/* Reset and Base Variables */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

:root {
    /* Tech/Cyber Color Palette for "智联网络" */
    --primary-color: #0ea5e9; /* Tech Cyan */
    --primary-hover: #0284c7;
    --secondary-color: #3b82f6; /* Smart Blue */
    --text-main: #f8fafc;
    --text-muted: #94a3b8;
    --bg-main: #020617; /* Deep Cyber Black */
    --bg-card: #0f172a; /* Dark Tech Blue */
    --border-color: #1e293b;
    --success: #10b981;
}

body {
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
    line-height: 1.6;
    color: var(--text-main);
    background-color: transparent;
    overflow-x: hidden;
}

/* 3D Cyber Network Animated Background */
.cyber-bg {
    position: fixed;
    top: 0; left: 0; right: 0; bottom: 0;
    z-index: -1;
    overflow: hidden;
    background: var(--bg-main);
    perspective: 1000px;
}

.cyber-grid {
    position: absolute;
    width: 200vw;
    height: 200vh;
    left: -50vw;
    top: 0;
    background-image: 
        linear-gradient(rgba(14, 165, 233, 0.9) 2px, transparent 2px),
        linear-gradient(90deg, rgba(14, 165, 233, 0.9) 2px, transparent 2px);
    background-size: 80px 80px;
    transform-origin: top center;
    transform: rotateX(60deg) translateY(0);
    animation: gridMove 3s linear infinite;
}

.cyber-glow {
    position: absolute;
    top: 0; left: 0; right: 0; bottom: 0;
    background: radial-gradient(circle at 50% 50%, transparent 0%, rgba(2, 6, 23, 0.5) 100%);
    pointer-events: none;
}

@keyframes gridMove {
    0% { transform: rotateX(70deg) translateY(0); }
    100% { transform: rotateX(70deg) translateY(60px); }
}

a {
    text-decoration: none;
    color: inherit;
}

/* Header & Navigation */
header {
    background: rgba(2, 6, 23, 0.85);
    backdrop-filter: blur(12px);
    padding: 1rem max(5%, calc((100vw - 1200px) / 2));
    display: flex;
    justify-content: space-between;
    align-items: center;
    border-bottom: 1px solid var(--border-color);
    position: sticky;
    top: 0;
    z-index: 100;
}

.logo, .logo a {
    font-size: 1.6rem;
    font-weight: 800;
    background: linear-gradient(90deg, #0ea5e9, #3b82f6);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    letter-spacing: 1px;
    text-decoration: none;
}

nav a {
    margin: 0 1.2rem;
    color: var(--text-muted);
    font-weight: 500;
    transition: color 0.3s ease;
}

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

/* Buttons */
.btn-primary {
    display: inline-block;
    background: linear-gradient(90deg, var(--primary-color), var(--secondary-color));
    color: #fff;
    padding: 0.6rem 1.5rem;
    border-radius: 6px;
    font-weight: 600;
    transition: all 0.3s ease;
    text-align: center;
    border: none;
    box-shadow: 0 4px 15px rgba(14, 165, 233, 0.25);
}

.btn-primary:hover {
    box-shadow: 0 6px 20px rgba(14, 165, 233, 0.4);
    transform: translateY(-2px);
    color: #fff;
}

.btn-primary:active {
    transform: scale(0.98);
}

.btn-secondary {
    display: inline-block;
    background: transparent;
    color: var(--text-main);
    border: 1px solid var(--border-color);
    padding: 0.6rem 1.5rem;
    border-radius: 6px;
    font-weight: 600;
    transition: all 0.3s ease;
    text-align: center;
}

.btn-secondary:hover {
    background: rgba(255, 255, 255, 0.05);
    border-color: var(--text-muted);
}

.btn-secondary:active {
    transform: scale(0.98);
}

.btn-large {
    padding: 1rem 2.5rem;
    font-size: 1.15rem;
    border-radius: 8px;
}

/* General Sections */
section {
    padding: 6rem 5%;
}

h2 {
    text-align: center;
    margin-bottom: 3.5rem;
    font-size: 2.2rem;
    color: var(--text-main);
    font-weight: 700;
    letter-spacing: 1px;
}

/* Hero Section */
.hero {
    text-align: center;
    padding: 8rem 5%;
    position: relative;
    border-bottom: 1px solid rgba(255,255,255,0.05);
}

.hero h1 {
    font-size: 3.5rem;
    margin-bottom: 1.5rem;
    color: #fff;
    line-height: 1.3;
    font-weight: 800;
    text-shadow: 0 0 30px rgba(14, 165, 233, 0.3);
    position: relative;
}

.hero p {
    font-size: 1.2rem;
    color: var(--text-muted);
    margin-bottom: 3rem;
    max-width: 700px;
    margin-inline: auto;
    position: relative;
}

.hero-buttons {
    display: flex;
    justify-content: center;
    gap: 1.5rem;
    flex-wrap: wrap;
    position: relative;
}

/* Card Containers */
.card-container {
    display: flex;
    justify-content: space-between;
    gap: 2rem;
    max-width: 1200px;
    margin: 0 auto;
}

.card {
    background: rgba(15, 23, 42, 0.4);
    backdrop-filter: blur(12px);
    -webkit-backdrop-filter: blur(12px);
    padding: 2.5rem 2rem;
    border-radius: 16px;
    border: 1px solid rgba(255, 255, 255, 0.08);
    box-shadow: 0 10px 30px rgba(0,0,0,0.3);
    flex: 1;
    transition: transform 0.4s ease, border-color 0.4s ease;
}

.card:hover {
    transform: translateY(-8px);
    border-color: var(--primary-color);
}

.card h3 {
    margin-bottom: 1.2rem;
    color: #fff;
    font-size: 1.4rem;
}

.card p {
    color: var(--text-muted);
}

/* Streaming and AI */
.streaming-ai .card {
    background: linear-gradient(145deg, rgba(15, 23, 42, 0.6), rgba(2, 6, 23, 0.6));
}

.streaming-ai .streaming h3 {
    color: #fb7185; /* Soft neon pink */
}

.streaming-ai .ai h3 {
    color: #34d399; /* Soft neon green */
}

/* Pricing Section */
.pricing {
    /* Transparent to show body background */
}

.price-card {
    text-align: center;
    position: relative;
    display: flex;
    flex-direction: column;
}

.price-card.popular {
    border: 2px solid var(--primary-color);
    transform: scale(1.05);
    z-index: 10;
    background: linear-gradient(180deg, rgba(15, 23, 42, 0.7) 0%, rgba(2, 6, 23, 0.7) 100%);
    box-shadow: 0 0 30px rgba(14, 165, 233, 0.15);
}

.price-card.popular:hover {
    transform: scale(1.05) translateY(-8px);
    box-shadow: 0 0 40px rgba(14, 165, 233, 0.25);
}

.badge {
    position: absolute;
    top: -15px;
    left: 50%;
    transform: translateX(-50%);
    background: linear-gradient(90deg, var(--primary-color), var(--secondary-color));
    color: #fff;
    padding: 0.4rem 1.2rem;
    border-radius: 20px;
    font-size: 0.9rem;
    font-weight: bold;
    box-shadow: 0 4px 10px rgba(14,165,233,0.3);
}

.price {
    font-size: 3rem;
    font-weight: 800;
    color: #fff;
    margin: 1.5rem 0;
}

.price span {
    font-size: 1.2rem;
    color: var(--text-muted);
    font-weight: normal;
}

.price-card ul {
    list-style: none;
    margin-bottom: 2.5rem;
    text-align: left;
    flex-grow: 1;
}

.price-card ul li {
    margin-bottom: 1rem;
    color: var(--text-muted);
    padding-left: 2rem;
    position: relative;
}

.price-card ul li::before {
    content: "✓";
    color: var(--primary-color);
    position: absolute;
    left: 0;
    font-weight: bold;
    font-size: 1.2rem;
}

.price-card .btn-primary {
    width: 100%;
}

/* FAQ Section */
.faq-list {
    max-width: 900px;
    margin: 0 auto;
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 2.5rem;
}

.faq-item h4 {
    margin-bottom: 0.8rem;
    color: #fff;
    font-size: 1.1rem;
}

.faq-item p {
    color: var(--text-muted);
    font-size: 0.95rem;
}

/* Reviews Section */
.review-card {
    display: flex;
    flex-direction: column;
    justify-content: space-between;
    background: rgba(15, 23, 42, 0.5);
    border: 1px solid var(--border-color);
}

.review-card p {
    font-style: italic;
    color: var(--text-muted);
    margin-bottom: 1.5rem;
    font-size: 1.05rem;
}

.review-card .author {
    font-weight: bold;
    color: #fff;
    text-align: right;
}

/* Subpage Styles (Terms, Privacy, About, Sitemap) */
.subpage-container {
    max-width: 800px;
    margin: 4rem auto;
    background: rgba(15, 23, 42, 0.4);
    backdrop-filter: blur(12px);
    -webkit-backdrop-filter: blur(12px);
    padding: 4rem;
    border-radius: 16px;
    border: 1px solid rgba(255, 255, 255, 0.08);
    box-shadow: 0 10px 40px rgba(0,0,0,0.3);
}

.subpage-container h1 {
    margin-bottom: 2.5rem;
    color: #fff;
    border-bottom: 1px solid var(--border-color);
    padding-bottom: 1rem;
    font-size: 2.2rem;
}

.subpage-container h2 {
    text-align: left;
    margin: 2.5rem 0 1rem;
    font-size: 1.5rem;
    color: var(--primary-color);
}

.subpage-container p {
    margin-bottom: 1.2rem;
    color: var(--text-muted);
    font-size: 1.05rem;
}

.subpage-container ul {
    margin-left: 2rem;
    margin-bottom: 1.5rem;
    color: var(--text-muted);
    font-size: 1.05rem;
}

.subpage-container li {
    margin-bottom: 0.5rem;
}

.subpage-container a {
    color: var(--primary-color);
}
.subpage-container a:hover {
    text-decoration: underline;
    color: var(--primary-hover);
}

/* Footer */
footer {
    background: #000;
    color: #64748b;
    text-align: center;
    padding: 4rem 5%;
    border-top: 1px solid var(--border-color);
}

.footer-links {
    margin-bottom: 2rem;
}

.footer-links a {
    margin: 0 1.5rem;
    transition: color 0.3s;
    font-size: 1rem;
}

.footer-links a:hover {
    color: #fff;
}

/* =========================================
   Responsive Design (Media Queries)
   ========================================= */
@media (max-width: 992px) {
    .card-container {
        flex-wrap: wrap;
    }
    .card {
        flex: 1 1 calc(50% - 2rem);
    }
    .price-card.popular {
        transform: scale(1);
    }
    .price-card.popular:hover {
        transform: translateY(-8px);
    }
}

@media (max-width: 768px) {
    /* Touch-friendly buttons for mobile */
    .btn-primary, .btn-secondary {
        padding: 1rem 1.5rem;
        width: 100%;
        display: block;
        font-size: 1.1rem;
    }
    
    header {
        flex-direction: column;
        gap: 1.2rem;
        padding: 1.5rem 5%;
    }
    
    nav {
        display: flex;
        flex-wrap: wrap;
        justify-content: center;
        gap: 1rem;
    }
    nav a {
        margin: 0;
    }

    .hero h1 {
        font-size: 2.2rem;
    }

    .hero p {
        font-size: 1.1rem;
    }
    
    /* Ensure perfect single column layout */
    .card-container {
        flex-direction: column;
        gap: 1.5rem;
    }
    .card {
        flex: 1 1 100%;
    }
    
    .faq-list {
        grid-template-columns: 1fr;
    }
    
    .footer-links {
        display: flex;
        flex-direction: column;
        gap: 1.5rem;
    }
    .footer-links a {
        margin: 0;
        padding: 0.5rem; /* Better touch target */
    }

    .subpage-container {
        margin: 2rem 5%;
        padding: 2rem;
    }
    
    .subpage-container h1 {
        font-size: 1.8rem;
    }
}

/* A11y & Mobile Improvements */
.skip-link {
    position: absolute;
    top: -50px;
    left: 0;
    background: var(--primary-color);
    color: #fff;
    padding: 10px 20px;
    z-index: 99999;
    font-weight: bold;
    transition: top 0.3s;
}
.skip-link:focus {
    top: 0;
}
section[id], main[id] {
    scroll-margin-top: 80px;
}
:focus-visible {
    outline: 2px solid var(--primary-color) !important;
    outline-offset: 4px !important;
}
header nav a, .footer-links a, .sitemap-links a {
    min-height: 44px;
    display: inline-flex;
    align-items: center;
}
details.faq-item {
    cursor: pointer;
    background: rgba(15, 23, 42, 0.4);
    backdrop-filter: blur(12px);
    padding: 2rem;
    border-radius: 12px;
    border: 1px solid rgba(255, 255, 255, 0.08);
    transition: all 0.3s ease;
}
details.faq-item:hover {
    border-color: var(--primary-color);
}
details.faq-item summary {
    list-style: none;
    outline: none;
}
details.faq-item summary::-webkit-details-marker {
    display: none;
}
details.faq-item summary h4 {
    display: inline-block;
    margin: 0;
    font-size: 1.2rem;
    color: #fff;
}
details.faq-item p {
    margin-top: 15px;
    color: var(--text-muted);
}

@media (prefers-reduced-motion: reduce) {
    *, ::before, ::after {
        animation-delay: -1ms !important;
        animation-duration: 1ms !important;
        animation-iteration-count: 1 !important;
        background-attachment: initial !important;
        scroll-behavior: auto !important;
        transition-duration: 0s !important;
        transition-delay: 0s !important;
    }
}