html, body {
  height: 100%;
  margin: 0;
  background: #111;
  display: grid;
  place-items: center;
}

#examCanvas {
  width: 700px;
  max-width: 95vw;
  height: 400px;
  border-radius: 12px;
  box-shadow: 0 10px 30px rgba(0,0,0,0.35);
}