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

:root {
    /* Color Palette */
    --primary: #2563EB;
    --secondary: #64748B;
    --background: #FFFFFF;
    --text: #1E293B;
    --accent: #0EA5E9;
    --subtle: #F8FAFC;
    --border: #E2E8F0;
    --success: #10B981;
    --warning: #F59E0B;
    
    /* Typography */
    --font-primary: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
    --font-secondary: 'Source Sans Pro', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
    
    /* Spacing */
    --spacing-xs: 5px;
    --spacing-sm: 10px;
    --spacing-md: 20px;
    --spacing-lg: 40px;
    --spacing-xl: 60px;
    --spacing-2xl: 80px;
    
    /* Borders */
    --border-radius: 8px;
    --border-radius-lg: 12px;
    
    /* Shadows */
    --shadow-sm: 0 1px 2px 0 rgba(0, 0, 0, 0.05);
    --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.1), 0 2px 4px -1px rgba(0, 0, 0, 0.06);
    --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.1), 0 4px 6px -2px rgba(0, 0, 0, 0.05);
    
    /* Transitions */
    --transition: all 0.3s ease;
}

html {
    scroll-behavior: smooth;
}

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

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

/* Navigation */
.navbar {
    background-color: var(--background);
    box-shadow: var(--shadow-sm);
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    z-index: 1000;
    transition: var(--transition);
}

.nav-container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 var(--spacing-md);
    display: flex;
    justify-content: space-between;
    align-items: center;
    height: 70px;
}

.nav-brand {
    display: flex;
    align-items: center;
    gap: var(--spacing-sm);
    text-decoration: none;
    color: var(--text);
}

.nav-logo {
    width: 40px;
    height: 40px;
}

.nav-title {
    font-weight: 600;
    font-size: 1.25rem;
    color: var(--primary);
}

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

.nav-link {
    text-decoration: none;
    color: var(--secondary);
    font-weight: 500;
    padding: var(--spacing-sm) var(--spacing-md);
    border-radius: var(--border-radius);
    transition: var(--transition);
}

.nav-link:hover {
    color: var(--primary);
    background-color: var(--subtle);
}

.nav-toggle {
    display: none;
    flex-direction: column;
    cursor: pointer;
    gap: 4px;
}

.bar {
    width: 25px;
    height: 3px;
    background-color: var(--text);
    transition: var(--transition);
}

/* Hero Section */
.hero {
    background: linear-gradient(135deg, var(--primary) 0%, var(--accent) 100%);
    color: white;
    padding: 140px 0 var(--spacing-2xl);
    text-align: center;
}

.hero-content {
    max-width: 800px;
    margin: 0 auto;
}

.hero-title {
    font-size: 3.5rem;
    font-weight: 700;
    margin-bottom: var(--spacing-md);
    line-height: 1.2;
    font-family: var(--font-secondary);
}

.hero-subtitle {
    font-size: 1.5rem;
    margin-bottom: var(--spacing-lg);
    opacity: 0.9;
    font-weight: 400;
}

.hero-buttons {
    display: flex;
    gap: var(--spacing-md);
    justify-content: center;
    flex-wrap: wrap;
}

/* Buttons */
.btn {
    display: inline-flex;
    align-items: center;
    gap: var(--spacing-sm);
    padding: 12px 24px;
    border: none;
    border-radius: var(--border-radius);
    text-decoration: none;
    font-weight: 600;
    font-size: 1rem;
    cursor: pointer;
    transition: var(--transition);
    white-space: nowrap;
}

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

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

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

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

.btn-large {
    padding: 16px 32px;
    font-size: 1.125rem;
}

/* Sections */
.section {
    padding: var(--spacing-2xl) 0;
}

.section-alt {
    background-color: var(--subtle);
}

.section-header {
    text-align: center;
    margin-bottom: var(--spacing-xl);
}

.section-header h2 {
    font-size: 2.5rem;
    font-weight: 700;
    color: var(--text);
    margin-bottom: var(--spacing-md);
    font-family: var(--font-secondary);
}

.section-description {
    font-size: 1.25rem;
    color: var(--secondary);
    max-width: 600px;
    margin: 0 auto;
}

/* Content Grid */
.content-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: var(--spacing-lg);
    margin-bottom: var(--spacing-xl);
}

.content-card {
    background: white;
    padding: var(--spacing-lg);
    border-radius: var(--border-radius-lg);
    box-shadow: var(--shadow-md);
    transition: var(--transition);
}

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

.card-icon {
    width: 60px;
    height: 60px;
    background: linear-gradient(135deg, var(--primary), var(--accent));
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    margin-bottom: var(--spacing-md);
}

.card-icon i {
    font-size: 1.5rem;
    color: white;
}

.content-card h3 {
    font-size: 1.5rem;
    font-weight: 600;
    margin-bottom: var(--spacing-md);
    color: var(--text);
}

.content-card p {
    color: var(--secondary);
    line-height: 1.7;
}

/* Heuristics Section */
.heuristics-section {
    background: white;
    padding: var(--spacing-lg);
    border-radius: var(--border-radius-lg);
    box-shadow: var(--shadow-md);
    margin-bottom: var(--spacing-xl);
}

.heuristics-section h3 {
    font-size: 1.75rem;
    font-weight: 600;
    margin-bottom: var(--spacing-lg);
    color: var(--text);
    text-align: center;
}

.heuristics-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: var(--spacing-md);
}

.heuristic-item {
    display: flex;
    align-items: center;
    gap: var(--spacing-md);
    padding: var(--spacing-md);
    background: var(--subtle);
    border-radius: var(--border-radius);
    transition: var(--transition);
}

.heuristic-item:hover {
    background: #E0F2FE;
}

.heuristic-item i {
    font-size: 1.25rem;
    color: var(--primary);
    width: 24px;
    text-align: center;
}

.heuristic-item span {
    font-weight: 500;
    color: var(--text);
}

/* Example Section */
.example-section {
    background: white;
    padding: var(--spacing-lg);
    border-radius: var(--border-radius-lg);
    box-shadow: var(--shadow-md);
}

.example-section h3 {
    font-size: 1.75rem;
    font-weight: 600;
    margin-bottom: var(--spacing-md);
    color: var(--text);
    text-align: center;
}

.example-section > p {
    color: var(--secondary);
    text-align: center;
    margin-bottom: var(--spacing-lg);
    line-height: 1.7;
}

.example-images {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: var(--spacing-lg);
}

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

.example-card img {
    /*width: 100%;*/
    /*height: 200px;*/
    object-fit: cover;
    border-radius: var(--border-radius);
    margin-bottom: var(--spacing-md);
    box-shadow: var(--shadow-md);
}

.example-info h4 {
    font-size: 1.25rem;
    font-weight: 600;
    margin-bottom: var(--spacing-sm);
    color: var(--text);
}

.origin-badge {
    display: inline-block;
    padding: 4px 12px;
    border-radius: 20px;
    font-size: 0.875rem;
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 0.5px;
}

.origin-badge.us {
    background: #DBEAFE;
    color: var(--primary);
}

.origin-badge.china {
    background: #FEF3C7;
    color: var(--warning);
}

/* Install Section */
.install-content {
    display: flex;
    justify-content: center;
}

.install-card {
    background: white;
    padding: var(--spacing-xl);
    border-radius: var(--border-radius-lg);
    box-shadow: var(--shadow-md);
    text-align: center;
    max-width: 500px;
    width: 100%;
}

.install-icon {
    width: 80px;
    height: 80px;
    background: linear-gradient(135deg, #FF6B35, #FF9500);
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    margin: 0 auto var(--spacing-md);
}

.install-icon i {
    font-size: 2rem;
    color: white;
}

.install-card h3 {
    font-size: 1.75rem;
    font-weight: 600;
    margin-bottom: var(--spacing-md);
    color: var(--text);
}

.install-card p {
    color: var(--secondary);
    margin-bottom: var(--spacing-lg);
    line-height: 1.7;
}

/* Configure Section */
.configure-content {
    max-width: 1000px;
    margin: 0 auto;
}

.configure-info {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: var(--spacing-lg);
    margin-bottom: var(--spacing-xl);
}

.info-card {
    background: white;
    padding: var(--spacing-lg);
    border-radius: var(--border-radius-lg);
    box-shadow: var(--shadow-md);
}

.info-card h3 {
    font-size: 1.5rem;
    font-weight: 600;
    margin-bottom: var(--spacing-md);
    color: var(--text);
}

.info-card p {
    color: var(--secondary);
    line-height: 1.7;
}

.configure-steps {
    background: white;
    padding: var(--spacing-lg);
    border-radius: var(--border-radius-lg);
    box-shadow: var(--shadow-md);
    margin-bottom: var(--spacing-xl);
}

.configure-steps h3 {
    font-size: 1.75rem;
    font-weight: 600;
    margin-bottom: var(--spacing-lg);
    color: var(--text);
    text-align: center;
}

.steps-list {
    display: grid;
    gap: var(--spacing-md);
}

.step {
    display: flex;
    align-items: flex-start;
    gap: var(--spacing-md);
    padding: var(--spacing-md);
    background: var(--subtle);
    border-radius: var(--border-radius);
}

.step-number {
    width: 32px;
    height: 32px;
    background: var(--primary);
    color: white;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    font-weight: 600;
    flex-shrink: 0;
}

.step-content h4 {
    font-size: 1.125rem;
    font-weight: 600;
    margin-bottom: var(--spacing-xs);
    color: var(--text);
}

.step-content p {
    color: var(--secondary);
    line-height: 1.6;
}

.configure-images {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: var(--spacing-lg);
}

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

.config-image img {
    width: 100%;
    max-width: 400px;
    height: auto;
    border-radius: var(--border-radius);
    box-shadow: var(--shadow-md);
    margin-bottom: var(--spacing-md);
}

.config-image p {
    color: var(--secondary);
    font-style: italic;
}

/* Privacy Section */
.privacy-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: var(--spacing-lg);
    margin-bottom: var(--spacing-xl);
}

.privacy-card {
    background: white;
    padding: var(--spacing-lg);
    border-radius: var(--border-radius-lg);
    box-shadow: var(--shadow-md);
    transition: var(--transition);
}

.privacy-card:hover {
    transform: translateY(-2px);
    box-shadow: var(--shadow-lg);
}

.privacy-card h3 {
    font-size: 1.5rem;
    font-weight: 600;
    margin-bottom: var(--spacing-md);
    color: var(--text);
}

.privacy-card p {
    color: var(--secondary);
    line-height: 1.7;
}

.privacy-guarantee {
    background: linear-gradient(135deg, var(--success), #059669);
    color: white;
    padding: var(--spacing-lg);
    border-radius: var(--border-radius-lg);
    text-align: center;
}

.guarantee-icon {
    width: 60px;
    height: 60px;
    background: rgba(255, 255, 255, 0.2);
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    margin: 0 auto var(--spacing-md);
}

.guarantee-icon i {
    font-size: 1.5rem;
    color: white;
}

.privacy-guarantee h3 {
    font-size: 1.75rem;
    font-weight: 600;
    margin-bottom: var(--spacing-md);
}

.privacy-guarantee p {
    font-size: 1.125rem;
    line-height: 1.6;
}

/* Limitations Section */
.limitations-content {
    max-width: 800px;
    margin: 0 auto;
}

.limitation-item {
    background: white;
    padding: var(--spacing-lg);
    border-radius: var(--border-radius-lg);
    box-shadow: var(--shadow-md);
    margin-bottom: var(--spacing-lg);
    display: flex;
    align-items: flex-start;
    gap: var(--spacing-md);
}

.limitation-icon {
    width: 48px;
    height: 48px;
    background: linear-gradient(135deg, var(--warning), #D97706);
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    flex-shrink: 0;
}

.limitation-icon i {
    font-size: 1.25rem;
    color: white;
}

.limitation-item h3 {
    font-size: 1.5rem;
    font-weight: 600;
    margin-bottom: var(--spacing-sm);
    color: var(--text);
}

.limitation-item p {
    color: var(--secondary);
    line-height: 1.7;
}

/* Footer */
.footer {
    background-color: var(--text);
    color: white;
    padding: var(--spacing-xl) 0 var(--spacing-lg);
}

.footer-content {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: var(--spacing-lg);
    flex-wrap: wrap;
    gap: var(--spacing-md);
}

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

.footer-logo {
    width: 32px;
    height: 32px;
    filter: brightness(0) invert(1);
}

.footer-title {
    font-weight: 600;
    font-size: 1.25rem;
}

.footer-links {
    display: flex;
    gap: var(--spacing-lg);
    flex-wrap: wrap;
}

.footer-links a {
    color: rgba(255, 255, 255, 0.8);
    text-decoration: none;
    transition: var(--transition);
}

.footer-links a:hover {
    color: white;
}

.footer-bottom {
    text-align: center;
    padding-top: var(--spacing-lg);
    border-top: 1px solid rgba(255, 255, 255, 0.1);
    color: rgba(255, 255, 255, 0.6);
}

/* Back to Top Button */
.back-to-top {
    position: fixed;
    bottom: var(--spacing-md);
    right: var(--spacing-md);
    width: 50px;
    height: 50px;
    background: var(--primary);
    color: white;
    border: none;
    border-radius: 50%;
    cursor: pointer;
    opacity: 0;
    visibility: hidden;
    transition: var(--transition);
    z-index: 1000;
}

.back-to-top.visible {
    opacity: 1;
    visibility: visible;
}

.back-to-top:hover {
    background: var(--accent);
    transform: translateY(-2px);
}

/* Responsive Design */
@media (max-width: 768px) {
    .nav-menu {
        position: fixed;
        left: -100%;
        top: 70px;
        flex-direction: column;
        background-color: white;
        width: 100%;
        text-align: center;
        transition: var(--transition);
        box-shadow: var(--shadow-lg);
        padding: var(--spacing-md) 0;
        gap: 0;
    }

    .nav-menu.active {
        left: 0;
    }

    .nav-menu .nav-link {
        padding: var(--spacing-md);
        display: block;
        width: 100%;
    }

    .nav-toggle {
        display: flex;
    }

    .nav-toggle.active .bar:nth-child(2) {
        opacity: 0;
    }

    .nav-toggle.active .bar:nth-child(1) {
        transform: translateY(7px) rotate(45deg);
    }

    .nav-toggle.active .bar:nth-child(3) {
        transform: translateY(-7px) rotate(-45deg);
    }

    .hero-title {
        font-size: 2.5rem;
    }

    .hero-subtitle {
        font-size: 1.25rem;
    }

    .hero-buttons {
        flex-direction: column;
        align-items: center;
    }

    .section-header h2 {
        font-size: 2rem;
    }

    .section-description {
        font-size: 1.125rem;
    }

    .content-grid {
        grid-template-columns: 1fr;
    }

    .heuristics-grid {
        grid-template-columns: 1fr;
    }

    .example-images {
        grid-template-columns: 1fr;
    }

    .configure-info {
        grid-template-columns: 1fr;
    }

    .configure-images {
        grid-template-columns: 1fr;
    }

    .privacy-grid {
        grid-template-columns: 1fr;
    }

    .footer-content {
        flex-direction: column;
        text-align: center;
    }

    .footer-links {
        justify-content: center;
    }
}

@media (max-width: 480px) {
    .container {
        padding: 0 var(--spacing-sm);
    }

    .hero {
        padding: 120px 0 var(--spacing-xl);
    }

    .hero-title {
        font-size: 2rem;
    }

    .hero-subtitle {
        font-size: 1.125rem;
    }

    .section {
        padding: var(--spacing-xl) 0;
    }

    .section-header h2 {
        font-size: 1.75rem;
    }

    .content-card,
    .info-card,
    .privacy-card {
        padding: var(--spacing-md);
    }

    .install-card {
        padding: var(--spacing-lg);
    }

    .configure-steps,
    .heuristics-section,
    .example-section {
        padding: var(--spacing-md);
    }

    .limitation-item {
        padding: var(--spacing-md);
        flex-direction: column;
        text-align: center;
    }
}

/* Print Styles */
@media print {
    .navbar,
    .back-to-top,
    .hero-buttons {
        display: none;
    }

    .hero {
        background: none;
        color: var(--text);
        padding: var(--spacing-lg) 0;
    }

    .section {
        padding: var(--spacing-md) 0;
    }

    .content-card,
    .info-card,
    .privacy-card,
    .install-card {
        box-shadow: none;
        border: 1px solid var(--border);
    }
}

/* Accessibility */
@media (prefers-reduced-motion: reduce) {
    * {
        animation-duration: 0.01ms !important;
        animation-iteration-count: 1 !important;
        transition-duration: 0.01ms !important;
    }

    html {
        scroll-behavior: auto;
    }
}

/* Focus styles for keyboard navigation */
.nav-link:focus,
.btn:focus,
.back-to-top:focus {
    outline: 2px solid var(--accent);
    outline-offset: 2px;
}

/* High contrast mode support */
@media (prefers-contrast: high) {
    :root {
        --shadow-sm: none;
        --shadow-md: none;
        --shadow-lg: none;
    }

    .content-card,
    .info-card,
    .privacy-card,
    .install-card {
        border: 2px solid var(--border);
    }
}