.app-wrapper {
  text-align: center;
}

.btn {
  display: inline-block;
  width: 80px;
  height: 80px;
  color: #444;
  border: 1px solid #ccc;
  box-shadow: 0 0 5px -1px rgba(0, 0, 0, 0.2);
  cursor: pointer;
  vertical-align: middle;
  padding: 5px;
  margin: 5px;
}

.cell-txt {
  font-size: 50px;
}

.reset-txt {
  font-size: 24px;
}