header.nav { position: sticky; top: 0; z-index: 20; display: flex; align-items: center; justify-content: space-between;
  padding: 16px 32px; backdrop-filter: blur(14px); background: rgba(6,10,20,0.55); border-bottom: 1px solid var(--border-cool); }
header.nav .brand { display: flex; align-items: center; gap: 12px; }
header.nav .brand img { width: 40px; height: 40px; border-radius: 50%; object-fit: cover; }
header.nav .brand .txt .en { font-family: "Cinzel",serif; font-size: 15px; letter-spacing: 0.18em; color: var(--moon); }
header.nav .brand .txt .cn { font-size: 12px; letter-spacing: 0.2em; color: var(--text-dim); margin-top: 2px; }
header.nav .actions { display: flex; gap: 12px; align-items: center; }
.nav-btn { padding: 9px 20px; border: 1px solid var(--border-cool); border-radius: 8px; font-size: 13px; letter-spacing: .1em;
  color: var(--gold-bright); background: rgba(140,175,235,0.06); transition: all .25s; cursor: pointer; text-decoration: none; }
.nav-btn:hover { background: rgba(140,175,235,0.16); box-shadow: 0 0 18px rgba(140,175,235,0.25); }
.nav-btn.ghost { border-color: var(--border-cool); color: var(--text-dim); background: transparent; }
.nav-btn.ghost:hover { color: var(--moon); border-color: var(--moon); box-shadow: none; }

.mail-wrap { position: relative; z-index: 1; max-width: 1120px; margin: 0 auto; padding: 40px 20px 80px; }
.mail-head { text-align: center; margin-bottom: 30px; }
.mail-head .en { font-family: "Cinzel",serif; font-size: 12px; letter-spacing: .5em; text-indent: .5em; color: var(--gold); }
.mail-head h1 { font-size: 30px; letter-spacing: .28em; text-indent: .28em; color: var(--gold-bright); margin: 10px 0 6px; }
.mail-head .sub { font-size: 13px; color: var(--text-dim); letter-spacing: .12em; }

.mailbox { display: grid; grid-template-columns: 240px 1fr; gap: 20px; align-items: start; }

/* 侧栏 */
.sidebar { background: var(--card); border: 1px solid var(--border-cool); border-radius: 18px; padding: 18px; backdrop-filter: blur(20px) saturate(1.4); }
.compose-btn { width: 100%; padding: 13px; border: 1px solid var(--gold); border-radius: 12px; background: linear-gradient(135deg, rgba(140,175,235,0.22), rgba(140,175,235,0.08));
  color: var(--gold-bright); font-family: inherit; font-size: 14px; letter-spacing: .15em; cursor: pointer; transition: all .25s; margin-bottom: 16px; }
.compose-btn:hover { box-shadow: 0 0 24px rgba(140,175,235,0.35); background: rgba(140,175,235,0.28); }
.folder { display: flex; align-items: center; gap: 11px; padding: 11px 13px; border-radius: 11px; cursor: pointer; color: var(--text-dim);
  font-size: 14px; letter-spacing: .04em; transition: all .2s; margin-bottom: 4px; }
.folder:hover { background: rgba(255,255,255,0.04); color: var(--moon); }
.folder.active { background: rgba(140,175,235,0.12); color: var(--gold-bright); }
.folder svg { width: 18px; height: 18px; flex-shrink: 0; }
.folder .fname { flex: 1; }
.folder .badge { background: var(--gold); color: #0c1424; font-size: 11px; font-weight: 600; min-width: 20px; height: 20px; border-radius: 10px;
  display: flex; align-items: center; justify-content: center; padding: 0 6px; }
.folder.active .badge { background: var(--gold-bright); }

/* 面板 */
.panel { background: var(--card); border: 1px solid var(--border-cool); border-radius: 18px; overflow: hidden;
  backdrop-filter: blur(20px) saturate(1.4); min-height: 520px; }
.panel-head { display: flex; align-items: center; justify-content: space-between; padding: 16px 22px; border-bottom: 1px solid var(--border-cool); }
.panel-head .ptitle { font-size: 15px; letter-spacing: .18em; color: var(--moon); }
.panel-head .pcount { font-size: 12px; color: var(--text-dim); }

/* 信件列表 */
.mail-list { max-height: 620px; overflow-y: auto; }
.mail-item { display: flex; gap: 14px; padding: 16px 22px; border-bottom: 1px solid rgba(140,170,220,0.08); cursor: pointer; transition: background .2s; position: relative; }
.mail-item:hover { background: rgba(255,255,255,0.03); }
.mail-item.unread::before { content: ""; position: absolute; left: 9px; top: 50%; transform: translateY(-50%); width: 6px; height: 6px; border-radius: 50%; background: var(--gold-bright); box-shadow: 0 0 8px var(--gold-bright); }
.mail-item .mi-body { flex: 1; min-width: 0; }
.mail-item .mi-top { display: flex; align-items: baseline; justify-content: space-between; gap: 10px; }
.mail-item .mi-from { font-size: 14px; color: var(--moon); letter-spacing: .03em; }
.mail-item.unread .mi-from { color: var(--gold-bright); font-weight: 500; }
.mail-item .mi-time { font-size: 11px; color: var(--text-dim); flex-shrink: 0; }
.mail-item .mi-subject { font-size: 13.5px; color: var(--text); margin: 3px 0; white-space: nowrap; overflow: hidden; text-overflow: ellipsis; }
.mail-item.unread .mi-subject { color: #fff; }
.mail-item .mi-preview { font-size: 12px; color: var(--text-dim); white-space: nowrap; overflow: hidden; text-overflow: ellipsis; }

/* 阅读视图 */
.reader { padding: 26px 30px; }
.reader .back { display: inline-flex; align-items: center; gap: 6px; border: 0; padding: 0; background: transparent; font: inherit; font-size: 13px; color: var(--text-dim); cursor: pointer; margin-bottom: 20px; transition: color .2s; }
.reader .back:hover { color: var(--gold-bright); }
.reader .r-subject { font-size: 21px; color: var(--gold-bright); letter-spacing: .04em; margin-bottom: 16px; line-height: 1.5; }
.reader .r-meta { display: flex; align-items: center; gap: 13px; padding-bottom: 18px; border-bottom: 1px solid var(--border-cool); margin-bottom: 22px; }
.reader .r-from { font-size: 15px; color: var(--moon); }
.reader .r-addr { font-size: 12px; color: var(--text-dim); margin-top: 3px; }
.reader .r-time { margin-left: auto; font-size: 12px; color: var(--text-dim); }
.reader .r-content { font-size: 15px; line-height: 2.05; color: var(--text); font-weight: 300; white-space: pre-wrap; }
.reader .r-actions { margin-top: 28px; display: flex; gap: 12px; }

/* 写信表单 */
.compose { padding: 26px 30px; }
.compose .field { margin-bottom: 18px; }
.compose label { display: block; font-size: 13px; color: var(--moon); letter-spacing: .08em; margin-bottom: 8px; }
.compose .input, .compose textarea { width: 100%; background: rgba(0,0,0,0.35); border: 1px solid var(--border-cool); border-radius: 10px;
  color: var(--text); font-family: inherit; font-size: 15px; padding: 12px 14px; transition: border-color .25s, box-shadow .25s; }
.compose .input:focus, .compose textarea:focus { outline: none; border-color: var(--gold); box-shadow: 0 0 18px rgba(140,175,235,0.2); }
.compose textarea { min-height: 220px; resize: vertical; line-height: 1.9; font-weight: 300; }
.compose .input::placeholder, .compose textarea::placeholder { color: var(--text-dim); }
.compose .c-actions { display: flex; gap: 12px; margin-top: 8px; }
.compose .cmsg { font-size: 12px; color: #e8756c; min-height: 16px; margin-top: 4px; letter-spacing: .04em; }

/* 空状态 */
.empty { display: flex; flex-direction: column; align-items: center; justify-content: center; padding: 90px 20px; color: var(--text-dim); text-align: center; }
.empty .et { font-size: 15px; letter-spacing: .1em; color: var(--moon); }
.empty .es { font-size: 12.5px; margin-top: 8px; }

@media (max-width: 760px) {
  .mailbox { grid-template-columns: 1fr; }
  .sidebar { display: flex; flex-wrap: wrap; gap: 8px; padding: 14px; }
  .compose-btn { flex: 1 1 100%; margin-bottom: 8px; }
  .folder { flex: 1; justify-content: center; margin-bottom: 0; }
  .folder .fname { flex: none; }
  header.nav { padding: 14px 18px; }
  header.nav .actions .nav-btn.ghost { display: none; }
  header.nav .brand .txt .cn { display: none; }
  header.nav .brand .txt .en { font-size: 12px; letter-spacing: .1em; }
  .mail-wrap { padding: 24px 12px calc(48px + env(safe-area-inset-bottom)); }
  .mail-head { margin-bottom: 20px; }
  .mail-head h1 { font-size: 25px; }
  .folder { min-height: 44px; }
  .panel { min-height: 420px; }
  .mail-item { padding: 14px 13px; gap: 10px; }
  .reader, .compose { padding: 20px 16px; }
  .reader .r-meta { align-items: flex-start; flex-wrap: wrap; }
  .reader .r-time { width: 100%; margin-left: 0; }
  .compose .c-actions { flex-direction: column; }
  .compose textarea { min-height: 180px; }
}