body {
  background-color: #888;
}

table {
  margin: auto;
  background-color: #222;
  text-align: center;
  border-radius: 4px;
  padding: 10px;
}

input:focus {
    outline: none;
}

.button {
  border: 0;
  color: #495069;
  border-radius: 4px;
  width: 60px;
  height: 50px;
  float: left;
  margin: 5px;
  font-size: 20px;
  margin-bottom: 15px;
  background-color: #fff;
}

.button:hover {
  box-shadow: 0 4px #d1d1d1;
}

.operator {
  border: 0;
  color: #495069;
  border-radius: 4px;
  width: 60px;
  height: 50px;
  float: left;
  margin: 5px;
  font-size: 20px;
  margin-bottom: 15px;
  background-color: #cee9ea;
}

.operator:hover {
  box-shadow: 0 4px #b0d2cf;
}

#clear {
  border: 0;
  color: #495069;
  border-radius: 4px;
  width: 60px;
  height: 50px;
  float: left;
  margin: 5px;
  font-size: 20px;
  margin-bottom: 15px;
  background-color: #ff9fa8;
}

#clear:hover {
  box-shadow: 0 4px #CC7F86;
}

#expr {
  border: 0;
  border-radius: 4px;
  width: 100%;
  font-size: 26px;
  text-align: right;
  background-color: #bcbd95;
  float: left;
  line-height: 1.8;
  padding: 0px 10px 0px 10px;
  margin-bottom: 12px;
}

h3 {
    text-align: center;
}