:root {
  --bg: #ffffff;
  --fg: #000000;
  --fg-muted: #333333;
  --border: #dddddd;
  --accent-red: #e53935;
  --accent-blue: #1967d2;
}

* {
  box-sizing: border-box;
}

html, body {
  margin: 0;
  padding: 0;
  background-color: var(--bg);
  color: var(--fg);
  font-family: -apple-system, BlinkMacSystemFont, "Helvetica Neue",
               Arial, "Noto Sans JP", "Hiragino Sans", "Yu Gothic",
               "Meiryo", sans-serif;
  font-size: 18px;
  line-height: 1.8;
}

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

a:hover {
  text-decoration: underline;
}

.page {
  max-width: 1200px;
  margin: 0 auto;
  padding: 48px 20px 104px;
}

/* HEADER --------------------------------------------------- */

.header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  flex-wrap: wrap;
  gap: 20px;
  background-image: linear-gradient(to right, #ffffff 20%, #cccccc 100%);
  border-radius: 12px;
  padding: 12px 0 12px 0;
}

.header-brand {
  display: flex;
  flex-direction: column;
  gap: 0;
  align-items: flex-start;
}

.logo {
  font-size: 24px;
  letter-spacing: 0.2em;
  font-weight: 700;
}

.nav {
  display: flex;
  flex: 0 1 auto;
  min-width: 0;
  flex-wrap: wrap;
  justify-content: flex-end;
  max-width: 100%;
  align-items: center;
  margin-left: auto;
  gap: 0 30px;
  font-size: 16px;
  font-weight: bold;
  text-transform: none;
  letter-spacing: 0.08em;
  background: #333333;
  color: #ffffff;
  padding: 14px 24px;

  border-radius: 6px 0 0 6px;

}

.nav-link {
  position: relative;
  padding-bottom: 2px;
}

.nav-link:hover {
  text-decoration: none;
}

.nav-link::after {
  content: "";
  position: absolute;
  left: 0;
  bottom: 0;
  width: 0;
  height: 1px;
  background: currentColor;
  transition: width 0.15s linear;
}

.nav-link:hover::after {
  width: 100%;
}

.intro-note {
  color: var(--fg-muted);
  font-size: 16px;
  margin: -6px 0 0;
  padding-left: 8px;
}

.lang-nav {
  display: inline-flex;
  align-items: center;
  border-left: 1px solid #ffffff;
  padding-left: 12px;
  font-size: 12px;
  letter-spacing: 0.08em;
}

.lang-nav a {
  text-transform: uppercase;
}

.lang-nav-divider {
  margin: 0 6px;
}

.lang-nav-current {
  font-weight: 600;
  color: #9999ff;
}

/* SECTIONS -------------------------------------------------- */

.section {
  border-top: 1px solid var(--border);
  padding-top: 36px;
  margin-top: 40px;
}

.section-header {
  margin-bottom: 22px;
}

.section-label {
  font-size: 20px;
  letter-spacing: 0.18em;
  color: var(--fg-muted);
  margin-bottom: 8px;
}

.section-title {
  font-size: 16px;
  font-weight: 600;
  letter-spacing: 0.14em;
  margin-bottom: 10px;
}

.section-title span {
  color: var(--accent-red);
}

.section-columns {
  display: grid;
  grid-template-columns: minmax(0, 1.1fr) minmax(0, 1fr);
  gap: 0px 30px;
  font-size: 15px;
  color: var(--fg-muted);
  margin-top: 8px;
}

.section-columns ul {
  padding-left: 20px;
  margin-top: 8px;
}

.section-columns li {
  margin-bottom: 6px;
}

.section-keyline {
  border-left: 2px solid var(--fg);
  padding-left: 18px;
  max-width: 38rem;
}

.section-detail {
  margin-top: 16px;
  padding: 12px;
  max-width: 38rem;
  background-color: #eeeeee;

  border-radius: 12px;
}

.section-meta {
  font-size: 12px;
  color: var(--fg-muted);
  border-top: 1px solid var(--border);
  padding-top: 10px;
  margin-top: 12px;
}

.page-link {
  color: var(--accent-blue);
}

/* FOOTER -------------------------------------------------- */

.footer {
  border-top: 1px solid var(--border);
  margin-top: 64px;
  padding-top: 16px;
  font-size: 14px;
  color: var(--fg-muted);
  display: flex;
  justify-content: space-between;
  flex-wrap: wrap;
  gap: 8px;
}

.footer a {
  font-size: 11px;
  letter-spacing: 0.12em;
}

/* REDIRECT PAGE ------------------------------------------- */

.redirect-message {
  font-size: 16px;
  color: var(--fg-muted);
  margin-bottom: 12px;
}

.redirect-links {
  font-size: 14px;
}

/* RESPONSIVE ---------------------------------------------- */

@media (max-width: 960px) {
  .section-columns {
    grid-template-columns: 1fr;
  }
}

@media (max-width: 720px) {
}

@media (max-width: 900px) {
  .nav {
    flex: 1 1 auto;
    margin-left: auto;
  }
}