:root {
  --paper: #f4eedf;
  --paper-deep: #efe4cd;
  --ink: #19150f;
  --ink-soft: #3d3528;
  --accent: #7b2f2a;
  --accent-soft: #a9625b;
  --accent-wash: rgba(123, 47, 42, 0.08);
  --line: #c9b796;
  --shadow: rgba(37, 29, 18, 0.14);
  --bg-highlight: rgba(255, 255, 255, 0.8);
  --bg-accent: rgba(164, 126, 103, 0.14);
  --bg-grain: rgba(0, 0, 0, 0.025);
  --sidebar-sheen: rgba(255, 255, 255, 0.28);
  --panel-bg: #f8f2e4;
  --code-bg: #f3ead8;
  --surface-soft: rgba(255, 255, 255, 0.5);
  --surface-mid: rgba(255, 255, 255, 0.43);
  --overlay: rgba(22, 16, 10, 0.38);
  --mono: "Courier Prime", "Courier New", Courier, monospace;
  --serif: "Iowan Old Style", "Palatino Linotype", "Book Antiqua", Palatino, serif;
}

:root[data-theme="dark"] {
  --paper: #2c241c;
  --paper-deep: #251e17;
  --ink: #e9dec9;
  --ink-soft: #c8bca8;
  --accent: #b08c67;
  --accent-soft: #9f7d5c;
  --accent-wash: rgba(176, 140, 103, 0.16);
  --line: #5a4b3c;
  --shadow: rgba(0, 0, 0, 0.3);
  --bg-highlight: rgba(244, 230, 210, 0.05);
  --bg-accent: rgba(146, 118, 90, 0.1);
  --bg-grain: rgba(255, 244, 228, 0.03);
  --sidebar-sheen: rgba(255, 241, 216, 0.04);
  --panel-bg: #32281f;
  --code-bg: #372d24;
  --surface-soft: rgba(56, 45, 35, 0.56);
  --surface-mid: rgba(50, 40, 31, 0.62);
  --overlay: rgba(8, 6, 4, 0.52);
}

:root[data-theme="kr"] {
  --paper: #fefefc;
  --paper-deep: #ffffff;
  --ink: #121212;
  --ink-soft: #2a2a2a;
  --accent: #9a3324;
  --accent-soft: #b7503a;
  --accent-wash: rgba(154, 51, 36, 0.07);
  --line: #c8c8c8;
  --shadow: rgba(0, 0, 0, 0.08);
  --bg-highlight: rgba(255, 255, 255, 0);
  --bg-accent: rgba(255, 255, 255, 0);
  --bg-grain: rgba(0, 0, 0, 0.01);
  --sidebar-sheen: rgba(255, 255, 255, 0);
  --panel-bg: #ffffff;
  --code-bg: #f6f6f4;
  --surface-soft: #ffffff;
  --surface-mid: #ffffff;
  --overlay: rgba(12, 12, 12, 0.24);
  --mono: "Courier New", Courier, monospace;
  --serif: "Times New Roman", Times, serif;
}

* {
  box-sizing: border-box;
}

html,
body {
  margin: 0;
  padding: 0;
  min-height: 100%;
}

body {
  color: var(--ink);
  font-family: var(--serif);
  line-height: 1.55;
  background:
    radial-gradient(circle at 20% 12%, var(--bg-highlight), transparent 42%),
    radial-gradient(circle at 86% 4%, var(--bg-accent), transparent 38%),
    repeating-linear-gradient(
      0deg,
      var(--bg-grain) 0,
      var(--bg-grain) 1px,
      transparent 1px,
      transparent 4px
    ),
    var(--paper);
}

:root[data-theme="kr"] body {
  background: var(--paper);
}

.page {
  width: 100%;
  margin: 0;
  min-height: 100vh;
  display: grid;
  grid-template-columns: 292px 1fr;
  animation: enter 520ms ease both;
}

:root[data-theme="kr"] .page {
  animation: none;
}

@keyframes enter {
  from {
    opacity: 0;
    transform: translateY(6px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

.sidebar {
  border-right: 1px solid var(--line);
  padding: 2.5rem 1.3rem 2rem;
  position: sticky;
  top: 0;
  height: 100vh;
  background:
    linear-gradient(160deg, var(--sidebar-sheen), transparent 55%),
    var(--paper-deep);
}

:root[data-theme="kr"] .sidebar {
  background: var(--paper-deep);
}

.brand {
  margin-bottom: 2rem;
}

.brand h1 {
  margin: 0;
  font-size: 2rem;
  letter-spacing: 0.05em;
}

.brand p {
  margin: 0.35rem 0 0;
  color: var(--ink-soft);
  font-size: 0.95rem;
}

.divider {
  height: 1px;
  background: var(--line);
  margin: 1.2rem 0;
}

.chapter-list {
  list-style: none;
  margin: 0;
  padding: 0;
}

.chapter-list li {
  margin: 0 0 0.55rem;
  opacity: 0;
  transform: translateX(-6px);
  animation: chapterIn 380ms ease forwards;
}

.chapter-list li:nth-child(1) { animation-delay: 90ms; }
.chapter-list li:nth-child(2) { animation-delay: 150ms; }
.chapter-list li:nth-child(3) { animation-delay: 210ms; }
.chapter-list li:nth-child(4) { animation-delay: 270ms; }
.chapter-list li:nth-child(5) { animation-delay: 330ms; }

:root[data-theme="kr"] .chapter-list li {
  opacity: 1;
  transform: none;
  animation: none;
}

@keyframes chapterIn {
  to {
    opacity: 1;
    transform: translateX(0);
  }
}

.chapter-list a {
  display: block;
  padding: 0.35rem 0.45rem;
  color: var(--ink-soft);
  text-decoration: none;
  border-left: 2px solid transparent;
  transition: all 150ms ease;
}

.chapter-list a:hover,
.chapter-list a[aria-current="page"] {
  color: var(--ink);
  border-left-color: var(--accent);
  background: var(--accent-wash);
}

.sidebar-note {
  margin-top: 1.4rem;
  font-size: 0.86rem;
  color: var(--ink-soft);
}

.content-wrap {
  padding: 2.3rem 3.5rem 3rem;
  width: 100%;
  max-width: 980px;
  justify-self: start;
}

.topbar {
  display: none;
  align-items: center;
  justify-content: space-between;
  gap: 0.6rem;
  margin-bottom: 1rem;
}

.topbar-actions {
  display: flex;
  align-items: center;
  gap: 0.45rem;
  margin-left: auto;
  min-width: 2.35rem;
  justify-content: flex-end;
}

.menu-toggle,
.utility-btn {
  appearance: none;
  border: 1px solid var(--line);
  background: var(--panel-bg);
  color: var(--ink);
  font-family: var(--mono);
  padding: 0.4rem 0.7rem;
  border-radius: 4px;
  cursor: pointer;
  min-height: 2.35rem;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 0.42rem;
}

.theme-switcher {
  display: inline-flex;
  align-items: center;
  gap: 0.26rem;
  white-space: nowrap;
}

.theme-switcher-side {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
}

.theme-choice {
  appearance: none;
  border: 1px solid var(--line);
  background: var(--panel-bg);
  color: var(--ink-soft);
  font-family: var(--mono);
  font-size: 0.82rem;
  line-height: 1;
  min-height: 2.05rem;
  padding: 0.22rem 0.44rem;
  border-radius: 3px;
  cursor: pointer;
  display: inline-flex;
  align-items: center;
  justify-content: center;
}

.theme-choice:hover {
  border-color: var(--accent-soft);
  background: var(--accent-wash);
  color: var(--ink);
}

.theme-choice:focus-visible {
  outline: 1px solid var(--accent-soft);
  outline-offset: 1px;
}

.theme-choice.is-active {
  background: var(--accent-wash);
  border-color: var(--accent-soft);
  color: var(--ink);
  font-weight: 600;
}

.menu-toggle {
  width: 2.35rem;
  padding: 0;
  font-size: 1.2rem;
  line-height: 1;
}

.menu-toggle:hover,
.utility-btn:hover {
  border-color: var(--accent-soft);
}

.sidebar-utilities {
  margin-top: 1.35rem;
  padding-top: 1rem;
  border-top: 1px solid var(--line);
  display: grid;
  gap: 0.45rem;
}

.sidebar-utilities .utility-btn {
  width: 100%;
  text-align: left;
  font-size: 0.73rem;
  padding: 0.3rem 0.45rem;
  white-space: nowrap;
}

.utility-link {
  text-decoration: none;
}

.sidebar-utilities .theme-switcher {
  width: 100%;
}

.sidebar-utilities .theme-choice {
  width: 100%;
  min-width: 0;
  text-align: center;
}

.kicker {
  margin: 0;
  font-size: 0.8rem;
  letter-spacing: 0.2em;
  text-transform: uppercase;
  color: var(--accent);
}

.page-title {
  margin: 0.35rem 0 0.2rem;
  font-size: clamp(2rem, 5vw, 3.3rem);
  line-height: 1.08;
}

.deck {
  margin-top: 0.8rem;
  color: var(--ink-soft);
  max-width: 64ch;
  font-size: 1.06rem;
}

.hero-grid {
  margin-top: 2rem;
  display: grid;
  grid-template-columns: 3fr 1fr;
  gap: 1.8rem;
}

.paper-card {
  background: var(--surface-soft);
  border: 1px solid var(--line);
  box-shadow: 0 12px 32px var(--shadow);
  border-radius: 10px;
  padding: 1.2rem 1.2rem 1.1rem;
}

.paper-card h3 {
  margin: 0 0 0.55rem;
  font-size: 1.1rem;
}

.paper-card p {
  margin: 0;
  color: var(--ink-soft);
  overflow-wrap: anywhere;
  word-break: normal;
}

.quote-list {
  margin: 0 0 0.7rem;
  padding-left: 1.35rem;
  color: var(--ink-soft);
}

.quote-list li {
  margin-bottom: 0.22rem;
}

.quote {
  font-size: 1.02rem;
  margin: 0;
  padding-left: 1rem;
  border-left: 2px solid var(--accent-soft);
  overflow-wrap: anywhere;
}

.code {
  margin-top: 0.8rem;
  font-family: var(--mono);
  background: var(--code-bg);
  border: 1px solid var(--line);
  border-radius: 8px;
  padding: 0.85rem;
  overflow-x: auto;
  white-space: pre-wrap;
  word-break: break-word;
  font-size: 0.92rem;
}

.section {
  margin-top: 2.4rem;
}

.section h2 {
  margin: 0 0 0.65rem;
  font-size: clamp(1.35rem, 2.6vw, 1.75rem);
}

.section p,
.section li {
  color: var(--ink-soft);
}

.section ul,
.section ol {
  padding-left: 1.15rem;
}

.chapter-grid {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 1rem;
}

.chapter-link {
  display: block;
  text-decoration: none;
  color: inherit;
  border: 1px solid var(--line);
  border-radius: 8px;
  padding: 1rem;
  background: var(--surface-mid);
  transition: transform 150ms ease, box-shadow 150ms ease, border-color 150ms ease;
}

.chapter-link:hover {
  transform: translateY(-2px);
  border-color: var(--accent-soft);
  box-shadow: 0 10px 26px var(--shadow);
}

:root[data-theme="kr"] .paper-card,
:root[data-theme="kr"] .chapter-link,
:root[data-theme="kr"] .topbar,
:root[data-theme="kr"] .shortcut-card,
:root[data-theme="kr"] pre,
:root[data-theme="kr"] .code,
:root[data-theme="kr"] .menu-toggle,
:root[data-theme="kr"] .theme-switcher,
:root[data-theme="kr"] .theme-choice,
:root[data-theme="kr"] .utility-btn,
:root[data-theme="kr"] .figure img {
  border-radius: 0;
  box-shadow: none;
}

:root[data-theme="kr"] .kicker {
  color: var(--ink-soft);
}

:root[data-theme="kr"] .page-title,
:root[data-theme="kr"] .section h2 {
  letter-spacing: 0;
}

.chapter-link strong {
  display: block;
  margin-bottom: 0.2rem;
}

.chapter-link span {
  color: var(--ink-soft);
  font-size: 0.95rem;
}

table {
  width: 100%;
  border-collapse: collapse;
  margin: 0.9rem 0;
  font-size: 0.95rem;
}

th,
td {
  text-align: left;
  border-bottom: 1px solid var(--line);
  padding: 0.52rem 0.4rem;
  vertical-align: top;
}

th {
  color: var(--ink);
}

code,
pre {
  font-family: var(--mono);
}

pre {
  margin: 0.7rem 0;
  background: var(--code-bg);
  border: 1px solid var(--line);
  border-radius: 8px;
  padding: 0.85rem;
  overflow-x: auto;
  white-space: pre-wrap;
  word-break: break-word;
  font-size: 0.9rem;
  line-height: 1.5;
}

.inline-note {
  font-size: 0.9rem;
  color: var(--ink-soft);
  border-left: 2px solid var(--line);
  padding-left: 0.8rem;
  margin: 0.8rem 0;
}

.figure-note {
  margin: 0.8rem 0 0;
  font-size: 0.9rem;
  color: var(--ink-soft);
}

.figure {
  margin: 0;
}

.figure img {
  width: 100%;
  max-width: 330px;
  border-radius: 8px;
  border: 1px solid var(--line);
  box-shadow: 0 10px 24px var(--shadow);
}

.footer {
  margin-top: 3rem;
  padding-top: 1.1rem;
  border-top: 1px solid var(--line);
  color: var(--ink-soft);
  font-size: 0.9rem;
}

.shortcut-panel {
  position: fixed;
  inset: 0;
  display: none;
  align-items: center;
  justify-content: center;
  padding: 1rem;
  background: var(--overlay);
  z-index: 60;
}

.shortcut-panel.is-open {
  display: flex;
}

.shortcut-card {
  width: min(560px, 100%);
  border: 1px solid var(--line);
  border-radius: 12px;
  background: var(--paper-deep);
  box-shadow: 0 18px 40px var(--shadow);
  padding: 1rem;
}

.shortcut-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 0.6rem;
  margin-bottom: 0.7rem;
}

.shortcut-header h2 {
  margin: 0;
  font-size: 1.15rem;
}

.shortcut-table {
  width: 100%;
  border-collapse: collapse;
  margin: 0;
}

.shortcut-table th,
.shortcut-table td {
  border-bottom: 1px solid var(--line);
  padding: 0.45rem 0.35rem;
  text-align: left;
  color: var(--ink-soft);
}

.shortcut-table th {
  color: var(--ink);
  width: 38%;
  white-space: nowrap;
}

kbd {
  font-family: var(--mono);
  font-size: 0.86em;
  padding: 0.08rem 0.34rem;
  border-radius: 4px;
  border: 1px solid var(--line);
  background: var(--code-bg);
}

@media (max-width: 980px) {
  .page {
    grid-template-columns: 1fr;
    position: relative;
  }

  .sidebar {
    position: fixed;
    left: 0;
    top: 0;
    width: min(82vw, 310px);
    transform: translateX(-103%);
    transition: transform 220ms ease;
    z-index: 42;
    box-shadow: 0 16px 40px rgba(0, 0, 0, 0.22);
  }

  .page.nav-open .sidebar {
    transform: translateX(0);
  }

  .page.nav-open::before {
    content: "";
    position: fixed;
    inset: 0;
    background: var(--overlay);
    z-index: 40;
  }

  .content-wrap {
    max-width: none;
    padding: 0.7rem 0.85rem 2.2rem;
  }

  .topbar {
    display: flex;
    position: sticky;
    top: 0.5rem;
    z-index: 30;
    padding: 0.45rem 0.5rem;
    margin-bottom: 0.9rem;
    border: 1px solid var(--line);
    border-radius: 10px;
    background: var(--surface-soft);
    box-shadow: 0 6px 16px var(--shadow);
  }

  .topbar .kicker {
    font-size: 0.7rem;
    letter-spacing: 0.17em;
    margin-right: 0.35rem;
  }

  .topbar-actions {
    margin-left: auto;
  }

  .topbar-actions .utility-btn {
    width: 2.35rem;
    min-width: 2.35rem;
    padding: 0;
  }

  .topbar-actions .theme-switcher {
    gap: 0.16rem;
    min-height: 2.35rem;
    align-items: stretch;
  }

  .topbar-actions .theme-choice {
    font-size: 0.68rem;
    min-height: 2.35rem;
    height: 2.35rem;
    width: 2.35rem;
    min-width: 2.35rem;
    padding: 0;
  }

  .topbar-actions .keys-toggle {
    display: none;
  }

  .hero-grid,
  .chapter-grid {
    grid-template-columns: 1fr;
  }

  .page-title {
    font-size: clamp(1.85rem, 8.8vw, 2.7rem);
  }

  .deck {
    font-size: 1rem;
  }

  .paper-card {
    padding: 0.95rem;
  }

  .figure img {
    max-width: 238px;
    margin: 0 auto;
    display: block;
  }

  .shortcut-table {
    display: table;
  }

  table {
    display: block;
    overflow-x: auto;
    white-space: nowrap;
  }

  pre,
  .code {
    font-size: 0.84rem;
  }
}