body {
	padding: 0;
	margin: 0;
	/*background: linear-gradient(to right, #00AAFF, #00FF6C);*/
	background-image: url('https://cdn.pixabay.com/photo/2014/07/06/13/55/calculator-385506_1280.jpg');
  }
  
  .calculator-grid {
	display: grid;
	justify-content: center;
	align-content: center;
	min-height: 100vh;
	grid-template-columns: repeat(4, 85px);
	grid-template-rows: minmax(120px, auto) repeat(5, 100px);
	
  }
  
  .calculator-grid > button {
	cursor: pointer;
	font-size: 2rem;
	border: 1px solid white;
	outline: none;
	background-color: rgba(255, 255, 255, .75);
  }
  
  .calculator-grid > button:hover {
	background-color: rgba(255, 255, 255, .9);
  }
  
  .span-two {
	grid-column: span 2;
	
  }
  
  .output {
	grid-column: 1 / -1;
	background-color: rgba(0, 0, 0, .75);
	display: flex;
	align-items: flex-end;
	justify-content: space-around;
	flex-direction: column;
	padding: 10px;
	word-wrap: break-word;
	word-break: break-all;
  }
  
  .output .previous-operand {
	color: rgba(255, 255, 255, .75);
	font-size: 1.5rem;
  }
  
  .output .current-operand {
	color: white;
	font-size: 2.5rem;
  }