/* ========== 基础样式 ========== */
:root {
    /* 色彩系统 - 气候政策主题 */
    --primary-green: #2e8b57;        /* 森林绿 */
    --deep-green: #1a5d3a;           /* 深绿 */
    --ocean-blue: #1e90ff;           /* 海洋蓝 */
    --sky-blue: #87ceeb;            /* 天空蓝 */
    --earth-brown: #8b7355;         /* 大地棕 */
    --stone-gray: #708090;          /* 岩石灰 */
    --light-gray: #f8f9fa;          /* 浅灰 */
    --dark-text: #2c3e50;           /* 深色文字 */
    --border-color: rgba(46, 139, 87, 0.1);

    /* 字体 */
    --font-sans: 'Inter', -apple-system, BlinkMacSystemFont, sans-serif;
    --font-serif: 'Playfair Display', Georgia, serif;

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

    /* 圆角 */
    --radius-sm: 8px;
    --radius-md: 12px;
    --radius-lg: 20px;

    /* 阴影 */
    --shadow-sm: 0 2px 8px rgba(0, 0, 0, 0.08);
    --shadow-md: 0 4px 20px rgba(0, 0, 0, 0.12);
    --shadow-lg: 0 10px 40px rgba(0, 0, 0, 0.15);

    /* 过渡 */
    --transition-fast: 0.2s ease;
    --transition-normal: 0.3s ease;
    --transition-slow: 0.5s ease;
}

/* 重置和基础 */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

html {
    scroll-behavior: smooth;
}

body {
    font-family: var(--font-sans);
    color: var(--dark-text);
    line-height: 1.6;
    background-color: white;
    overflow-x: hidden;
}

/* ========== 导航栏 ========== */
.main-nav {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    z-index: 1000;
    background: rgba(255, 255, 255, 0.95);
    backdrop-filter: blur(10px);
    border-bottom: 1px solid var(--border-color);
    transition: var(--transition-normal);
}

.main-nav.scrolled {
    box-shadow: var(--shadow-sm);
}

.nav-container {
    max-width: 1200px;
    margin: 0 auto;
    padding: var(--spacing-sm) var(--spacing-md);
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.nav-brand {
    display: flex;
    align-items: center;
    gap: var(--spacing-xs);
}

.brand-icon {
    font-size: 1.5rem;
}

.brand-text {
    font-family: var(--font-serif);
    font-size: 1.25rem;
    font-weight: 600;
    color: var(--deep-green);
}

.nav-links {
    display: flex;
    gap: var(--spacing-md);
}

.nav-link {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    padding: 0.5rem 1rem;
    border-radius: var(--radius-md);
    color: var(--dark-text);
    font-weight: 500;
    text-decoration: none;
    transition: var(--transition-fast);
}

.nav-link:hover, .nav-link.active {
    background-color: rgba(46, 139, 87, 0.1);
    color: var(--primary-green);
}

.nav-link i {
    font-size: 0.9rem;
}

.nav-menu-btn {
    display: none;
    background: none;
    border: none;
    font-size: 1.5rem;
    color: var(--dark-text);
    cursor: pointer;
}

/* ========== 页脚 ========== */
.main-footer {
    background: var(--dark-text);
    color: white;
    padding: var(--spacing-xl) 0 var(--spacing-lg);
    margin-top: var(--spacing-xl);
}

.footer-container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 var(--spacing-md);
    display: grid;
    grid-template-columns: 1fr 2fr;
    gap: var(--spacing-lg);
}

.footer-brand {
    display: flex;
    align-items: flex-start;
    gap: var(--spacing-sm);
}

.footer-icon {
    font-size: 2rem;
    margin-top: 0.5rem;
}

.footer-brand-text h3 {
    color: white;
    margin-bottom: 0.5rem;
    font-size: 1.3rem;
}

.footer-brand-text p {
    color: rgba(255, 255, 255, 0.7);
    margin: 0.25rem 0;
    font-size: 0.9rem;
}

.footer-links {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: var(--spacing-md);
}

.link-group h4 {
    color: white;
    margin-bottom: var(--spacing-sm);
    font-size: 1rem;
}

.link-group a {
    display: block;
    color: rgba(255, 255, 255, 0.7);
    margin-bottom: 0.5rem;
    font-size: 0.9rem;
    text-decoration: none;
    transition: var(--transition-fast);
}

.link-group a:hover {
    color: white;
    transform: translateX(5px);
}

.link-group a i {
    width: 20px;
    margin-right: 0.5rem;
    opacity: 0.7;
}

.footer-bottom {
    max-width: 1200px;
    margin: var(--spacing-lg) auto 0;
    padding: var(--spacing-md) var(--spacing-md) 0;
    border-top: 1px solid rgba(255, 255, 255, 0.1);
    text-align: center;
}

.footer-bottom p {
    color: rgba(255, 255, 255, 0.7);
    margin: 0.5rem 0;
    font-size: 0.9rem;
}

.footer-motto {
    font-style: italic;
    color: rgba(255, 255, 255, 0.5);
}


/* 容器 */
.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 var(--spacing-sm);
}

/* 通用标题 */
h1, h2, h3, h4 {
    font-weight: 600;
    line-height: 1.2;
}

h1 {
    font-size: 3.5rem;
    font-weight: 700;
}

h2 {
    font-size: 2.5rem;
}

h3 {
    font-size: 1.5rem;
}

h4 {
    font-size: 1.1rem;
}

/* 段落 */
p {
    margin-bottom: 1rem;
    color: var(--dark-text);
    opacity: 0.9;
}

/* 链接 */
a {
    color: var(--primary-green);
    text-decoration: none;
    transition: var(--transition-fast);
}

a:hover {
    color: var(--deep-green);
}

/* 按钮 */
.btn-primary, .btn-outline {
    display: inline-flex;
    align-items: center;
    gap: 0.5rem;
    padding: 0.75rem 1.5rem;
    border-radius: var(--radius-md);
    font-weight: 500;
    font-size: 0.95rem;
    transition: var(--transition-normal);
    cursor: pointer;
    border: none;
    outline: none;
}

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

.btn-primary:hover {
    background-color: var(--deep-green);
    transform: translateY(-2px);
    box-shadow: var(--shadow-md);
}

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

.btn-outline:hover {
    background-color: rgba(46, 139, 87, 0.05);
    transform: translateY(-2px);
}

/* 卡片 */
.card {
    background: white;
    border-radius: var(--radius-md);
    padding: var(--spacing-md);
    box-shadow: var(--shadow-sm);
    transition: var(--transition-normal);
    border: 1px solid var(--border-color);
}

.card:hover {
    box-shadow: var(--shadow-md);
    transform: translateY(-4px);
}

/* 工具类 */
.text-center { text-align: center; }
.text-right { text-align: right; }
.text-primary { color: var(--primary-green); }
.text-secondary { color: var(--stone-gray); }
.bg-light { background-color: var(--light-gray); }

/* 响应式容器 */
@media (max-width: 768px) {
    .container {
        padding: 0 var(--spacing-xs);
    }

    h1 { font-size: 2.5rem; }
    h2 { font-size: 2rem; }
    h3 { font-size: 1.3rem; }
}

/* 动画类 */
.fade-in {
    animation: fadeIn 0.6s ease forwards;
}

.slide-up {
    animation: slideUp 0.6s ease forwards;
}

@keyframes fadeIn {
    from { opacity: 0; }
    to { opacity: 1; }
}

@keyframes slideUp {
    from {
        opacity: 0;
        transform: translateY(20px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}