@font-face {
  font-family: Atkinson;
  src: url("/assets/atkinson.woff2") format("woff2");
  font-weight: 200 800;
  font-display: swap;
}

:root {
  color-scheme: light;
  --paper: #f6f7f9;
  --surface: #eef1f5;
  --ink: #20252d;
  --muted: #596472;
  --line: #d9dee6;
  --blue: #245cce;
  --blue-tint: #e4ebfa;
  --image-border: #dfe4eb;
  --shadow: 0 24px 60px -30px rgb(25 40 70 / 22%);
  font-family: Atkinson, "PingFang SC", "Microsoft YaHei", sans-serif;
  color: var(--ink);
  background: var(--paper);
}

@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) {
    color-scheme: dark;
    --paper: #151a22;
    --surface: #1c2330;
    --ink: #f0f2f6;
    --muted: #a9b4c5;
    --line: #333e50;
    --blue: #9ab8ff;
    --blue-tint: #202f4c;
    --image-border: #333e50;
    --shadow: 0 24px 60px -30px rgb(0 0 0 / 50%);
  }
}

:root[data-theme="dark"] {
  color-scheme: dark;
  --paper: #151a22;
  --surface: #1c2330;
  --ink: #f0f2f6;
  --muted: #a9b4c5;
  --line: #333e50;
  --blue: #9ab8ff;
  --blue-tint: #202f4c;
  --image-border: #333e50;
  --shadow: 0 24px 60px -30px rgb(0 0 0 / 50%);
}

* {
  box-sizing: border-box;
}
html {
  scroll-behavior: smooth;
  scroll-padding-top: 110px;
}
body {
  margin: 0;
}
a {
  color: inherit;
  text-decoration: none;
}
button {
  font: inherit;
}
select {
  font: inherit;
}
button,
a,
summary {
  -webkit-tap-highlight-color: transparent;
}
button,
summary {
  cursor: pointer;
}
img {
  display: block;
  max-width: 100%;
  height: auto;
}
figure,
p,
h1,
h2,
h3 {
  margin: 0;
}
::selection {
  background: var(--blue-tint);
  color: var(--ink);
}
:focus-visible {
  outline: 3px solid var(--blue);
  outline-offset: 6px;
  border-radius: 4px;
}
.section-width {
  width: min(1240px, calc(100% - 112px));
  margin-inline: auto;
}
.skip-link {
  position: fixed;
  top: 12px;
  left: 16px;
  padding: 12px 20px;
  background: var(--ink);
  color: var(--paper);
  z-index: 30;
  transform: translateY(-150%);
}
.skip-link:focus {
  transform: none;
}
/* Layer scale: content 0, sticky study 1, site header 20, skip link 30. */
.site-header {
  width: min(1400px, calc(100% - 80px));
  height: 80px;
  margin-inline: auto;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 32px;
}
.brand {
  display: inline-flex;
  align-items: center;
  gap: 11px;
  font-weight: 730;
  font-size: 19px;
  letter-spacing: -0.6px;
  white-space: nowrap;
}
.brand img {
  border-radius: 8px;
}
.site-header nav {
  display: flex;
  align-items: center;
  gap: 34px;
  font-size: 14px;
  color: var(--muted);
}
.site-header nav a:hover {
  color: var(--blue);
}
.header-actions {
  display: flex;
  align-items: center;
  gap: 24px;
}
.language-select {
  max-width: 114px;
  min-height: 34px;
  border: 1px solid var(--line);
  border-radius: 7px;
  background: var(--paper);
  color: var(--ink);
  padding: 5px 7px;
  font-size: 12px;
  cursor: pointer;
}
.language-select option {
  color: var(--ink);
  background: var(--paper);
}
.not-found .language-select {
  margin-left: 24px;
}
.theme-toggle {
  border: 1px solid var(--line);
  border-radius: 50%;
  width: 34px;
  height: 34px;
  background: transparent;
  color: var(--ink);
  font-size: 22px;
  display: grid;
  place-items: center;
}
.nav-cta {
  font-size: 14px;
  font-weight: 650;
  white-space: nowrap;
}
.nav-cta span {
  margin-left: 12px;
  color: var(--blue);
}
.hero {
  display: grid;
  grid-template-columns: 1.13fr 1fr;
  align-items: center;
  gap: 50px;
  padding-block: 58px 90px;
  min-height: min(820px, calc(100dvh - 80px));
}
.eyebrow {
  font-size: 12px;
  font-weight: 730;
  letter-spacing: 0.19em;
  color: var(--blue);
}
.hero h1 {
  font-size: clamp(40px, 4.1vw, 62px);
  font-weight: 650;
  letter-spacing: -0.055em;
  line-height: 1.44;
  margin-top: 28px;
  white-space: nowrap;
}
.hero :where(h1) span {
  color: var(--blue);
}
:where(:root:lang(en)) .hero h1 {
  font-size: clamp(27px, 3.1vw, 46px);
  letter-spacing: -0.055em;
}
:where(:root:lang(ja)) .hero h1,
:where(:root:lang(ko)) .hero h1 {
  font-size: clamp(27px, 3.1vw, 46px);
  letter-spacing: -0.055em;
}
:root:lang(ko) {
  word-break: keep-all;
  font-family: Atkinson, "Apple SD Gothic Neo", "Malgun Gothic", sans-serif;
}
:root:lang(ja) {
  font-family: Atkinson, "Hiragino Sans", "Yu Gothic", Meiryo, sans-serif;
}
.hero-description {
  font-size: 17px;
  line-height: 1.9;
  color: var(--muted);
  margin-top: 28px;
}
.hero-links {
  display: flex;
  align-items: center;
  gap: 30px;
  margin-top: 42px;
}
.button {
  display: inline-flex;
  align-items: center;
  justify-content: space-between;
  gap: 42px;
  white-space: nowrap;
  background: var(--ink);
  color: var(--paper);
  border-radius: 7px;
  padding: 18px 25px;
  font-size: 15px;
  font-weight: 650;
  transition:
    transform 280ms ease,
    background 280ms ease;
}
.button:hover {
  transform: translateY(-3px);
  background: var(--blue);
  color: var(--paper);
}
.button span {
  font-size: 22px;
  line-height: 1;
}
.text-link {
  display: inline-flex;
  align-items: center;
  gap: 14px;
  font-size: 14px;
}
.text-link:hover {
  color: var(--blue);
}
.hero-art {
  overflow: hidden;
  border-radius: 9px;
  aspect-ratio: 4 / 5;
  background: #e7e9ed;
}
.hero-art img {
  width: 100%;
  height: 100%;
  object-fit: cover;
}
.manifesto {
  display: grid;
  grid-template-columns: 1.1fr 1fr;
  gap: 70px;
  padding-block: 64px 100px;
  border-top: 1px solid var(--line);
}
.manifesto-lead {
  font-size: clamp(27px, 2.5vw, 38px);
  line-height: 1.6;
  font-weight: 600;
  letter-spacing: -0.04em;
}
.manifesto-lead span {
  color: var(--muted);
}
.manifesto-body {
  padding-top: 8px;
  max-width: 440px;
}
.manifesto-body p {
  font-size: 15px;
  line-height: 1.95;
  color: var(--muted);
}
.manifesto-body :where(p + p) {
  margin-top: 16px;
}
.section-heading {
  max-width: 750px;
  padding-bottom: 48px;
}
.section-heading .eyebrow {
  margin-bottom: 22px;
}
h2 {
  font-size: clamp(32px, 3.4vw, 49px);
  font-weight: 600;
  line-height: 1.5;
  letter-spacing: -0.055em;
}
.section-heading > p:last-child {
  font-size: 16px;
  color: var(--muted);
  line-height: 1.85;
  margin-top: 22px;
}
.reading-section {
  padding-block: 52px 114px;
}
.source-grid {
  display: grid;
  grid-template-columns: 0.85fr 1.15fr;
  gap: 24px;
  margin-bottom: 40px;
}
.source-feature {
  background: var(--blue-tint);
  border-radius: 9px;
  padding: 35px 38px;
  min-height: 302px;
  position: relative;
}
.source-symbol {
  position: absolute;
  right: 32px;
  top: 28px;
  color: var(--blue);
  font-size: 45px;
}
.source-feature h3 {
  font-size: 28px;
  line-height: 1.55;
  letter-spacing: -0.04em;
  font-weight: 600;
}
.source-feature p,
.source-plain p {
  margin-top: 18px;
  max-width: 310px;
  font-size: 14px;
  color: var(--muted);
  line-height: 1.9;
}
.source-format {
  display: block;
  font-size: 12px;
  margin-top: 26px;
  color: var(--blue);
}
.source-plain {
  border: 1px solid var(--line);
  border-radius: 9px;
  padding: 38px;
  display: flex;
  align-items: center;
  gap: 34px;
}
.format-display {
  font-size: 92px;
  letter-spacing: -0.09em;
  color: var(--blue);
  font-weight: 430;
}
.source-plain h3 {
  font-size: 22px;
  line-height: 1.65;
  font-weight: 600;
  letter-spacing: -0.035em;
}
.format-list {
  display: flex;
  gap: 24px;
  margin-top: 28px;
  font-size: 14px;
  color: var(--muted);
}
.reader-showcase {
  background: var(--surface);
  border: 1px solid var(--image-border);
  border-radius: 9px;
  overflow: hidden;
  box-shadow: var(--shadow);
}
.preview-toolbar {
  display: flex;
  justify-content: space-between;
  gap: 16px;
  padding: 16px 22px;
  font-size: 12px;
  color: var(--muted);
  border-bottom: 1px solid var(--line);
}
.reader-showcase picture,
.study-sticky picture {
  display: block;
}
.reader-showcase img {
  width: 100%;
}
.reader-caption {
  display: grid;
  grid-template-columns: 1fr 1.1fr;
  gap: 70px;
  padding-top: 35px;
}
.reader-caption h3 {
  font-size: 22px;
  font-weight: 600;
  letter-spacing: -0.04em;
}
.reader-caption p {
  color: var(--muted);
  font-size: 14px;
  line-height: 1.9;
  max-width: 480px;
}
.retain-section {
  padding-block: 60px 110px;
}
.retain-section h2 span {
  color: var(--blue);
}
.retain-layout {
  display: grid;
  grid-template-columns: 0.8fr 1.2fr;
  gap: 85px;
}
.retain-story {
  padding-block: 38px 56px;
  max-width: 350px;
}
.retain-story + .retain-story {
  border-top: 1px solid var(--line);
}
.story-word {
  font-size: 42px;
  color: var(--blue);
  font-weight: 420;
  letter-spacing: -1.8px;
}
.retain-story h3 {
  font-size: 23px;
  font-weight: 600;
  letter-spacing: -0.04em;
  margin-top: 20px;
  line-height: 1.6;
}
.retain-story p {
  font-size: 15px;
  color: var(--muted);
  line-height: 1.95;
  margin-top: 17px;
}
.study-sticky {
  position: sticky;
  top: 40px;
  border: 1px solid var(--image-border);
  border-radius: 9px;
  background: var(--surface);
  overflow: hidden;
  box-shadow: var(--shadow);
}
.study-sticky img {
  width: 100%;
}
.study-note {
  font-size: 13px;
  line-height: 1.9;
  color: var(--muted);
  padding: 24px;
}
.principles {
  padding: 72px 60px 68px;
  background: var(--surface);
  border-radius: 9px;
}
.principles h2 {
  font-size: clamp(29px, 3vw, 42px);
}
.principles-grid {
  display: grid;
  grid-template-columns: 1.15fr 1fr 1fr;
  gap: 55px;
  margin-top: 50px;
}
.principles-grid article > span {
  font-size: 29px;
  color: var(--blue);
}
.principles-grid h3 {
  font-size: 19px;
  margin-top: 18px;
  font-weight: 600;
}
.principles-grid p {
  font-size: 14px;
  line-height: 1.85;
  color: var(--muted);
  margin-top: 14px;
  max-width: 270px;
}
.faq-section {
  display: grid;
  grid-template-columns: 0.9fr 1.1fr;
  gap: 85px;
  padding-block: 148px 100px;
}
.faq-intro h2 {
  font-size: 35px;
}
.faq-intro p {
  color: var(--muted);
  font-size: 14px;
  margin-top: 22px;
  line-height: 1.85;
}
.faq-list details {
  border-bottom: 1px solid var(--line);
  padding-block: 24px;
}
.faq-list details:first-child {
  padding-top: 4px;
}
.faq-list summary {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 20px;
  font-size: 16px;
  line-height: 1.8;
  list-style: none;
}
.faq-list summary::-webkit-details-marker {
  display: none;
}
.faq-list summary > span {
  color: var(--blue);
  transition: transform 250ms ease;
  font-size: 20px;
}
.faq-list details[open] summary > span {
  transform: rotate(45deg);
}
.faq-list :where(details) > p {
  color: var(--muted);
  font-size: 14px;
  line-height: 1.95;
  margin-top: 18px;
  padding-right: 24px;
}
.closing {
  padding-block: 60px 115px;
  text-align: center;
}
.closing > p {
  font-size: clamp(64px, 8.7vw, 124px);
  font-weight: 450;
  letter-spacing: -0.065em;
  line-height: 1.1;
  color: var(--blue);
}
.closing h2 {
  font-size: 30px;
  line-height: 1.65;
  margin-block: 30px 34px;
}
.site-footer {
  border-top: 1px solid var(--line);
  padding-block: 35px;
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: 24px;
}
.site-footer .brand {
  font-size: 16px;
}
.site-footer p {
  color: var(--muted);
  font-size: 12px;
}
.site-footer > a:last-child {
  font-size: 13px;
  white-space: nowrap;
}
.not-found {
  padding-block: 110px;
}
.not-found > p {
  font-size: 90px;
  color: var(--blue);
  margin-top: 60px;
}
.not-found h1 {
  margin-block: 12px 35px;
  font-size: 35px;
}

@media (prefers-reduced-motion: no-preference) {
  .hero-enter {
    animation: enter 950ms cubic-bezier(0.2, 0.75, 0.25, 1) both;
  }
  .hero-copy .hero-enter:nth-child(2) {
    animation-delay: 100ms;
  }
  .hero-copy .hero-enter:nth-child(3) {
    animation-delay: 200ms;
  }
  .hero-copy .hero-enter:nth-child(4) {
    animation-delay: 300ms;
  }
  .hero-art {
    animation-delay: 180ms;
  }
  .motion-ready .reveal {
    opacity: 0;
    transform: translateY(30px);
    transition:
      opacity 850ms ease,
      transform 850ms cubic-bezier(0.2, 0.75, 0.25, 1);
  }
  .motion-ready .reveal.is-visible {
    opacity: 1;
    transform: none;
  }
  @supports (animation-timeline: view()) {
    .hero-art img {
      animation: art-drift linear both;
      animation-timeline: view();
      animation-range: exit 0% exit 100%;
    }
  }
}
@keyframes enter {
  from {
    opacity: 0;
    transform: translateY(24px);
  }
  to {
    opacity: 1;
    transform: none;
  }
}
@keyframes art-drift {
  from {
    transform: scale(1);
  }
  to {
    transform: scale(1.07) translateY(2%);
  }
}
@media (prefers-reduced-motion: reduce) {
  html {
    scroll-behavior: auto;
  }
  *,
  *::before,
  *::after,
  .button,
  .faq-list summary > span {
    animation: none;
    transition: none;
  }
  .reveal {
    opacity: 1;
    transform: none;
  }
}
@media (max-width: 1024px) {
  .section-width {
    width: calc(100% - 72px);
  }
  .site-header {
    width: calc(100% - 56px);
    gap: 16px;
  }
  .site-header nav {
    gap: 18px;
    font-size: 13px;
  }
  .header-actions {
    gap: 12px;
  }
  .hero {
    gap: 30px;
    padding-block: 50px 70px;
  }
  .hero h1 {
    font-size: 40px;
  }
  .hero-description {
    font-size: 15px;
  }
  .hero-links {
    gap: 20px;
  }
  .button {
    padding: 16px 20px;
    gap: 25px;
  }
  .manifesto,
  .reader-caption {
    gap: 40px;
  }
  .source-plain {
    flex-direction: column;
    align-items: flex-start;
    gap: 10px;
  }
  .format-display {
    font-size: 55px;
    line-height: 1;
  }
  .source-feature,
  .source-plain {
    padding: 30px;
  }
  .retain-layout {
    gap: 48px;
  }
  .principles {
    padding: 50px 38px;
  }
  .principles-grid {
    gap: 30px;
  }
  .faq-section {
    gap: 40px;
  }
  .site-footer p {
    max-width: 260px;
    line-height: 1.6;
  }
}
@media (max-width: 767px) {
  html {
    scroll-padding-top: 24px;
  }
  .section-width {
    width: calc(100% - 40px);
  }
  .site-header {
    width: calc(100% - 40px);
    height: 76px;
    gap: 15px;
  }
  .brand {
    font-size: 16px;
    gap: 8px;
  }
  .brand img {
    width: 30px;
    height: 30px;
  }
  .site-header nav {
    display: none;
  }
  .header-actions {
    gap: 10px;
  }
  .nav-cta {
    display: none;
  }
  .language-select {
    max-width: 96px;
    font-size: 12px;
    padding-inline: 5px;
  }
  .theme-toggle {
    width: 30px;
    height: 30px;
    font-size: 19px;
  }
  .hero {
    grid-template-columns: 1fr;
    gap: 42px;
    padding-block: 40px 60px;
    min-height: auto;
  }
  .hero h1 {
    font-size: clamp(32px, 8.5vw, 54px);
    margin-top: 23px;
    line-height: 1.5;
  }
  :where(:root:lang(en)) .hero h1 {
    font-size: clamp(25px, 7.4vw, 45px);
  }
  :where(:root:lang(ja)) .hero h1 {
    font-size: clamp(25px, 7vw, 42px);
  }
  :where(:root:lang(ko)) .hero h1 {
    font-size: clamp(23px, 6.2vw, 38px);
  }
  .hero-links {
    flex-wrap: wrap;
  }
  .hero-description {
    font-size: 15px;
    margin-top: 22px;
  }
  .hero-links {
    margin-top: 30px;
    gap: 24px;
  }
  .hero-art {
    aspect-ratio: 1.1;
  }
  .hero-art img {
    object-position: 50% 53%;
  }
  .manifesto {
    grid-template-columns: 1fr;
    gap: 24px;
    padding-block: 40px 70px;
  }
  .manifesto-lead {
    font-size: 28px;
  }
  .manifesto-body {
    padding-top: 0;
  }
  .reading-section {
    padding-block: 30px 75px;
  }
  .section-heading {
    padding-bottom: 30px;
  }
  .section-heading > p:last-child {
    font-size: 14px;
    margin-top: 18px;
  }
  .source-grid {
    grid-template-columns: 1fr;
    gap: 16px;
    margin-bottom: 25px;
  }
  .source-feature {
    min-height: auto;
  }
  .source-plain {
    flex-direction: row;
    gap: 27px;
    align-items: center;
  }
  .source-plain h3 {
    font-size: 19px;
  }
  .source-plain p {
    font-size: 13px;
  }
  .format-display {
    font-size: 58px;
    flex-shrink: 0;
  }
  .reader-showcase {
    overflow-x: auto;
  }
  .reader-showcase picture {
    width: 850px;
  }
  .preview-toolbar {
    padding: 14px 16px;
    font-size: 11px;
  }
  .reader-caption {
    grid-template-columns: 1fr;
    gap: 14px;
    padding-top: 25px;
  }
  .reader-caption h3 {
    font-size: 20px;
  }
  .retain-section {
    padding-block: 10px 70px;
  }
  .retain-layout {
    grid-template-columns: 1fr;
    gap: 24px;
  }
  .retain-story {
    max-width: none;
    padding-block: 25px 35px;
  }
  .story-word {
    font-size: 36px;
  }
  .retain-story h3 {
    font-size: 21px;
    margin-top: 12px;
  }
  .retain-story p {
    font-size: 14px;
    margin-top: 12px;
  }
  .study-sticky {
    position: static;
  }
  .principles {
    padding: 35px 26px;
  }
  .principles h2 {
    font-size: 27px;
  }
  .principles-grid {
    grid-template-columns: 1fr;
    gap: 30px;
    margin-top: 30px;
  }
  .principles-grid article {
    position: relative;
    padding-left: 44px;
  }
  .principles-grid article > span {
    position: absolute;
    top: 0;
    left: 0;
    font-size: 26px;
  }
  .principles-grid h3 {
    margin-top: 0;
    font-size: 18px;
  }
  .principles-grid p {
    margin-top: 8px;
    max-width: none;
  }
  .faq-section {
    grid-template-columns: 1fr;
    gap: 35px;
    padding-block: 75px 65px;
  }
  .faq-intro h2 {
    font-size: 30px;
  }
  .faq-list summary {
    font-size: 15px;
  }
  .closing {
    padding-block: 30px 75px;
  }
  .closing > p {
    font-size: clamp(54px, 12.5vw, 88px);
  }
  .closing h2 {
    font-size: 25px;
    margin-block: 25px;
  }
  .site-footer {
    display: grid;
    grid-template-columns: 1fr auto;
    gap: 20px;
    padding-block: 30px;
  }
  .site-footer p {
    grid-column: 1 / -1;
    grid-row: 2;
    max-width: none;
  }
  .site-footer .brand {
    font-size: 14px;
  }
}
@media (max-width: 360px) {
  .section-width,
  .site-header {
    width: calc(100% - 32px);
  }
  .brand {
    font-size: 14px;
  }
  .header-actions {
    gap: 10px;
  }
  .hero-links {
    gap: 18px;
  }
  .text-link {
    font-size: 12px;
  }
  .source-plain {
    padding: 24px;
    gap: 22px;
  }
}