:root {
  --blue: #2563eb;
  --gray: #f1f5f9;
  --text: #111827;
  --pad: 1rem;
  --radius: 12px;
}
* {
  box-sizing: border-box;
}
body {
  margin: 0;
  font-family: system-ui, sans-serif;
  background: var(--gray);
  color: var(--text);
}
header {
  background: var(--blue);
  color: white;
  padding: var(--pad);
  display: flex;
  justify-content: space-between;
  align-items: center;
}
main {
  padding: var(--pad);
  display: flex;
  flex-direction: column;
  gap: 1rem;
}
button {
  background: rebeccapurple;
  color: white;
  padding: 0.75rem 1rem;
  font-size: 1rem;
  border: none;
  border-radius: var(--radius);
  box-shadow: 0 2px 6px rgba(0,0,0,0.1);
}
footer {
  text-align: center;
  padding: 0.5rem;
  font-size: 0.8rem;
  color: #666;
}
iframe {
  width: 100%;
  height: 400px;
  border: none;
  border-radius: var(--radius);
}
.chat-box {
  background: white;
  padding: 1rem;
  border-radius: var(--radius);
  box-shadow: 0 1px 3px rgba(0,0,0,0.1);
}
.chat-log {
  max-height: 150px;
  overflow-y: auto;
  margin-bottom: 0.5rem;
  font-size: 0.9rem;
}
.user {
  font-weight: bold;
  font-size: 0.9rem;
}