/* Yukarı çık — Premium 2026 */
#back-to-top {
    --bt-accent: #6366f1;
    --bt-accent-2: #818cf8;
    position: fixed;
    bottom: 1.75rem;
    right: 1.75rem;
    z-index: 10000;
    display: flex;
    align-items: center;
    justify-content: center;
    width: 48px;
    height: 48px;
    padding: 0;
    border: none;
    border-radius: 50%;
    background: rgba(255, 255, 255, 0.94);
    backdrop-filter: blur(12px);
    -webkit-backdrop-filter: blur(12px);
    color: var(--bt-accent);
    text-decoration: none;
    box-shadow:
        0 4px 6px rgba(15, 23, 42, 0.04),
        0 12px 28px rgba(15, 23, 42, 0.12),
        inset 0 0 0 1px rgba(255, 255, 255, 0.8);
    opacity: 0;
    visibility: hidden;
    transform: translateY(12px) scale(0.92);
    transition:
        opacity 0.3s ease,
        visibility 0.3s ease,
        transform 0.3s cubic-bezier(0.34, 1.4, 0.64, 1),
        box-shadow 0.25s ease,
        background 0.25s ease,
        color 0.25s ease;
    cursor: pointer;
}

#back-to-top.is-visible {
    opacity: 1;
    visibility: visible;
    transform: translateY(0) scale(1);
}

#back-to-top:hover {
    background: linear-gradient(135deg, var(--bt-accent), #7c3aed);
    color: #fff;
    box-shadow:
        0 8px 20px rgba(99, 102, 241, 0.35),
        inset 0 0 0 1px rgba(255, 255, 255, 0.15);
    transform: translateY(-2px) scale(1.04);
}

#back-to-top:active {
    transform: translateY(0) scale(0.98);
}

#back-to-top .bt-icon {
    display: flex;
    align-items: center;
    justify-content: center;
    width: 100%;
    height: 100%;
    line-height: 1;
}

#back-to-top .bt-icon i {
    font-size: 1rem;
    font-weight: 600;
    padding: 0;
    margin: 0;
    transform: none;
    transition: transform 0.25s ease;
}

#back-to-top:hover .bt-icon i {
    transform: translateY(-2px);
}

#back-to-top .bt-ring {
    position: absolute;
    inset: -3px;
    border-radius: 50%;
    border: 2px solid transparent;
    border-top-color: var(--bt-accent);
    border-right-color: rgba(99, 102, 241, 0.25);
    opacity: 0.55;
    animation: bt-spin 2.5s linear infinite;
    pointer-events: none;
    transition: opacity 0.25s;
}

#back-to-top:hover .bt-ring {
    opacity: 0;
}

@keyframes bt-spin {
    to { transform: rotate(360deg); }
}

@media (max-width: 767px) {
    #back-to-top {
        bottom: 1.25rem;
        right: 1.25rem;
        width: 44px;
        height: 44px;
    }

    #back-to-top .bt-icon i {
        font-size: 0.9rem;
    }
}