*, 
*::before, 
*::after {
    box-sizing: border-box;
    font-family: 'Franklin Gothic Medium', 'Arial Narrow', Arial, sans-serif;
    font-weight: normal;
}
  
body {
    margin: 0;
    padding: 0;
    background: linear-gradient(to right, #2585b1, #49dfdf);
}
  
    .calculator-grid {
        display: grid;
        justify-content: center;
        align-content: center;
        min-height: 100vh;
        grid-template-columns: repeat(4, 100px);
        grid-template-rows: minmax(120px, auto) repeat(5, 100px);
    }
  
        .calculator-grid > button {
            cursor: pointer;
            font-size: 2rem;
            border: 1px, solid #FFFFFF;
            outline: none;
            background-color: rgba(255, 255, 255, 0.75);
        }
  
            .calculator-grid > button:hover {
                background-color: #a9a9a9;
            }
  
            .span-two {
              grid-column: span 2;
            }
  
            .output {
                grid-column: 1 / -1;
                background-color: rgba(0, 0, 0, 0.76);
                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, 0.75);
                font-size: 1.5rem;
            }
  
            .output .current-operand {
                color: white;
                font-size: 2.5rem;
            }