body {
    display: flex;
    justify-content: center;
    align-items: center;
    height: 100vh;
    background: linear-gradient(135deg, #1d1d1d, #3b3b3b);
    font-family: Arial, sans-serif;
    margin: 0;
}

.calculator {
    background: #222;
    padding: 20px;
    border-radius: 15px;
    box-shadow: 0px 4px 20px rgba(46, 46, 46, 0.5);
}

#display {
    width: 100%;
    height: 60px;
    background: #111;
    border: none;
    color: #0f0;
    font-size: 1.5em;
    padding: 10px;
    text-align: right;
    margin-bottom: 10px;
    border-radius: 10px;
}

.buttons {
    display: grid;
    grid-template-columns: repeat(4, 70px);
    gap: 10px;
}

button {
    background: #333;
    color: white;
    border: none;
    font-size: 1.2em;
    padding: 15px;
    border-radius: 8px;
    cursor: pointer;
    transition: background 0.2s;
}

button:hover {
    background: #2405eb;
}