:root {
  --bg: #f7f9fc;
  --card: #ffffff;
  --primary: #1f4b99;
  --text: #1d2230;
  --muted: #5c6473;
  --border: #e3e7ef;
  --bot: #f3f6fb;
  --page-bg-start: #f5f7fb;
  --page-bg-end: #eef2f8;
  --env-bg: #e8f0ff;
  --user-bubble: #e6ecfa;
  --user-border: #d3dcf8;
  --session-active: #eef3ff;
  --status-online-bg: #e6f4ea;
  --status-online-text: #1c7c3b;
  --input-bg: #ffffff;
  --shadow: 0 8px 24px rgba(0, 0, 0, 0.04);
}

body[data-theme="dark"] {
  --bg: #0f1420;
  --card: #151b2b;
  --primary: #79a6ff;
  --text: #e7ecf6;
  --muted: #a6b0c2;
  --border: #26314a;
  --bot: #1b2438;
  --page-bg-start: #0b0f19;
  --page-bg-end: #121826;
  --env-bg: #1d2a45;
  --user-bubble: #202c47;
  --user-border: #2b3a5e;
  --session-active: #1b2740;
  --status-online-bg: #153822;
  --status-online-text: #8fe2a4;
  --input-bg: #0f1420;
  --shadow: 0 10px 26px rgba(0, 0, 0, 0.35);
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  font-family: "Inter", system-ui, -apple-system, sans-serif;
  background: linear-gradient(135deg, var(--page-bg-start), var(--page-bg-end));
  color: var(--text);
}

.topbar {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 12px 20px;
  background: var(--card);
  border-bottom: 1px solid var(--border);
}

.brand {
  display: flex;
  gap: 10px;
  align-items: center;
}

.logo-image {
  width: 36px;
  height: 36px;
  border-radius: 10px;
  object-fit: contain;
  background: var(--card);
}

.title {
  display: flex;
  gap: 8px;
  align-items: baseline;
}

.app-name {
  font-weight: 700;
}

.env {
  padding: 2px 6px;
  border-radius: 6px;
  background: var(--env-bg);
  color: var(--primary);
  font-size: 12px;
  font-weight: 600;
}

.top-actions a {
  color: var(--primary);
  text-decoration: none;
  font-weight: 600;
}

.theme-toggle {
  margin-left: 10px;
  background: transparent;
  color: var(--text);
  border: 1px solid var(--border);
  padding: 6px 10px;
  border-radius: 999px;
  font-weight: 600;
}

.theme-toggle:hover {
  border-color: var(--primary);
}

.layout {
  display: grid;
  grid-template-columns: 280px 1fr;
  gap: 16px;
  padding: 16px;
  min-height: calc(100vh - 64px);
}

.sidebar, .chat {
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: 12px;
  box-shadow: var(--shadow);
}

.sidebar {
  padding: 12px;
}

.sidebar-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 12px;
}

.sidebar h2 {
  margin: 0;
  font-size: 16px;
}

button {
  border: none;
  background: var(--primary);
  color: white;
  padding: 8px 12px;
  border-radius: 8px;
  cursor: pointer;
  font-weight: 600;
}

button:disabled {
  opacity: 0.6;
  cursor: not-allowed;
}

.session-list {
  display: flex;
  flex-direction: column;
  gap: 8px;
}

.session {
  padding: 10px;
  border: 1px solid var(--border);
  border-radius: 10px;
  cursor: pointer;
}

.session.active {
  border-color: var(--primary);
  background: var(--session-active);
}

.chat {
  padding: 16px;
  display: grid;
  grid-template-rows: auto 1fr auto auto;
  gap: 12px;
}

.chat-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
}

.chat-title {
  font-weight: 700;
}

.chat-meta {
  color: var(--muted);
  font-size: 13px;
}

.status {
  padding: 6px 10px;
  border-radius: 999px;
  font-size: 12px;
  font-weight: 700;
}

.status.online {
  background: var(--status-online-bg);
  color: var(--status-online-text);
}

.messages {
  overflow-y: auto;
  display: flex;
  flex-direction: column;
  gap: 12px;
  padding-right: 6px;
}

.message {
  display: flex;
  flex-direction: column;
  max-width: 80%;
}

.message.user {
  align-self: flex-end;
  text-align: right;
}

.bubble {
  padding: 12px 14px;
  border-radius: 12px;
  border: 1px solid var(--border);
  background: var(--bot);
}

.message.user .bubble {
  background: var(--user-bubble);
  border-color: var(--user-border);
}

.meta {
  margin-top: 4px;
  color: var(--muted);
  font-size: 12px;
}

.sources {
  margin: 8px 0 0;
  padding-left: 18px;
  color: var(--muted);
  font-size: 13px;
}

.sources a {
  color: var(--primary);
  text-decoration: none;
}

.sources a:hover {
  text-decoration: underline;
}

.input-area {
  display: flex;
  gap: 8px;
}

textarea {
  flex: 1;
  border: 1px solid var(--border);
  border-radius: 10px;
  padding: 10px;
  resize: none;
  font-family: inherit;
  background: var(--input-bg);
  color: var(--text);
}

.hint {
  color: var(--muted);
  font-size: 12px;
}

@media (max-width: 900px) {
  .layout {
    grid-template-columns: 1fr;
  }
  .sidebar {
    order: 2;
  }
  .chat {
    order: 1;
  }
  .messages {
    max-height: 50vh;
  }
}