/* ============================================================
   shell.css — 顶栏导航 + 视图容器（冷档案）
   ============================================================ */

.site-header {
  position: fixed;
  top: 0; left: 0; right: 0;
  z-index: var(--z-ui);
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1.5rem;
  padding: 1.1rem clamp(1.2rem, 4vw, 3rem);
  background: linear-gradient(180deg, rgba(243, 245, 248, 0.96), rgba(243, 245, 248, 0.72) 70%, transparent);
  pointer-events: none;
  transition: opacity 0.45s ease, transform 0.45s ease;
}
.site-header > * { pointer-events: auto; }

/* 封面页隐藏顶栏（不用仅靠 opacity，避免被动效/缓存干扰） */
body.is-cover .site-header {
  visibility: hidden;
  opacity: 0;
  pointer-events: none;
  transform: translateY(-8px);
}

/* 氛围层：浅冷雾 */
.atmosphere {
  position: fixed;
  inset: 0;
  z-index: calc(var(--z-cosmic-haze) + 1);
  pointer-events: none;
  opacity: 0.85;
  transition: opacity 0.6s ease;
  background:
    radial-gradient(ellipse 70% 50% at 70% 12%, rgba(42, 95, 143, 0.05), transparent 55%),
    radial-gradient(ellipse 50% 45% at 12% 88%, rgba(20, 22, 28, 0.03), transparent 58%);
}
.atmosphere::after {
  content: '';
  position: absolute;
  inset: 0;
  opacity: 0;
}

.brand {
  display: flex;
  flex-direction: column;
  gap: 0.15rem;
  min-width: 0;
}
.brand-name {
  font-size: clamp(0.95rem, 1.4vw, 1.15rem);
  font-weight: 400;
  letter-spacing: 0.18em;
  color: var(--ink);
}
.brand-sub {
  font-size: clamp(0.55rem, 0.75vw, 0.68rem);
  letter-spacing: 0.28em;
  color: var(--mute);
  font-weight: 300;
}

.site-nav {
  display: flex;
  align-items: center;
  gap: clamp(1rem, 2.5vw, 2rem);
}
.site-nav a {
  display: flex;
  flex-direction: column;
  align-items: flex-end;
  gap: 0.15rem;
  opacity: 0.55;
  transition: opacity 0.25s, color 0.25s;
}
.site-nav a:hover,
.site-nav a.is-active {
  opacity: 1;
}
.nav-en {
  font-size: clamp(0.62rem, 0.85vw, 0.75rem);
  letter-spacing: 0.22em;
  text-transform: uppercase;
  color: var(--ink);
  font-weight: 400;
}
.nav-zh {
  font-size: clamp(0.55rem, 0.72vw, 0.65rem);
  letter-spacing: 0.18em;
  color: var(--mute);
  font-weight: 300;
}
.site-nav a.is-active .nav-en {
  color: var(--accent);
}

.site-main {
  position: relative;
  z-index: var(--z-page);
  min-height: 100vh;
  min-height: 100dvh;
  padding: clamp(5.5rem, 12vh, 7rem) clamp(1.2rem, 4vw, 3rem) clamp(3rem, 8vh, 5rem);
}

.view[hidden] { display: none !important; }
/* 视图切换不用 opacity 淡入：内容常在 hidden 下预渲染，否则会卡在透明 */
@media (prefers-reduced-motion: no-preference) {
  .view:not([hidden]) {
    animation: viewIn 0.4s var(--ease-dive) both;
  }
}
@keyframes viewIn {
  from { transform: translateY(8px); }
  to { transform: none; }
}

.view-inner {
  width: min(920px, 100%);
  margin: 0 auto;
}

.view-header {
  margin-bottom: clamp(1.8rem, 4vh, 2.8rem);
}
.view-kicker {
  font-size: clamp(0.58rem, 0.85vw, 0.72rem);
  letter-spacing: 0.5em;
  text-transform: uppercase;
  color: var(--accent);
  font-weight: 400;
  margin-bottom: 0.7em;
}
.view-title {
  font-weight: 300;
  font-size: clamp(1.8rem, 4vw, 2.8rem);
  letter-spacing: 0.18em;
  color: var(--ink);
  margin-bottom: 0.8em;
}
.view-intro {
  font-size: clamp(0.78rem, 1.05vw, 0.92rem);
  line-height: 1.9;
  font-weight: 300;
  color: var(--silver);
  letter-spacing: 0.04em;
  max-width: 42em;
}

@media (max-width: 640px) {
  .site-header {
    flex-direction: column;
    align-items: flex-start;
    gap: 0.9rem;
    padding-bottom: 1.4rem;
  }
  .site-nav {
    width: 100%;
    justify-content: flex-start;
    gap: 1.2rem;
  }
  .site-nav a { align-items: flex-start; }
  .site-main {
    padding-top: clamp(7.5rem, 18vh, 9rem);
  }
}