body {
    display: flex;
    justify-content: center;
    align-items: center;
    height: 100vh;
    margin: 0;
    font-family: Arial, sans-serif;
    background-color: black;
    color: white;
}

.calculator {
    background-color: #333;
    border-radius: 20px;
    box-shadow: 0px 0px 20px rgba(0, 0, 0, 0.1);
    width: 320px;
    padding: 20px;
    box-sizing: border-box;
}

.display {
    background-color: #444;
    border: none;
    border-bottom: 1px solid #555;
    font-size: 2.5em;
    text-align: right;
    margin-bottom: 20px;
    padding: 10px;
    width: 100%;
    box-sizing: border-box;
    color: #fff;
}

.buttons {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 10px;
}

button {
    background-color: #555;
    border: 1px solid #666;
    border-radius: 10px;
    font-size: 1.5em;
    padding: 20px;
    cursor: pointer;
    transition: background-color 0.3s;
    color: #fff;
}

button:hover {
    background-color: #666;
}

.operator {
    color: #f57c00;
}

.number {
    color: #fff;
}

.equals {
    background-color: #f57c00;
    color: #fff;
    grid-column: span 2;
}