* {
  box-sizing: border-box;
}

body {
  max-width: 360px;
	margin: 100px auto;
  font: 100 32px 'Roboto';
  display: flex;
  align-items: center;
  justify-content: center;
  vertical-align: center;
  
  /* get gradient background from uigradients.com */
  background: #74ebd5;  /*fallback for old browsers */
	background: -webkit-linear-gradient(to right, #ACB6E5, #74ebd5);  /*Chrome 10-25, Safari 5.1-6*/
	background: linear-gradient(to right, #ACB6E5, #74ebd5); /*W3C, IE 10+/ Edge, Firefox 16+, Chrome 26+, Opera 12+, Safari 7+*/
}

.calculater-body {
  align-items: center;
  justify-content: center;
  font-size: 32px;
}

.calculator-display {
  width: 320px;
  height: 80px;
  color: white;
  background: black;
  border: 1px solid #777;
  text-align: right;
}

button {
  width: 80px;
  height: 80px;
  background: gray;
  border: 1px solid black;
  padding: 0;
  font: 100%;
  color: white;
}