:root {
  color-scheme: light;
  --ink: #1f2a28;
  --ink-soft: #41514e;
  --bg: #fdfdfb;
  --accent: #2f5d50;
  --accent-soft: #eef6f2;
  --border: #d7ddd5;
  --warn: #823923;
  --warn-bg: #fff7f0;
}

* { box-sizing: border-box; }

html { font-size: 16px; }

body {
  margin: 0;
  background: var(--bg);
  color: var(--ink);
  font-family: "BIZ UDPGothic", "Yu Gothic UI", "Yu Gothic", "Hiragino Sans", "Meiryo", system-ui, sans-serif;
  line-height: 1.75;
}

.skip-link {
  position: fixed;
  top: 8px;
  left: 8px;
  z-index: 20;
  transform: translateY(-160%);
  border: 2px solid var(--accent);
  border-radius: 6px;
  background: #fff;
  color: var(--accent);
  padding: 8px 12px;
  font-weight: 700;
}

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

main {
  max-width: 880px;
  margin: 0 auto;
  padding: 28px 24px 80px;
}

header.page-header {
  position: sticky;
  top: 0;
  background: var(--bg);
  border-bottom: 1px solid var(--border);
  padding: 10px 24px;
  z-index: 10;
  display: grid;
  gap: 12px;
}

.header-main {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 16px;
}

header.page-header h1 {
  margin: 0;
  font-size: 1.1rem;
  color: var(--accent);
}

header.page-header nav {
  display: flex;
  gap: 8px;
  flex-wrap: wrap;
}

header.page-header .return-nav { justify-content: flex-end; }
header.page-header .return-nav .primary-action { background: var(--accent); color: #fff; }
header.page-header #nav { padding-top: 10px; border-top: 1px solid var(--border); }

header.page-header a {
  color: var(--accent);
  text-decoration: none;
  font-weight: 700;
  padding: 6px 10px;
  border: 1px solid var(--accent);
  border-radius: 6px;
  background: #fff;
  font-size: .9rem;
}

header.page-header a:hover { background: var(--accent-soft); }
header.page-header a.current { background: var(--accent); color: #fff; }
header.page-header a:focus-visible,
main a:focus-visible {
  outline: 3px solid #d7a84d;
  outline-offset: 2px;
}

h1, h2, h3, h4 { color: var(--accent); line-height: 1.4; }
h1 { font-size: 1.85rem; margin-top: 0; }
h2 { font-size: 1.4rem; border-bottom: 2px solid var(--border); padding-bottom: 6px; margin-top: 2.2em; }
h3 { font-size: 1.15rem; margin-top: 1.8em; }
h4 { font-size: 1.02rem; margin-top: 1.4em; color: var(--ink); }

p { margin: 1em 0; }

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

ul, ol { padding-left: 1.5em; }
li { margin: .4em 0; }

table {
  width: 100%;
  border-collapse: collapse;
  margin: 1.2em 0;
  font-size: .96rem;
}

th, td {
  border: 1px solid var(--border);
  padding: 8px 10px;
  vertical-align: top;
  text-align: left;
}

th { background: var(--accent-soft); color: var(--accent); }

blockquote {
  margin: 1.2em 0;
  padding: 12px 16px;
  border-left: 4px solid var(--accent);
  background: var(--accent-soft);
  color: var(--ink-soft);
  border-radius: 0 6px 6px 0;
}

blockquote strong { color: var(--warn); }

code {
  background: #eef0ec;
  padding: 1px 6px;
  border-radius: 4px;
  font-family: "BIZ UDPGothic", "Consolas", monospace;
  font-size: .95em;
}

pre {
  background: #2a3431;
  color: #f3f5f1;
  padding: 14px 16px;
  border-radius: 8px;
  overflow-x: auto;
  line-height: 1.5;
  font-size: .92rem;
}

pre code { background: transparent; color: inherit; padding: 0; }

.chapter-nav {
  display: flex;
  justify-content: space-between;
  margin-top: 3em;
  padding-top: 1em;
  border-top: 1px solid var(--border);
  gap: 12px;
}

.chapter-nav a {
  display: inline-block;
  padding: 10px 14px;
  border: 1px solid var(--accent);
  border-radius: 8px;
  background: #fff;
  font-weight: 700;
  text-decoration: none;
}

.chapter-nav a:hover { background: var(--accent-soft); }

.note-important {
  background: var(--warn-bg);
  border: 1px solid #e4b29f;
  border-radius: 8px;
  padding: 14px 18px;
  margin: 1.5em 0;
  color: var(--warn);
  font-weight: 700;
}

@media print {
  header.page-header { display: none; }
}

@media (max-width: 700px) {
  header.page-header { position: static; padding: 12px 16px; }
  .header-main { align-items: stretch; flex-direction: column; }
  header.page-header .return-nav { justify-content: flex-start; }
  header.page-header .return-nav a { flex: 1 1 180px; text-align: center; }
  header.page-header #nav { flex-wrap: nowrap; overflow-x: auto; padding-bottom: 6px; }
  header.page-header #nav a { flex: 0 0 auto; }
}