body {
    display: flex;
    justify-content: center;
    align-items: center;
    height: 100vh;
    background-color: #f0f0f0;
    font-family: sans-serif;
}

.calculator {
    width: 300px;
    border: 1px solid #ccc;
    border-radius: 10px;
    box-shadow: 0 0 10px rgba(0, 0, 0, 0.1);
    overflow: hidden;
}

.display {
    background-color: #222;
    color: #fff;
    font-size: 2.5em;
    padding: 20px;
    text-align: right;
    word-wrap: break-word;
}

.buttons {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
}

.btn {
    padding: 20px;
    font-size: 1.5em;
    border: 1px solid #ccc;
    cursor: pointer;
    background-color: #e0e0e0;
}

.btn:hover {
    background-color: #d0d0d0;
}

.operator {
    background-color: #f39c12;
    color: white;
}

.operator:hover {
    background-color: #e68a00;
}

.equal {
    background-color: #2ecc71;
    color: white;
    grid-column: 4;
    grid-row: 4 / 6;
}

.equal:hover {
    background-color: #27ae60;
}

.zero {
    grid-column: 1 / 3;
}