/* 
 * 现代化头部导航样式
 * 玻璃态效果 + 响应式设计
 */

/* ==================== 头部容器 ==================== */
header {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    z-index: 1000;
    background: rgba(250, 248, 245, 0.85);
    backdrop-filter: blur(20px);
    -webkit-backdrop-filter: blur(20px);
    border-bottom: 1px solid rgba(26, 71, 42, 0.08);
    transition: all var(--transition-base);
    padding: var(--space-md) 0;
}

header.scrolled {
    background: rgba(255, 255, 255, 0.95);
    box-shadow: var(--shadow-md);
    padding: var(--space-sm) 0;
}

/* ==================== 头部内容布局 ==================== */
.header-container {
    display: flex;
    align-items: center;
    justify-content: space-between;
    max-width: var(--container-xl);
    margin: 0 auto;
    padding: 0 var(--space-lg);
}

/* ==================== Logo样式 ==================== */
.logo {
    display: flex;
    align-items: center;
    gap: var(--space-md);
    text-decoration: none;
    transition: transform var(--transition-base);
}

.logo:hover {
    transform: scale(1.02);
}

.logo img {
    height: 48px;
    width: auto;
    object-fit: contain;
}

.logo span {
    font-family: var(--font-display);
    font-size: 1.25rem;
    font-weight: 700;
    color: var(--color-primary);
    letter-spacing: -0.01em;
    white-space: nowrap;
}

/* ==================== 导航菜单 ==================== */
nav {
    display: flex;
    align-items: center;
}

nav ul {
    display: flex;
    align-items: center;
    gap: var(--space-md);
    list-style: none;
    margin: 0;
    padding: 0;
}

nav ul li {
    position: relative;
}

nav ul li a {
    display: flex;
    align-items: center;
    gap: var(--space-xs);
    padding: var(--space-sm) var(--space-md);
    font-family: var(--font-body);
    font-size: 0.9375rem;
    font-weight: 500;
    color: var(--color-text-primary);
    text-decoration: none;
    border-radius: var(--radius-full);
    transition: all var(--transition-base);
    position: relative;
    overflow: hidden;
    white-space: nowrap;
}

nav ul li a::before {
    content: '';
    position: absolute;
    bottom: 0;
    left: 50%;
    width: 0;
    height: 2px;
    background: var(--color-accent);
    transition: all var(--transition-base);
    transform: translateX(-50%);
}

nav ul li a:hover {
    color: var(--color-primary);
    background: rgba(26, 71, 42, 0.05);
}

nav ul li a:hover::before {
    width: 80%;
}

nav ul li a.active {
    color: var(--color-primary);
    background: rgba(26, 71, 42, 0.08);
    font-weight: 600;
}

nav ul li a.active::before {
    width: 80%;
}

/* ==================== 移动端菜单按钮 ==================== */
.mobile-menu-btn {
    display: none;
    flex-direction: column;
    gap: 5px;
    background: transparent;
    border: none;
    cursor: pointer;
    padding: var(--space-sm);
    border-radius: var(--radius-sm);
    transition: all var(--transition-base);
    z-index: 1001;
}

.mobile-menu-btn span {
    display: block;
    width: 24px;
    height: 2px;
    background: var(--color-primary);
    border-radius: 2px;
    transition: all var(--transition-base);
}

.mobile-menu-btn:hover {
    background: rgba(26, 71, 42, 0.05);
}

.mobile-menu-btn.active span:nth-child(1) {
    transform: rotate(45deg) translate(5px, 5px);
}

.mobile-menu-btn.active span:nth-child(2) {
    opacity: 0;
}

.mobile-menu-btn.active span:nth-child(3) {
    transform: rotate(-45deg) translate(5px, -5px);
}

/* ==================== 响应式设计 ==================== */
@media (max-width: 992px) {
    nav ul {
        gap: var(--space-md);
    }
    
    nav ul li a {
        padding: var(--space-sm);
        font-size: 0.9375rem;
    }
}

@media (max-width: 768px) {
    header {
        padding: var(--space-sm) 0;
    }
    
    .header-container {
        padding: 0 var(--space-md);
    }
    
    .mobile-menu-btn {
        display: flex;
    }
    
    nav ul {
        position: fixed;
        top: 0;
        right: -100%;
        width: 85%;
        max-width: 400px;
        height: 100vh;
        background: var(--color-surface);
        flex-direction: column;
        align-items: flex-start;
        gap: 0;
        padding: var(--space-2xl) var(--space-xl);
        box-shadow: -8px 0 32px rgba(26, 71, 42, 0.2);
        transition: right var(--transition-slow);
        overflow-y: auto;
        z-index: 999;
    }
    
    nav ul.show {
        right: 0;
    }
    
    nav ul li {
        width: 100%;
        margin-bottom: var(--space-xs);
    }
    
    nav ul li a {
        width: 100%;
        padding: var(--space-md) var(--space-lg);
        font-size: 1.125rem;
        border-radius: var(--radius-md);
        background: transparent;
    }
    
    nav ul li a::before {
        display: none;
    }
    
    nav ul li a:hover,
    nav ul li a.active {
        background: rgba(26, 71, 42, 0.08);
        color: var(--color-primary);
    }
    
    .logo img {
        height: 40px;
    }
    
    .logo span {
        font-size: 1.25rem;
    }
    
    /* 遮罩层 */
    .menu-overlay {
        position: fixed;
        top: 0;
        left: 0;
        width: 100%;
        height: 100%;
        background: rgba(26, 71, 42, 0.3);
        backdrop-filter: blur(4px);
        -webkit-backdrop-filter: blur(4px);
        opacity: 0;
        visibility: hidden;
        transition: all var(--transition-base);
        z-index: 998;
    }
    
    .menu-overlay.show {
        opacity: 1;
        visibility: visible;
    }
    
    /* 禁止滚动 */
    body.menu-open {
        overflow: hidden;
    }
}

@media (max-width: 576px) {
    nav ul {
        width: 100%;
        max-width: none;
        padding: var(--space-xl) var(--space-lg);
    }
    
    .logo img {
        height: 36px;
    }
    
    .logo span {
        font-size: 1.125rem;
    }
}

/* ==================== 平滑滚动效果 ==================== */
html {
    scroll-behavior: smooth;
}

/* ==================== 滚动指示器 ==================== */
.scroll-indicator {
    position: fixed;
    top: 0;
    left: 0;
    height: 3px;
    background: linear-gradient(90deg, var(--color-primary), var(--color-accent));
    width: 0%;
    transition: width var(--transition-base);
    z-index: 1001;
}

/* ==================== 返回顶部按钮 ==================== */
.back-to-top {
    position: fixed;
    bottom: var(--space-xl);
    right: var(--space-xl);
    width: 56px;
    height: 56px;
    background: linear-gradient(135deg, var(--color-primary), var(--color-primary-light));
    color: var(--color-text-light);
    border: 3px solid var(--color-accent);
    border-radius: var(--radius-full);
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    box-shadow: var(--shadow-xl);
    opacity: 0;
    visibility: hidden;
    transform: translateY(20px);
    transition: all var(--transition-base);
    z-index: 999;
    animation: pulse 2s infinite;
}

@keyframes pulse {
    0% {
        box-shadow: 0 0 0 0 rgba(212, 165, 115, 0.7);
    }
    70% {
        box-shadow: 0 0 0 15px rgba(212, 165, 115, 0);
    }
    100% {
        box-shadow: 0 0 0 0 rgba(212, 165, 115, 0);
    }
}

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

.back-to-top:hover {
    background: linear-gradient(135deg, var(--color-accent), var(--color-accent-light));
    transform: translateY(-6px) scale(1.05);
    box-shadow: var(--shadow-glow);
    border-color: var(--color-primary);
}

.back-to-top svg {
    width: 32px;
    height: 32px;
    stroke-width: 3.5;
    stroke: var(--color-text-light);
    filter: drop-shadow(0 2px 4px rgba(0,0,0,0.3));
}

@media (max-width: 768px) {
    .back-to-top {
        bottom: var(--space-lg);
        right: var(--space-lg);
        width: 48px;
        height: 48px;
        border-width: 2px;
    }
    
    .back-to-top svg {
        width: 24px;
        height: 24px;
    }
}