.calculator {
  text-align: center;
  margin: 100px auto;
  width: 300px;
  box-shadow: 1px 1px 2px 1px #000;
}

.calculator-screen {
  width: 100%;
  height: 80px;
  background-color: #232323;
  color: #fff;
  text-align: right;
  font-size: 36px;
  border: 1px solid white;
  padding: 0 20px;
  box-sizing: border-box;
}

.calculator-keys {
  width: 100%;
}

.row {
  display: flex;
}

button {
  height: 70px;
  background-color: #79869c;
  border: 1px solid white;
  font-size: 30px;
  color: #fff;
  width: 25%;
  outline: none;
  transition: 0.3s;
}

button:hover {
  transform: scale(1.05);
}
.all-clear,
.zero-btn {
  width: 50%;
}

.operator,
.equel-sign {
  background-color: #143770;
}

button:hover {
  background-color: #b8c0cf;
}

.operator:hover,
.equel-sign:hover {
  background-color: #43669f;
}