.ai-bf-btn {
    position: fixed;
    z-index: 9998;
    width: var(--ai-bf-size);
    height: var(--ai-bf-size);
    min-width: var(--ai-bf-size);
    min-height: var(--ai-bf-size);
    border-radius: 999px;
    border: 0;
    padding: 0;
    margin: 0;
    display: inline-flex;
    align-items: center;
    justify-content: center;
    background: var(--ai-bf-bg);
    color: var(--ai-bf-color);
    cursor: pointer;
    text-decoration: none !important;
    box-shadow: 0 8px 24px rgba(0, 0, 0, .18);
    transition: transform .2s ease, opacity .2s ease, visibility .2s ease, box-shadow .2s ease;
}

.ai-bf-btn:hover,
.ai-bf-btn:focus {
    color: var(--ai-bf-color);
    transform: translateY(-3px);
    box-shadow: 0 10px 28px rgba(0, 0, 0, .24);
    outline: none;
}

.ai-bf-btn svg {
    width: var(--ai-bf-icon-size);
    height: var(--ai-bf-icon-size);
    display: block;
}

.ai-bf-right { right: var(--ai-bf-side); bottom: var(--ai-bf-bottom); }
.ai-bf-left { left: var(--ai-bf-side); bottom: var(--ai-bf-bottom); }

.ai-bf-scroll {
    opacity: 0;
    visibility: hidden;
    pointer-events: none;
}

.ai-bf-scroll.ai-bf-visible {
    opacity: 1;
    visibility: visible;
    pointer-events: auto;
}

@media (max-width: 767px) {
    .ai-bf-btn {
        box-shadow: 0 6px 18px rgba(0, 0, 0, .2);
    }
}