body {
    margin: 0;
    height: 100vh;
    display: flex;
    justify-content: center;
    align-items: center;
    background: linear-gradient(135deg, #000, #6a11cb);
    font-family: Arial, sans-serif;
}

.calculator {
    background: #111;
    padding: 20px;
    border-radius: 20px;
    box-shadow: 0 0 30px #9333ea;
    width: 300px;
}

#display {
    width: 100%;
    height: 60px;
    font-size: 26px;
    margin-bottom: 15px;
    text-align: right;
    padding-right: 10px;
    border: none;
    border-radius: 10px;
    background: #000;
    color: #fff;
}

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

button {
    height: 55px;
    font-size: 18px;
    border: none;
    border-radius: 12px;
    cursor: pointer;
    background: #1f1f1f;
    color: white;
    transition: 0.2s;
}

button:hover {
    background: #9333ea;
}

.operator {
    background: #6a11cb;
}

.equal {
    background: #22c55e;
    color: black;
}

.zero {
    grid-column: span 2;
}