:root {
  --bg-page: #0a0e17;
  --bg-surface: #121826;
  --bg-card: #182032;
  --bg-hover: #1e293f;
  --border-subtle: #243048;
  --border-focus: #38bdf8;
  --text-main: #f1f5f9;
  --text-muted: #94a3b8;
  --text-subtle: #64748b;
  --accent-blue: #38bdf8;
  --accent-green: #34d399;
  --accent-purple: #c084fc;
  --accent-danger: #f87171;
  --radius-sm: 6px;
  --radius-md: 12px;
  --radius-lg: 16px;
  --font-mono: "JetBrains Mono", monospace;
}

* { box-sizing: border-box; margin: 0; padding: 0; }
body {
  background-color: var(--bg-page);
  color: var(--text-main);
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
  height: 100vh;
  display: flex;
  flex-direction: column;
  overflow: hidden;
}

/* Header */
.app-header {
  background-color: var(--bg-surface);
  border-bottom: 1px solid var(--border-subtle);
  padding: 0.75rem 1.5rem;
  display: flex;
  justify-content: space-between;
  align-items: center;
  flex-shrink: 0;
}
.header-left { display: flex; align-items: center; gap: 0.75rem; }
.logo-icon { font-size: 1.4rem; }
.brand-title { font-weight: 700; font-size: 1.15rem; }
.brand-badge {
  background-color: rgba(56, 189, 248, 0.15);
  color: var(--accent-blue);
  border: 1px solid rgba(56, 189, 248, 0.3);
  font-size: 0.75rem;
  padding: 0.15rem 0.45rem;
  border-radius: var(--radius-sm);
  font-weight: 600;
}

.header-right { display: flex; align-items: center; gap: 1.25rem; }
.account-selector {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  font-size: 0.85rem;
  color: var(--text-muted);
}
.account-selector select {
  background-color: var(--bg-card);
  border: 1px solid var(--border-subtle);
  color: var(--text-main);
  padding: 0.35rem 0.6rem;
  border-radius: var(--radius-sm);
  font-size: 0.85rem;
  outline: none;
}
.account-selector select:focus { border-color: var(--border-focus); }

.lang-switcher {
  display: flex;
  background-color: var(--bg-card);
  border-radius: var(--radius-sm);
  overflow: hidden;
  border: 1px solid var(--border-subtle);
}
.btn-lang {
  background: transparent;
  border: none;
  color: var(--text-muted);
  padding: 0.25rem 0.55rem;
  font-size: 0.75rem;
  font-weight: 600;
  cursor: pointer;
}
.btn-lang.active { background-color: var(--accent-blue); color: #000; }

/* Main layout: 3-column split */
.mail-layout {
  display: flex;
  flex: 1;
  overflow: hidden;
}

/* Sidebar */
.mail-sidebar {
  width: 240px;
  background-color: var(--bg-surface);
  border-right: 1px solid var(--border-subtle);
  display: flex;
  flex-direction: column;
  padding: 1rem;
  gap: 1.25rem;
  flex-shrink: 0;
}
.btn-compose {
  width: 100%;
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 0.5rem;
  padding: 0.7rem;
  font-size: 0.9rem;
}
.folder-nav {
  display: flex;
  flex-direction: column;
  gap: 0.25rem;
}
.nav-item {
  display: flex;
  align-items: center;
  gap: 0.65rem;
  padding: 0.6rem 0.75rem;
  background: transparent;
  border: none;
  color: var(--text-muted);
  font-size: 0.9rem;
  font-weight: 500;
  border-radius: var(--radius-sm);
  cursor: pointer;
  text-align: left;
  transition: all 0.15s ease;
}
.nav-item:hover {
  background-color: var(--bg-hover);
  color: var(--text-main);
}
.nav-item.active {
  background-color: rgba(56, 189, 248, 0.12);
  color: var(--accent-blue);
  font-weight: 600;
}
.nav-label { flex: 1; }
.badge {
  background-color: var(--accent-blue);
  color: #000;
  font-size: 0.7rem;
  font-weight: 700;
  padding: 0.1rem 0.4rem;
  border-radius: 10px;
}
.badge:empty, .badge[data-count="0"] { display: none; }

.protocol-info-card {
  margin-top: auto;
  background-color: var(--bg-card);
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-sm);
  padding: 0.85rem;
  font-size: 0.75rem;
}
.protocol-info-card h4 {
  color: var(--text-main);
  font-size: 0.8rem;
  margin-bottom: 0.35rem;
}
.proto-desc {
  color: var(--text-subtle);
  margin-bottom: 0.5rem;
  line-height: 1.3;
}
.proto-row {
  display: flex;
  justify-content: space-between;
  margin-bottom: 0.25rem;
}
.proto-tag { color: var(--text-muted); font-weight: 600; }
.proto-row code {
  color: var(--accent-blue);
  font-family: var(--font-mono);
  font-size: 0.75rem;
}

/* Mail List Pane */
.mail-list-pane {
  width: 340px;
  background-color: var(--bg-page);
  border-right: 1px solid var(--border-subtle);
  display: flex;
  flex-direction: column;
  flex-shrink: 0;
}
.pane-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 1rem;
  border-bottom: 1px solid var(--border-subtle);
}
.pane-header h2 {
  font-size: 1.1rem;
  font-weight: 700;
}
.btn-icon {
  background: transparent;
  border: 1px solid var(--border-subtle);
  color: var(--text-muted);
  cursor: pointer;
  padding: 0.3rem 0.5rem;
  border-radius: var(--radius-sm);
  font-size: 0.85rem;
}
.btn-icon:hover { color: var(--text-main); background-color: var(--bg-hover); }

.message-list {
  flex: 1;
  overflow-y: auto;
  display: flex;
  flex-direction: column;
}
.mail-item {
  padding: 0.85rem 1rem;
  border-bottom: 1px solid var(--border-subtle);
  cursor: pointer;
  transition: background-color 0.15s ease;
  display: flex;
  flex-direction: column;
  gap: 0.3rem;
}
.mail-item:hover { background-color: var(--bg-surface); }
.mail-item.selected {
  background-color: var(--bg-card);
  border-left: 3px solid var(--accent-blue);
}
.mail-item.unread { font-weight: 600; }
.mail-item.unread .mail-sender { color: var(--accent-blue); }

.mail-item-top {
  display: flex;
  justify-content: space-between;
  align-items: center;
  font-size: 0.85rem;
}
.mail-sender {
  overflow: hidden;
  text-overflow: ellipsis;
  white-space: nowrap;
  max-width: 190px;
}
.mail-time {
  font-size: 0.72rem;
  color: var(--text-subtle);
  white-space: nowrap;
}
.mail-subject {
  font-size: 0.85rem;
  overflow: hidden;
  text-overflow: ellipsis;
  white-space: nowrap;
  color: var(--text-main);
}
.mail-preview {
  font-size: 0.78rem;
  color: var(--text-muted);
  overflow: hidden;
  text-overflow: ellipsis;
  white-space: nowrap;
}

.empty-state {
  padding: 2.5rem 1.5rem;
  text-align: center;
  color: var(--text-subtle);
  font-size: 0.85rem;
}

/* Detail Reading Pane */
.mail-detail-pane {
  flex: 1;
  background-color: var(--bg-surface);
  display: flex;
  flex-direction: column;
  overflow-y: auto;
}
.empty-detail {
  flex: 1;
  display: flex;
  flex-direction: column;
  justify-content: center;
  align-items: center;
  color: var(--text-subtle);
  gap: 1rem;
}
.empty-detail .empty-icon { font-size: 3rem; }

.active-detail {
  padding: 2rem;
  display: flex;
  flex-direction: column;
  gap: 1.5rem;
}
.detail-header {
  border-bottom: 1px solid var(--border-subtle);
  padding-bottom: 1.25rem;
  display: flex;
  flex-direction: column;
  gap: 1rem;
}
.detail-subject-line {
  display: flex;
  justify-content: space-between;
  align-items: flex-start;
  gap: 1rem;
}
.detail-subject-line h3 {
  font-size: 1.35rem;
  font-weight: 700;
  line-height: 1.3;
}
.detail-actions {
  display: flex;
  gap: 0.5rem;
  flex-shrink: 0;
}
.detail-meta {
  display: flex;
  flex-direction: column;
  gap: 0.35rem;
  font-size: 0.85rem;
  color: var(--text-muted);
}
.meta-row strong {
  color: var(--text-subtle);
  margin-right: 0.35rem;
}
.detail-body {
  font-size: 0.95rem;
  line-height: 1.6;
  white-space: pre-wrap;
  color: var(--text-main);
  background-color: var(--bg-page);
  padding: 1.5rem;
  border-radius: var(--radius-md);
  border: 1px solid var(--border-subtle);
}

/* Buttons */
.btn {
  border: none;
  border-radius: var(--radius-sm);
  padding: 0.5rem 1rem;
  font-weight: 600;
  font-size: 0.85rem;
  cursor: pointer;
  display: inline-flex;
  align-items: center;
  gap: 0.4rem;
  transition: all 0.15s ease;
}
.btn-primary {
  background-color: var(--accent-blue);
  color: #000;
}
.btn-primary:hover { background-color: #0284c7; color: #fff; }
.btn-secondary {
  background-color: var(--bg-card);
  border: 1px solid var(--border-subtle);
  color: var(--text-main);
}
.btn-secondary:hover { background-color: var(--bg-hover); }
.btn-danger {
  background-color: rgba(248, 113, 113, 0.12);
  border: 1px solid rgba(248, 113, 113, 0.3);
  color: var(--accent-danger);
}
.btn-danger:hover { background-color: var(--accent-danger); color: #000; }

/* Modal */
.modal-overlay {
  position: fixed;
  inset: 0;
  background-color: rgba(0, 0, 0, 0.7);
  backdrop-filter: blur(4px);
  display: flex;
  justify-content: center;
  align-items: center;
  padding: 1rem;
  z-index: 1000;
}
.modal-card {
  background-color: var(--bg-surface);
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-lg);
  width: 100%;
  max-width: 600px;
  box-shadow: 0 20px 40px rgba(0, 0, 0, 0.6);
  display: flex;
  flex-direction: column;
  overflow: hidden;
}
.modal-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 1.25rem 1.5rem;
  border-bottom: 1px solid var(--border-subtle);
}
.modal-header h3 { font-size: 1.15rem; font-weight: 700; }
.btn-close {
  background: transparent;
  border: none;
  color: var(--text-subtle);
  font-size: 1.5rem;
  cursor: pointer;
  line-height: 1;
}
.btn-close:hover { color: var(--text-main); }
.modal-body {
  padding: 1.5rem;
  display: flex;
  flex-direction: column;
  gap: 1rem;
}
.form-group {
  display: flex;
  flex-direction: column;
  gap: 0.35rem;
}
.form-group label {
  font-size: 0.85rem;
  color: var(--text-muted);
  font-weight: 600;
}
.form-group input, .form-group textarea {
  background-color: var(--bg-page);
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-sm);
  color: var(--text-main);
  padding: 0.6rem 0.75rem;
  font-size: 0.9rem;
  font-family: inherit;
  outline: none;
}
.form-group input:focus, .form-group textarea:focus {
  border-color: var(--border-focus);
}
.modal-footer {
  display: flex;
  justify-content: flex-end;
  gap: 0.75rem;
  margin-top: 0.5rem;
}