:root {
  color-scheme: light;
  --bg: oklch(0.975 0.006 236);
  --surface: oklch(0.995 0.003 236);
  --surface-2: oklch(0.948 0.014 236);
  --ink: oklch(0.18 0.035 252);
  --muted: oklch(0.43 0.04 248);
  --quiet: oklch(0.64 0.035 246);
  --blue: oklch(0.58 0.19 254);
  --blue-deep: oklch(0.33 0.12 252);
  --green: oklch(0.67 0.17 157);
  --line: oklch(0.86 0.018 238);
  --line-strong: oklch(0.68 0.045 242);
  --shadow: 0 12px 28px oklch(0.28 0.06 250 / 0.1);
  --max: 1180px;
  --ease: cubic-bezier(0.16, 1, 0.3, 1);
}

* {
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
}

body {
  margin: 0;
  min-height: 100vh;
  color: var(--ink);
  background:
    radial-gradient(
      circle at 78% 8%,
      oklch(0.87 0.075 158 / 0.44),
      transparent 25rem
    ),
    linear-gradient(
      135deg,
      oklch(0.985 0.006 236),
      var(--bg) 58%,
      oklch(0.93 0.018 241)
    );
  font-family:
    ui-sans-serif, 'Hiragino Sans GB', 'PingFang SC', 'Avenir Next', 'Segoe UI',
    sans-serif;
  text-rendering: geometricPrecision;
}

body::before {
  position: fixed;
  inset: 0;
  z-index: -1;
  content: '';
  background:
    linear-gradient(90deg, oklch(0.55 0.04 240 / 0.08) 1px, transparent 1px),
    linear-gradient(oklch(0.55 0.04 240 / 0.08) 1px, transparent 1px);
  background-size: 96px 96px;
  mask-image: linear-gradient(to bottom, black 0%, transparent 72%);
}

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

button,
.button {
  border: 0;
  font: inherit;
}

.section-shell {
  width: min(calc(100% - 40px), var(--max));
  margin: 0 auto;
}

.site-header {
  position: sticky;
  top: 16px;
  z-index: 10;
  display: grid;
  grid-template-columns: 1fr auto 1fr;
  align-items: center;
  gap: 18px;
  width: min(calc(100% - 40px), var(--max));
  margin: 16px auto 0;
  padding: 10px 10px 10px 14px;
  border: 1px solid var(--line);
  border-radius: 18px;
  background: oklch(0.985 0.004 236 / 0.86);
  backdrop-filter: blur(18px);
}

.brand,
.nav,
.hero-actions,
.principles,
.site-footer,
.panel-nav {
  display: flex;
  align-items: center;
}

.brand {
  gap: 10px;
  width: fit-content;
  font-weight: 850;
  letter-spacing: -0.02em;
}

.brand img {
  width: 30px;
  height: 30px;
}

.nav {
  gap: 4px;
  color: var(--muted);
  font-size: 0.94rem;
}

.nav a {
  padding: 9px 12px;
  border-radius: 10px;
}

.nav a:hover {
  color: var(--blue-deep);
  background: var(--surface-2);
}

.header-cta {
  justify-self: end;
  padding: 10px 14px;
  border-radius: 12px;
  color: white;
  background: var(--ink);
  font-size: 0.94rem;
  font-weight: 750;
}

.hero {
  display: grid;
  grid-template-columns: minmax(0, 0.9fr) minmax(410px, 1.1fr);
  gap: clamp(34px, 7vw, 92px);
  align-items: center;
  min-height: calc(100vh - 80px);
  padding: clamp(74px, 10vw, 124px) 0 84px;
}

.signal {
  margin: 0 0 18px;
  color: var(--blue-deep);
  font-size: 0.92rem;
  font-weight: 820;
  letter-spacing: 0.01em;
}

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

h1,
h2,
h3 {
  color: var(--ink);
  text-wrap: balance;
}

h1 {
  max-width: 11.2em;
  margin-bottom: 24px;
  font-family: 'Songti SC', 'STSong', 'Noto Serif CJK SC', Georgia, serif;
  font-size: clamp(3.25rem, 8.2vw, 6rem);
  font-weight: 850;
  line-height: 0.98;
  letter-spacing: -0.035em;
}

h2 {
  font-size: clamp(2.2rem, 5vw, 4.35rem);
  line-height: 1.02;
  letter-spacing: -0.035em;
}

h3 {
  font-size: clamp(1.25rem, 2vw, 1.6rem);
  line-height: 1.16;
  letter-spacing: -0.025em;
}

.hero-text,
.workspace-copy p,
.cta-section p {
  max-width: 45rem;
  color: var(--muted);
  font-size: clamp(1.05rem, 1.7vw, 1.24rem);
  line-height: 1.75;
  text-wrap: pretty;
}

.hero-actions {
  flex-wrap: wrap;
  gap: 12px;
  margin-top: 34px;
}

.button {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  min-height: 48px;
  padding: 0 18px;
  border-radius: 12px;
  font-weight: 820;
  transition:
    transform 180ms var(--ease),
    background 180ms var(--ease);
}

.button:hover {
  transform: translateY(-2px);
}

.button.primary {
  color: white;
  background: var(--blue);
}

.button.secondary {
  color: var(--blue-deep);
  background: var(--surface-2);
}

.hero-board {
  position: relative;
  min-height: 610px;
  padding: 34px;
  border: 1px solid var(--line);
  border-radius: 22px;
  background:
    linear-gradient(145deg, oklch(0.99 0.004 236), oklch(0.93 0.018 238)),
    var(--surface);
  box-shadow: var(--shadow);
  overflow: hidden;
  animation: board-in 860ms var(--ease) both;
}

.hero-board::after {
  position: absolute;
  right: -18%;
  bottom: -20%;
  width: 28rem;
  height: 28rem;
  content: '';
  border: 1px solid oklch(0.72 0.09 254 / 0.45);
  border-radius: 50%;
  background:
    radial-gradient(
      circle,
      transparent 0 34%,
      oklch(0.72 0.09 254 / 0.16) 34.4% 35%,
      transparent 35.4% 100%
    ),
    conic-gradient(
      from 90deg,
      transparent,
      oklch(0.58 0.19 254 / 0.14),
      transparent 45%
    );
}

.reading-line {
  position: relative;
  z-index: 1;
  padding: 20px 0;
  border-bottom: 1px solid var(--line);
  color: var(--quiet);
  font-family: ui-serif, Georgia, serif;
  font-size: clamp(1.4rem, 3vw, 2.25rem);
  line-height: 1.25;
}

.reading-line mark {
  margin-left: 8px;
  padding: 0 5px 3px;
  color: var(--ink);
  background: oklch(0.82 0.09 254 / 0.64);
}

.quick-menu {
  position: relative;
  z-index: 2;
  display: inline-flex;
  flex-wrap: wrap;
  gap: 8px;
  margin-top: 22px;
  padding: 8px;
  border: 1px solid var(--line);
  border-radius: 16px;
  background: var(--surface);
  box-shadow: 0 8px 18px oklch(0.28 0.06 250 / 0.08);
}

.quick-menu button {
  min-height: 38px;
  padding: 0 14px;
  border-radius: 10px;
  color: var(--blue-deep);
  background: var(--surface-2);
  font-weight: 820;
}

.quick-menu .selected {
  color: white;
  background: var(--blue);
}

.term-sheet {
  position: relative;
  z-index: 1;
  width: min(100%, 520px);
  margin: 54px 0 0 auto;
  padding: clamp(24px, 4vw, 36px);
  border: 1px solid var(--line);
  border-radius: 18px;
  background: oklch(0.995 0.004 236 / 0.92);
}

.sheet-head {
  display: flex;
  justify-content: space-between;
  gap: 16px;
  color: var(--quiet);
  font-size: 0.88rem;
  font-weight: 780;
}

.sync-state::before {
  display: inline-block;
  width: 7px;
  height: 7px;
  margin-right: 7px;
  content: '';
  border-radius: 50%;
  background: var(--green);
}

.term-sheet h2 {
  margin: 56px 0 10px;
  font-family: Georgia, 'Times New Roman', serif;
  font-size: clamp(3.2rem, 7vw, 5.2rem);
  font-weight: 700;
}

.translation {
  margin-bottom: 16px;
  color: var(--blue-deep);
  font-size: 1.45rem;
  font-weight: 840;
}

.definition {
  max-width: 28rem;
  color: var(--muted);
  font-size: 1.03rem;
  line-height: 1.65;
}

.memory-row {
  display: grid;
  grid-template-columns: 1fr auto 1fr auto;
  gap: 12px;
  align-items: center;
  margin-top: 34px;
  padding-top: 18px;
  border-top: 1px solid var(--line);
  color: var(--quiet);
}

.memory-row strong {
  color: var(--ink);
  font-size: 1.4rem;
}

.principles {
  justify-content: space-between;
  gap: 18px;
  padding: 22px 0 86px;
  border-top: 1px solid var(--line);
  color: var(--blue-deep);
  font-size: clamp(1rem, 1.6vw, 1.18rem);
  font-weight: 760;
}

.principles p {
  margin: 0;
}

.flow {
  display: grid;
  grid-template-columns: 0.8fr 1.2fr;
  gap: clamp(36px, 7vw, 90px);
  padding: 72px 0 104px;
}

.section-intro {
  position: sticky;
  top: 100px;
  align-self: start;
}

.flow-list {
  display: grid;
  gap: 0;
  border-top: 1px solid var(--line-strong);
}

.flow-list article {
  display: grid;
  grid-template-columns: 130px 0.72fr 1fr;
  gap: 24px;
  padding: 30px 0;
  border-bottom: 1px solid var(--line);
}

.flow-list span {
  color: var(--blue);
  font-weight: 850;
}

.flow-list h3 {
  margin: 0;
}

.flow-list p {
  margin: 0;
  color: var(--muted);
  line-height: 1.7;
}

.workspace {
  display: grid;
  grid-template-columns: 0.88fr 1.12fr;
  gap: clamp(32px, 6vw, 78px);
  align-items: center;
  padding: 78px clamp(22px, 5vw, 54px);
  border: 1px solid var(--line);
  border-radius: 22px;
  background: var(--ink);
  color: white;
}

.workspace h2,
.workspace .signal {
  color: white;
}

.workspace-copy p {
  color: oklch(0.82 0.025 245);
}

.workspace-panel {
  padding: 18px;
  border: 1px solid oklch(0.62 0.04 248 / 0.45);
  border-radius: 18px;
  background: oklch(0.23 0.045 252);
}

.panel-nav {
  gap: 8px;
  margin-bottom: 18px;
}

.panel-nav span {
  padding: 9px 12px;
  border-radius: 10px;
  color: oklch(0.76 0.035 245);
  background: oklch(0.28 0.05 252);
  font-size: 0.92rem;
  font-weight: 780;
}

.panel-nav .active {
  color: var(--ink);
  background: oklch(0.91 0.045 240);
}

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

.vocab-list div {
  display: flex;
  justify-content: space-between;
  gap: 18px;
  padding: 18px;
  border: 1px solid oklch(0.62 0.04 248 / 0.35);
  border-radius: 14px;
  background: oklch(0.2 0.04 252);
}

.vocab-list strong {
  font-family: Georgia, 'Times New Roman', serif;
  font-size: 1.4rem;
}

.vocab-list span {
  color: oklch(0.78 0.03 245);
}

.cta-section {
  display: grid;
  grid-template-columns: 1fr auto;
  gap: 28px;
  align-items: center;
  padding: 94px 0;
}

.cta-section p {
  margin-bottom: 0;
}

.site-footer {
  justify-content: space-between;
  gap: 18px;
  width: min(calc(100% - 40px), var(--max));
  margin: 0 auto;
  padding: 26px 0 42px;
  border-top: 1px solid var(--line);
  color: var(--muted);
  font-size: 0.95rem;
}

.site-footer span:first-child {
  color: var(--ink);
  font-weight: 850;
}

@keyframes board-in {
  from {
    opacity: 0;
    transform: translateY(18px) scale(0.98);
    filter: blur(10px);
  }

  to {
    opacity: 1;
    transform: translateY(0) scale(1);
    filter: blur(0);
  }
}

@media (max-width: 920px) {
  .site-header {
    grid-template-columns: 1fr auto;
  }

  .nav {
    display: none;
  }

  .hero,
  .flow,
  .workspace,
  .cta-section {
    grid-template-columns: 1fr;
  }

  .hero {
    min-height: auto;
    padding-top: 66px;
  }

  .hero-board {
    min-height: 560px;
  }

  .section-intro {
    position: static;
  }

  .flow-list article {
    grid-template-columns: 1fr;
    gap: 10px;
  }

  .cta-section .button {
    justify-self: start;
  }
}

@media (max-width: 580px) {
  .section-shell,
  .site-footer,
  .site-header {
    width: min(calc(100% - 24px), var(--max));
  }

  .site-header {
    top: 10px;
  }

  .header-cta {
    display: none;
  }

  h1 {
    font-size: clamp(2.9rem, 15vw, 4.3rem);
  }

  h2 {
    font-size: clamp(2rem, 12vw, 3.2rem);
  }

  .hero-board {
    min-height: 530px;
    padding: 20px;
  }

  .quick-menu {
    display: grid;
  }

  .term-sheet {
    margin-top: 28px;
  }

  .memory-row {
    grid-template-columns: 1fr auto;
  }

  .principles {
    align-items: flex-start;
    flex-direction: column;
    padding-bottom: 54px;
  }

  .workspace,
  .workspace-panel {
    border-radius: 16px;
  }

  .vocab-list div {
    flex-direction: column;
  }

  .site-footer {
    align-items: flex-start;
    flex-direction: column;
  }
}

@media (prefers-reduced-motion: reduce) {
  *,
  *::before,
  *::after {
    scroll-behavior: auto !important;
    animation-duration: 1ms !important;
    transition-duration: 1ms !important;
  }
}