:root {
  color-scheme: light;
  --bg: #f5f7fb;
  --card: #ffffff;
  --text: #111827;
  --muted: #6b7280;
  --border: #e5e7eb;
  --brand: #0b57d0;
  --brand-hover: #0947ab;
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  font-family: "IBM Plex Sans", "Segoe UI", sans-serif;
  background: linear-gradient(135deg, #eef4ff 0%, #f9fbff 45%, #f4f8ff 100%);
  color: var(--text);
}

.app-shell {
  display: grid;
  grid-template-columns: 320px 1fr;
  min-height: 100vh;
}

.sidebar {
  background: var(--card);
  border-right: 1px solid var(--border);
  padding: 16px;
  display: flex;
  flex-direction: column;
  gap: 14px;
}

.sidebar-top {
  display: flex;
  flex-direction: column;
  gap: 10px;
}

.sidebar h1 {
  margin: 0;
  font-size: 1.2rem;
}

.meta {
  font-size: 0.82rem;
  color: var(--muted);
  border: 1px solid var(--border);
  border-radius: 10px;
  background: #fafcff;
  padding: 10px;
}

.meta p {
  margin: 6px 0;
}

.chat-list {
  overflow-y: auto;
  display: flex;
  flex-direction: column;
  gap: 8px;
  padding-right: 4px;
}

.chat-item {
  border: 1px solid var(--border);
  border-radius: 10px;
  background: #fff;
  padding: 10px;
  cursor: pointer;
}

.chat-item.active {
  border-color: #c9dafd;
  background: #eef4ff;
}

.chat-title {
  font-size: 0.9rem;
  font-weight: 600;
  margin-bottom: 4px;
}

.chat-sub {
  color: var(--muted);
  font-size: 0.78rem;
}

.main-pane {
  display: flex;
  flex-direction: column;
  min-height: 100vh;
}

.messages {
  flex: 1;
  overflow-y: auto;
  padding: 24px;
  display: flex;
  flex-direction: column;
  gap: 12px;
}

.message {
  max-width: 80%;
  border-radius: 12px;
  padding: 10px 12px;
  line-height: 1.5;
  white-space: pre-wrap;
}

.message.user {
  background: #0b57d0;
  color: white;
  align-self: flex-end;
}

.message.assistant {
  background: #fff;
  border: 1px solid var(--border);
  align-self: flex-start;
}

.composer {
  border-top: 1px solid var(--border);
  background: #fff;
  padding: 14px;
  display: flex;
  gap: 10px;
}

textarea {
  width: 100%;
  resize: vertical;
  border: 1px solid var(--border);
  border-radius: 10px;
  padding: 10px;
  font: inherit;
  min-height: 52px;
}

button {
  border: none;
  border-radius: 10px;
  background: var(--brand);
  color: #fff;
  padding: 10px 14px;
  font-weight: 600;
  cursor: pointer;
}

button:hover {
  background: var(--brand-hover);
}

button:disabled {
  opacity: 0.65;
  cursor: not-allowed;
}

@media (max-width: 880px) {
  .app-shell {
    grid-template-columns: 1fr;
  }

  .sidebar {
    border-right: none;
    border-bottom: 1px solid var(--border);
    min-height: 230px;
  }

  .main-pane {
    min-height: calc(100vh - 230px);
  }

  .message {
    max-width: 95%;
  }
}