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

:root {
    --primary: #0066FF;
    --primary-hover: #0052cc;
    --bg-color: #F8FAFC;
    --surface-color: #FFFFFF;
    --text-main: #0F172A;
    --text-muted: #64748B;
    --border-color: #E2E8F0;
    --shadow-sm: 0 1px 3px rgba(0,0,0,0.05);
    --shadow-md: 0 4px 6px -1px rgba(0,0,0,0.05), 0 2px 4px -1px rgba(0,0,0,0.03);
    --shadow-lg: 0 10px 15px -3px rgba(0,0,0,0.05), 0 4px 6px -2px rgba(0,0,0,0.025);
    --radius-md: 12px;
    --radius-lg: 24px;
}

* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

body {
    font-family: 'Inter', system-ui, -apple-system, sans-serif;
    background-color: var(--bg-color);
    color: var(--text-main);
    line-height: 1.6;
    overflow-x: hidden;
    -webkit-font-smoothing: antialiased;
}

a {
    text-decoration: none;
    color: inherit;
    transition: all 0.2s ease;
}

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

/* Navbar */
.navbar {
    position: fixed;
    top: 0;
    width: 100%;
    background: rgba(255, 255, 255, 0.85);
    backdrop-filter: blur(12px);
    -webkit-backdrop-filter: blur(12px);
    border-bottom: 1px solid var(--border-color);
    z-index: 1000;
}

.nav-container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 1rem 2rem;
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.logo {
    font-size: 1.5rem;
    font-weight: 700;
    color: var(--primary);
    display: flex;
    align-items: center;
    gap: 0.5rem;
}

.nav-links {
    display: flex;
    gap: 2rem;
    align-items: center;
}

.nav-links a {
    font-weight: 500;
    color: var(--text-muted);
}

.nav-links a:hover, .nav-links a.active {
    color: var(--text-main);
}

.btn {
    display: inline-block;
    padding: 0.75rem 1.5rem;
    border-radius: var(--radius-md);
    font-weight: 600;
    text-align: center;
    cursor: pointer;
    transition: all 0.3s ease;
    border: none;
}

.btn-primary {
    background: var(--primary);
    color: white;
    box-shadow: 0 4px 14px 0 rgba(0, 102, 255, 0.39);
}

.btn-primary:hover {
    background: var(--primary-hover);
    transform: translateY(-2px);
    box-shadow: 0 6px 20px rgba(0, 102, 255, 0.4);
    color: white;
}

.btn-outline {
    background: transparent;
    border: 1px solid var(--border-color);
    color: var(--text-main);
}

.btn-outline:hover {
    border-color: var(--text-main);
}

/* Hero Section */
.hero {
    padding: 10rem 2rem 6rem;
    min-height: 100vh;
    display: flex;
    align-items: center;
    justify-content: center;
    text-align: center;
    position: relative;
    background: radial-gradient(circle at top right, rgba(0,102,255,0.05), transparent 40%),
                radial-gradient(circle at bottom left, rgba(0,102,255,0.05), transparent 40%);
}

.hero-content {
    max-width: 900px;
    z-index: 2;
}

.tag {
    display: inline-block;
    padding: 0.5rem 1rem;
    background: rgba(0, 102, 255, 0.1);
    color: var(--primary);
    border-radius: 20px;
    font-size: 0.875rem;
    font-weight: 600;
    margin-bottom: 1.5rem;
}

.hero h1 {
    font-size: clamp(2.5rem, 5vw, 4.5rem);
    font-weight: 800;
    letter-spacing: -0.02em;
    margin-bottom: 1.5rem;
    background: linear-gradient(135deg, #111 0%, #444 100%);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
}

.hero p {
    font-size: clamp(1.1rem, 2vw, 1.25rem);
    color: var(--text-muted);
    margin-bottom: 2.5rem;
    max-width: 600px;
    margin-inline: auto;
}

.hero-actions {
    display: flex;
    gap: 1rem;
    justify-content: center;
}

/* Features / Products Section */
.products {
    padding: 6rem 2rem;
    background: var(--surface-color);
    border-top: 1px solid var(--border-color);
}

.section-title {
    text-align: center;
    font-size: 2.5rem;
    font-weight: 700;
    margin-bottom: 1rem;
}
.section-subtitle {
    text-align: center;
    color: var(--text-muted);
    margin-bottom: 4rem;
    font-size: 1.125rem;
}

.products-grid {
    max-width: 1200px;
    margin: 0 auto;
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(350px, 1fr));
    gap: 2.5rem;
}

.product-card {
    background: var(--surface-color);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-lg);
    padding: 3rem 2rem;
    transition: all 0.4s cubic-bezier(0.175, 0.885, 0.32, 1.275);
    position: relative;
    overflow: hidden;
}

.product-card:hover {
    transform: translateY(-10px);
    box-shadow: var(--shadow-lg);
    border-color: rgba(0,102,255,0.2);
}

.product-icon {
    width: 64px;
    height: 64px;
    background: rgba(0, 102, 255, 0.1);
    color: var(--primary);
    border-radius: 16px;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 2rem;
    margin-bottom: 1.5rem;
}

.product-card h3 {
    font-size: 1.5rem;
    margin-bottom: 1rem;
}

.product-card p {
    color: var(--text-muted);
    margin-bottom: 2rem;
}

/* Pricing / Recharge */
.pricing {
    padding: 6rem 2rem;
    background: var(--surface-color);
}
.pricing-grid {
    max-width: 1000px;
    margin: 0 auto;
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: 2rem;
}
.price-card {
    border: 1px solid var(--border-color);
    border-radius: var(--radius-lg);
    padding: 3rem 2rem;
    text-align: center;
    transition: transform 0.3s ease, box-shadow 0.3s ease;
    background: var(--surface-color);
    position: relative;
}
.price-card:hover {
    transform: translateY(-5px);
    box-shadow: var(--shadow-lg);
}
.price-card.popular {
    border: 2px solid var(--primary);
    box-shadow: var(--shadow-md);
}
.popular-badge {
    position: absolute;
    top: -12px;
    left: 50%;
    transform: translateX(-50%);
    background: var(--primary);
    color: white;
    padding: 0.25rem 1rem;
    border-radius: 20px;
    font-size: 0.875rem;
    font-weight: 600;
}
.price-currency { font-size: 1.5rem; font-weight: 600; vertical-align: top; }
.price-amount { font-size: 3.5rem; font-weight: 800; letter-spacing: -1px; }
.price-period { color: var(--text-muted); }
.price-features { margin: 2rem 0; list-style: none; text-align: left; }
.price-features li { padding: 0.5rem 0; color: var(--text-muted); display: flex; align-items: center; gap: 0.5rem; }

/* Payment Methods */
.payment-methods {
    text-align: center;
    margin-top: 3rem;
    padding-top: 2rem;
    border-top: 1px solid var(--border-color);
}
.alipay-logo {
    display: inline-flex;
    align-items: center;
    gap: 0.5rem;
    color: #1677FF;
    font-weight: 600;
    font-size: 1.2rem;
}

/* Generic Page */
.page-container {
    max-width: 1000px;
    margin: 8rem auto 4rem;
    padding: 2rem;
    background: var(--surface-color);
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow-sm);
}
.page-title {
    font-size: 2.5rem;
    font-weight: 700;
    margin-bottom: 2rem;
    padding-bottom: 1rem;
    border-bottom: 1px solid var(--border-color);
}
.content-block h2 { font-size: 1.75rem; margin: 2rem 0 1rem; }
.content-block h3 { font-size: 1.25rem; margin: 1.5rem 0 0.5rem; }
.content-block p { margin-bottom: 1rem; color: var(--text-muted); }
.content-block ul { margin-left: 1.5rem; margin-bottom: 1.5rem; color: var(--text-muted); }
.content-block li { margin-bottom: 0.5rem; }

/* FAQ */
.faq-item {
    border-bottom: 1px solid var(--border-color);
    padding: 1.5rem 0;
}
.faq-question {
    font-size: 1.125rem;
    font-weight: 600;
    cursor: pointer;
    display: flex;
    justify-content: space-between;
    align-items: center;
}
.faq-answer {
    margin-top: 1rem;
    color: var(--text-muted);
    display: none;
    line-height: 1.6;
}
.faq-item.active .faq-answer { display: block; }
.faq-toggle { transition: transform 0.3s ease; color: var(--primary); font-size: 1.5rem; }
.faq-item.active .faq-toggle { transform: rotate(45deg); }

/* Testimonials Marquee */
.testimonials {
    padding: 6rem 0;
    background: var(--surface-color);
    overflow: hidden;
    position: relative;
    border-top: 1px solid var(--border-color);
}
.testimonials-title {
    text-align: center;
    font-size: 2.25rem;
    font-weight: 700;
    margin-bottom: 4rem;
}
.marquee-track {
    width: 100%;
    overflow: hidden;
    position: relative;
    -webkit-mask-image: linear-gradient(to right, transparent, black 5%, black 95%, transparent);
    mask-image: linear-gradient(to right, transparent, black 5%, black 95%, transparent);
}
.marquee {
    display: flex;
    gap: 2rem;
    width: max-content;
    animation: scroll 35s linear infinite;
    padding: 1rem 0;
}
.marquee:hover {
    animation-play-state: paused;
}
.testimonial-card {
    background: var(--surface-color);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-lg);
    padding: 2rem;
    width: 380px;
    box-shadow: var(--shadow-sm);
    flex-shrink: 0;
    transition: transform 0.3s ease, box-shadow 0.3s ease;
}
.testimonial-card:hover {
    transform: translateY(-5px);
    box-shadow: var(--shadow-md);
}
.testimonial-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 1.5rem;
}
.user-info {
    display: flex;
    align-items: center;
    gap: 1rem;
}
.avatar {
    width: 44px;
    height: 44px;
    border-radius: 50%;
    color: white;
    display: flex;
    align-items: center;
    justify-content: center;
    font-weight: 700;
    font-size: 1.2rem;
    background: var(--primary);
}
.user-name { font-weight: 700; font-size: 1.05rem; }
.user-device { font-size: 0.85rem; color: var(--text-muted); margin-top: 0.2rem; }
.stars { color: #F59E0B; font-size: 1.2rem; }
.testimonial-text { color: var(--text-main); font-size: 0.95rem; line-height: 1.6; }

@keyframes scroll {
    0% { transform: translateX(0); }
    100% { transform: translateX(calc(-50% - 1rem)); } 
}

/* Footer */
footer {
    background: #0F172A;
    color: #94A3B8;
    padding: 4rem 2rem 2rem;
}
.footer-container {
    max-width: 1200px;
    margin: 0 auto;
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
    gap: 3rem;
    margin-bottom: 3rem;
}
.footer-col h4 { color: white; font-size: 1.125rem; margin-bottom: 1.5rem; }
.footer-col ul { list-style: none; }
.footer-col ul li { margin-bottom: 0.75rem; }
.footer-col ul li a:hover { color: white; }
.footer-bottom {
    max-width: 1200px;
    margin: 0 auto;
    padding-top: 2rem;
    border-top: 1px solid rgba(255,255,255,0.1);
    text-align: center;
    font-size: 0.875rem;
}

/* Tutorial Layout */
.tutorial-layout { display: flex; gap: 3rem; align-items: flex-start; }
.tutorial-sidebar { width: 250px; flex-shrink: 0; position: sticky; top: 100px; }
.tutorial-sidebar a {
    display: block; padding: 0.75rem 1rem; border-radius: var(--radius-md);
    color: var(--text-muted); margin-bottom: 0.5rem;
}
.tutorial-sidebar a:hover, .tutorial-sidebar a.active {
    background: rgba(0, 102, 255, 0.05); color: var(--primary); font-weight: 600;
}
.tutorial-content { flex-grow: 1; }

.mobile-menu-btn { display: none; background: none; border: none; font-size: 1.5rem; cursor: pointer; color: var(--text-main); }
@media (max-width: 768px) {
    .mobile-menu-btn { display: block; }
    .nav-links {
        display: none; position: absolute; top: 100%; left: 0; width: 100%;
        background: var(--surface-color); flex-direction: column; padding: 1rem 0;
        box-shadow: var(--shadow-md);
    }
    .nav-links.show { display: flex; }
    .nav-links a, .nav-links .btn { width: 100%; text-align: center; padding: 1rem; }
    .tutorial-layout { flex-direction: column; }
    .tutorial-sidebar { width: 100%; position: static; }
}