body {
    background: #f5f5f5;
    display: flex;
    justify-content: center;
    align-items: center;
    height: 100vh;
    font-family: Arial;
    }

    .calculator {
        background: #ffffff;
        padding: 20px;
        border-radius: 12px;
        box-shadow: 0 5px 20px rgba(0,0,0,0.1);
        width: 320px;
    }
    .display {
        width: 100%;
        height: 60px;
        font-size: 28px;
        text-align: right;
        padding: 10px;
        border: 2px solid #ccc;
        border-radius: 8px;
        margin-bottom: 15px;
    }

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

    button {
        height: 60px;
        font-size: 18px;
        border: none;
        border-radius: 8px;
        background: #e0e0e0;
        cursor: pointer;
    }

    button:hover {
        background: #d5d5d5;
    }

    .operator {
        background: #dfe6e9;
    }

    .equal {
        background: #4aa3df;
        color: white;
    }

    .equal:hover {
        background: #3a8cc1;
    }