*,*::before,*::after{
 box-sizing: border-box;
 font-family: 'Franklin Gothic Medium', 'Arial Narrow', Arial, sans-serif;
 font-weight: normal;
}

body{
 padding: 0;
 margin: 0;
 background: linear-gradient(to right, #00AAFF, #00FF6C);
}

.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 white;
 outline: none;
 background-color: rgba(255, 255, 255, .75);
}

.calculator-grid > button:hover {
 background-color: rgba(255, 255, 255, .90);
}

.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;
}