body {  
    display: flex;  
    justify-content: center;  
    align-items: center;  
    height: 100vh;  
    margin: 0;  
    background-color: #f0f0f0;  
}
.calculator {
    background-color: white;
    padding: 20px;
    border-radius: 10px;
    box-shadow: 0 0 10px rgba(0, 0, 0, 0.1);
}  
.display {
    background-color: #222;
    color: white;
    text-align: right;
    padding: 20px;
    font-size: 2em;
    border-radius: 5px;
    margin-bottom: 10px;
}  
.buttons {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 10px;
}  
button {
    padding: 20px;
    font-size: 1.5em;
    border: none;
    border-radius: 5px;
    cursor: pointer;
    transition: background-color 0.3s;
}
button:hover {
    background-color: #eee;
}