/* ============================================================
   Site · 全站统一导航与页脚
   Apple 风格：毛玻璃导航条、极细分隔线、悬停下滑子菜单
   组件统一使用 sn- / sf- 前缀，不与各模块旧样式（.nav / .unav）冲突
   ============================================================ */
:root {
  --sn-ink: #1d1d1f;
  --sn-muted: #6e6e73;
  --sn-line: rgba(0, 0, 0, .09);
  --sn-accent: #0071e3;
  --sn-tile: #f5f5f7;
  --sn-nav-h: 56px;
  --sn-font: -apple-system, BlinkMacSystemFont, "SF Pro Text", "Helvetica Neue",
    "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", sans-serif;
}

.site-nav { box-sizing: border-box; }
.site-nav *, .site-footer * { box-sizing: border-box; }

/* ===== 导航条 ===== */
.site-nav {
  position: sticky; top: 0; z-index: 90;
  background: rgba(255, 255, 255, .78);
  -webkit-backdrop-filter: saturate(180%) blur(20px);
  backdrop-filter: saturate(180%) blur(20px);
  border-bottom: 1px solid var(--sn-line);
  font-family: var(--sn-font);
  transition: box-shadow .3s ease;
}
.site-nav.is-scrolled { box-shadow: 0 1px 24px rgba(0, 0, 0, .07); }
.sn-inner {
  position: relative;
  max-width: 1200px; margin: 0 auto; padding: 0 24px;
  min-height: var(--sn-nav-h);
  display: flex; align-items: center; gap: 24px;
}
.sn-brand {
  display: inline-flex; align-items: baseline; gap: 8px; white-space: nowrap;
  color: var(--sn-ink); font-size: 1.06rem; font-weight: 700;
  letter-spacing: -.02em; text-decoration: none;
}
.sn-brand span {
  font-size: .64rem; font-weight: 600; letter-spacing: .14em;
  text-transform: uppercase; color: var(--sn-muted);
}
.sn-menu, .sn-actions { display: flex; align-items: center; gap: 2px; list-style: none; margin: 0; padding: 0; }
.sn-actions { margin-left: auto; gap: 6px; }
.sn-item { position: relative; }
.sn-link {
  display: inline-flex; align-items: center; gap: 6px; white-space: nowrap;
  height: 34px; padding: 0 13px; border-radius: 999px;
  font-size: .9rem; font-weight: 500; color: var(--sn-ink);
  text-decoration: none; transition: background .2s, color .2s;
}
.sn-link:hover { background: rgba(0, 0, 0, .045); }
.sn-link.is-active { color: var(--sn-accent); }

/* 小箭头：悬停时向上翻转 */
.sn-caret {
  width: 6px; height: 6px; margin-top: -3px;
  border-right: 1.5px solid currentColor; border-bottom: 1.5px solid currentColor;
  transform: rotate(45deg);
  transition: transform .26s cubic-bezier(.22, .61, .36, 1), margin .26s;
}
.sn-item:hover > .sn-link .sn-caret,
.sn-item:focus-within > .sn-link .sn-caret,
.sn-item.is-open > .sn-link .sn-caret { transform: rotate(225deg); margin-top: 3px; }

/* ===== 悬停下滑子菜单 ===== */
.sn-sub {
  position: absolute; top: 100%; left: 50%; padding-top: 8px;
  opacity: 0; visibility: hidden;
  transform: translate(-50%, -10px);
  transition: opacity .28s cubic-bezier(.22, .61, .36, 1),
              transform .28s cubic-bezier(.22, .61, .36, 1),
              visibility .28s;
}
.sn-sub-right { left: auto; right: 0; transform: translateY(-10px); }
.sn-item:hover > .sn-sub,
.sn-item:focus-within > .sn-sub,
.sn-item.is-open > .sn-sub { opacity: 1; visibility: visible; transform: translate(-50%, 0); }
.sn-item:hover > .sn-sub-right,
.sn-item:focus-within > .sn-sub-right,
.sn-item.is-open > .sn-sub-right { transform: translateY(0); }

.sn-drop {
  min-width: 268px; padding: 8px; background: #fff;
  border: 1px solid var(--sn-line); border-radius: 18px;
  box-shadow: 0 20px 54px rgba(0, 0, 0, .16);
}
.sn-drop-link { display: block; padding: 10px 13px; border-radius: 12px; text-decoration: none; transition: background .16s; }
.sn-drop-link:hover { background: var(--sn-tile); }
.sn-drop-t { display: block; font-size: .92rem; font-weight: 600; color: var(--sn-ink); }
.sn-drop-d { display: block; margin-top: 3px; font-size: .78rem; line-height: 1.45; color: var(--sn-muted); }

/* ===== 右侧：语言 / 账号 ===== */
.sn-lang {
  display: inline-flex; align-items: center; height: 30px; padding: 0 11px;
  border-radius: 999px; font-size: .78rem; font-weight: 600; letter-spacing: .04em;
  color: var(--sn-muted); text-decoration: none; transition: background .2s, color .2s;
}
.sn-lang:hover { background: rgba(0, 0, 0, .045); color: var(--sn-ink); }
.sn-user {
  display: inline-flex; align-items: center; gap: 7px; max-width: 190px;
  height: 36px; padding: 0 12px 0 4px; border-radius: 999px;
  color: var(--sn-ink); font-size: .88rem; font-weight: 600;
  text-decoration: none; transition: background .2s;
}
.sn-user:hover { background: rgba(0, 0, 0, .045); }
.sn-user.is-active { color: var(--sn-accent); }
.sn-user-name { overflow: hidden; text-overflow: ellipsis; white-space: nowrap; }
.sn-login {
  display: inline-flex; align-items: center; height: 34px; padding: 0 16px;
  border-radius: 999px; background: var(--sn-ink); color: #fff;
  font-size: .86rem; font-weight: 600; text-decoration: none; transition: background .2s;
}
.sn-login:hover { background: #000; }
.sn-signup {
  display: inline-flex; align-items: center; height: 34px; padding: 0 13px;
  border-radius: 999px; color: var(--sn-accent);
  font-size: .86rem; font-weight: 600; text-decoration: none; transition: background .2s;
}
.sn-signup:hover { background: rgba(0, 113, 227, .08); }
.sn-burger { display: none; }
/* 移动端专用「账号」分组：桌面端隐藏（桌面用右侧头像） */
.sn-mobile-account { display: none; }

/* ===== 移动端：汉堡菜单 + 手风琴 ===== */
@media (max-width: 900px) {
  .sn-inner { padding: 0 16px; gap: 0; }
  .sn-brand { margin-right: auto; }
  .sn-burger {
    display: inline-flex; flex-direction: column; justify-content: center; gap: 5px;
    width: 40px; height: 40px; margin-left: 8px;
    background: none; border: 0; padding: 0; cursor: pointer;
  }
  .sn-burger i { display: block; width: 18px; height: 1.5px; margin: 0 auto; background: var(--sn-ink); transition: transform .28s, opacity .2s; }
  .site-nav.sn-open .sn-burger i:first-child { transform: translateY(3.3px) rotate(45deg); }
  .site-nav.sn-open .sn-burger i:last-child { transform: translateY(-3.3px) rotate(-45deg); }

  .sn-menu {
    position: absolute; top: 100%; left: 0; right: 0; z-index: 5;
    flex-direction: column; align-items: stretch; gap: 0;
    padding: 6px 16px 14px;
    background: #fff;
    -webkit-backdrop-filter: blur(20px); backdrop-filter: blur(20px);
    border-bottom: 1px solid var(--sn-line);
    box-shadow: 0 18px 40px rgba(0, 0, 0, .1);
    max-height: calc(100vh - var(--sn-nav-h)); overflow: auto;
    opacity: 0; visibility: hidden; transform: translateY(-12px);
    transition: opacity .28s cubic-bezier(.22, .61, .36, 1),
                transform .28s cubic-bezier(.22, .61, .36, 1), visibility .28s;
  }
  .site-nav.sn-open .sn-menu { opacity: 1; visibility: visible; transform: translateY(0); }
  .sn-link { height: 44px; padding: 0 10px; border-radius: 12px; justify-content: space-between; font-size: .98rem; }
  /* ⚠️ 必须用与桌面 hover 规则相同的选择器权重来重置 transform：
     只写 `.sn-sub { transform: none }`（0,1,0）会被
     `.sn-item.is-open > .sn-sub { transform: translate(-50%, 0) }`（0,2,0）压过去，
     导致移动端展开的子菜单被平移出屏幕左侧（left: -163px）。 */
  .sn-sub, .sn-sub-right,
  .sn-item:hover > .sn-sub, .sn-item:focus-within > .sn-sub, .sn-item.is-open > .sn-sub,
  .sn-item:hover > .sn-sub-right, .sn-item:focus-within > .sn-sub-right, .sn-item.is-open > .sn-sub-right {
    position: static; display: none; padding: 0 0 6px 6px;
    opacity: 1; visibility: visible; transform: none;
  }
  .sn-item.is-open > .sn-sub { display: block; }
  .sn-drop { min-width: 0; padding: 0; background: transparent; border: 0; border-radius: 0; box-shadow: none; }
  .sn-drop-link { padding: 9px 12px; }
  .sn-item-auth { display: none; }          /* 登录/注册移到菜单面板的「账号」分组 */
  .sn-item-user { display: none; }          /* 头像菜单同上 */
  .sn-mobile-account { display: block; margin-top: 6px; padding-top: 8px; border-top: 1px solid var(--sn-line); }
  .sn-mobile-label { padding: 4px 10px 2px; font-size: .72rem; font-weight: 600; letter-spacing: .1em; text-transform: uppercase; color: var(--sn-muted); }
}

/* ===== 页脚 ===== */
.site-footer {
  margin-top: 0; background: #1d1d1f; color: #a1a1a6;
  padding: 56px 24px 28px; font-family: var(--sn-font);
}
.sf-inner { max-width: 1200px; margin: 0 auto; display: grid; grid-template-columns: 1.1fr 2fr; gap: 44px; }
.sf-logo { color: #fff; font-size: 1.2rem; font-weight: 700; letter-spacing: -.02em; }
.sf-brand p { margin: 10px 0 0; font-size: .88rem; line-height: 1.65; max-width: 320px; }
.sf-links { display: grid; grid-template-columns: repeat(3, 1fr); gap: 24px; }
.sf-col h4 { margin: 0 0 14px; color: #fff; font-size: .78rem; font-weight: 600; letter-spacing: .08em; text-transform: uppercase; }
.sf-col ul { list-style: none; margin: 0; padding: 0; display: grid; gap: 10px; }
.sf-col a { color: #a1a1a6; font-size: .88rem; text-decoration: none; transition: color .18s; }
.sf-col a:hover { color: #fff; }
.sf-bottom {
  max-width: 1200px; margin: 44px auto 0; padding-top: 20px;
  border-top: 1px solid rgba(255, 255, 255, .12);
  font-size: .78rem; color: #6e6e73;
}
@media (max-width: 760px) {
  .sf-inner { grid-template-columns: 1fr; gap: 28px; }
  .sf-links { grid-template-columns: repeat(2, 1fr); }
}