/* Apple-inspired CSS Variables */
:root {
    --primary-color: #007AFF;
    --primary-dark: #0056CC;
    --secondary-color: #8E8E93;
    --accent-color: #FF9500;
    --text-primary: #1D1D1F;
    --text-secondary: #86868B;
    --text-light: #A1A1A6;
    --background: #FFFFFF;
    --surface: #F5F5F7;
    --surface-secondary: #FBFBFD;
    --border: #D2D2D7;
    --shadow-sm: 0 1px 3px rgba(0, 0, 0, 0.1);
    --shadow-md: 0 4px 6px rgba(0, 0, 0, 0.07);
    --shadow-lg: 0 25px 50px rgba(0, 0, 0, 0.15);
    --radius: 12px;
    --radius-lg: 20px;
    --transition: all 0.3s cubic-bezier(0.25, 0.46, 0.45, 0.94);
    --font-display: 'SF Pro Display', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
    --font-text: 'SF Pro Text', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
}

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

html {
    scroll-behavior: smooth;
}

body {
    font-family: var(--font-text);
    line-height: 1.6;
    color: var(--text-primary);
    background: var(--background);
    font-size: 17px;
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
}

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

/* Navigation */
.nav {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    background: rgba(255, 255, 255, 0.8);
    backdrop-filter: blur(20px);
    -webkit-backdrop-filter: blur(20px);
    border-bottom: 1px solid var(--border);
    z-index: 1000;
    transition: var(--transition);
}

.nav-container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 20px;
    display: flex;
    justify-content: space-between;
    align-items: center;
    height: 60px;
}

.nav-logo {
    font-family: var(--font-display);
    font-size: 20px;
    font-weight: 600;
    color: var(--text-primary);
    text-decoration: none;
    transition: var(--transition);
}

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

.nav-links {
    display: flex;
    gap: 32px;
}

.nav-link {
    color: var(--text-primary);
    text-decoration: none;
    font-weight: 400;
    font-size: 17px;
    transition: var(--transition);
    position: relative;
}

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

.nav-link::after {
    content: '';
    position: absolute;
    bottom: -8px;
    left: 0;
    width: 0;
    height: 2px;
    background: var(--primary-color);
    transition: var(--transition);
}

.nav-link:hover::after {
    width: 100%;
}

/* Hero Section */
.hero {
    min-height: 100vh;
    display: flex;
    align-items: center;
    justify-content: center;
    background: linear-gradient(135deg, var(--surface) 0%, var(--surface-secondary) 100%);
    position: relative;
    overflow: hidden;
    padding: 80px 20px 40px;
}

.hero::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: radial-gradient(circle at 30% 20%, rgba(0, 122, 255, 0.1) 0%, transparent 50%),
                radial-gradient(circle at 70% 80%, rgba(255, 149, 0, 0.1) 0%, transparent 50%);
    pointer-events: none;
}

.hero-container {
    text-align: center;
    z-index: 2;
    position: relative;
    max-width: 800px;
}

.hero-title {
    font-family: var(--font-display);
    font-size: clamp(48px, 8vw, 80px);
    font-weight: 700;
    line-height: 1.1;
    color: var(--text-primary);
    margin-bottom: 24px;
    letter-spacing: -0.02em;
}

.hero-subtitle {
    font-size: 24px;
    color: var(--text-secondary);
    margin-bottom: 40px;
    font-weight: 400;
    line-height: 1.4;
}

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

.btn-primary, .btn-secondary {
    padding: 16px 32px;
    border-radius: var(--radius);
    text-decoration: none;
    font-weight: 500;
    font-size: 17px;
    transition: var(--transition);
    display: inline-flex;
    align-items: center;
    justify-content: center;
    min-width: 160px;
}

.btn-primary {
    background: var(--primary-color);
    color: white;
    border: 2px solid var(--primary-color);
}

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

.btn-secondary {
    background: transparent;
    color: var(--primary-color);
    border: 2px solid var(--primary-color);
}

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

/* Hero Visual */
.hero-visual {
    position: absolute;
    top: 50%;
    right: 10%;
    transform: translateY(-50%);
    z-index: 1;
}

.floating-cards {
    position: relative;
    width: 300px;
    height: 300px;
}

.card {
    position: absolute;
    width: 80px;
    height: 80px;
    background: rgba(255, 255, 255, 0.9);
    backdrop-filter: blur(20px);
    border-radius: var(--radius);
    display: flex;
    align-items: center;
    justify-content: center;
    font-weight: 600;
    font-size: 14px;
    color: var(--text-primary);
    box-shadow: var(--shadow-md);
    animation: float 6s ease-in-out infinite;
}

.card-1 {
    top: 20px;
    left: 50px;
    animation-delay: 0s;
    background: linear-gradient(135deg, #FF6B6B, #FF8E8E);
    color: white;
}

.card-2 {
    top: 80px;
    right: 20px;
    animation-delay: 1s;
    background: linear-gradient(135deg, #4ECDC4, #44A08D);
    color: white;
}

.card-3 {
    bottom: 100px;
    left: 20px;
    animation-delay: 2s;
    background: linear-gradient(135deg, #FFD93D, #FF9500);
    color: white;
}

.card-4 {
    bottom: 40px;
    right: 60px;
    animation-delay: 3s;
    background: linear-gradient(135deg, #A8E6CF, #7FCDCD);
    color: white;
}

.card-5 {
    top: 140px;
    left: 120px;
    animation-delay: 4s;
    background: linear-gradient(135deg, #DDA0DD, #9370DB);
    color: white;
}

@keyframes float {
    0%, 100% {
        transform: translateY(0px) rotate(0deg);
    }
    50% {
        transform: translateY(-20px) rotate(5deg);
    }
}

/* Section Styles */
section {
    padding: 80px 0;
}

.section-header {
    text-align: center;
    margin-bottom: 60px;
}

.section-title {
    font-family: var(--font-display);
    font-size: clamp(36px, 5vw, 56px);
    font-weight: 700;
    color: var(--text-primary);
    margin-bottom: 16px;
    letter-spacing: -0.02em;
}

.section-subtitle {
    font-size: 21px;
    color: var(--text-secondary);
    font-weight: 400;
    max-width: 600px;
    margin: 0 auto;
}

/* About Section */
.about {
    background: var(--surface);
}

.about-content {
    display: grid;
    grid-template-columns: 2fr 1fr;
    gap: 60px;
    align-items: center;
}

.about-text {
    font-size: 19px;
    line-height: 1.6;
}

.about-text .lead {
    font-size: 24px;
    color: var(--text-primary);
    margin-bottom: 24px;
    font-weight: 500;
}

.about-text p {
    color: var(--text-secondary);
    margin-bottom: 20px;
}

.about-stats {
    display: grid;
    gap: 32px;
}

.stat {
    text-align: center;
    padding: 24px;
    background: white;
    border-radius: var(--radius);
    box-shadow: var(--shadow-sm);
}

.stat-number {
    display: block;
    font-family: var(--font-display);
    font-size: 48px;
    font-weight: 700;
    color: var(--primary-color);
    margin-bottom: 8px;
}

.stat-label {
    font-size: 15px;
    color: var(--text-secondary);
    font-weight: 500;
    text-transform: uppercase;
    letter-spacing: 0.5px;
}

/* Expertise Section */
.expertise-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(350px, 1fr));
    gap: 24px;
}

.expertise-card {
    background: white;
    border-radius: var(--radius-lg);
    padding: 32px;
    text-decoration: none;
    color: inherit;
    transition: var(--transition);
    border: 1px solid var(--border);
    position: relative;
    overflow: hidden;
}

.expertise-card::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: linear-gradient(135deg, var(--primary-color), var(--accent-color));
    opacity: 0;
    transition: var(--transition);
}

.expertise-card:hover::before {
    opacity: 0.05;
}

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

.card-icon {
    width: 48px;
    height: 48px;
    margin-bottom: 20px;
    color: var(--primary-color);
    position: relative;
    z-index: 1;
}

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

.expertise-card h3 {
    font-family: var(--font-display);
    font-size: 24px;
    font-weight: 600;
    margin-bottom: 12px;
    color: var(--text-primary);
    position: relative;
    z-index: 1;
}

.expertise-card p {
    color: var(--text-secondary);
    line-height: 1.5;
    margin-bottom: 20px;
    position: relative;
    z-index: 1;
}

.card-arrow {
    font-size: 24px;
    color: var(--primary-color);
    font-weight: 600;
    position: relative;
    z-index: 1;
    transition: var(--transition);
}

.expertise-card:hover .card-arrow {
    transform: translateX(8px);
}

/* Contact Section */
.contact {
    background: var(--surface);
}

.contact-content {
    max-width: 600px;
    margin: 0 auto;
}

.contact-info {
    display: grid;
    gap: 24px;
}

.contact-item {
    display: flex;
    align-items: center;
    gap: 20px;
    padding: 24px;
    background: white;
    border-radius: var(--radius);
    box-shadow: var(--shadow-sm);
    transition: var(--transition);
}

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

.contact-icon {
    width: 24px;
    height: 24px;
    color: var(--primary-color);
    flex-shrink: 0;
}

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

.contact-item h4 {
    font-size: 17px;
    font-weight: 600;
    color: var(--text-primary);
    margin-bottom: 4px;
}

.contact-item p {
    color: var(--text-secondary);
    font-size: 15px;
}

.contact-item a {
    color: var(--primary-color);
    text-decoration: none;
    transition: var(--transition);
    border-bottom: 1px solid transparent;
}

.contact-item a:hover {
    color: var(--primary-dark);
    border-bottom-color: var(--primary-dark);
}

/* Topic Pages Styles */
.topic-hero {
    background: linear-gradient(135deg, var(--primary-color) 0%, var(--secondary-color) 100%);
    color: white;
    padding: 120px 0 80px;
}

.topic-hero .hero-title,
.topic-hero .hero-subtitle {
    color: white;
}

.topic-stats {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(150px, 1fr));
    gap: 32px;
    margin-top: 48px;
}

.topic-stats .stat {
    text-align: center;
    background: rgba(255, 255, 255, 0.1);
    padding: 24px;
    border-radius: var(--radius);
    backdrop-filter: blur(10px);
}

.topic-stats .stat-number {
    display: block;
    font-size: 40px;
    font-weight: 700;
    color: white;
}

.topic-stats .stat-label {
    font-size: 14px;
    opacity: 0.9;
    margin-top: 8px;
}

/* Content Grid for Topic Pages */
.content-grid {
    display: grid;
    grid-template-columns: 2fr 1fr;
    gap: 64px;
    margin-top: 32px;
}

.content-main h2 {
    font-size: 32px;
    margin-bottom: 16px;
    color: var(--text-primary);
    font-family: var(--font-display);
    font-weight: 600;
}

.content-main h3 {
    font-size: 24px;
    margin: 32px 0 16px;
    color: var(--text-primary);
    font-family: var(--font-display);
    font-weight: 600;
}

.content-main h4 {
    font-size: 19px;
    margin-bottom: 8px;
    color: var(--primary-color);
    font-weight: 600;
}

.content-main p {
    line-height: 1.7;
    margin-bottom: 24px;
    color: var(--text-secondary);
    font-size: 17px;
}

/* Tech Grid */
.tech-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: 24px;
    margin: 32px 0;
}

.tech-card {
    background: white;
    padding: 24px;
    border-radius: var(--radius);
    box-shadow: var(--shadow-sm);
    border: 1px solid var(--border);
    transition: var(--transition);
}

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

/* Achievement List */
.achievement-list {
    list-style: none;
    padding: 0;
    margin: 24px 0;
}

.achievement-list li {
    padding: 12px 0;
    border-bottom: 1px solid var(--border);
    position: relative;
    padding-left: 24px;
    color: var(--text-secondary);
}

.achievement-list li:before {
    content: '✓';
    position: absolute;
    left: 0;
    color: var(--primary-color);
    font-weight: bold;
}

/* Challenge Grid */
.challenge-grid,
.research-grid,
.quality-grid,
.threat-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
    gap: 24px;
    margin: 32px 0;
}

.challenge-card,
.research-item,
.quality-item,
.threat-item {
    background: var(--surface);
    padding: 24px;
    border-radius: var(--radius);
    border-left: 4px solid var(--primary-color);
}

/* Sidebar Styles */
.content-sidebar {
    display: flex;
    flex-direction: column;
    gap: 32px;
}

.sidebar-card {
    background: white;
    padding: 24px;
    border-radius: var(--radius);
    box-shadow: var(--shadow-sm);
    border: 1px solid var(--border);
}

.sidebar-card h3 {
    margin: 0 0 16px 0;
    font-size: 19px;
    color: var(--text-primary);
    font-family: var(--font-display);
    font-weight: 600;
}

/* Tech Tags */
.tech-tags {
    display: flex;
    flex-wrap: wrap;
    gap: 8px;
}

.tech-tag {
    background: var(--primary-color);
    color: white;
    padding: 4px 12px;
    border-radius: 20px;
    font-size: 13px;
    font-weight: 500;
}

/* Metrics */
.metric-item {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 12px 0;
    border-bottom: 1px solid var(--border);
}

.metric-item:last-child {
    border-bottom: none;
}

.metric-label {
    color: var(--text-secondary);
    font-size: 14px;
}

.metric-value {
    color: var(--primary-color);
    font-weight: 600;
}

/* Certification List */
.cert-list {
    list-style: none;
    padding: 0;
    margin: 0;
}

.cert-list li {
    padding: 8px 0;
    border-bottom: 1px solid var(--border);
    font-size: 14px;
    color: var(--text-secondary);
}

.cert-list li:last-child {
    border-bottom: none;
}

/* Code Container */
.code-container {
    background: #1a1a1a;
    border-radius: var(--radius);
    overflow: hidden;
    margin: 32px 0;
}

.code-container pre {
    margin: 0;
    padding: 32px;
    overflow-x: auto;
    font-family: 'Monaco', 'Menlo', 'Ubuntu Mono', monospace;
    font-size: 14px;
    line-height: 1.5;
    color: #f8f8f2;
}

.code-container code {
    background: none;
    padding: 0;
    border-radius: 0;
}

/* Architecture Diagram */
.architecture-diagram {
    background: white;
    border-radius: var(--radius);
    padding: 2rem;
    box-shadow: var(--shadow-sm);
    border: 1px solid var(--border);
    margin: 2rem 0;
}

.architecture-diagram svg {
    width: 100%;
    height: auto;
    max-width: 800px;
    margin: 0 auto;
    display: block;
}

/* Topic Navigation */
.topic-navigation {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: 24px;
    margin-top: 32px;
}

.topic-nav-card {
    background: white;
    padding: 24px;
    border-radius: var(--radius);
    box-shadow: var(--shadow-sm);
    border: 1px solid var(--border);
    text-decoration: none;
    color: inherit;
    transition: var(--transition);
}

.topic-nav-card:hover {
    transform: translateY(-4px);
    box-shadow: var(--shadow-md);
    text-decoration: none;
}

.topic-nav-card h3 {
    margin: 0 0 8px 0;
    color: var(--primary-color);
    font-size: 19px;
    font-family: var(--font-display);
    font-weight: 600;
}

.topic-nav-card p {
    margin: 0;
    color: var(--text-secondary);
    font-size: 14px;
}

/* Background Light Section */
.bg-light {
    background: var(--surface);
}

/* Footer */
.footer {
    background: var(--text-primary);
    color: white;
    padding: 40px 0;
    text-align: center;
}

.footer p {
    color: var(--text-light);
    font-size: 15px;
}

/* Responsive Design */
@media (max-width: 768px) {
    .nav-links {
        display: none;
    }
    
    .hero {
        padding: 100px 20px 60px;
    }
    
    .hero-visual {
        display: none;
    }
    
    .hero-cta {
        flex-direction: column;
        align-items: center;
    }
    
    .about-content {
        grid-template-columns: 1fr;
        gap: 40px;
    }
    
    .expertise-grid {
        grid-template-columns: 1fr;
    }
    
    .section-title {
        font-size: 36px;
    }
    
    .hero-title {
        font-size: 48px;
    }
    
    /* Topic page responsive */
    .content-grid {
        grid-template-columns: 1fr;
        gap: 32px;
    }
    
    .topic-stats {
        grid-template-columns: repeat(2, 1fr);
        gap: 16px;
    }
    
    .tech-grid,
    .challenge-grid,
    .research-grid,
    .quality-grid,
    .threat-grid {
        grid-template-columns: 1fr;
    }
    
    .topic-navigation {
        grid-template-columns: 1fr;
    }
    
    .code-container pre {
        padding: 16px;
        font-size: 13px;
    }
}

@media (max-width: 480px) {
    .container {
        padding: 0 16px;
    }
    
    .nav-container {
        padding: 0 16px;
    }
    
    .expertise-card {
        padding: 24px;
    }
    
    .hero-title {
        font-size: 36px;
    }
    
    .hero-subtitle {
        font-size: 19px;
    }
}

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

.fade-in {
    animation: fadeInUp 0.6s ease-out;
}

/* Smooth scrolling for Safari */
@media screen and (prefers-reduced-motion: no-preference) {
    html {
        scroll-behavior: smooth;
    }
}