/* 説明ページ（howto.html / privacy.html）共通のスタイル。index.html とは別に持つ */
:root {
  --ink: #0f1b3d;
  --ink-2: #6b7385;
  --paper: #fafafa;
  --field: #f1f3f8;
  --line: #e3e7f0;
  --navy-2: #1b3a82;
  --gold: #e9b200;
}
* { box-sizing: border-box; }
body {
  margin: 0;
  background: var(--paper);
  color: var(--ink);
  font-family: "Hiragino Sans", "Noto Sans JP", system-ui, sans-serif;
  line-height: 1.85;
  padding: 0 20px 64px;
}
.wrap { max-width: 640px; margin: 0 auto; }
.top {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 20px 0 8px;
}
.brand { display: flex; align-items: center; gap: 10px; color: var(--ink); text-decoration: none; }
.brand img { width: 36px; height: 36px; }
.brand span { font-size: 20px; font-weight: 800; letter-spacing: -0.03em; }
.back { font-size: 13px; color: var(--navy-2); text-decoration: none; }
.back:hover { text-decoration: underline; }
h1 { font-size: 26px; margin: 32px 0 6px; letter-spacing: -0.01em; line-height: 1.4; }
.updated { font-size: 12px; color: var(--ink-2); margin: 0 0 8px; }
h2 {
  font-size: 18px;
  margin: 44px 0 8px;
  padding-left: 12px;
  border-left: 4px solid var(--gold);
  line-height: 1.5;
}
p, li { font-size: 15px; }
p { margin: 10px 0; }
ul, ol { padding-left: 22px; margin: 10px 0; }
li { margin: 4px 0; }
a { color: var(--navy-2); }
.formula {
  background: #fff;
  border: 1px solid var(--line);
  border-radius: 14px;
  padding: 16px 18px;
  font-size: 15px;
  font-variant-numeric: tabular-nums;
  margin: 14px 0;
}
table {
  width: 100%;
  border-collapse: collapse;
  background: #fff;
  border: 1px solid var(--line);
  border-radius: 14px;
  overflow: hidden;
  font-size: 14px;
  font-variant-numeric: tabular-nums;
  margin: 14px 0;
}
th, td { padding: 10px 14px; text-align: right; border-bottom: 1px solid var(--line); }
th:first-child, td:first-child { text-align: left; }
th { background: var(--field); font-weight: 700; font-size: 13px; }
tr:last-child td { border-bottom: 0; }
.note {
  font-size: 13px;
  color: var(--ink-2);
  background: var(--field);
  border-radius: 12px;
  padding: 12px 16px;
}
footer {
  margin-top: 56px;
  padding-top: 20px;
  border-top: 1px solid var(--line);
  font-size: 12px;
  color: var(--ink-2);
  display: flex;
  gap: 16px;
  flex-wrap: wrap;
}
footer a { color: var(--ink-2); }