.checkout-popup {
    position: fixed;
    bottom: 20px;
    right: 20px;
    background: #333;
    color: #fff;
    padding: 15px 20px;
    border-radius: 8px;
    box-shadow: 0 2px 8px rgba(0,0,0,0.3);
    font-size: 14px;
    opacity: 0;
    transition: opacity 0.5s ease-in-out;
    max-width: 260px;
    line-height: 1.4;
}
.checkout-popup.show {
    opacity: 1;
}