html {
    box-sizing: border-box;
}
*, *:before, *:after {
    box-sizing: inherit;
}
body {
  padding: 0;
  margin: 0;
}
.wrapper {
    width: 400px;
    background-color:black;
    color:white;
}

.calc-button-row{
  display:flex;
  flex-flow: row nowrap;
  justify-content: space-between;
  margin-bottom:0.5%;
}

.screen{
  text-align:right;
  font-family:"Courier New", "Courier", monospace;
  padding: 20px 5px;
  font-size:40px;
}

.calc-button{
  background-color:#d8d9db;
  color:black;
  font-size:40px;
  height:100px;
  flex-basis:24.5%;
}

.calc-button:hover{
  background-color:#ebebeb;
}

..calc-button:active{
  background-color:#bbbcbe;
}
.double{
  flex-basis:49.7%;
}

.triple{
  flex-basis:74.8%;
}

.calc-button:last-child{
  background-color:#df974c;
  color:white;
}

.calc-button:last-child:hover{
  background-color:#dfb07e;
}