body {
    background: linear-gradient(135deg, #1e3c72, #2a5298);
    display: flex;
    justify-content: center;
    align-items: center;
    height: 100vh;
    font-family: Arial, sans-serif;
}

.calculator {
    background: #222;
    padding: 20px;
    border-radius: 15px;
    width: 320px;
    box-shadow: 0 10px 25px rgba(0,0,0,0.4);
}

#display {
    width: 100%;
    height: 60px;
    font-size: 22px;
    text-align: right;
    margin-bottom: 15px;
    padding: 10px;
    border-radius: 8px;
    border: none;
}

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

button {
    padding: 15px;
    font-size: 18px;
    border: none;
    border-radius: 8px;
    cursor: pointer;
    background: #444;
    color: white;
    transition: 0.2s;
}

button:hover {
    background: #666;
}

.equal {
    background: #ff9800;
}

.equal:hover {
    background: #e68900;
}