/* ========================================
   浙江致诚钢构有限公司 - 企业官网样式表
   ======================================== */

/* ========================================
   1. CSS 变量系统
   ======================================== */
:root {
    /* 颜色 */
    --primary-color: #1a365d;
    --secondary-color: #ed8936;
    --accent-color: #f6ad55;
    --text-color-dark: #333;
    --text-color-medium: #4a5568;
    --text-color-light: #718096;
    --background-light: #f7fafc;
    --background-white: #ffffff;
    --border-color: #e2e8f0;
    --overlay-dark: rgba(26, 54, 93, 0.8);
    --overlay-light: rgba(74, 85, 104, 0.6);

    /* 字体 */
    --font-family-base: 'Noto Sans SC', sans-serif;
    --font-size-base: 16px;
    --font-size-h1: 3.5rem;
    --font-size-h2: 2.5rem;
    --font-size-h3: 1.8rem;
    --font-size-h4: 1.3rem;
    --font-size-small: 0.9rem;
    --font-weight-light: 300;
    --font-weight-normal: 400;
    --font-weight-medium: 500;
    --font-weight-bold: 700;
    --font-weight-extrabold: 900;
    --line-height-base: 1.6;
    --line-height-heading: 1.2;

    /* 间距 */
    --spacing-xs: 0.5rem;
    --spacing-sm: 1rem;
    --spacing-md: 1.5rem;
    --spacing-lg: 2rem;
    --spacing-xl: 3rem;
    --spacing-xxl: 4rem;
    --spacing-xxxl: 6rem;

    /* 圆角 */
    --border-radius-sm: 5px;
    --border-radius-md: 10px;
    --border-radius-lg: 15px;
    --border-radius-xl: 20px;
    --border-radius-full: 9999px;

    /* 阴影 */
    --shadow-sm: 0 1px 3px 0 rgba(0, 0, 0, 0.1), 0 1px 2px 0 rgba(0, 0, 0, 0.06);
    --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.1), 0 2px 4px -1px rgba(0, 0, 0, 0.06);
    --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.1), 0 4px 6px -2px rgba(0, 0, 0, 0.05);
    --shadow-xl: 0 20px 25px -5px rgba(0, 0, 0, 0.1), 0 10px 10px -5px rgba(0, 0, 0, 0.04);
    --shadow-hover: 0 20px 40px rgba(0, 0, 0, 0.15);

    /* 过渡 */
    --transition-base: all 0.3s ease;
    --transition-fast: all 0.2s ease;
    --transition-slow: all 0.5s ease;

    /* 容器 */
    --container-max-width: 1200px;
    --container-padding: 20px;

    /* 导航栏 */
    --navbar-height: 70px;
}

/* ========================================
   2. 重置样式
   ======================================== */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

html {
    scroll-behavior: smooth;
}

body {
    font-family: var(--font-family-base);
    font-size: var(--font-size-base);
    line-height: var(--line-height-base);
    color: var(--text-color-dark);
    overflow-x: hidden;
    background-color: var(--background-white);
}

img {
    max-width: 100%;
    height: auto;
    display: block;
}

a {
    text-decoration: none;
    color: inherit;
    transition: var(--transition-base);
}

ul, ol {
    list-style: none;
}

button {
    border: none;
    background: none;
    cursor: pointer;
    font-family: inherit;
}

/* ========================================
   3. 通用工具类
   ======================================== */
.container {
    max-width: var(--container-max-width);
    margin: 0 auto;
    padding: 0 var(--container-padding);
}

.section {
    padding: var(--spacing-xxxl) 0;
}

.section-header {
    text-align: center;
    margin-bottom: var(--spacing-xxl);
}

.section-title {
    font-size: var(--font-size-h2);
    font-weight: var(--font-weight-bold);
    color: var(--primary-color);
    margin-bottom: var(--spacing-sm);
    position: relative;
    display: inline-block;
}

.section-title::after {
    content: '';
    position: absolute;
    bottom: -10px;
    left: 50%;
    transform: translateX(-50%);
    width: 80px;
    height: 4px;
    background: linear-gradient(135deg, var(--secondary-color), var(--accent-color));
    border-radius: 2px;
}

.section-subtitle {
    font-size: var(--font-size-h4);
    color: var(--text-color-medium);
    opacity: 0.8;
}

/* ========================================
   4. 导航栏样式
   ======================================== */
.navbar {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    background: rgba(26, 54, 93, 0.95);
    backdrop-filter: blur(10px);
    z-index: 1000;
    transition: var(--transition-base);
    box-shadow: var(--shadow-md);
}

.navbar.scrolled {
    background: var(--primary-color);
    box-shadow: var(--shadow-lg);
}

.nav-container {
    max-width: var(--container-max-width);
    margin: 0 auto;
    padding: 0 var(--container-padding);
    display: flex;
    justify-content: space-between;
    align-items: center;
    height: var(--navbar-height);
}

.nav-logo h2 {
    color: var(--secondary-color);
    font-weight: var(--font-weight-bold);
    font-size: 1.8rem;
    transition: var(--transition-base);
}

.nav-logo h2:hover {
    color: var(--accent-color);
}

.nav-menu {
    display: flex;
    list-style: none;
    gap: var(--spacing-lg);
    align-items: center;
}

.nav-item {
    position: relative;
}

.nav-link {
    color: var(--background-white);
    text-decoration: none;
    font-weight: var(--font-weight-medium);
    transition: var(--transition-base);
    position: relative;
    padding: var(--spacing-xs) 0;
    display: block;
}

.nav-link:hover {
    color: var(--secondary-color);
}

.nav-link::after {
    content: '';
    position: absolute;
    bottom: -5px;
    left: 0;
    width: 0;
    height: 2px;
    background: var(--secondary-color);
    transition: var(--transition-base);
}

.nav-link:hover::after {
    width: 100%;
}

/* 二级下拉菜单样式 */
.nav-item.has-dropdown {
    position: relative;
}

.nav-item.has-dropdown > .nav-link::before {
    content: '';
    display: inline-block;
    width: 0;
    height: 0;
    margin-left: 8px;
    margin-bottom: 2px;
    vertical-align: middle;
    border-left: 5px solid transparent;
    border-right: 5px solid transparent;
    border-top: 5px solid currentColor;
    transition: transform 0.3s ease;
}

.nav-item.has-dropdown:hover > .nav-link::before {
    transform: rotate(180deg);
}

.dropdown-menu {
    position: absolute;
    top: 100%;
    left: 0;
    background: var(--background-white);
    min-width: 200px;
    border-radius: var(--border-radius-md);
    box-shadow: var(--shadow-xl);
    opacity: 0;
    visibility: hidden;
    transform: translateY(-10px);
    transition: var(--transition-base);
    margin-top: var(--spacing-sm);
    overflow: hidden;
}

.nav-item.has-dropdown:hover .dropdown-menu {
    opacity: 1;
    visibility: visible;
    transform: translateY(0);
}

.dropdown-menu li {
    border-bottom: 1px solid var(--border-color);
}

.dropdown-menu li:last-child {
    border-bottom: none;
}

.dropdown-menu a {
    display: block;
    padding: var(--spacing-sm) var(--spacing-md);
    color: var(--text-color-dark);
    font-weight: var(--font-weight-normal);
    transition: var(--transition-base);
}

.dropdown-menu a:hover {
    background: var(--background-light);
    color: var(--secondary-color);
    padding-left: var(--spacing-lg);
}

/* 移动端汉堡菜单 */
.hamburger {
    display: none;
    flex-direction: column;
    cursor: pointer;
    z-index: 1001;
}

.hamburger span {
    width: 25px;
    height: 3px;
    background: var(--background-white);
    margin: 3px 0;
    transition: var(--transition-base);
    border-radius: var(--border-radius-sm);
}

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

.hamburger.active span:nth-child(2) {
    opacity: 0;
}

.hamburger.active span:nth-child(3) {
    transform: rotate(-45deg) translate(7px, -6px);
}

/* ========================================
   5. 按钮样式
   ======================================== */
.btn {
    padding: 12px 30px;
    border: none;
    border-radius: var(--border-radius-full);
    font-weight: var(--font-weight-bold);
    text-decoration: none;
    transition: var(--transition-base);
    cursor: pointer;
    display: inline-block;
    text-align: center;
}

.btn-primary {
    background: linear-gradient(135deg, var(--secondary-color), var(--accent-color));
    color: var(--background-white);
    box-shadow: 0 4px 15px rgba(237, 137, 54, 0.3);
}

.btn-primary:hover {
    transform: translateY(-2px);
    box-shadow: 0 6px 20px rgba(237, 137, 54, 0.4);
}

.btn-secondary {
    background: transparent;
    color: var(--background-white);
    border: 2px solid var(--background-white);
}

.btn-secondary:hover {
    background: var(--background-white);
    color: var(--primary-color);
}

.btn-outline {
    background: transparent;
    color: var(--primary-color);
    border: 2px solid var(--primary-color);
}

.btn-outline:hover {
    background: var(--primary-color);
    color: var(--background-white);
}

/* ========================================
   6. 卡片样式
   ======================================== */
.card {
    background: var(--background-white);
    border-radius: var(--border-radius-xl);
    box-shadow: var(--shadow-lg);
    overflow: hidden;
    transition: var(--transition-base);
}

.card:hover {
    transform: translateY(-10px);
    box-shadow: var(--shadow-hover);
}

.card-image {
    width: 100%;
    height: 200px;
    object-fit: cover;
}

.card-content {
    padding: var(--spacing-lg);
}

.card-title {
    font-size: var(--font-size-h4);
    font-weight: var(--font-weight-bold);
    color: var(--primary-color);
    margin-bottom: var(--spacing-sm);
}

.card-text {
    color: var(--text-color-medium);
    line-height: var(--line-height-base);
    margin-bottom: var(--spacing-md);
}

/* ========================================
   7. Grid 布局
   ======================================== */
.grid {
    display: grid;
    gap: var(--spacing-lg);
}

.grid-2 {
    grid-template-columns: repeat(2, 1fr);
}

.grid-3 {
    grid-template-columns: repeat(3, 1fr);
}

.grid-4 {
    grid-template-columns: repeat(4, 1fr);
}

/* ========================================
   8. 页脚样式
   ======================================== */
.footer {
    background: var(--primary-color);
    color: var(--background-white);
    padding: var(--spacing-xxl) 0 var(--spacing-lg);
}

.footer-content {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: var(--spacing-xl);
    margin-bottom: var(--spacing-xl);
}

.footer-section h3 {
    color: var(--secondary-color);
    margin-bottom: var(--spacing-md);
    font-size: var(--font-size-h4);
}

.footer-section p,
.footer-section a {
    color: rgba(255, 255, 255, 0.8);
    line-height: 1.8;
    transition: var(--transition-base);
}

.footer-section a:hover {
    color: var(--secondary-color);
    padding-left: var(--spacing-xs);
}

.footer-section ul li {
    margin-bottom: var(--spacing-xs);
}

.footer-bottom {
    text-align: center;
    padding-top: var(--spacing-lg);
    border-top: 1px solid rgba(255, 255, 255, 0.1);
    color: rgba(255, 255, 255, 0.6);
}

/* ========================================
   9. 响应式设计
   ======================================== */

/* 平板设备 (768px - 1024px) */
@media (max-width: 1024px) {
    :root {
        --font-size-h1: 3rem;
        --font-size-h2: 2rem;
        --font-size-h3: 1.5rem;
        --spacing-xxxl: 4rem;
    }

    .grid-3 {
        grid-template-columns: repeat(2, 1fr);
    }

    .grid-4 {
        grid-template-columns: repeat(2, 1fr);
    }
}

/* 移动设备 (小于768px) */
@media (max-width: 768px) {
    :root {
        --font-size-h1: 2.5rem;
        --font-size-h2: 1.8rem;
        --font-size-h3: 1.3rem;
        --spacing-xxxl: 3rem;
        --spacing-xxl: 2rem;
    }

    .nav-menu {
        position: fixed;
        top: var(--navbar-height);
        left: -100%;
        width: 100%;
        height: calc(100vh - var(--navbar-height));
        background: var(--primary-color);
        flex-direction: column;
        justify-content: flex-start;
        align-items: center;
        padding: var(--spacing-xl) 0;
        transition: var(--transition-base);
        overflow-y: auto;
        gap: 0;
    }

    .nav-menu.active {
        left: 0;
    }

    .nav-item {
        width: 100%;
        text-align: center;
        border-bottom: 1px solid rgba(255, 255, 255, 0.1);
    }

    .nav-link {
        padding: var(--spacing-md) 0;
        font-size: 1.1rem;
    }

    .hamburger {
        display: flex;
    }

    /* 移动端下拉菜单 */
    .dropdown-menu {
        position: static;
        opacity: 1;
        visibility: visible;
        transform: none;
        box-shadow: none;
        background: rgba(0, 0, 0, 0.2);
        margin-top: 0;
        max-height: 0;
        overflow: hidden;
        transition: max-height 0.3s ease;
    }

    .nav-item.has-dropdown.active .dropdown-menu {
        max-height: 500px;
    }

    .dropdown-menu a {
        color: rgba(255, 255, 255, 0.9);
        padding: var(--spacing-sm) var(--spacing-xl);
    }

    .dropdown-menu a:hover {
        background: rgba(237, 137, 54, 0.2);
        color: var(--accent-color);
    }

    .grid-2,
    .grid-3,
    .grid-4 {
        grid-template-columns: 1fr;
    }

    .section {
        padding: var(--spacing-xxl) 0;
    }
}

/* 小屏幕移动设备 (小于480px) */
@media (max-width: 480px) {
    :root {
        --font-size-h1: 2rem;
        --font-size-h2: 1.5rem;
        --font-size-h3: 1.2rem;
        --container-padding: 15px;
    }

    .nav-logo h2 {
        font-size: 1.3rem;
    }
}

/* ========================================
   10. 动画效果
   ======================================== */
@keyframes fadeIn {
    from {
        opacity: 0;
        transform: translateY(20px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

@keyframes slideInLeft {
    from {
        opacity: 0;
        transform: translateX(-50px);
    }
    to {
        opacity: 1;
        transform: translateX(0);
    }
}

@keyframes slideInRight {
    from {
        opacity: 0;
        transform: translateX(50px);
    }
    to {
        opacity: 1;
        transform: translateX(0);
    }
}

.fade-in {
    animation: fadeIn 0.6s ease-out;
}

.slide-in-left {
    animation: slideInLeft 0.6s ease-out;
}

.slide-in-right {
    animation: slideInRight 0.6s ease-out;
}

/* ========================================
   11. 辅助类
   ======================================== */
.text-center {
    text-align: center;
}

.text-left {
    text-align: left;
}

.text-right {
    text-align: right;
}

.mt-sm { margin-top: var(--spacing-sm); }
.mt-md { margin-top: var(--spacing-md); }
.mt-lg { margin-top: var(--spacing-lg); }
.mt-xl { margin-top: var(--spacing-xl); }

.mb-sm { margin-bottom: var(--spacing-sm); }
.mb-md { margin-bottom: var(--spacing-md); }
.mb-lg { margin-bottom: var(--spacing-lg); }
.mb-xl { margin-bottom: var(--spacing-xl); }

.pt-sm { padding-top: var(--spacing-sm); }
.pt-md { padding-top: var(--spacing-md); }
.pt-lg { padding-top: var(--spacing-lg); }
.pt-xl { padding-top: var(--spacing-xl); }

.pb-sm { padding-bottom: var(--spacing-sm); }
.pb-md { padding-bottom: var(--spacing-md); }
.pb-lg { padding-bottom: var(--spacing-lg); }
.pb-xl { padding-bottom: var(--spacing-xl); }



/* ========================================
   图片懒加载样式
   ======================================== */
img.lazy {
    opacity: 0;
    transition: opacity 0.3s ease-in;
    background-color: #f0f0f0;
}

img.lazy-loaded {
    opacity: 1;
}

/* 加载占位符效果 */
img.lazy::before {
    content: '';
    display: block;
    padding-bottom: 100%;
    background: linear-gradient(90deg, #f0f0f0 25%, #e0e0e0 50%, #f0f0f0 75%);
    background-size: 200% 100%;
    animation: loading 1.5s infinite;
}

@keyframes loading {
    0% { background-position: 200% 0; }
    100% { background-position: -200% 0; }
}


/* 服务卡片链接样式 */
.service-card-link {
    text-decoration: none;
    color: inherit;
    display: block;
}

.service-card-link:hover .service-card {
    transform: translateY(-10px);
    box-shadow: var(--shadow-hover);
}

/* 项目卡片链接样式 */
.project-card-link {
    text-decoration: none;
    color: inherit;
    display: block;
}

.project-card-link:hover .project-item {
    transform: translateY(-8px);
    box-shadow: var(--shadow-hover);
}



/* 响应式设计 - 业务服务和工程案例 */
@media (max-width: 1400px) {
    .services-grid,
    .projects-grid {
        grid-template-columns: repeat(4, 1fr);
    }
}

@media (max-width: 1200px) {
    .services-grid,
    .projects-grid {
        grid-template-columns: repeat(2, 1fr);
    }
}

@media (max-width: 768px) {
    .services-grid,
    .projects-grid {
        grid-template-columns: 1fr;
    }
}