#cstt-scroll-top {
    position: fixed;
    z-index: 9999;
    width: 50px;
    height: 50px;
    background: #333;
    color: #fff;
    border-radius: 50%;
    box-shadow: 0 4px 10px rgba(0,0,0,0.25);
    opacity: 0;
    visibility: hidden;
    transition: all 0.3s ease;
    display: flex;
    align-items: center;
    justify-content: center;
    text-decoration: none;
}

#cstt-scroll-top.show {
    opacity: 0.85;
    visibility: visible;
}

#cstt-scroll-top:hover {
    opacity: 1;
    transform: scale(1.08);
}

/* Позиции */
.cstt-left-bottom   { bottom: 25px; left:  25px; }
.cstt-right-bottom  { bottom: 25px; right: 25px; }
.cstt-left-top      { top:    25px; left:  25px; }
.cstt-right-top     { top:    25px; right: 25px; }
.cstt-center-bottom {
    bottom: 25px;
    left: 50%;
    transform: translateX(-50%);
}

/* Иконка */
.cstt-icon {
    display: block;
    width: 28px;
    height: 28px;
    background-size: contain;
    background-repeat: no-repeat;
    background-position: center;
}