#pageUpBtn {
    position: fixed;
    bottom: 20px;
    right: 20px;

    width: 54px;
    height: 54px;

    border: none;
    border-radius: 50%;

    background: #87CEEB; /* Himmelblau */
    color: #000; /* schwarzer Pfeil */

    font-size: 22px;
    font-weight: 900;

    cursor: pointer;
    z-index: 9999;

    display: flex;
    align-items: center;
    justify-content: center;

    opacity: 0;
    visibility: hidden;
    transform: translateY(10px);

    transition: all 0.25s ease;

    box-shadow: 0 6px 18px rgba(0,0,0,0.15);
}

/* sichtbar */
#pageUpBtn.show {
    opacity: 1;
    visibility: visible;
    transform: translateY(0);
}

/* hover */
#pageUpBtn:hover {
    background: #76c7e6;
}

/* klick */
#pageUpBtn:active {
    transform: scale(0.95);
}

/* mobile */
@media (max-width: 768px) {
    #pageUpBtn {
        width: 48px;
        height: 48px;
        font-size: 20px;
        bottom: 16px;
        right: 16px;
    }
}