style.css

.main{
  border: 0.03px solid buttonface;
  width: 586px;
  height: auto;
  padding: 50px 20px 30px 20px;
  box-shadow: 0px 4px 4px #f2f0f0;
  font-family: sans-serif;
  display: block;
  margin: auto;
}

.display{
  border: 0.001em solid buttonface;
  height: 50px;
  margin-bottom: 20px;
  width: 562px;
  box-shadow: 0px 1px 4px #f2f0f0;
  text-align: right;
  font-size: 2.5em;
  padding: 6px 15px 0px 2px;
}
.keys{
  margin: auto;
  padding: 0;
  margin-top: 15px;
  width: 590px;

}
button{
  width: 76px;
  padding: 10px 0 10px 0;
  margin: 0px;
  margin-right: 4px;
  margin-bottom: 6px;
  border: 1px solid #f2f0f0;
  border-radius: 2px;
  outline: 0;
  color: #212529;
  font-family: sans-serif;
}

.operator{
  background-color: buttonface;
}
.digit{
  background-color: #f8f8f8;
}
#equals{
  color: #fff;
  background-color: #701abc;
}