/* ============================================================
   03 · Navigation (desktop bar + mobile overlay)
   ============================================================ */

.site-nav {
  position: fixed; top: 0; left: 0; right: 0; z-index: 1100;
  transition: background .35s ease, box-shadow .35s ease, backdrop-filter .35s;
}
.site-nav.scrolled {
  background: rgba(255, 255, 255, .82);
  backdrop-filter: blur(16px);
  -webkit-backdrop-filter: blur(16px);
  border-bottom: 1px solid rgba(148, 163, 184, .14);
  box-shadow: 0 10px 40px -20px rgba(15, 23, 42, .12);
}
.nav-inner {
  max-width: var(--container); margin: 0 auto; padding: 0 var(--pad);
  height: var(--nav-h); display: flex; align-items: center; justify-content: space-between;
}

.brand { display: inline-flex; align-items: center; gap: 12px; }
.brand-mark {
  width: 40px; height: 40px; border-radius: 12px; display: grid; place-items: center;
  font-family: var(--font-display); font-weight: 800; font-size: .95rem; color: #fff;
  background: linear-gradient(135deg, var(--blue-500), var(--violet-600));
  box-shadow: 0 6px 20px -6px rgba(124, 58, 237, .6);
  position: relative; overflow: hidden;
}
.brand-mark::after {
  content: ""; position: absolute; inset: 0;
  background: linear-gradient(120deg, transparent 30%, rgba(255,255,255,.35), transparent 70%);
  transform: translateX(-100%);
  animation: sheen 4.5s var(--ease) infinite;
}
@keyframes sheen { 0%, 55% { transform: translateX(-100%); } 80%, 100% { transform: translateX(100%); } }
.brand-text {
  font-family: var(--font-display); font-weight: 700; font-size: 1.05rem;
  letter-spacing: -.01em; color: var(--white);
}
.brand-dot { color: var(--violet-400); }

.nav-links { display: flex; align-items: center; gap: 34px; margin-left: auto; margin-right: 34px; }
.nav-link {
  position: relative; font-family: var(--font-display); font-size: .8rem; font-weight: 600;
  letter-spacing: .06em; text-transform: uppercase; color: var(--slate-300);
  padding: 6px 0; transition: color .25s;
}
.nav-link .nav-idx {
  font-family: var(--font-mono); font-size: .6rem; color: var(--violet-400);
  margin-right: 4px; vertical-align: 1px;
}
.nav-link::after {
  content: ""; position: absolute; left: 0; bottom: 0; height: 2px; width: 0;
  background: var(--grad); border-radius: 2px; transition: width .35s var(--ease);
}
.nav-link:hover, .nav-link.active { color: var(--white); }
.nav-link:hover::after, .nav-link.active::after { width: 100%; }

.nav-burger {
  display: none; width: 44px; height: 44px; border-radius: 12px; border: 1px solid rgba(148,163,184,.25);
  background: rgba(255, 255, 255, .7); flex-direction: column; align-items: center; justify-content: center; gap: 5px;
  cursor: pointer;
}
.nav-burger span { display: block; width: 20px; height: 2px; background: var(--slate-100); border-radius: 2px; transition: transform .3s var(--ease), opacity .3s; }
.nav-burger.open span:nth-child(1) { transform: translateY(7px) rotate(45deg); }
.nav-burger.open span:nth-child(2) { opacity: 0; }
.nav-burger.open span:nth-child(3) { transform: translateY(-7px) rotate(-45deg); }

.nav-overlay {
  position: fixed; inset: 0; z-index: 1000; background: rgba(243, 246, 252, .97);
  backdrop-filter: blur(20px); -webkit-backdrop-filter: blur(20px);
  display: flex; flex-direction: column; align-items: center; justify-content: center; gap: 30px;
  opacity: 0; visibility: hidden; transition: opacity .4s ease, visibility .4s ease;
}
.nav-overlay.open { opacity: 1; visibility: visible; }
.overlay-links { text-align: center; display: flex; flex-direction: column; gap: 22px; }
.overlay-links a {
  font-family: var(--font-display); font-size: 1.8rem; font-weight: 700; color: var(--white);
  transition: color .2s, transform .3s var(--ease); display: inline-block;
}
.overlay-links a:hover { color: var(--blue-300); transform: translateX(6px); }
.overlay-links .nav-idx { font-family: var(--font-mono); font-size: .9rem; color: var(--violet-400); }
.overlay-mail { margin-top: 8px; }