*,
*::before,
*::after {
   box-sizing: border-box;
   font-family: Gotham Rounded, 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, .9);
}

.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;
}