.container {
  display: flex;
  row-gap: 15px;
  flex-flow: column;
  width: 300px;
  margin: 0 auto;
}

.box {
  display: flex;
  justify-content: space-between;
}

.hidden {
  visibility: hidden;
}

#computeBtn {
  margin: 0 auto;
}

h1,
h3 {
  text-align: center;
}