:root {
  --bg: #ffffff;
  --bg-elev: #f7f7f8;
  --bg-sidebar: #f0f0f3;
  --border: #e1e1e6;
  --text: #1c1c1e;
  --text-muted: #6b6b76;
  --accent: #1976d2;
  --accent-hover: #1565c0;
  --user-bubble: #e3f2fd;
  --assistant-bubble: #ffffff;
  --danger: #c62828;
  --radius: 8px;
  --sidebar-w: 260px;
}

@media (prefers-color-scheme: dark) {
  :root {
    --bg: #1a1a1c;
    --bg-elev: #232327;
    --bg-sidebar: #161618;
    --border: #2e2e33;
    --text: #ececef;
    --text-muted: #9a9aa3;
    --accent: #60a5fa;
    --accent-hover: #93bcfa;
    --user-bubble: #233141;
    --assistant-bubble: #232327;
    --danger: #ef5350;
  }
}

* { box-sizing: border-box; }
html, body { height: 100%; }
body {
  margin: 0;
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", system-ui, sans-serif;
  background: var(--bg);
  color: var(--text);
  font-size: 15px;
  line-height: 1.5;
}

.layout {
  display: grid;
  grid-template-columns: var(--sidebar-w) 1fr;
  height: 100vh;
}

/* ───── Sidebar ───── */
.sidebar {
  background: var(--bg-sidebar);
  border-right: 1px solid var(--border);
  display: flex;
  flex-direction: column;
  min-height: 0;
}
.sidebar-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 1rem 1rem 0.5rem;
  border-bottom: 1px solid var(--border);
}
.brand {
  font-weight: 600;
  letter-spacing: -0.02em;
  font-size: 1rem;
}
.new-chat {
  background: var(--accent);
  color: #fff;
  border: none;
  padding: 0.35rem 0.75rem;
  border-radius: var(--radius);
  cursor: pointer;
  font-size: 0.85rem;
}
.new-chat:hover { background: var(--accent-hover); }

.session-list {
  flex: 1;
  overflow-y: auto;
  padding: 0.5rem;
}
.session-group {
  margin-bottom: 0.5rem;
}
.session-group-label {
  font-size: 0.7rem;
  color: var(--text-muted);
  text-transform: uppercase;
  letter-spacing: 0.05em;
  padding: 0.5rem 0.5rem 0.25rem;
}
.session-item {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  padding: 0.45rem 0.5rem;
  border-radius: 6px;
  cursor: pointer;
  font-size: 0.88rem;
  color: var(--text);
  position: relative;
}
.session-item:hover { background: var(--bg-elev); }
.session-item.active {
  background: var(--bg-elev);
  font-weight: 500;
}
.session-item .title {
  flex: 1;
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
}
.session-item .delete {
  opacity: 0;
  background: none;
  border: none;
  color: var(--text-muted);
  cursor: pointer;
  padding: 2px 4px;
  font-size: 0.9rem;
}
.session-item:hover .delete { opacity: 1; }
.session-item .delete:hover { color: var(--danger); }
.session-empty {
  padding: 1rem;
  color: var(--text-muted);
  font-size: 0.85rem;
  font-style: italic;
}

/* ───── Sidebar toggle (mobile) ───── */
.sidebar-toggle {
  display: none;
  position: fixed;
  top: 0.5rem;
  left: 0.5rem;
  z-index: 10;
  background: var(--bg-elev);
  color: var(--text);
  border: 1px solid var(--border);
  padding: 0.35rem 0.6rem;
  border-radius: 6px;
  cursor: pointer;
}

/* ───── Main pane ───── */
.chat {
  display: flex;
  flex-direction: column;
  min-height: 0;
}
.chat-header {
  display: flex;
  align-items: baseline;
  gap: 0.75rem;
  padding: 1rem 1.5rem;
  border-bottom: 1px solid var(--border);
}
.chat-header h1 {
  margin: 0;
  font-size: 1.1rem;
  font-weight: 600;
}
.session-info {
  color: var(--text-muted);
  font-size: 0.85rem;
}

.messages {
  flex: 1;
  overflow-y: auto;
  padding: 1.5rem;
  background: var(--bg);
}
.msg {
  max-width: 760px;
  margin: 0 auto 0.85rem;
  padding: 0.65rem 0.9rem;
  border-radius: var(--radius);
}
.msg.user {
  background: var(--user-bubble);
}
.msg.assistant {
  background: var(--assistant-bubble);
  border: 1px solid var(--border);
}
.msg pre, .msg p {
  margin: 0;
  white-space: pre-wrap;
  word-wrap: break-word;
}
.msg .role {
  display: block;
  font-size: 0.7rem;
  color: var(--text-muted);
  text-transform: uppercase;
  letter-spacing: 0.05em;
  margin-bottom: 0.25rem;
}

.activity {
  padding: 0 1.5rem;
  font-family: ui-monospace, "SF Mono", Menlo, monospace;
  font-size: 0.8rem;
  color: var(--text-muted);
  min-height: 1.2em;
}
.activity .dispatched { color: #2e7d32; }
@media (prefers-color-scheme: dark) {
  .activity .dispatched { color: #4caf50; }
}

.composer {
  border-top: 1px solid var(--border);
  padding: 0.75rem 1.5rem;
  display: flex;
  flex-direction: column;
  gap: 0.5rem;
  background: var(--bg-elev);
}
.composer textarea {
  width: 100%;
  padding: 0.6rem 0.75rem;
  background: var(--bg);
  color: var(--text);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  font: inherit;
  resize: vertical;
}
.composer textarea:focus {
  outline: 2px solid var(--accent);
  outline-offset: -1px;
  border-color: transparent;
}
.composer-row {
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: 0.5rem;
}
.composer button {
  padding: 0.5rem 1rem;
  background: var(--accent);
  color: white;
  border: none;
  border-radius: var(--radius);
  cursor: pointer;
  font-weight: 500;
}
.composer button:hover { background: var(--accent-hover); }
.composer button:disabled { opacity: 0.5; cursor: not-allowed; }
.composer input[type="file"] {
  font-size: 0.8rem;
  color: var(--text-muted);
}

/* ───── Mobile ───── */
@media (max-width: 720px) {
  .layout {
    grid-template-columns: 1fr;
  }
  .sidebar {
    position: fixed;
    top: 0;
    left: 0;
    width: var(--sidebar-w);
    height: 100vh;
    z-index: 9;
    transform: translateX(-100%);
    transition: transform 0.2s ease;
  }
  .sidebar.open { transform: translateX(0); }
  .sidebar-toggle { display: block; }
  .chat-header { padding-left: 3.5rem; }
}