*, *::before, *::after {
    box-sizing: border-box;
    font-family: 'Lucida Sans', 'Lucida Sans Regular', 'Lucida Grande', 'Lucida Sans Unicode', Geneva, Verdana, sans-serif;
    font-weight: bold;
    color: #ffffff;
}

body {
    padding: 0;
    margin: 0;
    background: linear-gradient(to right, #b3ff00, #009632);
    display: flex;
    justify-content: center;
    align-items: center;
    height: 100vh;
}

button {
    background-color: #252525;
    border: 1px solid white;
    outline: none;
    font-size: 2rem;
    cursor: pointer;
    transition: background-color 0.2s;
}

button:hover {
    background-color: rgba(0, 0, 0, 0.9);
}

.calculator-grid {
    display: grid;
    justify-content: center;
    grid-template-columns: repeat(4, 100px); /* Four columns */
    grid-template-rows: auto; /* Dynamic rows */
    gap: 10px;
    padding: 10px;
}

.output {
    grid-column: 1 / -1;
    background-color: rgba(0, 0, 0, 0.75);
    display: flex;
    flex-direction: column;
    justify-content: space-between;
    align-items: flex-end;
    padding: 20px;
    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;
}

.span-two {
    grid-column: span 2; /* Make buttons span two columns */
}