body{
    display: flex;
    justify-content: center;
    align-items: center;
    height: 100vh;
    background: #111;
    font-family: sans-serif;
}

.calculator{
    background: #222;
    padding: 20px;
    border-radius: 10px;
    box-shadow: 0 0 10px cyan;
    width: 260px;
}

#display{
    width: 100px;
    height: 50px;
    font-size: 24px;
    margin-bottom: 10px;
    text-align: right;
    padding: 10px;
    border: none;
    background: #000;
    color: cyan;
    border-radius: 5px;
}

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

button{
    padding: 20px;
    font-size: 18px;
    background: #333;
    color: cyan;
    border: none;
    border-radius: 5px;
    cursor: pointer;
    transition: background 0.3s;
}

button:hover{
    background: #444;
}

.zero{
    grid-column: span 2;
}