fieldset {
  display: grid;
  gap: 1rem;
}

#main {
  display: flex;
}

#video {
  width: 50%;
}

@media (width < 1000px) {
  #main {
    display: grid;
  }
  #video, #textarea {
    width: 100%;
    height: 36rem;
  }
}

#textarea {
  flex: auto;
  font-family: monospace;
  min-width: 12rem;
  min-height: 8rem;
}