#wrapper {
  width: 960px;
  margin: 0 auto;
  display: flex;
  flex-direction: column;
}

h1 {
  text-align: center;
  margin: 0 auto;
  padding: 1em 10px;
}

#screen {
  border: solid 1px black;
  width: 960px;
  margin: 0 auto;
}

#control_keys {
  width: 320px; 
  margin: 1em auto;
}

#control_keys td {
  text-align: center;
  width: 160px;
}