/* ==========================================================================
   冲上云霄 (chongshangyunxiao.cyou) - Main Stylesheet
   Theme: Pure White Background, Cloud Elements, Premium Purple Accents
   ========================================================================== */

/* Google Fonts Import */
@import url('https://fonts.googleapis.com/css2?family=Inter:wght@300;400;500;600;700;800&display=swap');

:root {
    --primary-color: #6c5ce7;      /* Core Purple */
    --primary-hover: #5b4bc4;
    --primary-light: #f3f0ff;      /* Very light purple background */
    --accent-color: #a29bfe;       /* Pastel Purple */
    --dark-purple: #3f2b96;        /* Deep Indigo Purple for headings */
    --heading-color: #2d3436;      /* Slate black for primary text */
    --text-color: #4a5568;         /* Muted gray for body text */
    --bg-white: #ffffff;           /* Base background */
    --bg-light: #faf9ff;           /* Subtle lavender tinted off-white */
    --border-color: #e8e6f5;       /* Soft purple-grey borders */
    --shadow-sm: 0 4px 6px -1px rgba(108, 92, 231, 0.05);
    --shadow-md: 0 10px 15px -3px rgba(108, 92, 231, 0.08), 0 4px 6px -2px rgba(108, 92, 231, 0.03);
    --shadow-lg: 0 20px 25px -5px rgba(108, 92, 231, 0.12), 0 10px 10px -5px rgba(108, 92, 231, 0.04);
    --shadow-glow: 0 0 20px rgba(108, 92, 231, 0.35);
    --radius-sm: 8px;
    --radius-md: 16px;
    --radius-lg: 24px;
    --transition-fast: 0.2s cubic-bezier(0.4, 0, 0.2, 1);
    --transition-normal: 0.3s cubic-bezier(0.4, 0, 0.2, 1);
}

/* Reset & Base Styles */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

html {
    scroll-behavior: smooth;
    font-size: 16px;
}

body {
    font-family: 'Inter', -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
    background-color: var(--bg-white);
    color: var(--text-color);
    line-height: 1.65;
    overflow-x: hidden;
}

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

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

ul, ol {
    list-style: none;
}

h1, h2, h3, h4, h5, h6 {
    color: var(--dark-purple);
    font-weight: 700;
    line-height: 1.25;
}

/* Layout Utilities */
.container {
    width: 100%;
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 24px;
}

.section {
    padding: 80px 0;
    position: relative;
}

.section-bg-light {
    background-color: var(--bg-light);
}

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

.section-header {
    max-width: 700px;
    margin: 0 auto 50px auto;
}

.section-header h2 {
    font-size: 2.25rem;
    margin-bottom: 16px;
    position: relative;
    display: inline-block;
}

.section-header h2::after {
    content: '';
    display: block;
    width: 60px;
    height: 4px;
    background: linear-gradient(90deg, var(--primary-color), var(--accent-color));
    margin: 12px auto 0 auto;
    border-radius: 2px;
}

.section-header p {
    font-size: 1.125rem;
    color: var(--text-color);
}

/* Premium Cloud Elements */
.cloud-background {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    overflow: hidden;
    z-index: 0;
    pointer-events: none;
}

.cloud {
    position: absolute;
    fill: rgba(224, 212, 255, 0.15);
    filter: blur(4px);
    animation: floatCloud var(--duration, 40s) linear infinite;
    opacity: 0.8;
}

.cloud-1 {
    top: 10%;
    left: -200px;
    --duration: 50s;
    transform: scale(0.8);
}

.cloud-2 {
    top: 40%;
    left: -300px;
    --duration: 65s;
    transform: scale(1.2);
}

.cloud-3 {
    top: 75%;
    left: -150px;
    --duration: 45s;
    transform: scale(0.6);
}

@keyframes floatCloud {
    0% {
        transform: translateX(-100%) scale(var(--scale, 1));
    }
    100% {
        transform: translateX(110vw) scale(var(--scale, 1));
    }
}

/* Buttons */
.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    padding: 12px 28px;
    font-size: 1rem;
    font-weight: 600;
    border-radius: var(--radius-md);
    cursor: pointer;
    transition: var(--transition-normal);
    border: 2px solid transparent;
}

.btn-primary {
    background: linear-gradient(135deg, var(--primary-color), #8f2dde);
    color: var(--bg-white);
    box-shadow: 0 4px 15px rgba(108, 92, 231, 0.3);
}

.btn-primary:hover {
    transform: translateY(-2px);
    box-shadow: 0 6px 20px rgba(108, 92, 231, 0.45);
    color: var(--bg-white);
}

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

.btn-secondary:hover {
    background-color: var(--primary-light);
    transform: translateY(-2px);
}

/* Header & Navigation */
header {
    background-color: rgba(255, 255, 255, 0.9);
    backdrop-filter: blur(10px);
    border-bottom: 1px solid var(--border-color);
    position: sticky;
    top: 0;
    z-index: 1000;
    padding: 16px 0;
}

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

.logo {
    display: flex;
    align-items: center;
    gap: 8px;
    font-size: 1.5rem;
    font-weight: 800;
    color: var(--primary-color);
}

.logo svg {
    fill: var(--primary-color);
    width: 32px;
    height: 32px;
}

nav ul {
    display: flex;
    gap: 32px;
}

nav ul li a {
    color: var(--heading-color);
    font-weight: 500;
}

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

/* Hero Section */
.hero {
    position: relative;
    padding: 120px 0 100px 0;
    text-align: center;
    background: radial-gradient(circle at 50% 50%, rgba(243, 240, 255, 0.6) 0%, rgba(255, 255, 255, 1) 100%);
    overflow: hidden;
}

.hero-content {
    position: relative;
    z-index: 1;
    max-width: 800px;
    margin: 0 auto;
}

.hero h1 {
    font-size: 3.5rem;
    letter-spacing: -1px;
    line-height: 1.15;
    margin-bottom: 24px;
    background: linear-gradient(135deg, var(--dark-purple), var(--primary-color), #8f2dde);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
}

.hero p {
    font-size: 1.25rem;
    color: var(--text-color);
    margin-bottom: 40px;
    font-weight: 400;
}

.hero-ctas {
    display: flex;
    gap: 16px;
    justify-content: center;
}

/* Features Grid */
.features-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
    gap: 32px;
    position: relative;
    z-index: 1;
}

.feature-card {
    background-color: var(--bg-white);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    padding: 40px 32px;
    text-align: left;
    transition: var(--transition-normal);
    box-shadow: var(--shadow-sm);
}

.feature-card:hover {
    transform: translateY(-8px);
    box-shadow: var(--shadow-lg);
    border-color: var(--accent-color);
}

.feature-icon {
    width: 60px;
    height: 60px;
    border-radius: var(--radius-sm);
    background-color: var(--primary-light);
    display: flex;
    align-items: center;
    justify-content: center;
    margin-bottom: 24px;
    color: var(--primary-color);
}

.feature-icon svg {
    width: 30px;
    height: 30px;
    fill: currentColor;
}

.feature-card h3 {
    font-size: 1.35rem;
    margin-bottom: 12px;
}

.feature-card p {
    font-size: 0.95rem;
    color: var(--text-color);
}

/* Pricing Section */
.pricing-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(260px, 1fr));
    gap: 32px;
    position: relative;
    z-index: 1;
}

.pricing-card {
    background-color: var(--bg-white);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-lg);
    padding: 40px 32px;
    text-align: center;
    position: relative;
    transition: var(--transition-normal);
    box-shadow: var(--shadow-sm);
    display: flex;
    flex-direction: column;
}

.pricing-card.popular {
    border: 2px solid var(--primary-color);
    box-shadow: var(--shadow-md);
}

.pricing-card.popular::before {
    content: '最受欢迎';
    position: absolute;
    top: -14px;
    left: 50%;
    transform: translateX(-50%);
    background-color: var(--primary-color);
    color: var(--bg-white);
    padding: 4px 16px;
    font-size: 0.75rem;
    font-weight: 700;
    border-radius: 20px;
    text-transform: uppercase;
    letter-spacing: 1px;
}

.pricing-card:hover {
    transform: scale(1.03);
    box-shadow: var(--shadow-lg);
}

.pricing-name {
    font-size: 1.25rem;
    color: var(--heading-color);
    margin-bottom: 12px;
}

.pricing-price {
    margin-bottom: 24px;
}

.price-currency {
    font-size: 1.5rem;
    font-weight: 700;
    color: var(--primary-color);
    vertical-align: top;
}

.price-num {
    font-size: 3rem;
    font-weight: 800;
    color: var(--primary-color);
    line-height: 1;
}

.price-period {
    font-size: 0.9rem;
    color: var(--text-color);
}

.pricing-features {
    margin-bottom: 32px;
    text-align: left;
    flex-grow: 1;
}

.pricing-features li {
    font-size: 0.95rem;
    margin-bottom: 12px;
    display: flex;
    align-items: center;
    gap: 8px;
}

.pricing-features li svg {
    width: 18px;
    height: 18px;
    fill: var(--primary-color);
    flex-shrink: 0;
}

/* Articles Section */
.articles-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(320px, 1fr));
    gap: 32px;
    position: relative;
    z-index: 1;
}

.article-card {
    background-color: var(--bg-white);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    overflow: hidden;
    box-shadow: var(--shadow-sm);
    transition: var(--transition-normal);
    display: flex;
    flex-direction: column;
    height: 100%;
}

.article-card:hover {
    transform: translateY(-6px);
    box-shadow: var(--shadow-lg);
    border-color: var(--accent-color);
}

.article-image-placeholder {
    height: 160px;
    background: linear-gradient(135deg, var(--primary-light), var(--bg-light));
    display: flex;
    align-items: center;
    justify-content: center;
    position: relative;
    border-bottom: 1px solid var(--border-color);
    color: var(--primary-color);
}

.article-image-placeholder svg {
    width: 50px;
    height: 50px;
    opacity: 0.75;
}

.article-content {
    padding: 24px;
    display: flex;
    flex-direction: column;
    flex-grow: 1;
}

.article-meta {
    font-size: 0.8rem;
    color: var(--text-color);
    margin-bottom: 8px;
    display: flex;
    gap: 12px;
}

.article-title {
    font-size: 1.2rem;
    margin-bottom: 12px;
    line-height: 1.4;
}

.article-excerpt {
    font-size: 0.9rem;
    color: var(--text-color);
    margin-bottom: 20px;
    flex-grow: 1;
    display: -webkit-box;
    -webkit-line-clamp: 3;
    -webkit-box-orient: vertical;
    overflow: hidden;
}

.article-readmore {
    font-weight: 600;
    font-size: 0.9rem;
    display: flex;
    align-items: center;
    gap: 4px;
}

.article-readmore svg {
    width: 16px;
    height: 16px;
    fill: currentColor;
    transition: var(--transition-fast);
}

.article-card:hover .article-readmore svg {
    transform: translateX(4px);
}

/* Detailed Article Page Styling */
.article-page {
    padding: 60px 0;
}

.article-breadcrumb {
    margin-bottom: 24px;
    font-size: 0.9rem;
}

.article-breadcrumb a {
    color: var(--text-color);
}

.article-breadcrumb span {
    color: var(--primary-color);
}

.article-header {
    max-width: 800px;
    margin: 0 auto 40px auto;
    text-align: center;
}

.article-header h1 {
    font-size: 2.5rem;
    margin-bottom: 16px;
    line-height: 1.25;
}

.article-body {
    max-width: 800px;
    margin: 0 auto;
    font-size: 1.05rem;
    color: var(--text-color);
    line-height: 1.8;
}

.article-body h2 {
    font-size: 1.75rem;
    margin: 40px 0 20px 0;
}

.article-body h3 {
    font-size: 1.35rem;
    margin: 30px 0 15px 0;
}

.article-body p {
    margin-bottom: 24px;
}

.article-body ul {
    list-style: disc;
    padding-left: 24px;
    margin-bottom: 24px;
}

.article-body ul li {
    margin-bottom: 8px;
}

.article-body blockquote {
    border-left: 4px solid var(--primary-color);
    background-color: var(--primary-light);
    padding: 16px 24px;
    margin: 32px 0;
    font-style: italic;
    border-radius: 0 var(--radius-sm) var(--radius-sm) 0;
}

.article-navigation {
    display: flex;
    justify-content: space-between;
    margin-top: 60px;
    padding-top: 30px;
    border-top: 1px solid var(--border-color);
}

.nav-link-card {
    max-width: 48%;
    background-color: var(--bg-light);
    border: 1px solid var(--border-color);
    padding: 16px 24px;
    border-radius: var(--radius-md);
    transition: var(--transition-normal);
}

.nav-link-card:hover {
    border-color: var(--primary-color);
    background-color: var(--bg-white);
}

.nav-link-card span {
    font-size: 0.8rem;
    color: var(--text-color);
    text-transform: uppercase;
    display: block;
    margin-bottom: 4px;
}

.nav-link-card a {
    font-weight: 600;
    color: var(--dark-purple);
}

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

/* User Reviews Section */
.reviews-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: 32px;
}

.review-card {
    background-color: var(--bg-white);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    padding: 32px;
    box-shadow: var(--shadow-sm);
    transition: var(--transition-normal);
}

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

.review-stars {
    display: flex;
    gap: 4px;
    margin-bottom: 16px;
    color: #f1c40f;
}

.review-stars svg {
    width: 18px;
    height: 18px;
    fill: currentColor;
}

.review-text {
    font-size: 0.95rem;
    color: var(--text-color);
    margin-bottom: 24px;
}

.review-user {
    display: flex;
    align-items: center;
    gap: 12px;
}

.review-avatar {
    width: 48px;
    height: 48px;
    border-radius: 50%;
    background-color: var(--primary-light);
    color: var(--primary-color);
    font-weight: 700;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 1.1rem;
}

.review-user-info h4 {
    font-size: 0.95rem;
    color: var(--heading-color);
}

.review-user-info span {
    font-size: 0.8rem;
    color: var(--text-color);
}

/* FAQ Accordion */
.faq-list {
    max-width: 800px;
    margin: 0 auto;
}

.faq-item {
    border-bottom: 1px solid var(--border-color);
    padding: 24px 0;
}

.faq-question {
    font-size: 1.15rem;
    font-weight: 600;
    color: var(--heading-color);
    display: flex;
    justify-content: space-between;
    align-items: center;
    cursor: pointer;
    user-select: none;
}

.faq-question svg {
    width: 20px;
    height: 20px;
    fill: var(--primary-color);
    transition: var(--transition-normal);
}

.faq-answer {
    max-height: 0;
    overflow: hidden;
    transition: var(--transition-normal);
    color: var(--text-color);
    font-size: 0.95rem;
}

.faq-answer p {
    padding-top: 16px;
}

.faq-item.active .faq-answer {
    max-height: 500px; /* arbitrary height to slide down */
}

.faq-item.active .faq-question svg {
    transform: rotate(180deg);
}

/* Call to Action Section (Bottom banner) */
.cta-banner {
    background: linear-gradient(135deg, var(--dark-purple), var(--primary-color));
    color: var(--bg-white);
    padding: 80px 0;
    text-align: center;
    position: relative;
    overflow: hidden;
}

.cta-banner h2 {
    color: var(--bg-white);
    font-size: 2.25rem;
    margin-bottom: 16px;
}

.cta-banner p {
    font-size: 1.125rem;
    max-width: 600px;
    margin: 0 auto 32px auto;
    opacity: 0.9;
}

.cta-banner .btn {
    box-shadow: 0 4px 15px rgba(0, 0, 0, 0.2);
}

/* Footer Styling */
footer {
    background-color: var(--bg-light);
    border-top: 1px solid var(--border-color);
    padding: 60px 0 30px 0;
}

.footer-grid {
    display: grid;
    grid-template-columns: 2fr repeat(2, 1fr);
    gap: 40px;
    margin-bottom: 40px;
}

.footer-col h3 {
    font-size: 1.1rem;
    margin-bottom: 20px;
    text-transform: uppercase;
    letter-spacing: 0.5px;
}

.footer-col p {
    font-size: 0.95rem;
    margin-bottom: 16px;
    max-width: 320px;
}

.footer-col ul li {
    margin-bottom: 10px;
}

.footer-col ul li a {
    color: var(--text-color);
    font-size: 0.95rem;
}

.footer-col ul li a:hover {
    color: var(--primary-color);
    padding-left: 4px;
}

.footer-bottom {
    border-top: 1px solid var(--border-color);
    padding-top: 30px;
    display: flex;
    justify-content: space-between;
    align-items: center;
    font-size: 0.85rem;
}

.footer-bottom p {
    color: var(--text-color);
}

.footer-bottom-links {
    display: flex;
    gap: 20px;
}

.footer-bottom-links a {
    color: var(--text-color);
}

/* Responsive Breakpoints */
@media (max-width: 992px) {
    .hero h1 {
        font-size: 2.75rem;
    }
    .footer-grid {
        grid-template-columns: 1fr;
        gap: 30px;
    }
    .footer-col {
        text-align: center;
    }
    .footer-col p {
        margin-left: auto;
        margin-right: auto;
    }
    .footer-bottom {
        flex-direction: column;
        gap: 16px;
        text-align: center;
    }
}

@media (max-width: 768px) {
    .header-container {
        flex-direction: column;
        gap: 16px;
    }
    nav ul {
        gap: 20px;
        flex-wrap: wrap;
        justify-content: center;
    }
    .hero {
        padding: 80px 0;
    }
    .hero h1 {
        font-size: 2.25rem;
    }
    .hero-ctas {
        flex-direction: column;
        align-items: center;
        gap: 12px;
    }
    .hero-ctas .btn {
        width: 100%;
        max-width: 280px;
    }
    .article-navigation {
        flex-direction: column;
        gap: 20px;
    }
    .nav-link-card {
        max-width: 100%;
    }
    .section {
        padding: 60px 0;
    }
    .section-header h2 {
        font-size: 1.8rem;
    }
}