:root {
  --gold: #9aa5b1;
  --gold-bright: #ffffff;
  --gold-line: rgba(170,178,188,0.35);
  --ink: #ffffff;
  --ink-dim: #ffffff;
  --ink-faint: #a8adb3;
  --bg: #0a0a0c;
  --panel: rgba(18,19,22,0.72);
  --panel-solid: #131417;
  /* 変数名は歴史的経緯でserifのままだが、明朝体は使わずゴシック体(本文と同じ
     フォント)に統一する。 */
  --serif: 'Segoe UI', 'Hiragino Sans', sans-serif;
}
* { box-sizing: border-box; }
html { scroll-behavior: smooth; }
body {
  margin: 0; min-height: 100vh; min-height: 100dvh;
  background: radial-gradient(ellipse at 50% 0%, #14161a 0%, var(--bg) 60%);
  color: var(--ink);
  font-family: 'Segoe UI', 'Hiragino Sans', sans-serif;
  line-height: 1.7;
  padding-bottom: 60px;
}
a { color: var(--gold-bright); }

header {
  position: sticky; top: 0; z-index: 5;
  display: flex; align-items: center; justify-content: space-between; gap: 12px;
  flex-wrap: wrap;
  padding: 14px 24px;
  padding-top: calc(14px + env(safe-area-inset-top, 0px));
  background: rgba(10,10,12,0.85);
  backdrop-filter: blur(10px);
  border-bottom: 1px solid var(--gold-line);
}
header .brand { font-family: var(--serif); font-size: 1.25rem; color: var(--ink); letter-spacing: .04em; }
header .brand small { display: block; font-family: inherit; font-size: 0.68rem; color: #fff; letter-spacing: .22em; text-transform: uppercase; margin-top: 2px; }
.home-btn {
  display: inline-flex; align-items: center; gap: 6px;
  padding: 9px 18px; border-radius: 999px;
  background: linear-gradient(180deg, #d8dde3, var(--gold) 60%, #7a838f);
  color: #1c1f24; font-weight: 700; font-size: 0.8rem;
  letter-spacing: .08em; text-decoration: none;
  box-shadow: 0 6px 16px rgba(170,178,188,0.25), inset 0 1px 0 rgba(255,255,255,0.5);
  white-space: nowrap;
}

.lede {
  max-width: 760px; margin: 34px auto 0; padding: 0 24px;
  text-align: center;
}
.lede .eyebrow { font-size: 11px; letter-spacing: .32em; text-transform: uppercase; color: #fff; margin: 0 0 12px; }
.lede h1 { font-family: var(--serif); font-weight: 500; font-size: clamp(26px, 5vw, 38px); margin: 0 0 12px; color: var(--ink); }
.lede p { color: var(--ink-dim); font-size: 0.92rem; margin: 0; }
.rule { height: 1px; width: 64px; margin: 22px auto; background: linear-gradient(90deg, transparent, var(--gold), transparent); }

nav.toc {
  max-width: 900px; margin: 0 auto; padding: 0 24px;
  display: flex; flex-wrap: wrap; gap: 8px; justify-content: center;
}
nav.toc a {
  padding: 7px 14px; border-radius: 999px;
  border: 1px solid var(--gold-line); background: rgba(170,178,188,0.06);
  font-size: 0.78rem; text-decoration: none; color: var(--ink-dim);
  transition: background .15s, color .15s;
}
nav.toc a:hover { background: rgba(170,178,188,0.18); color: var(--gold-bright); }

main { max-width: 900px; margin: 0 auto; padding: 8px 24px 0; }

section {
  margin-top: 46px; padding: 26px 28px;
  background: var(--panel); border: 1px solid var(--gold-line); border-radius: 4px;
  backdrop-filter: blur(8px);
  scroll-margin-top: 84px;
}
section h2 {
  display: flex; align-items: center; gap: 10px;
  font-family: var(--serif); font-weight: 500; font-size: 1.3rem; color: var(--gold-bright);
  margin: 0 0 6px;
}
section h2 .num { font-size: 0.7rem; color: #fff; letter-spacing: .1em; }
section > .desc { color: var(--ink-faint); font-size: 0.84rem; margin: 0 0 20px; }

h3 {
  font-size: 0.72rem; color: #fff; text-transform: uppercase;
  letter-spacing: .16em; margin: 22px 0 10px;
  border-bottom: 1px solid var(--gold-line); padding-bottom: 6px;
}
h3:first-of-type { margin-top: 0; }
.subnote { color: var(--ink-dim); font-size: 0.86rem; margin: 0 0 8px; }

.grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(240px, 1fr)); gap: 10px; }
.card {
  display: flex; align-items: flex-start; gap: 10px;
  padding: 12px 14px; border-radius: 4px;
  background: rgba(0,0,0,0.22); border: 1px solid rgba(170,178,188,0.15);
}
.card .icon { font-size: 1.15rem; flex-shrink: 0; line-height: 1.3; }
.card .body b { display: block; font-size: 0.86rem; color: var(--ink); margin-bottom: 2px; }
.card .body span { font-size: 0.78rem; color: var(--ink-dim); }

kbd {
  display: inline-flex; align-items: center; justify-content: center;
  min-width: 26px; height: 22px; padding: 0 7px;
  border: 1px solid var(--gold-line); border-radius: 4px;
  background: rgba(255,255,255,0.03); color: var(--gold-bright);
  font-size: 11px; font-family: inherit; letter-spacing: .02em;
}

table { width: 100%; border-collapse: collapse; font-size: 0.84rem; }
table th, table td { text-align: left; padding: 9px 10px; border-bottom: 1px solid rgba(170,178,188,0.15); }
table th { color: #fff; font-size: 0.7rem; text-transform: uppercase; letter-spacing: .1em; font-weight: 600; }
table td { color: var(--ink-dim); }
table td:first-child { white-space: nowrap; }
table tr:last-child td { border-bottom: none; }

ul.plain { margin: 0; padding-left: 1.2em; color: var(--ink-dim); font-size: 0.86rem; }
ul.plain li { margin-bottom: 6px; }
ul.plain b { color: var(--ink); }

.zone-list { display: grid; grid-template-columns: repeat(auto-fill, minmax(200px, 1fr)); gap: 8px; }
.zone-list .z {
  padding: 10px 12px; border-radius: 4px;
  background: rgba(0,0,0,0.22); border: 1px solid rgba(170,178,188,0.15);
  font-size: 0.82rem; color: var(--ink-dim);
}
.zone-list .z b { color: var(--ink); font-weight: 600; }

.note {
  margin-top: 18px; padding: 12px 14px; border-radius: 4px;
  background: rgba(170,178,188,0.07); border: 1px solid var(--gold-line);
  font-size: 0.8rem; color: var(--ink-dim);
}
.note b { color: var(--gold-bright); }

.cta { margin-top: 18px; }
.thanks { max-width: 900px; margin: 40px auto 0; padding: 0 24px; text-align: center; color: var(--ink-dim); font-size: 0.9rem; }

footer {
  max-width: 900px; margin: 50px auto 0; padding: 0 24px;
  text-align: center; color: var(--ink-faint); font-size: 0.76rem;
}

@media (max-width: 600px) {
  section { padding: 20px 18px; }
  header { padding: 12px 16px; }
}