/* ========================================
   许曦瑶个人简历 - 样式表
   ======================================== */

/* CSS Variables */
:root {
    --primary: #6366f1;
    --primary-dark: #4f46e5;
    --secondary: #8b5cf6;
    --accent: #06b6d4;
    --dark: #0f172a;
    --dark-light: #1e293b;
    --gray-50: #f8fafc;
    --gray-100: #f1f5f9;
    --gray-200: #e2e8f0;
    --gray-300: #cbd5e1;
    --gray-400: #94a3b8;
    --gray-500: #64748b;
    --gray-600: #475569;
    --gray-700: #334155;
    --gray-800: #1e293b;
    --gray-900: #0f172a;
    --white: #ffffff;
    --amber: #f59e0b;
    --rose: #f43f5e;
    --emerald: #10b981;
    
    --shadow-sm: 0 1px 2px 0 rgb(0 0 0 / 0.05);
    --shadow: 0 1px 3px 0 rgb(0 0 0 / 0.1), 0 1px 2px -1px rgb(0 0 0 / 0.1);
    --shadow-md: 0 4px 6px -1px rgb(0 0 0 / 0.1), 0 2px 4px -2px rgb(0 0 0 / 0.1);
    --shadow-lg: 0 10px 15px -3px rgb(0 0 0 / 0.1), 0 4px 6px -4px rgb(0 0 0 / 0.1);
    --shadow-xl: 0 20px 25px -5px rgb(0 0 0 / 0.1), 0 8px 10px -6px rgb(0 0 0 / 0.1);
    
    --radius-sm: 0.375rem;
    --radius: 0.5rem;
    --radius-md: 0.75rem;
    --radius-lg: 1rem;
    --radius-xl: 1.5rem;
    --radius-2xl: 2rem;
    --radius-full: 9999px;
    
    --transition-fast: 150ms ease;
    --transition: 300ms ease;
}

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

html {
    font-size: 16px;
    scroll-behavior: smooth;
    -webkit-text-size-adjust: 100%;
}

@media (max-width: 375px) {
    html { font-size: 14px; }
}

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, 'Noto Sans SC', sans-serif;
    line-height: 1.6;
    color: var(--gray-800);
    background: var(--white);
    overflow-x: hidden;
    -webkit-font-smoothing: antialiased;
}

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

ul {
    list-style: none;
}

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

/* Container */
.container {
    width: 100%;
    max-width: 900px;
    margin: 0 auto;
    padding: 0 1rem;
}

@media (min-width: 640px) {
    .container {
        padding: 0 1.5rem;
    }
}

/* ========================================
   Navigation
   ======================================== */
.nav {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    z-index: 1000;
    background: rgba(255, 255, 255, 0.95);
    backdrop-filter: blur(10px);
    border-bottom: 1px solid var(--gray-200);
}

.nav-container {
    max-width: 900px;
    margin: 0 auto;
    padding: 0.75rem 1rem;
    display: flex;
    align-items: center;
    justify-content: space-between;
}

@media (min-width: 640px) {
    .nav-container {
        padding: 1rem 1.5rem;
    }
}

.nav-brand {
    display: flex;
    align-items: center;
    gap: 0.75rem;
}

.nav-logo {
    width: 2rem;
    height: 2rem;
    background: linear-gradient(135deg, var(--primary), var(--secondary));
    border-radius: var(--radius-md);
    display: flex;
    align-items: center;
    justify-content: center;
    color: var(--white);
    font-weight: 700;
    font-size: 0.875rem;
}

@media (min-width: 640px) {
    .nav-logo {
        width: 2.5rem;
        height: 2.5rem;
        font-size: 1rem;
    }
}

.nav-title {
    font-weight: 600;
    color: var(--gray-900);
    font-size: 1rem;
}

@media (min-width: 640px) {
    .nav-title {
        font-size: 1.125rem;
    }
}

.nav-links {
    display: none;
}

@media (min-width: 768px) {
    .nav-links {
        display: flex;
        align-items: center;
        gap: 0.25rem;
    }
}

.nav-link {
    padding: 0.5rem 0.75rem;
    font-size: 0.875rem;
    color: var(--gray-600);
    border-radius: var(--radius);
    transition: all var(--transition-fast);
}

.nav-link:hover {
    color: var(--primary);
    background: rgba(99, 102, 241, 0.05);
}

.btn-download {
    display: none;
}

@media (min-width: 768px) {
    .btn-download {
        display: inline-flex;
        align-items: center;
        gap: 0.5rem;
        padding: 0.5rem 1rem;
        background: linear-gradient(135deg, var(--primary), var(--secondary));
        color: var(--white);
        font-size: 0.875rem;
        font-weight: 500;
        border-radius: var(--radius-md);
        transition: all var(--transition-fast);
    }
    
    .btn-download:hover {
        transform: translateY(-1px);
        box-shadow: 0 4px 12px rgba(99, 102, 241, 0.3);
    }
}

.nav-menu-btn {
    width: 2.5rem;
    height: 2.5rem;
    display: flex;
    align-items: center;
    justify-content: center;
    color: var(--gray-600);
    border-radius: var(--radius);
    cursor: pointer;
    transition: all var(--transition-fast);
}

.nav-menu-btn:hover {
    color: var(--primary);
    background: rgba(99, 102, 241, 0.05);
}

@media (min-width: 768px) {
    .nav-menu-btn {
        display: none;
    }
}

/* Mobile Menu */
.mobile-menu {
    position: absolute;
    top: 100%;
    left: 0;
    right: 0;
    background: var(--white);
    border-bottom: 1px solid var(--gray-200);
    padding: 0.5rem;
    box-shadow: var(--shadow-lg);
    display: none;
}

.mobile-menu.active {
    display: block;
}

.mobile-link {
    display: block;
    padding: 0.875rem 1rem;
    color: var(--gray-700);
    font-size: 0.9375rem;
    border-radius: var(--radius);
    transition: all var(--transition-fast);
}

.mobile-link:hover {
    color: var(--primary);
    background: rgba(99, 102, 241, 0.05);
}

.mobile-download {
    display: flex;
    align-items: center;
    gap: 0.75rem;
    margin-top: 0.5rem;
    padding: 0.875rem 1rem;
    background: linear-gradient(135deg, var(--primary), var(--secondary));
    color: var(--white);
    font-weight: 500;
    border-radius: var(--radius);
}

/* ========================================
   Hero Section with Animated Background
   ======================================== */
.hero {
    position: relative;
    padding: 6rem 0 3rem;
    background: linear-gradient(135deg, #f8fafc 0%, #e2e8f0 100%);
    overflow: hidden;
}

/* Animated Background Shapes */
.hero::before,
.hero::after {
    content: '';
    position: absolute;
    border-radius: 50%;
    filter: blur(60px);
    opacity: 0.5;
    animation: float 20s infinite ease-in-out;
}

.hero::before {
    width: 400px;
    height: 400px;
    background: linear-gradient(135deg, #6366f1 0%, #8b5cf6 100%);
    top: -100px;
    right: -100px;
    animation-delay: 0s;
}

.hero::after {
    width: 300px;
    height: 300px;
    background: linear-gradient(135deg, #06b6d4 0%, #22d3ee 100%);
    bottom: -50px;
    left: -50px;
    animation-delay: -10s;
}

/* Additional floating orbs */
.hero-orb {
    position: absolute;
    border-radius: 50%;
    filter: blur(40px);
    opacity: 0.3;
    animation: float 15s infinite ease-in-out;
    z-index: 0;
}

.hero-orb-1 {
    width: 200px;
    height: 200px;
    background: #f59e0b;
    top: 50%;
    left: 20%;
    animation-delay: -5s;
}

.hero-orb-2 {
    width: 150px;
    height: 150px;
    background: #ec4899;
    top: 30%;
    right: 30%;
    animation-delay: -8s;
}

@keyframes float {
    0%, 100% {
        transform: translate(0, 0) scale(1);
    }
    25% {
        transform: translate(30px, -30px) scale(1.1);
    }
    50% {
        transform: translate(-20px, 20px) scale(0.95);
    }
    75% {
        transform: translate(20px, 10px) scale(1.05);
    }
}

/* Animated gradient overlay */
.hero-bg {
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: 
        radial-gradient(circle at 20% 80%, rgba(99, 102, 241, 0.1) 0%, transparent 50%),
        radial-gradient(circle at 80% 20%, rgba(6, 182, 212, 0.1) 0%, transparent 50%),
        radial-gradient(circle at 40% 40%, rgba(245, 158, 11, 0.05) 0%, transparent 40%);
    animation: bg-shift 15s ease-in-out infinite;
    z-index: 0;
}

@keyframes bg-shift {
    0%, 100% {
        transform: scale(1);
        opacity: 1;
    }
    50% {
        transform: scale(1.1);
        opacity: 0.8;
    }
}

@media (min-width: 640px) {
    .hero {
        padding: 8rem 0 4rem;
    }
}
    position: absolute;
    inset: 0;
    background: 
        radial-gradient(circle at 20% 50%, rgba(99, 102, 241, 0.1) 0%, transparent 50%),
        radial-gradient(circle at 80% 20%, rgba(139, 92, 246, 0.1) 0%, transparent 50%);
    pointer-events: none;
}

.hero-content {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 1.5rem;
    text-align: center;
}

@media (min-width: 640px) {
    .hero-content {
        flex-direction: row;
        text-align: left;
        gap: 2.5rem;
    }
}

/* Avatar */
.hero-avatar {
    position: relative;
    flex-shrink: 0;
}

.avatar-ring {
    width: 7rem;
    height: 7rem;
    border-radius: var(--radius-full);
    padding: 0.25rem;
    background: linear-gradient(135deg, var(--primary), var(--secondary), var(--accent));
    position: relative;
}

@media (min-width: 640px) {
    .avatar-ring {
        width: 9rem;
        height: 9rem;
        padding: 0.375rem;
    }
}

.avatar-img {
    width: 100%;
    height: 100%;
    border-radius: var(--radius-full);
    object-fit: cover;
    border: 3px solid var(--white);
}

.online-indicator {
    position: absolute;
    bottom: 0.5rem;
    right: 0.5rem;
    width: 1.25rem;
    height: 1.25rem;
    background: var(--emerald);
    border: 3px solid var(--white);
    border-radius: var(--radius-full);
}

@media (min-width: 640px) {
    .online-indicator {
        width: 1.5rem;
        height: 1.5rem;
        bottom: 0.75rem;
        right: 0.75rem;
    }
}

/* Hero Info */
.hero-info {
    flex: 1;
}

.hero-name {
    font-size: 2rem;
    font-weight: 700;
    color: var(--gray-900);
    margin-bottom: 0.25rem;
    background: linear-gradient(135deg, var(--primary), var(--secondary));
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

@media (min-width: 640px) {
    .hero-name {
        font-size: 2.5rem;
    }
}

.hero-title {
    font-size: 1.125rem;
    color: var(--gray-500);
    margin-bottom: 1rem;
}

@media (min-width: 640px) {
    .hero-title {
        font-size: 1.25rem;
    }
}

.hero-meta {
    display: grid;
    gap: 0.75rem;
    margin-bottom: 1.5rem;
}

@media (min-width: 640px) {
    .hero-meta {
        grid-template-columns: repeat(2, 1fr);
    }
}

.meta-item {
    display: flex;
    align-items: center;
    gap: 0.75rem;
    color: var(--gray-600);
    font-size: 0.9375rem;
}

.meta-item i {
    width: 1.25rem;
    color: var(--primary);
}

/* Buttons */
.hero-actions {
    display: flex;
    flex-wrap: wrap;
    gap: 0.75rem;
    justify-content: center;
}

@media (min-width: 640px) {
    .hero-actions {
        justify-content: flex-start;
    }
}

.btn {
    display: inline-flex;
    align-items: center;
    gap: 0.5rem;
    padding: 0.625rem 1.25rem;
    font-size: 0.875rem;
    font-weight: 500;
    border-radius: var(--radius-md);
    cursor: pointer;
    transition: all var(--transition-fast);
    border: none;
}

.btn-primary {
    background: linear-gradient(135deg, var(--primary), var(--secondary));
    color: var(--white);
}

.btn-primary:hover {
    transform: translateY(-1px);
    box-shadow: 0 4px 12px rgba(99, 102, 241, 0.3);
}

.btn-secondary {
    background: var(--white);
    color: var(--gray-700);
    border: 1px solid var(--gray-200);
}

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

.btn-accent {
    background: linear-gradient(135deg, #f59e0b, #f97316);
    color: var(--white);
}

.btn-accent:hover {
    transform: translateY(-1px);
    box-shadow: 0 4px 12px rgba(245, 158, 11, 0.3);
}

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

.btn-white:hover {
    transform: translateY(-1px);
    box-shadow: var(--shadow-lg);
}

/* ========================================
   Section Base
   ======================================== */
.section {
    padding: 2.5rem 0;
}

@media (min-width: 640px) {
    .section {
        padding: 3.5rem 0;
    }
}

.section-dark {
    background: linear-gradient(135deg, var(--dark) 0%, var(--dark-light) 100%);
    color: var(--white);
}

.section-gray {
    background: var(--gray-50);
}

.section-header {
    display: flex;
    align-items: center;
    gap: 0.75rem;
    margin-bottom: 1.5rem;
}

@media (min-width: 640px) {
    .section-header {
        margin-bottom: 2rem;
    }
}

.section-header.light .section-title {
    color: var(--white);
}

.section-icon {
    width: 2.5rem;
    height: 2.5rem;
    background: linear-gradient(135deg, var(--primary), var(--secondary));
    border-radius: var(--radius-lg);
    display: flex;
    align-items: center;
    justify-content: center;
    color: var(--white);
    font-size: 1rem;
}

@media (min-width: 640px) {
    .section-icon {
        width: 3rem;
        height: 3rem;
        font-size: 1.25rem;
    }
}

.section-title {
    font-size: 1.375rem;
    font-weight: 700;
    color: var(--gray-900);
}

@media (min-width: 640px) {
    .section-title {
        font-size: 1.75rem;
    }
}

/* ========================================
   Timeline (Education)
   ======================================== */
.timeline {
    position: relative;
    padding-left: 1.5rem;
}

@media (min-width: 640px) {
    .timeline {
        padding-left: 2rem;
    }
}

.timeline::before {
    content: '';
    position: absolute;
    left: 0.375rem;
    top: 0;
    bottom: 0;
    width: 2px;
    background: linear-gradient(180deg, var(--primary), var(--secondary));
}

.timeline-item {
    position: relative;
    padding-bottom: 1.5rem;
}

.timeline-item:last-child {
    padding-bottom: 0;
}

.timeline-marker {
    position: absolute;
    left: -1.5rem;
    top: 0.25rem;
    width: 0.75rem;
    height: 0.75rem;
    background: var(--white);
    border: 2px solid var(--primary);
    border-radius: var(--radius-full);
}

@media (min-width: 640px) {
    .timeline-marker {
        left: -2rem;
        width: 1rem;
        height: 1rem;
        border-width: 3px;
    }
}

.timeline-content {
    background: var(--white);
    border: 1px solid var(--gray-200);
    border-radius: var(--radius-lg);
    padding: 1rem;
}

@media (min-width: 640px) {
    .timeline-content {
        padding: 1.25rem;
    }
}

.timeline-header {
    display: flex;
    flex-wrap: wrap;
    align-items: flex-start;
    justify-content: space-between;
    gap: 0.5rem;
    margin-bottom: 0.75rem;
}

.timeline-title h3 {
    font-size: 1rem;
    font-weight: 600;
    color: var(--gray-900);
}

@media (min-width: 640px) {
    .timeline-title h3 {
        font-size: 1.125rem;
    }
}

.timeline-badge {
    display: inline-block;
    padding: 0.25rem 0.625rem;
    background: linear-gradient(135deg, var(--primary), var(--secondary));
    color: var(--white);
    font-size: 0.75rem;
    font-weight: 500;
    border-radius: var(--radius);
    margin-left: 0.5rem;
}

.timeline-badge.secondary {
    background: linear-gradient(135deg, var(--secondary), var(--accent));
}

.timeline-date {
    font-size: 0.875rem;
    color: var(--gray-500);
    background: var(--gray-100);
    padding: 0.25rem 0.75rem;
    border-radius: var(--radius);
}

.timeline-body {
    color: var(--gray-600);
    font-size: 0.9375rem;
}

.timeline-body p {
    margin-bottom: 0.5rem;
}

.timeline-body p:last-child {
    margin-bottom: 0;
}

.timeline-body strong {
    color: var(--gray-800);
}

.timeline-body .major {
    font-weight: 600;
    color: var(--gray-800);
}

.timeline-stats {
    display: flex;
    flex-wrap: wrap;
    gap: 0.5rem;
    margin-top: 0.75rem;
    padding-top: 0.75rem;
    border-top: 1px solid var(--gray-200);
}

.stat-tag {
    padding: 0.375rem 0.875rem;
    background: var(--gray-100);
    color: var(--gray-700);
    font-size: 0.875rem;
    border-radius: var(--radius);
}

.stat-tag.highlight {
    background: rgba(99, 102, 241, 0.1);
    color: var(--primary);
    font-weight: 500;
}

/* ========================================
   Research Section
   ======================================== */
.research-card {
    background: rgba(255, 255, 255, 0.05);
    border: 1px solid rgba(255, 255, 255, 0.1);
    border-radius: var(--radius-xl);
    padding: 1.25rem;
}

@media (min-width: 640px) {
    .research-card {
        padding: 1.75rem;
    }
}

.research-header {
    margin-bottom: 1.25rem;
    padding-bottom: 1rem;
    border-bottom: 1px solid rgba(255, 255, 255, 0.1);
}

.research-title h3 {
    font-size: 1.0625rem;
    font-weight: 600;
    color: var(--white);
    margin-bottom: 0.5rem;
}

@media (min-width: 640px) {
    .research-title h3 {
        font-size: 1.25rem;
    }
}

.research-date {
    font-size: 0.875rem;
    color: rgba(255, 255, 255, 0.6);
}

.research-content {
    display: grid;
    gap: 1rem;
}

@media (min-width: 640px) {
    .research-content {
        grid-template-columns: repeat(3, 1fr);
    }
}

.research-item {
    background: rgba(255, 255, 255, 0.05);
    border: 1px solid rgba(255, 255, 255, 0.1);
    border-radius: var(--radius-lg);
    padding: 1rem;
}

.research-icon {
    width: 2.5rem;
    height: 2.5rem;
    background: rgba(99, 102, 241, 0.2);
    border-radius: var(--radius-md);
    display: flex;
    align-items: center;
    justify-content: center;
    color: var(--white);
    margin-bottom: 0.75rem;
}

.research-text h4 {
    font-size: 0.9375rem;
    font-weight: 600;
    color: var(--white);
    margin-bottom: 0.5rem;
}

.research-text p {
    font-size: 0.875rem;
    color: rgba(255, 255, 255, 0.7);
    line-height: 1.6;
}

/* ========================================
   Experience Section
   ======================================== */
.experience-list {
    display: grid;
    gap: 1rem;
}

.experience-card {
    background: var(--white);
    border: 1px solid var(--gray-200);
    border-radius: var(--radius-lg);
    padding: 1rem;
    transition: all var(--transition-fast);
}

@media (min-width: 640px) {
    .experience-card {
        padding: 1.25rem;
    }
}

.experience-card:hover {
    box-shadow: var(--shadow-md);
}

.experience-header {
    display: flex;
    flex-wrap: wrap;
    align-items: flex-start;
    justify-content: space-between;
    gap: 0.75rem;
    margin-bottom: 0.875rem;
    padding-bottom: 0.75rem;
    border-bottom: 1px solid var(--gray-100);
}

.experience-company {
    display: flex;
    align-items: center;
    gap: 0.875rem;
}

.company-icon {
    width: 2.5rem;
    height: 2.5rem;
    background: linear-gradient(135deg, var(--amber), #f97316);
    border-radius: var(--radius-md);
    display: flex;
    align-items: center;
    justify-content: center;
    color: var(--white);
    font-size: 1rem;
    flex-shrink: 0;
}

.company-icon.alt {
    background: linear-gradient(135deg, var(--rose), #ec4899);
}

.company-info h3 {
    font-size: 0.9375rem;
    font-weight: 600;
    color: var(--gray-900);
}

.company-info .position {
    font-size: 0.875rem;
    color: var(--primary);
    font-weight: 500;
}

.experience-date {
    font-size: 0.875rem;
    color: var(--gray-500);
    background: var(--gray-100);
    padding: 0.25rem 0.75rem;
    border-radius: var(--radius);
}

.experience-card ul {
    padding-left: 1.25rem;
}

.experience-card li {
    position: relative;
    padding-left: 1.25rem;
    margin-bottom: 0.5rem;
    font-size: 0.9375rem;
    color: var(--gray-600);
    line-height: 1.6;
}

.experience-card li:last-child {
    margin-bottom: 0;
}

.experience-card li::before {
    content: '';
    position: absolute;
    left: 0;
    top: 0.5rem;
    width: 6px;
    height: 6px;
    background: var(--primary);
    border-radius: var(--radius-full);
}

/* ========================================
   Skills Section
   ======================================== */
.skills-grid {
    display: grid;
    gap: 1rem;
}

@media (min-width: 640px) {
    .skills-grid {
        grid-template-columns: repeat(3, 1fr);
    }
}

.skill-card {
    background: var(--white);
    border: 1px solid var(--gray-200);
    border-radius: var(--radius-lg);
    padding: 1.25rem;
    transition: all var(--transition-fast);
}

.skill-card:hover {
    box-shadow: var(--shadow-md);
}

.skill-icon {
    width: 2.5rem;
    height: 2.5rem;
    background: linear-gradient(135deg, var(--primary), var(--secondary));
    border-radius: var(--radius-md);
    display: flex;
    align-items: center;
    justify-content: center;
    color: var(--white);
    margin-bottom: 0.875rem;
}

.skill-icon.secondary {
    background: linear-gradient(135deg, var(--secondary), var(--rose));
}

.skill-icon.accent {
    background: linear-gradient(135deg, var(--accent), #22d3ee);
}

.skill-content h3 {
    font-size: 1rem;
    font-weight: 600;
    color: var(--gray-900);
    margin-bottom: 0.5rem;
}

.skill-content p {
    font-size: 0.9375rem;
    color: var(--gray-600);
    line-height: 1.6;
}

/* ========================================
   Contact Section
   ======================================== */
.contact-section {
    padding: 2rem 0 3rem;
    background: linear-gradient(135deg, var(--primary), var(--secondary));
}

@media (min-width: 640px) {
    .contact-section {
        padding: 3rem 0 4rem;
    }
}

.contact-card {
    background: rgba(255, 255, 255, 0.1);
    backdrop-filter: blur(10px);
    border: 1px solid rgba(255, 255, 255, 0.2);
    border-radius: var(--radius-xl);
    padding: 1.5rem;
    text-align: center;
    color: var(--white);
}

@media (min-width: 640px) {
    .contact-card {
        padding: 2.5rem;
    }
}

.contact-card h2 {
    font-size: 1.375rem;
    font-weight: 700;
    margin-bottom: 0.5rem;
}

@media (min-width: 640px) {
    .contact-card h2 {
        font-size: 1.75rem;
    }
}

.contact-card p {
    font-size: 1rem;
    opacity: 0.9;
    margin-bottom: 1.25rem;
}

.contact-actions {
    display: flex;
    flex-wrap: wrap;
    justify-content: center;
    gap: 0.75rem;
}

/* ========================================
   Footer
   ======================================== */
.footer {
    padding: 1.5rem 0;
    background: var(--gray-900);
    text-align: center;
}

.footer p {
    color: var(--gray-500);
    font-size: 0.875rem;
}

/* ========================================
   Back to Top
   ======================================== */
.back-to-top {
    position: fixed;
    bottom: 1.5rem;
    right: 1.5rem;
    width: 2.75rem;
    height: 2.75rem;
    background: linear-gradient(135deg, var(--primary), var(--secondary));
    color: var(--white);
    border: none;
    border-radius: var(--radius-full);
    cursor: pointer;
    opacity: 0;
    visibility: hidden;
    transition: all var(--transition-fast);
    z-index: 100;
    box-shadow: 0 4px 12px rgba(99, 102, 241, 0.3);
}

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

.back-to-top:hover {
    transform: translateY(-2px);
    box-shadow: 0 6px 16px rgba(99, 102, 241, 0.4);
}

/* ========================================
   Utilities
   ======================================== */
.sr-only {
    position: absolute;
    width: 1px;
    height: 1px;
    padding: 0;
    margin: -1px;
    overflow: hidden;
    clip: rect(0, 0, 0, 0);
    white-space: nowrap;
    border: 0;
}

/* Focus states */
a:focus-visible,
button:focus-visible {
    outline: 2px solid var(--primary);
    outline-offset: 2px;
}

/* Print styles */
@media print {
    .nav,
    .back-to-top,
    .hero-actions {
        display: none;
    }
    
    body {
        background: white;
    }
    
    .hero {
        padding-top: 2rem;
    }
    
    .section {
        page-break-inside: avoid;
    }
}