* {
  box-sizing: border-box;
}

body {
  padding: 0 25px;
}

#main-app {
  display: flex;
  gap: 5%;
  min-width: 980px;
}

video,
#demo {
  flex: 1;
}

video,
#demo > p {
  border: 1px solid #ccc;
  margin: 0;
}

video {
  max-width: 50%;
  aspect-ratio: 4/3;
}

#demo > h2 {
  margin-top: 0;
}

#demo > p {
  padding: 5px;
  height: 320px;
}