<div id="global-back-to-top" class="back-to-top-btn" onclick="scrollToTop()" 
     style="position: fixed; bottom: 30px; right: 30px; background: rgba(255, 255, 255, 0.15); color: #ffffff; border: 1px solid rgba(255, 255, 255, 0.3); border-radius: 50%; width: 56px; height: 56px; cursor: pointer; font-size: 1.2rem; opacity: 0; visibility: hidden; z-index: 1000; display: flex; align-items: center; justify-content: center; box-shadow: 0 4px 15px rgba(0, 0, 0, 0.2); backdrop-filter: blur(10px); text-shadow: 1px 1px 3px rgba(0, 0, 0, 0.8); transition: all 0.3s ease;">
    ↑
</div>

<script>
function scrollToTop() {
    window.scrollTo({
        top: 0,
        behavior: 'smooth'
    });
}

window.addEventListener('scroll', function() {
    const backToTopBtn = document.getElementById('global-back-to-top');
    
    // Вычисляем высоту страницы и положение скролла
    const documentHeight = document.documentElement.scrollHeight;
    const windowHeight = window.innerHeight;
    const scrollTop = window.pageYOffset || document.documentElement.scrollTop;
    
    // Показываем кнопку только в последней трети страницы
    const scrollPercent = (scrollTop + windowHeight) / documentHeight;
    
    if (scrollPercent > 0.66) { // Показываем когда прокрутили 66% страницы
        backToTopBtn.style.opacity = '1';
        backToTopBtn.style.visibility = 'visible';
    } else {
        backToTopBtn.style.opacity = '0';
        backToTopBtn.style.visibility = 'hidden';
    }
});

// Добавляем hover эффекты
document.addEventListener('DOMContentLoaded', function() {
    const backToTopBtn = document.getElementById('global-back-to-top');
    
    backToTopBtn.addEventListener('mouseenter', function() {
        this.style.background = 'rgba(255, 255, 255, 0.3)';
        this.style.transform = 'translateY(-2px) scale(1.05)';
        this.style.boxShadow = '0 6px 20px rgba(0, 0, 0, 0.4)';
    });
    
    backToTopBtn.addEventListener('mouseleave', function() {
        this.style.background = 'rgba(255, 255, 255, 0.15)';
        this.style.transform = 'translateY(0) scale(1)';
        this.style.boxShadow = '0 4px 15px rgba(0, 0, 0, 0.2)';
    });
});
</script>