html {
  -webkit-box-sizing: border-box;
  -moz-box-sizing: border-box;
  box-sizing: border-box;
}

html {
  font-family:Arial, Helvetica, sans-serif;
  font-weight: 100;
}
body {
  display: flex;
  justify-content: center;
  margin-top: 1em;
  font-size: 2em;
  background-color: #bbb;
}
.calculator {
  display: flex;
  flex-wrap: wrap;
  flex-direction: row;
  width: 300px;
  box-shadow: 0px 3px 10px 3px #aaa;
  border-right: 0.1em solid #333;
  border-bottom: 0.1em solid #333;
  border-radius: 10px;
}
.result {
  width: 100%;
  background-color: rgba(0, 0, 0, 0.829);
  min-height: 2em;
  color: white;
  border-radius: 10px;
}
.result > p {
  padding: 0 1em;
  text-align: right;
  line-height: 2em;
}
span {
  box-sizing: border-box;
  text-align: center;
  cursor: pointer;
  width: 18%;
  margin: 0.5rem;
  background-color: #ccc;
  line-height: 1.5em;
  border-top: 0.01em solid #333;
  border-left: 0.01em solid #333;
  border-radius: 50px;
  font-weight:bold;
}
.operator {
  background-color: #FF9500;
  color: white;
}
.double {
  width: 50%;
}
.grey {
  background-color: #aaa;
}
.clicked {
  background-color: darken(orange, 10%);
}
span:hover{
  color:rgb(197, 48, 48);
}

.copyright{
  font-size: small;
  text-align:end;
  margin: 0;
  font-style: italic;
}