#stt-wrapper {
    pointer-events: none;
}

.scroll-to-top-btn {
    pointer-events: auto;
    width: var(--scroll-btn-size, 50px);
    height: var(--scroll-btn-size, 50px);
    border-radius: 50%;
    border: none;
    background: var(--scroll-btn-bg, #007bff);
    color: var(--scroll-btn-icon, #ffffff);
    display: flex;
    align-items: center;
    justify-content: center;
    cursor: pointer;
    opacity: 0;
    visibility: hidden;
    transform: translateY(20px);
    transition: all .25s ease-out;
    box-shadow: 0 4px 10px rgba(0,0,0,.3);
    z-index: 9999;
    position: relative;
}

.scroll-to-top-btn i {
    font-size: calc(var(--scroll-btn-size, 50px) * 0.5);
    position: relative;
    z-index: 2;
}

.scroll-to-top-btn:hover {
    background: var(--scroll-btn-hover, #0056b3);
}

.scroll-to-top-btn:focus {
    outline: 2px solid var(--scroll-btn-hover, #0056b3);
    outline-offset: 3px;
}

.stt-visible {
    opacity: 1;
    visibility: visible;
    transform: translateY(0);
}

/* Progress-Ring via conic-gradient */
.stt-with-progress .scroll-to-top-btn::before {
    content: "";
    position: absolute;
    inset: -4px;
    border-radius: 50%;
    background: conic-gradient(
        rgba(255, 255, 255, 1) var(--stt-progress, 0%),
        rgba(255, 255, 255, 0.3) var(--stt-progress, 0%)
    );
    z-index: 1;
    padding: 3px;
    -webkit-mask: 
        linear-gradient(#fff 0 0) content-box, 
        linear-gradient(#fff 0 0);
    -webkit-mask-composite: xor;
    mask-composite: exclude;
}

/* Alternative Progress-Ring via clip-path (Fallback) */
@supports not (background: conic-gradient(red, blue)) {
    .stt-with-progress .scroll-to-top-btn::before {
        content: "";
        position: absolute;
        inset: -4px;
        border-radius: 50%;
        border: 3px solid rgba(255, 255, 255, 0.3);
    }
    
    .stt-with-progress .scroll-to-top-btn::after {
        content: "";
        position: absolute;
        inset: -4px;
        border-radius: 50%;
        border: 3px solid rgba(255, 255, 255, 1);
        border-right-color: transparent;
        border-bottom-color: transparent;
        transform: rotate(-90deg);
        transform-origin: center;
        transition: transform 0.1s linear;
    }
}

/* Animation */
.stt-animated .scroll-to-top-btn:hover {
    transform: translateY(-3px);
    box-shadow: 0 6px 15px rgba(0, 0, 0, 0.4);
}

.stt-animated .scroll-to-top-btn {
    transition: all .3s cubic-bezier(0.4, 0, 0.2, 1);
}

/* Mobile Optimierung */
@media (max-width: 768px) {
    .scroll-to-top-btn {
        width: 44px;
        height: 44px;
    }
    .scroll-to-top-btn i {
        font-size: 20px;
    }
}

/* Accessibility: Reduce motion */
@media (prefers-reduced-motion: reduce) {
    .scroll-to-top-btn,
    .stt-animated .scroll-to-top-btn {
        transition: opacity .1s, visibility .1s;
        transform: none !important;
    }
}

/* Dark mode support */
@media (prefers-color-scheme: dark) {
    .scroll-to-top-btn {
        box-shadow: 0 4px 10px rgba(0, 0, 0, 0.6);
    }
}