style.css

.container {
  max-width: 400px;
  margin: 10vh auto 0 auto;
  border: 5px solid green;
  border-radius: 5px;
  box-shadow: 0px 0px 43px 17px rgba(153, 153, 153, 1);

  background-color: lightgoldenrodyellow;
}

.buttons {
  display: grid;
  border-bottom: 1px solid #999;
  border-left: 1px solid#999;
  grid-template-columns: 1fr 1fr 1fr 1fr;
}

.buttons > div {
  border-top: 1px solid #999;
  border-right: 1px solid#999;
}

.button {
  border: 0.5px solid blue;
  border-radius: 5px;
  margin: 2px;
  line-height: 100px;
  text-align: center;
  font-size: 25px;
  cursor: pointer;
}

#equals {
  background-color: rgb(85, 85, 255);
  color: white;
  font-size: 75px;
}

#input_box {
  border: 2px solid blue;
  border-radius: 5px;
  text-align: right;
  padding-right: 5px;
  font-size: 25px;
  height: 70px;
  line-height: 30px;
  background-color: lightcyan;
}

#input_box span{
    right: 0 !important;
    top:0;

    text-align: right !important;
    padding: 0;
    margin: 0;
}


.operators {
  font-size: 45px;
}

.button:hover {
  background-color: #323330;
  color: white;
  transition: 0.5s ease-in-out;
}