:root {
  --bg: #f4f5f7;
  --surface: #ffffff;
  --border: #e2e5ea;
  --text: #1f2933;
  --muted: #7b8794;
  --accent: #6a34c4;
  --accent-soft: #efe7fb;
  --self: #6a34c4;
  --self-text: #ffffff;
  --peer: #eef0f3;
  --peer-text: #1f2933;
  --warn: #b45309;
  --space: 8px;
}

* { box-sizing: border-box; }

html, body {
  margin: 0;
  height: 100%;
  font-family: -apple-system, "Segoe UI", "PingFang TC", "Microsoft JhengHei", sans-serif;
  color: var(--text);
  background: var(--bg);
}

body {
  display: flex;
  flex-direction: column;
  height: 100vh;
}

.app-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 16px;
  padding: 16px 24px;
  background: var(--surface);
  border-bottom: 1px solid var(--border);
}

.app-title h1 { font-size: 20px; margin: 0; }
.subtitle { margin: 4px 0 0; font-size: 13px; color: var(--muted); }

.btn {
  display: inline-block;
  padding: 10px 16px;
  background: var(--accent);
  color: #fff;
  border-radius: 8px;
  font-size: 14px;
  cursor: pointer;
  border: none;
}
.btn:hover { filter: brightness(1.05); }

.status-bar {
  display: flex;
  gap: 24px;
  padding: 8px 24px;
  font-size: 13px;
  color: var(--muted);
  background: var(--surface);
  border-bottom: 1px solid var(--border);
}
.status-bar .warn { color: var(--warn); }

.progress {
  padding: 8px 24px;
  font-size: 13px;
  color: var(--accent);
  background: var(--accent-soft);
}

.layout {
  display: flex;
  flex: 1;
  min-height: 0;
}

.sidebar {
  width: 320px;
  flex-shrink: 0;
  display: flex;
  flex-direction: column;
  border-right: 1px solid var(--border);
  background: var(--surface);
}

.filter-group {
  padding: 8px 16px;
  display: flex;
  flex-direction: column;
  gap: 4px;
}
.filter-group label { font-size: 12px; color: var(--muted); }
.filter-group select,
.filter-group input {
  padding: 8px;
  border: 1px solid var(--border);
  border-radius: 6px;
  font-size: 14px;
  background: #fff;
}

.conversation-list {
  list-style: none;
  margin: 0;
  padding: 8px 0;
  overflow-y: auto;
  flex: 1;
}
.conversation-list li {
  padding: 10px 16px;
  cursor: pointer;
  border-left: 3px solid transparent;
}
.conversation-list li:hover { background: var(--bg); }
.conversation-list li.active {
  background: var(--accent-soft);
  border-left-color: var(--accent);
}
.conv-name { font-size: 14px; font-weight: 600; }
.conv-sub { font-size: 12px; color: var(--muted); margin-top: 2px; }

.content {
  flex: 1;
  display: flex;
  flex-direction: column;
  min-width: 0;
}

.conversation-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 16px;
  padding: 12px 24px;
  border-bottom: 1px solid var(--border);
  background: var(--surface);
}
.conversation-header h2 { margin: 0; font-size: 17px; }
.conv-meta { margin: 2px 0 0; font-size: 12px; color: var(--muted); }
.header-tools { display: flex; align-items: flex-end; gap: 16px; }
.date-picker { display: flex; flex-direction: column; gap: 4px; }
.date-picker label { font-size: 12px; color: var(--muted); }
.date-picker select {
  padding: 6px 8px;
  border: 1px solid var(--border);
  border-radius: 6px;
  font-size: 13px;
}

.export-controls { display: flex; flex-direction: column; gap: 4px; }
.export-controls > label { font-size: 12px; color: var(--muted); }
.export-row { display: flex; gap: 6px; }
.export-row select {
  padding: 6px 8px;
  border: 1px solid var(--border);
  border-radius: 6px;
  font-size: 13px;
  background: #fff;
}
.export-row .btn { padding: 6px 14px; font-size: 13px; }

.messages {
  flex: 1;
  overflow-y: auto;
  padding: 16px 24px;
}

.empty-state {
  height: 100%;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  color: var(--muted);
  gap: 4px;
}

.day-divider {
  text-align: center;
  font-size: 12px;
  color: var(--muted);
  margin: 16px 0 8px;
}

.msg-row {
  display: flex;
  margin-bottom: 8px;
}
.msg-row.self { justify-content: flex-end; }

.bubble {
  max-width: 70%;
  padding: 8px 12px;
  border-radius: 12px;
  font-size: 14px;
  line-height: 1.5;
  word-break: break-word;
  white-space: pre-wrap;
}
.msg-row.self .bubble { background: var(--self); color: var(--self-text); border-bottom-right-radius: 4px; }
.msg-row.peer .bubble { background: var(--peer); color: var(--peer-text); border-bottom-left-radius: 4px; }

.msg-sender { font-size: 12px; color: var(--muted); margin-bottom: 2px; }
.msg-time { font-size: 11px; opacity: 0.7; margin-top: 4px; text-align: right; }

mark { background: #ffe58a; padding: 0 1px; }

@media (max-width: 768px) {
  .layout { flex-direction: column; }
  .sidebar { width: 100%; height: 40vh; border-right: none; border-bottom: 1px solid var(--border); }
  .bubble { max-width: 85%; }
  .header-tools { flex-wrap: wrap; }
}