.calc {
  width: 100%;
  border-collapse: collapse;
}

.calc th {
  text-align: center;
  font-weight: bold;
}

.calc td {
  padding: 5px;
}

.calc input[type="text"] {
  width: 80%;
  text-align: center;
}

.formula {
  font-style: italic;
  margin-bottom: 10px;
}

.layer {
  font-size: small;
  color: gray;
}

.separator {
  background-color: silver;
  height: 5px;
  margin: 5px 5px;
}