/* ===== CSS Variables ===== */
:root {
    --primary-color: #00689D;
    --primary-dark: #004d75;
    --secondary-color: #4C9F38;
    --accent-color: #E5243B;
    --text-color: #333333;
    --text-light: #666666;
    --bg-color: #ffffff;
    --bg-light: #f8f9fa;
    --bg-dark: #1a1a2e;
    --border-color: #e0e0e0;
    --shadow: 0 2px 8px rgba(0, 0, 0, 0.1);
    --shadow-lg: 0 4px 20px rgba(0, 0, 0, 0.15);
    --radius: 8px;
    --radius-lg: 16px;
    --transition: all 0.3s ease;
    --font-cn: 'Noto Serif SC', serif;
    --font-en: 'Inter', sans-serif;
}

/* ===== Reset & Base ===== */
*, *::before, *::after {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
}

html {
    scroll-behavior: smooth;
}

body {
    font-family: var(--font-en);
    font-size: 16px;
    line-height: 1.6;
    color: var(--text-color);
    background-color: var(--bg-color);
}

.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 20px;
}

/* ===== Navigation ===== */
.navbar {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    background: rgba(255, 255, 255, 0.98);
    backdrop-filter: blur(10px);
    box-shadow: var(--shadow);
    z-index: 1000;
    padding: 15px 0;
}

.navbar .container {
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.logo {
    display: flex;
    flex-direction: column;
    text-decoration: none;
}

.logo-cn {
    font-family: var(--font-cn);
    font-size: 1.25rem;
    font-weight: 700;
    color: var(--primary-color);
}

.logo-en {
    font-size: 0.75rem;
    color: var(--text-light);
    letter-spacing: 0.5px;
}

.nav-menu {
    display: flex;
    list-style: none;
    gap: 30px;
    align-items: center;
}

.nav-menu a {
    text-decoration: none;
    color: var(--text-color);
    font-weight: 500;
    transition: var(--transition);
}

.nav-menu a:hover {
    color: var(--primary-color);
}

.nav-highlight {
    background: var(--primary-color);
    color: white !important;
    padding: 8px 20px;
    border-radius: 20px;
}

.nav-highlight:hover {
    background: var(--primary-dark);
    color: white !important;
}

.lang-switch select {
    padding: 6px 12px;
    border: 1px solid var(--border-color);
    border-radius: 4px;
    font-size: 0.875rem;
    cursor: pointer;
}

.mobile-toggle {
    display: none;
    flex-direction: column;
    gap: 5px;
    background: none;
    border: none;
    cursor: pointer;
}

.mobile-toggle span {
    width: 25px;
    height: 3px;
    background: var(--text-color);
    border-radius: 2px;
    transition: var(--transition);
}

/* ===== Hero Section ===== */
.hero {
    position: relative;
    min-height: 100vh;
    display: flex;
    align-items: center;
    justify-content: center;
    background: linear-gradient(135deg, #00689D 0%, #1a1a2e 50%, #4C9F38 100%);
    overflow: hidden;
}

.hero::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: url('data:image/svg+xml,<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 100 100"><circle cx="50" cy="50" r="40" fill="none" stroke="rgba(255,255,255,0.1)" stroke-width="0.5"/><circle cx="50" cy="50" r="30" fill="none" stroke="rgba(255,255,255,0.1)" stroke-width="0.5"/><circle cx="50" cy="50" r="20" fill="none" stroke="rgba(255,255,255,0.1)" stroke-width="0.5"/></svg>');
    background-size: 200px;
    opacity: 0.3;
}

.hero-content {
    position: relative;
    text-align: center;
    color: white;
    padding: 100px 20px;
}

.hero-title {
    font-family: var(--font-cn);
    font-size: 4rem;
    font-weight: 700;
    margin-bottom: 20px;
    text-shadow: 0 2px 10px rgba(0, 0, 0, 0.3);
    animation: fadeInUp 1s ease;
}

.hero-subtitle {
    font-family: var(--font-cn);
    font-size: 1.5rem;
    margin-bottom: 10px;
    opacity: 0.95;
    animation: fadeInUp 1s ease 0.2s both;
}

.hero-desc {
    font-size: 1.125rem;
    opacity: 0.8;
    margin-bottom: 40px;
    animation: fadeInUp 1s ease 0.4s both;
}

.hero-buttons {
    display: flex;
    gap: 20px;
    justify-content: center;
    flex-wrap: wrap;
    animation: fadeInUp 1s ease 0.6s both;
}

/* ===== Buttons ===== */
.btn {
    display: inline-block;
    padding: 12px 30px;
    font-size: 1rem;
    font-weight: 600;
    text-decoration: none;
    border-radius: 30px;
    transition: var(--transition);
    cursor: pointer;
    border: none;
}

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

.btn-primary:hover {
    background: var(--primary-dark);
    transform: translateY(-2px);
    box-shadow: var(--shadow-lg);
}

.btn-outline {
    background: transparent;
    color: white;
    border: 2px solid white;
}

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

.btn-large {
    padding: 16px 40px;
    font-size: 1.125rem;
}

/* ===== Stats Section ===== */
.stats-section {
    padding: 80px 0;
    background: var(--bg-light);
    text-align: center;
}

.stats-title {
    font-family: var(--font-cn);
    font-size: 2rem;
    margin-bottom: 50px;
    color: var(--text-color);
}

.stats-grid {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 30px;
    margin-bottom: 40px;
}

.stat-card {
    background: white;
    padding: 40px 20px;
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow);
    transition: var(--transition);
}

.stat-card:hover {
    transform: translateY(-5px);
    box-shadow: var(--shadow-lg);
}

.stat-number {
    font-size: 3.5rem;
    font-weight: 700;
    color: var(--primary-color);
    line-height: 1;
    margin-bottom: 10px;
}

.stat-label {
    font-size: 1rem;
    color: var(--text-light);
}

.stats-cta {
    margin-top: 30px;
}

/* ===== Principles Section ===== */
.principles-section {
    padding: 80px 0;
}

.section-title {
    font-family: var(--font-cn);
    font-size: 2rem;
    text-align: center;
    margin-bottom: 50px;
    color: var(--text-color);
}

.principles-grid {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 30px;
}

.principle-card {
    text-align: center;
    padding: 40px 30px;
    border-radius: var(--radius-lg);
    background: var(--bg-light);
    transition: var(--transition);
}

.principle-card:hover {
    transform: translateY(-5px);
    box-shadow: var(--shadow-lg);
}

.principle-icon {
    width: 80px;
    height: 80px;
    margin: 0 auto 20px;
    color: var(--primary-color);
}

.principle-icon svg {
    width: 100%;
    height: 100%;
}

.principle-card h3 {
    font-family: var(--font-cn);
    font-size: 1.25rem;
    margin-bottom: 15px;
    color: var(--text-color);
}

.principle-card p {
    color: var(--text-light);
    line-height: 1.8;
}

/* ===== Recent Signatures ===== */
.recent-section {
    padding: 80px 0;
    background: var(--bg-light);
}

.recent-list {
    max-width: 700px;
    margin: 0 auto;
}

.recent-item {
    display: flex;
    align-items: center;
    gap: 15px;
    padding: 15px 20px;
    background: white;
    border-radius: var(--radius);
    margin-bottom: 10px;
    transition: var(--transition);
}

.recent-item:hover {
    transform: translateX(5px);
    box-shadow: var(--shadow);
}

.recent-flag {
    font-size: 1.5rem;
}

.recent-name {
    flex: 1;
    font-weight: 600;
}

.recent-type {
    padding: 4px 12px;
    background: var(--bg-light);
    border-radius: 20px;
    font-size: 0.75rem;
    color: var(--text-light);
}

.recent-country {
    color: var(--text-light);
    font-size: 0.875rem;
}

.recent-time {
    color: var(--text-light);
    font-size: 0.75rem;
}

/* ===== SDGs Bar ===== */
.sdgs-bar {
    display: flex;
    height: 10px;
    width: 100%;
}

.sdgs-bar a {
    flex: 1;
    transition: var(--transition);
    position: relative;
}

.sdgs-bar a:hover {
    transform: scaleY(2);
    z-index: 10;
}

.sdgs-bar a::after {
    content: attr(title);
    position: absolute;
    bottom: 100%;
    left: 50%;
    transform: translateX(-50%);
    background: rgba(0, 0, 0, 0.8);
    color: white;
    padding: 5px 10px;
    border-radius: 4px;
    font-size: 0.75rem;
    white-space: nowrap;
    opacity: 0;
    pointer-events: none;
    transition: var(--transition);
}

.sdgs-bar a:hover::after {
    opacity: 1;
}

/* ===== Footer ===== */
.footer {
    background: var(--bg-dark);
    color: white;
    padding: 60px 0 30px;
}

.footer-content {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 40px;
    margin-bottom: 40px;
}

.footer-section h4 {
    font-family: var(--font-cn);
    font-size: 1.125rem;
    margin-bottom: 20px;
    color: white;
}

.footer-section p {
    color: rgba(255, 255, 255, 0.7);
    margin-bottom: 8px;
}

.footer-section ul {
    list-style: none;
}

.footer-section ul a {
    color: rgba(255, 255, 255, 0.7);
    text-decoration: none;
    transition: var(--transition);
}

.footer-section ul a:hover {
    color: white;
}

.footer-bottom {
    text-align: center;
    padding-top: 30px;
    border-top: 1px solid rgba(255, 255, 255, 0.1);
}

.footer-bottom p {
    color: rgba(255, 255, 255, 0.5);
    font-size: 0.875rem;
    margin-bottom: 5px;
}

/* ===== Animations ===== */
@keyframes fadeInUp {
    from {
        opacity: 0;
        transform: translateY(30px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

@keyframes countUp {
    from {
        opacity: 0;
        transform: scale(0.5);
    }
    to {
        opacity: 1;
        transform: scale(1);
    }
}

/* ===== Responsive ===== */
@media (max-width: 992px) {
    .stats-grid {
        grid-template-columns: repeat(2, 1fr);
    }
    
    .principles-grid {
        grid-template-columns: 1fr;
    }
    
    .footer-content {
        grid-template-columns: 1fr;
        text-align: center;
    }
}

@media (max-width: 768px) {
    .hero-title {
        font-size: 2.5rem;
    }
    
    .hero-subtitle {
        font-size: 1.25rem;
    }
    
    .nav-menu {
        position: fixed;
        top: 70px;
        left: 0;
        right: 0;
        background: white;
        flex-direction: column;
        padding: 20px;
        box-shadow: var(--shadow);
        transform: translateY(-100%);
        opacity: 0;
        pointer-events: none;
        transition: var(--transition);
    }
    
    .nav-menu.active {
        transform: translateY(0);
        opacity: 1;
        pointer-events: all;
    }
    
    .mobile-toggle {
        display: flex;
    }
    
    .stat-number {
        font-size: 2.5rem;
    }
    
    .stats-grid {
        grid-template-columns: repeat(2, 1fr);
        gap: 15px;
    }
    
    .stat-card {
        padding: 25px 15px;
    }
    
    .recent-item {
        flex-wrap: wrap;
        gap: 10px;
    }
}

@media (max-width: 480px) {
    .hero-title {
        font-size: 2rem;
    }
    
    .hero-buttons {
        flex-direction: column;
        align-items: center;
    }
    
    .btn {
        width: 100%;
        max-width: 250px;
    }
}