:root {
  color-scheme: light;
  --bg: #f5f7fb;
  --panel: #ffffff;
  --text: #1f2937;
  --muted: #6b7280;
  --brand: #0f4c81;
  --brand-dark: #0b3a61;
  --border: #e5e7eb;
  --user: #e8f1fb;
  --assistant: #ffffff;
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  font-family: Arial, Helvetica, sans-serif;
  background: var(--bg);
  color: var(--text);
}

.app {
  max-width: 860px;
  margin: 0 auto;
  height: 100vh;
  height: 100dvh;
  display: grid;
  grid-template-rows: auto minmax(0, 1fr) auto auto;
  padding: 16px;
  gap: 12px;
  overflow: hidden;
}

.header {
  background: var(--panel);
  border: 1px solid var(--border);
  border-radius: 16px;
  padding: 20px 24px;
}

.header h1 {
  margin: 0 0 4px;
  font-size: 1.5rem;
}

.header p {
  margin: 0;
  color: var(--muted);
}

.chat {
  background: var(--panel);
  border: 1px solid var(--border);
  border-radius: 16px;
  padding: 20px;
  overflow-y: auto;
  overflow-x: hidden;
  display: flex;
  flex-direction: column;
  gap: 12px;
  min-height: 0;
  scroll-behavior: smooth;
}

.message {
  max-width: 85%;
  padding: 12px 14px;
  border-radius: 14px;
  line-height: 1.5;
  white-space: pre-wrap;
}

.message.user {
  align-self: flex-end;
  background: var(--user);
}

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

.message.loading {
  color: var(--muted);
  font-style: italic;
}

.composer {
  display: grid;
  grid-template-columns: 1fr auto;
  gap: 10px;
}

.composer input {
  border: 1px solid var(--border);
  border-radius: 12px;
  padding: 14px 16px;
  font-size: 1rem;
}

.composer button {
  border: none;
  border-radius: 12px;
  padding: 0 20px;
  background: var(--brand);
  color: white;
  font-size: 1rem;
  cursor: pointer;
}

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

.composer button:hover:not(:disabled) {
  background: var(--brand-dark);
}

.error {
  margin: 0;
  color: #b91c1c;
}

@media (max-width: 640px) {
  .app {
    padding: 10px;
  }

  .message {
    max-width: 100%;
  }
}