/* ═══════════════════════════════════════════════
   VAS · Home v2 · 設計 token
   只宣告變數，不綁元素。進 repo 後應被 base.css.v3-proposal
   的 token 層吸收——此檔是過渡期的獨立拷貝。
   ═══════════════════════════════════════════════ */

:root {
  /* ─── 煉金曗場 · 底色 ─────────────────────── */
  --vas-void:     #0e0b1a;  /* 主背景 · 帶一點紫的深暗 */
  --vas-void-up:  #15121f;  /* 提亮一階 · 瀏覽器框殼 */
  --vas-void-up2: #1b1825;  /* 提亮二階 · 備用 */

  /* ─── 瓶子的光 · 只用在瓶子的暈光，不進背景 ── */
  --vas-aurora-violet: #c471f5;
  --vas-aurora-pink:   #fa71cd;
  --vas-aurora-blue:   #4facfe;

  /* ─── 字色：窯燒陶灰 · 可讀度底線已拉高一階 ── */
  --vas-ash-0: rgba(240, 232, 220, 0.94);  /* 主文 / 標題 */
  --vas-ash-1: rgba(240, 232, 220, 0.78);  /* 一般敘述 */
  --vas-ash-2: rgba(240, 232, 220, 0.60);  /* 次要描述 / mono 標籤 */
  --vas-ash-3: rgba(240, 232, 220, 0.42);  /* 微標籤 */
  --vas-ash-4: rgba(240, 232, 220, 0.24);  /* 版權頁微微字 */

  /* ─── 分隔線 ──────────────────────────────── */
  --vas-rule:        rgba(240, 232, 220, 0.08);
  --vas-rule-strong: rgba(240, 232, 220, 0.18);

  /* ─── 字體 · 和 base.css.v3-proposal 對齊 ───
     進 repo 時建議移除本區塊，改用 base 的 --font-serif / --font-mono。
     此處定義是讓 index-B.html 能獨立預覽。
     ─────────────────────────────────────── */
  --vas-serif:    'Shippori Mincho', 'Fraunces', 'Noto Serif TC', serif;
  --vas-serif-en: 'Fraunces', 'Shippori Mincho', serif;
  --vas-mono:     'JetBrains Mono', 'SF Mono', monospace;
}
/* 簡中模式改用 Noto Serif SC 優先，避免系統 fallback 造成基線浮動 */
html[lang="zh-Hans"] {
  --vas-serif: 'Noto Serif SC', 'Shippori Mincho', 'Fraunces', serif;
}

/* ─── base reset · 作用在頁面整體 ──────────── */
* { box-sizing: border-box; margin: 0; padding: 0; }
html { scroll-behavior: smooth; }
body {
  background: var(--vas-void);
  color: var(--vas-ash-0);
  font-family: var(--vas-serif);
  font-size: 16px;
  line-height: 1.9;
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
  overflow-x: hidden;
}
a { color: inherit; text-decoration: none; }
img { display: block; max-width: 100%; }

/* ═══════════════════════════════════════════════
   站內 nav · 靜一點的頂部導覽
   ═══════════════════════════════════════════════ */
.site-nav {
  position: sticky;
  top: 0;
  z-index: 50;
  background: rgba(14, 11, 26, 0.88);
  backdrop-filter: blur(16px);
  -webkit-backdrop-filter: blur(16px);
  display: flex; align-items: center; justify-content: space-between;
  padding: 28px 48px;
  border-bottom: 1px solid var(--vas-rule);
  transition: border-color .3s;
}
.site-nav-brand {
  display: flex; align-items: center; gap: 12px;
  font-family: var(--vas-serif);
  font-size: 15px;
  font-weight: 500;
  letter-spacing: 0.02em;
}
a.site-nav-brand { color: inherit; text-decoration: none; cursor: pointer; transition: color .2s; }
a.site-nav-brand:hover { color: var(--vas-ash-0); }
.site-nav-brand .mark {
  width: 8px; height: 8px;
  border-radius: 50%;
  background: radial-gradient(circle,
    var(--vas-aurora-violet) 0%,
    var(--vas-aurora-pink) 60%,
    transparent 100%);
  box-shadow: 0 0 12px rgba(196, 113, 245, 0.6);
  animation: vas-breathe 6s ease-in-out infinite;
}
@keyframes vas-breathe {
  0%, 100% { opacity: 0.75; transform: scale(1); }
  50%      { opacity: 1;    transform: scale(1.15); }
}
@media (max-width: 960px) {
  body:not(.is-home) .site-nav-brand .mark { animation: none; }
}
.site-nav-links {
  display: flex; gap: 32px;
  position: absolute; left: 50%; transform: translateX(-50%);
  font-family: var(--vas-mono);
  font-size: 13px;
  letter-spacing: 0.14em;
  text-transform: uppercase;
  color: var(--vas-ash-2);
}
.site-nav-links a { transition: color .2s; }
.site-nav-links a:hover { color: var(--vas-ash-0); }
.site-nav-lang {
  font-family: var(--vas-mono);
  font-size: 11px;
  color: var(--vas-ash-3);
  letter-spacing: 0.1em;
}
.lang-flat-row  { display: flex; align-items: center; gap: 4px; flex-wrap: nowrap; }
.lang-flat-row .lang-opt {
  font-family: var(--vas-mono);
  font-size: 12px;
  letter-spacing: 0.14em;
  text-transform: uppercase;
  padding: 4px 6px;
}
.lang-mobile-dd { display: none; position: relative; }

@media (max-width: 768px) {
  .site-nav { padding: 20px 24px; }
  .lang-flat-row  { display: none; }
  .lang-mobile-dd { display: block; }
  .site-nav-links { gap: 16px; font-size: 10px; }
}
@media (max-width: 560px) {
  .is-home .site-nav-links { display: none; }
}

/* Hamburger button (inner pages only, shown at narrow widths) */
.nav-hamburger {
  display: none;
  align-items: center;
  gap: 5px;
  padding: 6px 10px;
  border-radius: 999px;
  background: transparent;
  border: 1px solid var(--vas-rule);
  color: var(--vas-ash-2);
  font-family: var(--vas-mono);
  font-size: 10px;
  letter-spacing: 0.08em;
  cursor: pointer;
  transition: background .2s, color .2s;
}
.nav-hamburger:hover { background: rgba(240,232,220,0.07); color: var(--vas-ash-0); }
.nav-hamburger svg { flex-shrink: 0; }

/* Mobile nav dropdown menu */
.nav-mobile-menu {
  display: none;
  position: absolute;
  top: 100%;
  left: 0;
  right: 0;
  flex-direction: column;
  gap: 0;
  background: var(--vas-void-up, #1a1814);
  border-top: 1px solid var(--vas-rule);
  padding: 8px 0;
  z-index: 200;
}
.nav-mobile-menu.open { display: flex; }
.nav-mobile-menu a {
  padding: 12px 28px;
  font-family: var(--vas-mono);
  font-size: 11px;
  letter-spacing: 0.06em;
  color: var(--vas-ash-2);
  text-decoration: none;
  transition: color .2s;
}
.nav-mobile-menu a:hover { color: var(--vas-ash-0); }

@media (max-width: 680px) {
  .site-nav-links { display: none; }
  .nav-hamburger { display: flex; }
}

/* Mobile-only line break helper */
.m-br { display: none; }
@media (max-width: 768px) { .m-br { display: block; } }

/* Sticky nav offset for all anchor targets */
[id] { scroll-margin-top: 96px; }