/* ═══════════════════════════════════════════════════════════════════════════════
   CONSUMER EXPERIENCE RESEARCH - COMPREHENSIVE STYLESHEET
   Color Palette:
   - Electric Blue: #4DA3FF
   - Citrus Pop: #FFD55E
   - Leaf Green: #52D681
   - Purple Splash: #B490FF
   - Peach Pop: #FF9E8C
   - Coral (Female): #F26B6B
   - Teal (Male): #2AA8A1
   ═══════════════════════════════════════════════════════════════════════════════ */

/* ─────────────────────────────────────────────────────────────────────────────────
   CSS VARIABLES
   ───────────────────────────────────────────────────────────────────────────────── */
:root {
    /* Primary Color Palette */
    --electric-blue: #4DA3FF;
    --citrus-pop: #FFD55E;
    --leaf-green: #52D681;
    --purple-splash: #B490FF;
    --peach-pop: #FF9E8C;
    
    /* Gender Colors */
    --coral-female: #F26B6B;
    --teal-male: #2AA8A1;
    
    /* Neutral Colors */
    --dark: #1a1a2e;
    --dark-secondary: #16213e;
    --gray-900: #212529;
    --gray-800: #343a40;
    --gray-700: #495057;
    --gray-600: #6c757d;
    --gray-500: #adb5bd;
    --gray-400: #ced4da;
    --gray-300: #dee2e6;
    --gray-200: #e9ecef;
    --gray-100: #f8f9fa;
    --white: #ffffff;
    
    /* Semantic Colors */
    --success: #52D681;
    --warning: #FFD55E;
    --danger: #F26B6B;
    --info: #4DA3FF;
    
    /* Gradients */
    --gradient-primary: linear-gradient(135deg, #4DA3FF 0%, #B490FF 100%);
    --gradient-secondary: linear-gradient(135deg, #52D681 0%, #2AA8A1 100%);
    --gradient-warm: linear-gradient(135deg, #FFD55E 0%, #FF9E8C 100%);
    --gradient-cool: linear-gradient(135deg, #4DA3FF 0%, #2AA8A1 100%);
    --gradient-hero: linear-gradient(135deg, #1a1a2e 0%, #16213e 50%, #0f3460 100%);
    
    /* Typography */
    --font-primary: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
    --font-display: 'Playfair Display', Georgia, serif;
    
    /* Spacing */
    --space-xs: 0.25rem;
    --space-sm: 0.5rem;
    --space-md: 1rem;
    --space-lg: 1.5rem;
    --space-xl: 2rem;
    --space-2xl: 3rem;
    --space-3xl: 4rem;
    --space-4xl: 6rem;
    
    /* Border Radius */
    --radius-sm: 4px;
    --radius-md: 8px;
    --radius-lg: 12px;
    --radius-xl: 16px;
    --radius-2xl: 24px;
    --radius-full: 9999px;
    
    /* Shadows */
    --shadow-sm: 0 1px 2px 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);
    --shadow-xl: 0 20px 25px -5px rgba(0, 0, 0, 0.1), 0 10px 10px -5px rgba(0, 0, 0, 0.04);
    --shadow-2xl: 0 25px 50px -12px rgba(0, 0, 0, 0.25);
    --shadow-glow: 0 0 40px rgba(77, 163, 255, 0.3);
    
    /* Transitions */
    --transition-fast: 150ms ease;
    --transition-base: 250ms ease;
    --transition-slow: 400ms ease;
    --transition-smooth: 500ms cubic-bezier(0.4, 0, 0.2, 1);
    
    /* Z-index layers */
    --z-dropdown: 100;
    --z-sticky: 200;
    --z-fixed: 300;
    --z-modal-backdrop: 400;
    --z-modal: 500;
    --z-tooltip: 600;
}

/* ─────────────────────────────────────────────────────────────────────────────────
   RESET & BASE STYLES
   ───────────────────────────────────────────────────────────────────────────────── */
*, *::before, *::after {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

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

body {
    font-family: var(--font-primary);
    font-weight: 400;
    line-height: 1.6;
    color: var(--gray-800);
    background-color: var(--white);
    overflow-x: hidden;
}

/* Selection styling */
::selection {
    background: var(--electric-blue);
    color: var(--white);
}

/* Scrollbar styling */
::-webkit-scrollbar {
    width: 10px;
}

::-webkit-scrollbar-track {
    background: var(--gray-100);
}

::-webkit-scrollbar-thumb {
    background: var(--gray-400);
    border-radius: var(--radius-full);
}

::-webkit-scrollbar-thumb:hover {
    background: var(--gray-500);
}

/* ─────────────────────────────────────────────────────────────────────────────────
   TYPOGRAPHY
   ───────────────────────────────────────────────────────────────────────────────── */
h1, h2, h3, h4, h5, h6 {
    font-family: var(--font-primary);
    font-weight: 700;
    line-height: 1.2;
    color: var(--gray-900);
}

h1 { font-size: clamp(2rem, 5vw, 3.5rem); }
h2 { font-size: clamp(1.75rem, 4vw, 2.5rem); }
h3 { font-size: clamp(1.25rem, 3vw, 1.75rem); }
h4 { font-size: 1.25rem; }
h5 { font-size: 1.125rem; }
h6 { font-size: 1rem; }

p {
    margin-bottom: var(--space-md);
    color: var(--gray-700);
}

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

a:hover {
    color: var(--purple-splash);
}

strong, b {
    font-weight: 600;
}

/* ─────────────────────────────────────────────────────────────────────────────────
   LAYOUT
   ───────────────────────────────────────────────────────────────────────────────── */
.container {
    width: 100%;
    max-width: 1280px;
    margin: 0 auto;
    padding: 0 var(--space-lg);
}

.section {
    padding: var(--space-4xl) 0;
}

.section-alt {
    background-color: var(--gray-100);
}

.section-header {
    text-align: center;
    margin-bottom: var(--space-3xl);
}

.section-tag {
    display: inline-block;
    font-size: 0.75rem;
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 0.1em;
    color: var(--electric-blue);
    background: rgba(77, 163, 255, 0.1);
    padding: var(--space-xs) var(--space-md);
    border-radius: var(--radius-full);
    margin-bottom: var(--space-md);
}

.section-title {
    margin-bottom: var(--space-md);
}

.section-description {
    font-size: 1.125rem;
    color: var(--gray-600);
    max-width: 600px;
    margin: 0 auto;
}

/* ─────────────────────────────────────────────────────────────────────────────────
   NAVIGATION
   ───────────────────────────────────────────────────────────────────────────────── */
.navbar {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    z-index: var(--z-fixed);
    background: rgba(255, 255, 255, 0.95);
    backdrop-filter: blur(10px);
    border-bottom: 1px solid var(--gray-200);
    transition: all var(--transition-base);
}

.navbar.scrolled {
    box-shadow: var(--shadow-md);
}

.nav-container {
    display: flex;
    align-items: center;
    justify-content: space-between;
    max-width: 1400px;
    margin: 0 auto;
    padding: var(--space-md) var(--space-lg);
}

.nav-logo {
    display: flex;
    align-items: center;
    gap: var(--space-sm);
    font-weight: 700;
    font-size: 0.95rem;
    color: var(--gray-900);
}

.nav-logo i {
    color: var(--electric-blue);
    font-size: 1.25rem;
}

.nav-menu {
    display: flex;
    align-items: center;
    gap: var(--space-xs);
    list-style: none;
}

.nav-link {
    position: relative;
    padding: var(--space-sm) var(--space-md);
    font-size: 0.875rem;
    font-weight: 500;
    color: var(--gray-700);
    border-radius: var(--radius-md);
    transition: all var(--transition-fast);
}

.nav-link:hover,
.nav-link.active {
    color: var(--electric-blue);
    background: rgba(77, 163, 255, 0.1);
}

.nav-toggle {
    display: none;
    flex-direction: column;
    gap: 5px;
    background: none;
    border: none;
    cursor: pointer;
    padding: var(--space-sm);
}

.nav-toggle span {
    display: block;
    width: 24px;
    height: 2px;
    background: var(--gray-800);
    border-radius: var(--radius-full);
    transition: all var(--transition-base);
}

/* Progress Bar */
.progress-container {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    height: 3px;
    z-index: calc(var(--z-fixed) + 1);
    background: transparent;
}

.progress-bar {
    height: 100%;
    width: 0%;
    background: var(--gradient-primary);
    transition: width 100ms ease;
}

/* ─────────────────────────────────────────────────────────────────────────────────
   HERO SECTION
   ───────────────────────────────────────────────────────────────────────────────── */
.hero-section {
    position: relative;
    min-height: 100vh;
    display: flex;
    align-items: center;
    justify-content: center;
    overflow: hidden;
    background: var(--gradient-hero);
    padding-top: 80px;
}

.hero-background {
    position: absolute;
    inset: 0;
    overflow: hidden;
}

.hero-shapes {
    position: absolute;
    inset: 0;
}

.shape {
    position: absolute;
    border-radius: 50%;
    filter: blur(60px);
    opacity: 0.5;
    animation: float 20s ease-in-out infinite;
}

.shape-1 {
    width: 400px;
    height: 400px;
    background: var(--electric-blue);
    top: -10%;
    right: -5%;
    animation-delay: 0s;
}

.shape-2 {
    width: 300px;
    height: 300px;
    background: var(--purple-splash);
    bottom: 10%;
    left: -5%;
    animation-delay: -5s;
}

.shape-3 {
    width: 250px;
    height: 250px;
    background: var(--leaf-green);
    top: 40%;
    right: 20%;
    animation-delay: -10s;
}

.shape-4 {
    width: 200px;
    height: 200px;
    background: var(--citrus-pop);
    bottom: 30%;
    right: 40%;
    animation-delay: -15s;
}

@keyframes float {
    0%, 100% { transform: translate(0, 0) scale(1); }
    25% { transform: translate(30px, -30px) scale(1.05); }
    50% { transform: translate(-20px, 20px) scale(0.95); }
    75% { transform: translate(20px, 30px) scale(1.02); }
}

.hero-content {
    position: relative;
    z-index: 1;
    text-align: center;
    max-width: 900px;
    padding: var(--space-xl);
}

.hero-badge {
    display: inline-flex;
    align-items: center;
    gap: var(--space-sm);
    font-size: 0.875rem;
    font-weight: 600;
    color: var(--citrus-pop);
    background: rgba(255, 213, 94, 0.15);
    padding: var(--space-sm) var(--space-lg);
    border-radius: var(--radius-full);
    margin-bottom: var(--space-xl);
    border: 1px solid rgba(255, 213, 94, 0.3);
}

.hero-title {
    font-size: clamp(2.5rem, 6vw, 4rem);
    font-weight: 800;
    color: var(--white);
    margin-bottom: var(--space-lg);
    line-height: 1.1;
}

.gradient-text {
    background: linear-gradient(135deg, var(--electric-blue), var(--purple-splash), var(--peach-pop));
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.hero-subtitle {
    font-size: 1.25rem;
    color: var(--gray-400);
    margin-bottom: var(--space-2xl);
    max-width: 700px;
    margin-left: auto;
    margin-right: auto;
}

/* Hero Stats */
.hero-stats {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: var(--space-lg);
    margin-bottom: var(--space-2xl);
}

.stat-card {
    display: flex;
    align-items: center;
    gap: var(--space-md);
    background: rgba(255, 255, 255, 0.05);
    backdrop-filter: blur(10px);
    border: 1px solid rgba(255, 255, 255, 0.1);
    padding: var(--space-lg);
    border-radius: var(--radius-xl);
    transition: all var(--transition-base);
}

.stat-card:hover {
    background: rgba(255, 255, 255, 0.1);
    transform: translateY(-5px);
    box-shadow: var(--shadow-glow);
}

.stat-icon {
    width: 50px;
    height: 50px;
    display: flex;
    align-items: center;
    justify-content: center;
    background: var(--gradient-primary);
    border-radius: var(--radius-lg);
    font-size: 1.25rem;
    color: var(--white);
}

.stat-info {
    text-align: left;
}

.stat-number {
    display: block;
    font-size: 1.75rem;
    font-weight: 800;
    color: var(--white);
    line-height: 1;
}

.stat-label {
    font-size: 0.875rem;
    color: var(--gray-400);
}

/* Hero CTA */
.hero-cta {
    display: flex;
    gap: var(--space-md);
    justify-content: center;
}

.btn {
    display: inline-flex;
    align-items: center;
    gap: var(--space-sm);
    padding: var(--space-md) var(--space-xl);
    font-size: 1rem;
    font-weight: 600;
    border-radius: var(--radius-lg);
    cursor: pointer;
    transition: all var(--transition-base);
    border: 2px solid transparent;
}

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

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

.btn-outline {
    background: transparent;
    color: var(--white);
    border-color: rgba(255, 255, 255, 0.3);
}

.btn-outline:hover {
    background: rgba(255, 255, 255, 0.1);
    border-color: rgba(255, 255, 255, 0.5);
    color: var(--white);
}

/* Scroll Indicator */
.scroll-indicator {
    position: absolute;
    bottom: var(--space-xl);
    left: 50%;
    transform: translateX(-50%);
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: var(--space-sm);
    color: var(--gray-500);
    font-size: 0.75rem;
    animation: bounce 2s ease-in-out infinite;
}

.mouse {
    width: 24px;
    height: 38px;
    border: 2px solid var(--gray-500);
    border-radius: 12px;
    position: relative;
}

.wheel {
    width: 4px;
    height: 8px;
    background: var(--gray-500);
    border-radius: var(--radius-full);
    position: absolute;
    top: 6px;
    left: 50%;
    transform: translateX(-50%);
    animation: scroll 2s ease-in-out infinite;
}

@keyframes bounce {
    0%, 100% { transform: translateX(-50%) translateY(0); }
    50% { transform: translateX(-50%) translateY(10px); }
}

@keyframes scroll {
    0%, 100% { opacity: 1; transform: translateX(-50%) translateY(0); }
    50% { opacity: 0.3; transform: translateX(-50%) translateY(10px); }
}

/* ─────────────────────────────────────────────────────────────────────────────────
   OVERVIEW SECTION
   ───────────────────────────────────────────────────────────────────────────────── */
.overview-grid {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: var(--space-xl);
}

.overview-card {
    background: var(--white);
    border-radius: var(--radius-xl);
    padding: var(--space-xl);
    box-shadow: var(--shadow-md);
    border: 1px solid var(--gray-200);
    transition: all var(--transition-base);
}

.overview-card:hover {
    transform: translateY(-5px);
    box-shadow: var(--shadow-xl);
}

.overview-icon {
    width: 60px;
    height: 60px;
    display: flex;
    align-items: center;
    justify-content: center;
    border-radius: var(--radius-lg);
    font-size: 1.5rem;
    color: var(--white);
    margin-bottom: var(--space-lg);
}

.overview-card h3 {
    margin-bottom: var(--space-md);
    font-size: 1.25rem;
}

.overview-card p {
    color: var(--gray-600);
    font-size: 0.9375rem;
}

.overview-list {
    list-style: none;
    padding: 0;
}

.overview-list li {
    position: relative;
    padding-left: var(--space-lg);
    margin-bottom: var(--space-sm);
    color: var(--gray-600);
    font-size: 0.9375rem;
}

.overview-list li::before {
    content: '';
    position: absolute;
    left: 0;
    top: 8px;
    width: 6px;
    height: 6px;
    background: var(--electric-blue);
    border-radius: 50%;
}

/* ─────────────────────────────────────────────────────────────────────────────────
   METHODOLOGY SECTION
   ───────────────────────────────────────────────────────────────────────────────── */
.methodology-content {
    display: grid;
    grid-template-columns: 1.2fr 1fr;
    gap: var(--space-2xl);
    align-items: start;
}

.methodology-left {
    display: flex;
    flex-direction: column;
    gap: var(--space-lg);
}

.method-card {
    display: flex;
    gap: var(--space-lg);
    background: var(--white);
    padding: var(--space-lg);
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow-sm);
    border: 1px solid var(--gray-200);
    transition: all var(--transition-base);
}

.method-card:hover {
    box-shadow: var(--shadow-md);
    border-color: var(--electric-blue);
}

.method-number {
    flex-shrink: 0;
    width: 48px;
    height: 48px;
    display: flex;
    align-items: center;
    justify-content: center;
    background: var(--gradient-primary);
    color: var(--white);
    font-weight: 700;
    font-size: 1.125rem;
    border-radius: var(--radius-lg);
}

.method-content h4 {
    margin-bottom: var(--space-xs);
    font-size: 1rem;
}

.method-content p {
    font-size: 0.8125rem;
    color: var(--gray-600);
    margin: 0;
    line-height: 1.5;
}

.methodology-right {
    display: flex;
    flex-direction: column;
    gap: var(--space-lg);
}

.specs-card {
    background: var(--white);
    padding: var(--space-xl);
    border-radius: var(--radius-xl);
    box-shadow: var(--shadow-md);
    border: 1px solid var(--gray-200);
}

.specs-card h4 {
    display: flex;
    align-items: center;
    gap: var(--space-sm);
    margin-bottom: var(--space-lg);
    font-size: 1.125rem;
    color: var(--gray-900);
}

.specs-card h4 i {
    color: var(--electric-blue);
}

.specs-grid {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: var(--space-md);
}

.spec-item {
    display: flex;
    flex-direction: column;
    gap: var(--space-xs);
}

.spec-label {
    font-size: 0.75rem;
    font-weight: 500;
    text-transform: uppercase;
    letter-spacing: 0.05em;
    color: var(--gray-500);
}

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

.analysis-flow {
    background: var(--white);
    padding: var(--space-xl);
    border-radius: var(--radius-xl);
    box-shadow: var(--shadow-md);
    border: 1px solid var(--gray-200);
}

.analysis-flow h4 {
    display: flex;
    align-items: center;
    gap: var(--space-sm);
    margin-bottom: var(--space-lg);
    font-size: 1.125rem;
    color: var(--gray-900);
}

.analysis-flow h4 i {
    color: var(--purple-splash);
}

.flow-items {
    display: flex;
    flex-direction: column;
    gap: var(--space-md);
    position: relative;
    padding-left: var(--space-lg);
}

.flow-items::before {
    content: '';
    position: absolute;
    left: 5px;
    top: 0;
    bottom: 0;
    width: 2px;
    background: linear-gradient(to bottom, var(--electric-blue), var(--purple-splash), var(--leaf-green));
    border-radius: var(--radius-full);
}

.flow-item {
    display: flex;
    align-items: center;
    gap: var(--space-md);
    font-size: 0.9375rem;
    font-weight: 500;
    color: var(--gray-700);
}

.flow-dot {
    width: 12px;
    height: 12px;
    background: var(--electric-blue);
    border-radius: 50%;
    position: relative;
    z-index: 1;
    margin-left: -22px;
    box-shadow: 0 0 0 4px var(--white);
}

.flow-item:nth-child(2) .flow-dot { background: var(--citrus-pop); }
.flow-item:nth-child(3) .flow-dot { background: var(--leaf-green); }
.flow-item:nth-child(4) .flow-dot { background: var(--purple-splash); }
.flow-item:nth-child(5) .flow-dot { background: var(--peach-pop); }
.flow-item:nth-child(6) .flow-dot { background: var(--teal-male); }

/* ─────────────────────────────────────────────────────────────────────────────────
   NAVIGATION CARDS
   ───────────────────────────────────────────────────────────────────────────────── */
.nav-cards-grid {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: var(--space-lg);
}

.nav-card {
    display: flex;
    flex-direction: column;
    background: var(--white);
    border-radius: var(--radius-xl);
    padding: var(--space-xl);
    box-shadow: var(--shadow-md);
    border: 1px solid var(--gray-200);
    text-decoration: none;
    transition: all var(--transition-base);
    position: relative;
    overflow: hidden;
}

.nav-card:hover {
    transform: translateY(-8px);
    box-shadow: var(--shadow-xl);
    border-color: var(--electric-blue);
}

.nav-card-icon {
    width: 56px;
    height: 56px;
    display: flex;
    align-items: center;
    justify-content: center;
    border-radius: var(--radius-lg);
    font-size: 1.5rem;
    color: var(--white);
    margin-bottom: var(--space-lg);
}

.nav-card-content h3 {
    font-size: 1.125rem;
    margin-bottom: var(--space-sm);
    color: var(--gray-900);
}

.nav-card-content p {
    font-size: 0.875rem;
    color: var(--gray-600);
    margin: 0;
    line-height: 1.5;
}

.nav-card-arrow {
    margin-top: auto;
    padding-top: var(--space-md);
    color: var(--electric-blue);
    font-size: 1.125rem;
    transition: transform var(--transition-base);
}

.nav-card:hover .nav-card-arrow {
    transform: translateX(5px);
}

/* ─────────────────────────────────────────────────────────────────────────────────
   LOADING PLACEHOLDER
   ───────────────────────────────────────────────────────────────────────────────── */
.loading-placeholder {
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    padding: var(--space-4xl);
    background: var(--white);
    border-radius: var(--radius-xl);
    border: 2px dashed var(--gray-300);
}

.loading-placeholder i {
    font-size: 2rem;
    color: var(--electric-blue);
    margin-bottom: var(--space-md);
}

.loading-placeholder p {
    color: var(--gray-500);
    margin: 0;
}

/* ─────────────────────────────────────────────────────────────────────────────────
   FOOTER
   ───────────────────────────────────────────────────────────────────────────────── */
.footer {
    background: var(--dark);
    color: var(--gray-400);
    padding: var(--space-3xl) 0 var(--space-xl);
}

.footer-content {
    display: grid;
    grid-template-columns: 2fr 1fr 1fr;
    gap: var(--space-2xl);
    padding-bottom: var(--space-2xl);
    border-bottom: 1px solid rgba(255, 255, 255, 0.1);
}

.footer-brand h3 {
    display: flex;
    align-items: center;
    gap: var(--space-sm);
    color: var(--white);
    margin-bottom: var(--space-md);
}

.footer-brand h3 i {
    color: var(--electric-blue);
}

.footer-brand p {
    color: var(--gray-500);
    font-size: 0.9375rem;
}

.footer-links h4,
.footer-stats h4 {
    color: var(--white);
    font-size: 1rem;
    margin-bottom: var(--space-lg);
}

.footer-links ul {
    list-style: none;
}

.footer-links li {
    margin-bottom: var(--space-sm);
}

.footer-links a {
    color: var(--gray-500);
    font-size: 0.9375rem;
    transition: color var(--transition-fast);
}

.footer-links a:hover {
    color: var(--electric-blue);
}

.footer-stat {
    margin-bottom: var(--space-md);
}

.footer-stat-value {
    display: block;
    font-size: 1.5rem;
    font-weight: 700;
    color: var(--electric-blue);
}

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

.footer-bottom {
    text-align: center;
    padding-top: var(--space-xl);
}

.footer-bottom p {
    color: var(--gray-600);
    font-size: 0.875rem;
    margin: 0;
}

/* ─────────────────────────────────────────────────────────────────────────────────
   BACK TO TOP BUTTON
   ───────────────────────────────────────────────────────────────────────────────── */
.back-to-top {
    position: fixed;
    bottom: var(--space-xl);
    right: var(--space-xl);
    width: 48px;
    height: 48px;
    display: flex;
    align-items: center;
    justify-content: center;
    background: var(--gradient-primary);
    color: var(--white);
    border: none;
    border-radius: var(--radius-full);
    cursor: pointer;
    opacity: 0;
    visibility: hidden;
    transform: translateY(20px);
    transition: all var(--transition-base);
    box-shadow: var(--shadow-lg);
    z-index: var(--z-sticky);
}

.back-to-top.visible {
    opacity: 1;
    visibility: visible;
    transform: translateY(0);
}

.back-to-top:hover {
    transform: translateY(-5px);
    box-shadow: var(--shadow-xl);
}

/* ─────────────────────────────────────────────────────────────────────────────────
   RESPONSIVE DESIGN
   ───────────────────────────────────────────────────────────────────────────────── */
@media (max-width: 1200px) {
    .nav-cards-grid {
        grid-template-columns: repeat(2, 1fr);
    }
}

@media (max-width: 992px) {
    .nav-toggle {
        display: flex;
    }
    
    .nav-menu {
        position: fixed;
        top: 70px;
        left: 0;
        right: 0;
        background: var(--white);
        flex-direction: column;
        padding: var(--space-lg);
        gap: var(--space-xs);
        border-bottom: 1px solid var(--gray-200);
        box-shadow: var(--shadow-lg);
        transform: translateY(-100%);
        opacity: 0;
        visibility: hidden;
        transition: all var(--transition-base);
    }
    
    .nav-menu.active {
        transform: translateY(0);
        opacity: 1;
        visibility: visible;
    }
    
    .hero-stats {
        grid-template-columns: repeat(2, 1fr);
    }
    
    .overview-grid {
        grid-template-columns: 1fr;
    }
    
    .methodology-content {
        grid-template-columns: 1fr;
    }
    
    .footer-content {
        grid-template-columns: 1fr;
        text-align: center;
    }
}

@media (max-width: 768px) {
    .hero-stats {
        grid-template-columns: 1fr;
    }
    
    .stat-card {
        justify-content: center;
    }
    
    .hero-cta {
        flex-direction: column;
    }
    
    .btn {
        width: 100%;
        justify-content: center;
    }
    
    .nav-cards-grid {
        grid-template-columns: 1fr;
    }
    
    .specs-grid {
        grid-template-columns: 1fr;
    }
}

@media (max-width: 576px) {
    .section {
        padding: var(--space-2xl) 0;
    }
    
    .container {
        padding: 0 var(--space-md);
    }
    
    .hero-content {
        padding: var(--space-md);
    }
    
    .hero-badge {
        font-size: 0.75rem;
        padding: var(--space-xs) var(--space-md);
    }
}

/* ─────────────────────────────────────────────────────────────────────────────────
   UTILITY CLASSES
   ───────────────────────────────────────────────────────────────────────────────── */
.text-center { text-align: center; }
.text-left { text-align: left; }
.text-right { text-align: right; }

.mt-1 { margin-top: var(--space-md); }
.mt-2 { margin-top: var(--space-lg); }
.mt-3 { margin-top: var(--space-xl); }
.mt-4 { margin-top: var(--space-2xl); }

.mb-1 { margin-bottom: var(--space-md); }
.mb-2 { margin-bottom: var(--space-lg); }
.mb-3 { margin-bottom: var(--space-xl); }
.mb-4 { margin-bottom: var(--space-2xl); }

.hidden { display: none !important; }
.visible { display: block !important; }

/* Animation utilities */
.fade-in {
    animation: fadeIn 0.6s ease forwards;
}

@keyframes fadeIn {
    from {
        opacity: 0;
        transform: translateY(20px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

.slide-in-left {
    animation: slideInLeft 0.6s ease forwards;
}

@keyframes slideInLeft {
    from {
        opacity: 0;
        transform: translateX(-30px);
    }
    to {
        opacity: 1;
        transform: translateX(0);
    }
}

.slide-in-right {
    animation: slideInRight 0.6s ease forwards;
}

@keyframes slideInRight {
    from {
        opacity: 0;
        transform: translateX(30px);
    }
    to {
        opacity: 1;
        transform: translateX(0);
    }
}