid-row: 1 / 3;
  width: 100%;
  height: 100%;
  min-height: 335px;
  max-height: 530px;
  border: 1px solid #c2b39a;
  object-fit: cover;
}
.pair-heading {
  grid-column: 2;
  grid-row: 1;
  display: flex;
  align-items: baseline;
  gap: 16px;
  margin: 10px 0 18px;
  border-bottom: 1px solid #c7bba6;
  padding-bottom: 16px;
}
.pair-heading b {
  font-family: var(--serif);
  font-size: clamp(23px, 2.2vw, 32px);
  font-weight: 900;
  letter-spacing: .03em;
}
.pair-heading span { color: var(--muted); font-family: var(--serif); font-size: 13px; }
.pair-keys {
  grid-column: 2;
  grid-row: 2;
  display: grid;
  gap: 12px;
  align-content: start;
}
.context-group .pair-keys { grid-template-columns: 1fr; }
.sentence-group .pair-keys { grid-template-columns: repeat(3, minmax(0, 1fr)); }
.word-group .pair-keys { grid-template-columns: repeat(2, minmax(0, 1fr)); }
.key {
  min-width: 0;
  padding: 19px;
  border: 1px solid #d2c7b4;
  background: rgba(251,247,239,.92);
}
.key-top { display: flex; align-items: center; gap: 9px; color: var(--vermilion); }
.direct-marker {
  display: inline-grid;
  place-items: center;
  min-width: 27px;
  height: 27px;
  padding: 0 3px;
  border: 1px solid currentColor;
  font-family: var(--serif);
  font-size: 15px;
  font-weight: 900;
  line-height: 1;
}
.seal-marker { outline: 1px solid var(--vermilion); outline-offset: 2px; }
.order-marker { min-width: 48px; font-size: 13px; }
.break-marker { font-size: 22px; }
.key-icon {
  position: relative;
  display: inline-block;
  width: 31px;
  height: 23px;
  flex: 0 0 auto;
}
.key-icon::before {
  position: absolute;
  top: 4px;
  left: 0;
  width: 12px;
  height: 12px;
  border: 2px solid var(--vermilion);
  border-radius: 50%;
  content: "";
}
.key-icon::after {
  position: absolute;
  top: 10px;
  left: 14px;
  width: 17px;
  height: 5px;
  background: var(--vermilion);
  clip-path: polygon(0 0,100% 0,100% 50%,78% 50%,78% 100%,58% 100%,58% 50%,0 50%);
  content: "";
}
.problem-label { font-family: var(--serif); font-size: 12px; font-weight: 700; }
.card-title-line { margin: 16px 0 11px; }
.key h3 {
  margin-bottom: 7px;
  font-family: var(--serif);
  font-size: clamp(19px, 1.6vw, 24px);
  font-weight: 900;
  line-height: 1.3;
}
.card-definition {
  color: #625e54;
  font-size: 12px;
  line-height: 1.65;
}
.card-example {
  border-top: 1px solid #e2d9ca;
  padding-top: 10px;
  color: #46453e;
  font-family: var(--serif);
  font-size: 13px;
  line-height: 1.8;
}
.card-example b { color: var(--vermilion); font-family: var(--sans); font-size: 12px; }
footer {
  padding: 23px clamp(24px, 5.2vw, 76px);
  border-top: 1px solid var(--rule);
  color: #746e61;
  font-family: var(--serif);
  font-size: 12px;
  letter-spacing: .08em;
}

@media (max-width: 1080px) {
  .hero-copy { width: 58%; }
  .key-pair { grid-template-columns: minmax(210px, 30%) minmax(0, 1fr); }
  .sentence-group .pair-keys { grid-template-columns: 1fr; }
  .start { display: block; }
  .start-button { display: inline-block; margin-top: 17px; }
}
@media (max-width: 760px) {
  .page { width: 100%; margin: 0; border: 0; box-shadow: none; }
  .topbar { min-height: 58px; padding: 10px 19px; }
  .brand { font-size: 16px; }
  .top-note { display: none; }
  .hero { display: block; min-height: 0; }
  .hero-art { position: relative; z-index: auto; width: 100%; height: 300px; object-position: 72% center; }
  .hero::before { display: none; }
  .hero-copy { width: auto; padding: 26px 24px 38px; }
  .eyebrow { margin-bottom: 12px; font-size: 11px; }
  h1 { font-size: clamp(49px, 11vw, 72px); }
  .hero-lead { margin-top: 14px; font-size: 15px; }
  .hero-link { margin-top: 19px; }
  .hero-seal { top: 228px; right: 20px; bottom: auto; width: 48px; height: 48px; font-size: 15px; background: rgba(247,241,228,.86); }
  .main-content { padding: 0 20px 56px; }
  .lesson-search { grid-template-columns: 1fr; gap: 18px; margin-top: 22px; padding: 22px; }
  .lesson-search-intro h2 { font-size: 30px; }
  .lesson-search-results { grid-template-columns: 1fr; }
  .grade-entries { grid-template-columns: 1fr; gap: 12px; margin-top: 22px; }
  .start { min-height: 150px; padding: 22px; }
  .start h2 { font-size: 29px; }
  .section-rule { margin-top: 66px; }
  .principle { margin-bottom: 26px; font-size: 14px; }
  .key-map { gap: 18px; }
  .key-pair { grid-template-columns: 1fr; padding: 13px; }
  .chapter-art { grid-column: 1; grid-row: 1; height: 240px; min-height: 0; max-height: none; object-position: center 42%; }
  .pair-heading { grid-column: 1; grid-row: 2; margin: 20px 5px 15px; }
  .pair-keys { grid-column: 1; grid-row: 3; }
  .sentence-group .pair-keys, .word-group .pair-keys { grid-template-columns: 1fr; }
  .key { padding: 18px; }
}
@media (max-width: 400px) {
  .hero-art { height: 250px; }
  .hero-seal { top: 184px; }
  .pair-heading { display: block; }
  .pair-heading span { display: block; margin-top: 6px; }
  .lesson-search-controls { grid-template-columns: 1fr; }
  .lesson-search-controls button { width: 100%; }
}
@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  .hero-link, .start-button, .lesson-search-result { transition: none; }
}