body {
  padding: 0;
  margin: 0;
  font-family: "Roboto", sans-serif;
  background: green;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  height: 100vh;
}

* {
  box-sizing: border-box;
}

#demo {
  opacity: 0;
  width: auto;
  height: auto;
  max-height: calc(90% - 100px);
  max-width: 96%;
  margin-top: 10px;
}

#action {
  padding: 10px;
  font-size: 0.875em;
  margin: 10px;
  cursor: pointer;
  font-weight: 700;
  font-family: "Roboto", sans-serif;
}

#controls {
  display: flex;
  flex-direction: row;
  opacity: 0;
}

#controls div {
  width: 108px;
  height: 108px;
  background: black;
  margin: 10px;
  cursor: pointer;
  border: solid 4px black;
}