/* ── Reset & Base ─────────────────────────────────────────────── */
*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }

:root {
  --navy:    #1a2e4a;
  --blue:    #2563a8;
  --blue-lt: #3b7dd8;
  --gray-dk: #2d2d2d;
  --gray:    #555;
  --gray-lt: #888;
  --border:  #dde1e7;
  --bg:      #ffffff;
  --bg-lt:   #f7f8fa;
  --max-w:   900px;
  --sans:    -apple-system, BlinkMacSystemFont, 'Segoe UI', 'Hiragino Sans', 'Noto Sans JP', Helvetica, Arial, sans-serif;
}

html { font-size: 16px; }

body {
  font-family: var(--sans);
  color: var(--gray-dk);
  background: var(--bg);
  line-height: 1.75;
}

a { color: var(--blue); text-decoration: none; }
a:hover { color: var(--blue-lt); text-decoration: underline; }

/* ── Header / Nav ─────────────────────────────────────────────── */
header {
  background: var(--navy);
  border-bottom: 3px solid var(--blue);
  position: sticky;
  top: 0;
  z-index: 100;
}

nav {
  max-width: var(--max-w);
  margin: 0 auto;
  padding: 0 2rem;
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 56px;
}

.nav-name {
  font-size: 1rem;
  font-weight: 600;
  color: #fff;
  letter-spacing: 0.01em;
}

.nav-links {
  display: flex;
  gap: 1.75rem;
  list-style: none;
}

.nav-links a {
  color: rgba(255,255,255,0.82);
  font-size: 0.875rem;
  font-weight: 400;
  letter-spacing: 0.02em;
  transition: color 0.15s;
}

.nav-links a:hover,
.nav-links a.active {
  color: #fff;
  text-decoration: none;
}

.nav-lang {
  display: flex;
  align-items: center;
  margin-left: 2rem;
}

.nav-lang a {
  color: rgba(255,255,255,0.6);
  font-size: 0.8rem;
  border: 1px solid rgba(255,255,255,0.3);
  padding: 2px 8px;
  border-radius: 3px;
  transition: all 0.15s;
}

.nav-lang a:hover {
  color: #fff;
  border-color: rgba(255,255,255,0.7);
  text-decoration: none;
}

.nav-right {
  display: flex;
  align-items: center;
}

/* ── Main Container ───────────────────────────────────────────── */
main {
  max-width: var(--max-w);
  margin: 0 auto;
  padding: 3.5rem 2rem 5rem;
}

/* ── Footer ───────────────────────────────────────────────────── */
footer {
  background: var(--bg-lt);
  border-top: 1px solid var(--border);
  padding: 1.5rem 2rem;
  text-align: center;
  font-size: 0.8rem;
  color: var(--gray-lt);
}

/* ── Responsive ───────────────────────────────────────────────── */
@media (max-width: 640px) {
  nav { padding: 0.6rem 1.25rem; flex-wrap: wrap; height: auto; }
  .nav-name { flex: 1; }
  .nav-right { width: 100%; justify-content: center; padding: 0.3rem 0 0.4rem; }
  .nav-links { gap: 1rem; flex-wrap: wrap; justify-content: center; }
  .nav-lang { margin-left: 1rem; }
  main { padding: 2rem 1.25rem 4rem; }
}