.simpleCalculatorSec #calculator {
  padding: 30px;
  background-color: #000000;
  margin: 0;
}
.simpleCalculatorSec .box {
  text-align: right;
  font-size: 35px;
  line-height: 3vh;
  padding: 1em;
  border: 2px solid #e68a00;
  color: white;
  border-radius: 15px;
  background-color: #000000;
}
.simpleCalculatorSec #last_operation_history {
  height: 1.8vh;
  font-size: 1.8vh;
  text-align: right;
  padding-right: 1.5vh;
  color: rgb(177, 176, 176);
  background-color: black;
}
.simpleCalculatorSec button {
  width: 70px;
  height: 70px;
  font-weight: bold;
  font-size: 25px;
  color: #ffffff;
  background-color: #2563eb;
  border-radius: 50%;
  border: 1px solid #000000;
  margin: 7px;
}
.simpleCalculatorSec #backspace_btn {
  background-repeat: no-repeat;
  background-position: 50% 50%;
  background-size: 1.7em;
}
.simpleCalculatorSec button:hover {
  cursor: pointer;
}
.simpleCalculatorSec .operator {
  background-color: #e68a00;
}
.simpleCalculatorSec .operator:hover {
  background-color: #ffd11a;
}