:root {
  --paper: #fffdf8;
  --background: #f3efe6;
  --text: #24211c;
  --muted: #6f695e;
  --line: #ddd5c7;
  --accent: #d4522b;
  --accent-dark: #96381d;
  --accent-soft: #fff0e8;
  --blue: #286b7a;
  --blue-soft: #e9f4f5;
  color-scheme: light;
}

* {
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
}

body {
  margin: 0;
  color: var(--text);
  background:
    radial-gradient(circle at 10% 5%, rgba(212, 82, 43, 0.08), transparent 24rem),
    var(--background);
  font-family: "Hiragino Sans", "Yu Gothic", system-ui, sans-serif;
  line-height: 1.85;
}

a {
  color: var(--accent-dark);
}

.skip-link {
  position: fixed;
  z-index: 10;
  top: 0.5rem;
  left: 0.5rem;
  padding: 0.55rem 0.8rem;
  color: #fff;
  background: var(--accent-dark);
  transform: translateY(-160%);
}

.skip-link:focus {
  transform: translateY(0);
}

.site-header {
  min-height: 58px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
  padding: 0.7rem clamp(1rem, 4vw, 2rem);
  border-bottom: 1px solid var(--line);
  background: rgba(255, 253, 248, 0.92);
  font-weight: 800;
  letter-spacing: 0.04em;
}

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

.page-layout {
  width: min(1160px, 100%);
  display: grid;
  grid-template-columns: 250px minmax(0, 760px);
  gap: clamp(2rem, 6vw, 5.5rem);
  margin: 0 auto;
  padding: 2.5rem clamp(1rem, 4vw, 2rem) 7rem;
}

.sidebar {
  position: sticky;
  top: 1rem;
  align-self: start;
  max-height: calc(100vh - 2rem);
  overflow-y: auto;
  padding: 1.2rem;
  border: 1px solid var(--line);
  border-top: 4px solid var(--accent);
  border-radius: 4px 4px 12px 12px;
  background: var(--paper);
  box-shadow: 0 8px 24px rgba(50, 42, 28, 0.05);
  font-size: 0.9rem;
}

.sidebar-label {
  margin: 0;
  color: var(--accent);
  font-size: 0.72rem;
  font-weight: 900;
  letter-spacing: 0.14em;
}

.sidebar-title {
  margin: 0.25rem 0 0.8rem;
  font-weight: 800;
  line-height: 1.55;
}

.sidebar ul {
  margin: 0;
  padding-left: 1.1rem;
}

.sidebar li {
  margin: 0.4rem 0;
}

.sidebar li ul {
  margin-top: 0.35rem;
  padding-left: 1rem;
}

.sidebar a {
  color: var(--text);
  text-decoration: none;
}

.sidebar a:hover {
  color: var(--accent-dark);
  text-decoration: underline;
}

.content {
  min-width: 0;
  padding: clamp(1.5rem, 5vw, 3.5rem);
  border: 1px solid var(--line);
  border-radius: 6px;
  background: var(--paper);
  box-shadow: 0 14px 40px rgba(50, 42, 28, 0.07);
}

.content > section {
  margin-top: 5rem;
}

.content > section:first-of-type {
  margin-top: 0;
}

h1,
h2,
h3 {
  line-height: 1.45;
  scroll-margin-top: 1rem;
}

h1 {
  margin: 0 0 1rem;
  font-size: clamp(1.7rem, 5vw, 2.6rem);
  letter-spacing: -0.035em;
}

h1 {
  padding-bottom: 0.55rem;
  border-bottom: 2px solid var(--line);
  font-size: clamp(1.9rem, 6vw, 3rem);
}

.document-title {
  margin: 0 0 0.35rem;
  color: var(--accent-dark);
  font-size: clamp(1.25rem, 4vw, 1.75rem);
  font-weight: 800;
  letter-spacing: -0.035em;
  line-height: 1.45;
}

h2 {
  margin: 2.5rem 0 0.8rem;
  font-size: clamp(1.35rem, 4vw, 1.7rem);
}

h3 {
  margin: 2rem 0 0.7rem;
  font-size: 1.12rem;
}

p,
ul,
ol,
table,
blockquote {
  margin-top: 0.9rem;
  margin-bottom: 0.9rem;
}

li + li {
  margin-top: 0.35rem;
}

blockquote {
  margin: 1.6rem 0;
  padding: 1rem 1.2rem;
  border: 1px solid #e9bea9;
  border-left: 5px solid var(--accent);
  border-radius: 0 8px 8px 0;
  background: var(--accent-soft);
}

blockquote p {
  margin: 0;
}

table {
  width: 100%;
  border-collapse: collapse;
  background: #fff;
  font-size: 0.94rem;
}

th,
td {
  padding: 0.7rem 0.8rem;
  border: 1px solid var(--line);
  text-align: left;
  vertical-align: top;
}

th {
  background: #f2ede3;
}

.key-message {
  margin: 1.8rem 0;
  padding: 1.2rem 1.4rem;
  border-left: 5px solid var(--blue);
  border-radius: 0 8px 8px 0;
  background: var(--blue-soft);
  color: #174d58;
  font-weight: 800;
}

.key-message p {
  margin: 0;
}

.misconception {
  margin: 1.8rem 0;
  padding: 1rem 1.2rem;
  border-left: 5px solid #9a651b;
  border-radius: 0 8px 8px 0;
  background: #fff5df;
  color: #68420e;
}

.comparison {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 0.8rem;
  margin: 1.6rem 0;
}

.comparison div {
  display: grid;
  gap: 0.3rem;
  padding: 1rem;
  border: 1px solid var(--line);
  border-radius: 8px;
  background: #fff;
}

.comparison div:last-child {
  border-color: #8fb9c2;
  background: var(--blue-soft);
}

.comparison span {
  color: var(--muted);
  font-size: 0.78rem;
  font-weight: 800;
}

.flow {
  display: flex;
  align-items: stretch;
  gap: 0.6rem;
  margin: 1.8rem 0;
}

.flow > div {
  flex: 1;
  display: grid;
  gap: 0.2rem;
  align-content: start;
  padding: 0.9rem;
  border: 1px solid var(--line);
  border-radius: 8px;
  background: #fff;
}

.flow div > span {
  color: var(--accent);
  font-size: 0.75rem;
  font-weight: 900;
}

.flow small,
.cycle small {
  color: var(--muted);
  line-height: 1.55;
}

.flow-arrow {
  align-self: center;
  color: var(--accent);
  font-weight: 900;
}

.cycle {
  display: grid;
  grid-template-columns: repeat(4, minmax(0, 1fr));
  gap: 0.7rem;
  margin: 1.8rem 0;
  counter-reset: cycle;
}

.cycle div {
  position: relative;
  display: grid;
  gap: 0.35rem;
  align-content: start;
  min-height: 128px;
  padding: 2.5rem 0.9rem 0.9rem;
  border-radius: 8px;
  color: #fff;
  background: var(--blue);
  counter-increment: cycle;
}

.cycle div::before {
  content: counter(cycle, decimal-leading-zero);
  position: absolute;
  top: 0.55rem;
  left: 0.8rem;
  color: rgba(255, 255, 255, 0.65);
  font-size: 0.72rem;
  font-weight: 900;
}

.cycle span {
  font-weight: 900;
}

.cycle small {
  color: rgba(255, 255, 255, 0.84);
}

.chapter-summary {
  padding-top: 0.9rem;
  border-top-color: var(--accent) !important;
}

.companion-nav {
  margin: 0.8rem 0 2rem;
  padding: 0.8rem 1rem;
  border: 1px solid #8fb9c2;
  border-radius: 8px;
  background: var(--blue-soft);
}

.companion-nav a {
  color: #174d58;
  font-weight: 800;
  text-decoration: none;
}

.companion-nav a:hover {
  text-decoration: underline;
}

.start-guide .content > section {
  margin-top: 4rem;
}

.start-guide input[type="checkbox"] {
  width: 1rem;
  min-height: auto;
  margin-right: 0.35rem;
  accent-color: var(--accent);
}

@media print {
  body {
    background: #fff;
    font-size: 10.5pt;
  }

  .site-header,
  .sidebar,
  .skip-link,
  .companion-nav {
    display: none;
  }

  .page-layout {
    display: block;
    width: auto;
    padding: 0;
  }

  .content {
    padding: 0;
    border: 0;
    box-shadow: none;
  }

  .content > section {
    break-before: page;
  }

  .content > section:first-of-type {
    break-before: auto;
  }

  h1,
  h2,
  h3,
  table,
  blockquote,
  .comparison,
  .cycle,
  .key-message {
    break-inside: avoid;
  }

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

@media (max-width: 860px) {
  .page-layout {
    grid-template-columns: 1fr;
    gap: 1.5rem;
  }

  .sidebar {
    position: static;
    max-height: none;
  }

  .sidebar nav > ul {
    columns: 2;
  }
}

@media (max-width: 620px) {
  .content {
    padding: 1.25rem;
  }

  .sidebar nav > ul {
    columns: 1;
  }

  .comparison,
  .cycle {
    grid-template-columns: 1fr;
  }

  .flow {
    display: grid;
  }

  .flow-arrow {
    justify-self: center;
    transform: rotate(90deg);
  }

  table {
    display: block;
    overflow-x: auto;
  }
}