body {
  font-family: helvetica, arial, sans-serif;
  margin: 2em;
  height: 100vh;
}

h1 {
  margin-block-end: 0;
}

body > a {
  display: block;
  margin-block-end: 1.4em;
}

video {
  background: black;
  width: 100%;
  padding: 4px;
  border-radius: 4px;
}

button {
  text-align: center;
  margin-bottom: 4px;
}

#logs {
  white-space: pre-wrap;
}

#logs span {
  color: red;
}

@media screen and (min-width: 640px) {
  body {
    margin: 2em auto;
    max-width: calc(640px - 2em);
  }
}