/* ================================
   ENHANCED DESIGN SYSTEM v2.0
   Современный дизайн с glassmorphism,
   продвинутыми анимациями и микро-взаимодействиями
   ================================ */

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

/* Enhanced Custom Properties with fluid design */
:root {
    /* Color System - Расширенная палитра */
    --primary-50: #eef2ff;
    --primary-100: #e0e7ff;
    --primary-500: #6366f1;
    --primary-600: #5145cd;
    --primary-700: #4338ca;
    --primary-900: #312e81;
    
    --accent-400: #f59e0b;
    --accent-500: #d97706;
    --accent-600: #b45309;
    
    /* Glass morphism colors */
    --glass-bg: rgba(255, 255, 255, 0.08);
    --glass-border: rgba(255, 255, 255, 0.12);
    --glass-backdrop: rgba(15, 23, 42, 0.7);
    
    /* Enhanced backgrounds */
    --bg-primary: #0a0f1c;
    --bg-secondary: #1e2749;
    --bg-tertiary: #2d3561;
    --bg-gradient-1: linear-gradient(135deg, #667eea 0%, #764ba2 50%, #f093fb 100%);
    --bg-gradient-2: linear-gradient(135deg, #4facfe 0%, #00f2fe 100%);
    --bg-gradient-3: linear-gradient(135deg, #43e97b 0%, #38f9d7 100%);
    
    /* Typography scale - Fluid typography */
    --font-xs: clamp(0.75rem, 0.7rem + 0.25vw, 0.875rem);
    --font-sm: clamp(0.875rem, 0.8rem + 0.375vw, 1rem);
    --font-base: clamp(1rem, 0.9rem + 0.5vw, 1.125rem);
    --font-lg: clamp(1.125rem, 1rem + 0.625vw, 1.375rem);
    --font-xl: clamp(1.25rem, 1.1rem + 0.75vw, 1.75rem);
    --font-2xl: clamp(1.5rem, 1.3rem + 1vw, 2.25rem);
    --font-3xl: clamp(1.875rem, 1.6rem + 1.375vw, 3rem);
    --font-4xl: clamp(2.25rem, 1.9rem + 1.75vw, 4rem);
    
    /* Spacing system — УМЕНЬШЕНО НА 30% */
    --space-xs: clamp(0.175rem, 0.14rem + 0.175vw, 0.35rem);
    --space-sm: clamp(0.35rem, 0.28rem + 0.35vw, 0.7rem);
    --space-md: clamp(0.7rem, 0.56rem + 0.7vw, 1.4rem);
    --space-lg: clamp(1.05rem, 0.84rem + 1.05vw, 2.1rem);
    --space-xl: clamp(1.4rem, 1.12rem + 1.4vw, 2.8rem);
    --space-2xl: clamp(2.1rem, 1.68rem + 2.1vw, 4.2rem);
    
    /* Enhanced shadows with multiple layers */
    --shadow-glow: 0 0 20px rgba(99, 102, 241, 0.3);
    --shadow-soft: 0 2px 4px rgba(0, 0, 0, 0.1), 0 8px 16px rgba(0, 0, 0, 0.1);
    --shadow-medium: 0 4px 8px rgba(0, 0, 0, 0.12), 0 16px 32px rgba(0, 0, 0, 0.12);
    --shadow-large: 0 8px 16px rgba(0, 0, 0, 0.15), 0 32px 64px rgba(0, 0, 0, 0.15);
    --shadow-glass: 0 8px 32px rgba(31, 38, 135, 0.37);
    
    /* Animation timing functions */
    --ease-out-expo: cubic-bezier(0.16, 1, 0.3, 1);
    --ease-in-out-quart: cubic-bezier(0.76, 0, 0.24, 1);
    --ease-spring: cubic-bezier(0.34, 1.56, 0.64, 1);
    
    /* Border radius system */
    --radius-sm: 0.5rem;
    --radius-md: 0.75rem;
    --radius-lg: 1rem;
    --radius-xl: 1.5rem;
    --radius-2xl: 2rem;
    --radius-full: 9999px;

    /* Text color variables */
    --text-primary: #e5e7eb;
    --text-secondary: #cbd5e1;
    --text-muted: #94a3b8;
}

/* Enhanced typography with variable fonts */
@import url('https://fonts.googleapis.com/css2?family=Inter:wght@100..900&display=swap');

/* Screen reader improvements */
.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;
}

.sr-only:focus {
    position: static;
    width: auto;
    height: auto;
    padding: var(--space-sm);
    margin: 0;
    overflow: visible;
    clip: auto;
    white-space: normal;
    background: var(--primary-600);
    color: white;
    border-radius: var(--radius-md);
    text-decoration: none;
    z-index: 10000;
}

/* Base HTML and Body with improved performance */
html {
    scroll-behavior: smooth;
    text-rendering: optimizeLegibility;
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
}

body {
    font-family: 'Inter', system-ui, -apple-system, sans-serif;
    font-variation-settings: 'wght' 400;
    background: var(--bg-primary);
    color: var(--text-primary);
    line-height: 1.6;
    overflow-x: hidden;
    position: relative;
}

/* Advanced animated background with particles effect */
.background-animation {
    position: fixed;
    top: 0;
    left: 0;
    width: 100vw;
    height: 100vh;
    z-index: -2;
    background: 
        radial-gradient(circle at 20% 80%, rgba(120, 119, 198, 0.3) 0%, transparent 50%),
        radial-gradient(circle at 80% 20%, rgba(255, 119, 198, 0.3) 0%, transparent 50%),
        radial-gradient(circle at 40% 40%, rgba(120, 255, 198, 0.3) 0%, transparent 50%),
        linear-gradient(135deg, var(--bg-primary) 0%, var(--bg-secondary) 50%, var(--bg-tertiary) 100%);
    animation: backgroundShift 20s ease infinite;
    will-change: background-position;
}

/* Floating particles background layer */
.background-animation::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background-image: 
        radial-gradient(2px 2px at 20% 30%, rgba(255, 255, 255, 0.2), transparent),
        radial-gradient(2px 2px at 40% 70%, rgba(99, 102, 241, 0.3), transparent),
        radial-gradient(1px 1px at 90% 40%, rgba(255, 119, 198, 0.4), transparent);
    background-size: 200px 200px, 300px 300px, 150px 150px;
    animation: floatingParticles 30s linear infinite;
}

@keyframes backgroundShift {
    0%, 100% { background-position: 0% 50%; }
    50% { background-position: 100% 50%; }
}

@keyframes floatingParticles {
    0% { transform: translateY(0px) rotate(0deg); }
    100% { transform: translateY(-100vh) rotate(360deg); }
}

/* Enhanced header with glassmorphism */
.header {
    padding: var(--space-lg) 0;
    text-align: center;
    position: relative;
    backdrop-filter: blur(24px) saturate(180%);
    background: var(--glass-bg);
    border-bottom: 1px solid var(--glass-border);
    border-radius: 0 0 var(--radius-2xl) var(--radius-2xl);
    margin: 0 var(--space-md);
    margin-bottom: var(--space-md);
}

/* Navigation styling */
.nav-link {
    color: var(--text-secondary);
    text-decoration: none;
    padding: var(--space-xs) var(--space-sm);
    border-radius: var(--radius-md);
    transition: all 0.3s ease;
    margin: 0 var(--space-xs);
}

.nav-link:hover,
.nav-link.active {
    color: var(--primary-500);
    background: rgba(99, 102, 241, 0.1);
}

/* Language selector styling */
#langSelect {
    appearance: none;
    background: rgba(255, 255, 255, 0.18);
    color: var(--text-primary);
    border: 1px solid rgba(255, 255, 255, 0.24);
    backdrop-filter: blur(12px) saturate(160%);
    border-radius: var(--radius-full);
    padding: 0.5rem 2.25rem 0.5rem 0.875rem;
    margin-top: var(--space-sm);
    margin-left: var(--space-sm);
    font: inherit;
    line-height: 1.2;
    cursor: pointer;
    position: relative;
}

#langSelect:focus-visible {
    outline: 3px solid var(--primary-500);
    outline-offset: 2px;
}

/* Custom dropdown arrow */
#langSelect {
    background-image: linear-gradient(45deg, transparent 50%, var(--text-primary) 50%),
                      linear-gradient(135deg, var(--text-primary) 50%, transparent 50%);
    background-position: right 0.8rem top 1.05rem, right 0.5rem top 1.05rem;
    background-size: 8px 8px, 8px 8px;
    background-repeat: no-repeat;
}

#langSelect:hover {
    background: rgba(255, 255, 255, 0.24);
    border-color: rgba(255, 255, 255, 0.3);
}

.header::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: var(--bg-gradient-1);
    opacity: 0.05;
    border-radius: inherit;
    z-index: -1;
}

.logo {
    font-size: var(--font-4xl);
    font-variation-settings: 'wght' 800;
    background: linear-gradient(135deg, #a78bfa 0%, #60a5fa 100%);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
    margin-bottom: var(--space-sm);
    display: inline-block;
    position: relative;
    transition: transform 0.3s var(--ease-out-expo);
    text-shadow: 0 2px 18px rgba(99, 102, 241, 0.45);
}

.logo:hover {
    transform: scale(1.05);
    animation: logoGlow 2s ease-in-out infinite alternate;
}

@keyframes logoGlow {
    from { filter: drop-shadow(0 0 5px rgba(99, 102, 241, 0.3)); }
    to { filter: drop-shadow(0 0 20px rgba(99, 102, 241, 0.6)); }
}

.tagline {
    color: var(--text-secondary);
    font-size: var(--font-lg);
    max-width: 600px;
    margin: 0 auto;
    font-variation-settings: 'wght' 400;
    opacity: 0.9;
}

/* Enhanced container with better responsive behavior */
.container {
    max-width: min(1200px, 100vw - 2rem);
    margin: 0 auto;
    padding: 0 var(--space-md);
}

/* Revolutionary quote card with advanced glassmorphism */
.quote-section {
    padding: var(--space-2xl) 0;
    text-align: center;
    position: relative;
}

.quote-card {
    background: var(--glass-bg);
    backdrop-filter: blur(40px) saturate(180%);
    border: 1px solid var(--glass-border);
    border-radius: var(--radius-2xl);
    padding: var(--space-xl) var(--space-lg);
    margin: var(--space-lg) auto;
    max-width: 800px;
    box-shadow: var(--shadow-glass);
    position: relative;
    overflow: hidden;
    transition: all 0.6s var(--ease-out-expo);
    isolation: isolate;
}

/* Multiple gradient overlays for depth */
.quote-card::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: var(--bg-gradient-1);
    opacity: 0.03;
    z-index: -1;
    transition: opacity 0.6s ease;
}

.quote-card::after {
    content: '';
    position: absolute;
    inset: -1px;
    background: var(--bg-gradient-1);
    border-radius: inherit;
    z-index: -2;
    opacity: 0;
    transition: opacity 0.6s ease;
}

.quote-card:hover {
    transform: translateY(-8px) scale(1.02);
    box-shadow: 
        var(--shadow-large),
        0 0 60px rgba(99, 102, 241, 0.2);
}

.quote-card:hover::before {
    opacity: 0.08;
}

.quote-card:hover::after {
    opacity: 0.1;
}

/* Enhanced quote typography with better spacing */
.quote-text {
    font-size: var(--font-2xl);
    font-variation-settings: 'wght' 300;
    line-height: 1.7;
    margin-bottom: var(--space-lg);
    color: var(--text-primary);
    position: relative;
    font-style: italic;
    letter-spacing: 0.01em;
}

/* Improved quote marks with gradient and glow */
.quote-text::before,
.quote-text::after {
    content: '"';
    font-size: 4rem;
    color: var(--text-primary);
    position: absolute;
    line-height: 1;
    font-variation-settings: 'wght' 700;
    text-shadow: 0 4px 18px rgba(229, 231, 235, 0.18);
}

.quote-text::before {
    top: -1rem;
    left: -1.5rem;
}

.quote-text::after {
    bottom: -2.5rem;
    right: -1rem;
}

.quote-author {
    font-size: var(--font-lg);
    color: var(--text-secondary);
    font-style: italic;
    font-variation-settings: 'wght' 500;
    position: relative;
}

.quote-author::before {
    content: '— ';
    color: var(--primary-500);
}

/* Advanced loading animation */
.loading {
    display: inline-block;
    width: 40px;
    height: 40px;
    border: 3px solid transparent;
    border-radius: 50%;
    border-top: 3px solid var(--primary-500);
    animation: 
        spin 1s linear infinite,
        pulse 2s ease-in-out infinite;
    position: relative;
}

.loading::after {
    content: '';
    position: absolute;
    inset: 6px;
    border: 2px solid transparent;
    border-top: 2px solid var(--accent-400);
    border-radius: 50%;
    animation: spin 1.5s linear infinite reverse;
}

@keyframes spin {
    to { transform: rotate(360deg); }
}

@keyframes pulse {
    0%, 100% { opacity: 1; transform: scale(1); }
    50% { opacity: 0.7; transform: scale(1.1); }
}

/* Revolutionary button system with micro-interactions */
.controls {
    display: flex;
    gap: var(--space-md);
    justify-content: center;
    flex-wrap: wrap;
    margin: var(--space-xl) 0;
}

.btn {
    padding: var(--space-md) var(--space-lg);
    border: none;
    border-radius: var(--radius-xl);
    font-size: var(--font-base);
    font-variation-settings: 'wght' 600;
    cursor: pointer;
    transition: all 0.4s var(--ease-out-expo);
    text-decoration: none;
    display: inline-flex;
    align-items: center;
    gap: var(--space-sm);
    position: relative;
    overflow: hidden;
    background: transparent;
    isolation: isolate;
    letter-spacing: 0.025em;
}

/* Advanced button shine effect */
.btn::before {
    content: '';
    position: absolute;
    top: 0;
    left: -100%;
    width: 100%;
    height: 100%;
    background: linear-gradient(
        90deg, 
        transparent, 
        rgba(255, 255, 255, 0.2), 
        transparent
    );
    transition: left 0.6s var(--ease-out-expo);
    z-index: 1;
}

.btn:hover::before {
    left: 100%;
}

/* Focus states with improved accessibility */
.btn:focus-visible {
    outline: 3px solid var(--primary-500);
    outline-offset: 3px;
    box-shadow: 0 0 0 6px rgba(99, 102, 241, 0.2);
}

/* Primary button with enhanced gradient */
.btn-primary {
    background: var(--bg-gradient-1);
    color: white;
    box-shadow: var(--shadow-medium);
    border: 1px solid rgba(255, 255, 255, 0.1);
}

.btn-primary:hover {
    transform: translateY(-3px) scale(1.05);
    box-shadow: var(--shadow-large), var(--shadow-glow);
    background: var(--bg-gradient-2);
}

.btn-primary:active {
    transform: translateY(-1px) scale(1.02);
}

/* Secondary button with glassmorphism */
.btn-secondary {
    background: var(--glass-bg);
    color: var(--text-primary);
    border: 1px solid var(--glass-border);
    backdrop-filter: blur(20px);
}

.btn-secondary:hover {
    background: rgba(255, 255, 255, 0.12);
    transform: translateY(-3px);
    box-shadow: var(--shadow-medium);
    border-color: rgba(255, 255, 255, 0.2);
}

/* Enhanced features section */
.features {
    padding: var(--space-2xl) 0;
    background: var(--glass-bg);
    backdrop-filter: blur(20px);
    position: relative;
    overflow: hidden;
}

.features::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: var(--bg-gradient-1);
    opacity: 0.02;
    z-index: -1;
}

.section-title {
    text-align: center;
    font-size: var(--font-3xl);
    font-variation-settings: 'wght' 700;
    margin-bottom: var(--space-md);
    color: #eaf2ff;
    text-shadow: 0 2px 14px rgba(99, 102, 241, 0.35);
}

.section-description {
    text-align: center;
    color: var(--text-secondary);
    margin-bottom: var(--space-xl);
    max-width: 600px;
    margin-left: auto;
    margin-right: auto;
    font-size: var(--font-lg);
    line-height: 1.6;
}

/* Advanced grid with better responsive behavior */
.features-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(min(300px, 100%), 1fr));
    gap: var(--space-lg);
    margin-top: var(--space-xl);
}

/* Revolutionary feature cards */
.feature-card {
    background: var(--glass-bg);
    backdrop-filter: blur(20px);
    padding: var(--space-lg);
    border-radius: var(--radius-xl);
    border: 1px solid var(--glass-border);
    transition: all 0.5s var(--ease-out-expo);
    position: relative;
    overflow: hidden;
    isolation: isolate;
}

.feature-card::before {
    content: '';
    position: absolute;
    inset: 0;
    background: var(--bg-gradient-1);
    opacity: 0;
    transition: opacity 0.5s ease;
    z-index: -1;
}

.feature-card:hover {
    transform: translateY(-8px) scale(1.02);
    box-shadow: var(--shadow-large);
    border-color: rgba(255, 255, 255, 0.2);
}

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

/* Enhanced feature icons with gradient backgrounds */
.feature-icon {
    width: 70px;
    height: 70px;
    background: var(--bg-gradient-1);
    border-radius: var(--radius-lg);
    display: flex;
    align-items: center;
    justify-content: center;
    margin-bottom: var(--space-md);
    font-size: 1.75rem;
    position: relative;
    transition: all 0.4s var(--ease-spring);
    box-shadow: var(--shadow-soft);
}

.feature-card:hover .feature-icon {
    transform: scale(1.1) rotate(5deg);
    box-shadow: var(--shadow-medium), var(--shadow-glow);
}

.feature-title {
    font-size: var(--font-xl);
    font-variation-settings: 'wght' 600;
    margin-bottom: var(--space-md);
    color: var(--text-primary);
}

.feature-description {
    color: var(--text-secondary);
    line-height: 1.7;
    font-size: var(--font-base);
}

/* Authors and quotes grids */
.authors-grid,
.quotes-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(min(320px, 100%), 1fr));
    gap: var(--space-lg);
}

.author-card {
    cursor: pointer;
}

.author-card.feature-card .feature-icon {
    font-size: 1.5rem;
}

/* Articles grid and cards */
.articles-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(min(320px, 100%), 1fr));
    gap: var(--space-lg);
    margin-top: var(--space-xl);
}

.article-card {
    background: var(--glass-bg);
    backdrop-filter: blur(24px) saturate(180%);
    border: 1px solid var(--glass-border);
    border-radius: var(--radius-2xl);
    padding: var(--space-lg);
    box-shadow: var(--shadow-glass);
    transition: transform 0.4s var(--ease-out-expo), box-shadow 0.4s var(--ease-out-expo);
}

.article-card:hover {
    transform: translateY(-6px);
    box-shadow: var(--shadow-large);
}

.article-title {
    font-size: var(--font-xl);
    font-variation-settings: 'wght' 650;
    margin-bottom: var(--space-sm);
}

.article-meta {
    color: var(--text-muted);
    font-size: var(--font-sm);
    margin-bottom: var(--space-sm);
}

.article-excerpt {
    color: var(--text-secondary);
    font-size: var(--font-base);
    line-height: 1.7;
}

.article-excerpt ul {
    margin-left: var(--space-lg);
}

.article-excerpt li {
    margin-bottom: var(--space-xs);
}

/* Enhanced notification system */
.notification {
    position: fixed;
    top: var(--space-md);
    right: var(--space-md);
    background: var(--glass-bg);
    backdrop-filter: blur(20px);
    color: var(--text-primary);
    padding: var(--space-md) var(--space-lg);
    border-radius: var(--radius-xl);
    border: 1px solid var(--glass-border);
    box-shadow: var(--shadow-large);
    transform: translateX(400px);
    transition: transform 0.6s var(--ease-out-expo);
    z-index: 10000;
    max-width: 350px;
}

.notification.show {
    transform: translateX(0);
}

.notification::before {
    content: '';
    position: absolute;
    inset: 0;
    background: var(--bg-gradient-1);
    opacity: 0.1;
    border-radius: inherit;
    z-index: -1;
}

/* Enhanced footer */
.footer {
    padding: var(--space-xl) 0;
    text-align: center;
    border-top: 1px solid var(--glass-border);
    background: var(--glass-bg);
    backdrop-filter: blur(20px);
    position: relative;
}

.footer-content {
    color: var(--text-muted);
    margin-bottom: var(--space-md);
    font-size: var(--font-base);
}

.footer-links {
    display: flex;
    justify-content: center;
    gap: var(--space-lg);
    flex-wrap: wrap;
}

.footer-link {
    color: var(--text-secondary);
    text-decoration: none;
    transition: all 0.3s ease;
    cursor: pointer;
    background: transparent;
    border: none;
    font-size: inherit;
    padding: var(--space-xs) var(--space-sm);
    border-radius: var(--radius-md);
    position: relative;
}

.footer-link:hover,
.footer-link:focus-visible {
    color: var(--primary-500);
    background: rgba(99, 102, 241, 0.1);
    transform: translateY(-2px);
}

/* Enhanced modal system */
.modal-overlay {
    position: fixed;
    inset: 0;
    background: var(--glass-backdrop);
    backdrop-filter: blur(8px);
    display: flex;
    align-items: center;
    justify-content: center;
    z-index: 10000;
    opacity: 0;
    visibility: hidden;
    transition: all 0.4s var(--ease-out-expo);
}

.modal-overlay.active {
    opacity: 1;
    visibility: visible;
}

.modal {
    background: var(--glass-bg);
    backdrop-filter: blur(40px);
    border-radius: var(--radius-2xl);
    border: 1px solid var(--glass-border);
    max-width: min(600px, 90vw);
    max-height: 80vh;
    overflow-y: auto;
    padding: var(--space-xl);
    position: relative;
    transform: translateY(20px) scale(0.95);
    transition: transform 0.4s var(--ease-out-expo);
    box-shadow: var(--shadow-large);
}

.modal-overlay.active .modal {
    transform: translateY(0) scale(1);
}

.modal-close {
    position: absolute;
    top: var(--space-md);
    right: var(--space-md);
    background: rgba(255, 255, 255, 0.1);
    border: none;
    color: var(--text-secondary);
    font-size: 1.5rem;
    cursor: pointer;
    width: 36px;
    height: 36px;
    display: flex;
    align-items: center;
    justify-content: center;
    border-radius: var(--radius-full);
    transition: all 0.3s ease;
    backdrop-filter: blur(10px);
}

.modal-close:hover,
.modal-close:focus-visible {
    background: rgba(255, 255, 255, 0.2);
    color: var(--text-primary);
    transform: scale(1.1);
}

.modal-title {
    font-size: var(--font-2xl);
    font-variation-settings: 'wght' 600;
    margin-bottom: var(--space-lg);
    color: var(--text-primary);
    text-align: center;
}

.modal-content {
    color: var(--text-secondary);
    line-height: 1.7;
    font-size: var(--font-base);
}

.modal-content p {
    margin-bottom: var(--space-md);
}

.modal-content h3 {
    color: var(--text-primary);
    margin: var(--space-lg) 0 var(--space-md) 0;
    font-variation-settings: 'wght' 600;
}

.modal-content ul {
    margin: var(--space-md) 0;
    padding-left: var(--space-lg);
}

.modal-content li {
    margin-bottom: var(--space-sm);
}

/* Enhanced VK button integration */
.social-section {
    padding: var(--space-sm) 0 var(--space-xs) 0;
    background: transparent;
    backdrop-filter: none;
    border-bottom: none;
    position: relative;
}

.vk-community-block {
    display: flex;
    justify-content: center;
    align-items: center;
}

.vk-button {
    display: inline-flex;
    align-items: center;
    gap: var(--space-sm);
    padding: var(--space-md) var(--space-lg);
    background: linear-gradient(135deg, rgba(70,128,194,0.85) 0%, rgba(81,129,184,0.85) 100%);
    color: white;
    text-decoration: none;
    border-radius: var(--radius-xl);
    font-variation-settings: 'wght' 600;
    font-size: var(--font-base);
    transition: all 0.4s var(--ease-out-expo);
    box-shadow: var(--shadow-medium);
    position: relative;
    overflow: hidden;
    isolation: isolate;
}

.vk-button::before {
    content: '';
    position: absolute;
    top: 0;
    left: -100%;
    width: 100%;
    height: 100%;
    background: linear-gradient(90deg, transparent, rgba(255, 255, 255, 0.3), transparent);
    transition: left 0.6s var(--ease-out-expo);
    z-index: 1;
}

.vk-button:hover::before {
    left: 100%;
}

.vk-button:hover {
    transform: translateY(-3px) scale(1.05);
    box-shadow: var(--shadow-large), 0 8px 20px rgba(70, 128, 194, 0.4);
    background: linear-gradient(135deg, #5181B8 0%, #4680C2 100%);
}

.vk-button:focus-visible {
    outline: 3px solid #4680C2;
    outline-offset: 3px;
}

.vk-button:active {
    transform: translateY(-1px) scale(1.02);
}

.vk-icon {
    width: 24px;
    height: 24px;
    flex-shrink: 0;
    z-index: 2;
    position: relative;
}

.vk-text {
    font-variation-settings: 'wght' 600;
    letter-spacing: 0.025em;
    z-index: 2;
    position: relative;
}

.vk-platform {
    font-size: var(--font-sm);
    opacity: 0.9;
    font-variation-settings: 'wght' 500;
    z-index: 2;
    position: relative;
}

/* Advanced responsive design */
@media (max-width: 768px) {
    .container {
        padding: 0 var(--space-sm);
    }

    .header {
        margin: 0 var(--space-sm);
        border-radius: 0 0 var(--radius-xl) var(--radius-xl);
    }

    .quote-card {
        padding: var(--space-lg) var(--space-md);
        margin: var(--space-md) auto;
    }

    .quote-text {
        font-size: var(--font-xl);
    }

    .controls {
        flex-direction: column;
        align-items: center;
        gap: var(--space-sm);
    }

    .btn {
        width: 100%;
        max-width: 280px;
        justify-content: center;
    }

    .features-grid {
        grid-template-columns: 1fr;
        gap: var(--space-md);
    }
    
    .footer-links {
        flex-direction: column;
        gap: var(--space-sm);
    }
    
    .social-section {
        padding: var(--space-md) 0 var(--space-sm) 0;
    }
    
    .vk-button {
        padding: var(--space-sm) var(--space-md);
        font-size: var(--font-sm);
        gap: var(--space-xs);
    }
    
    .vk-text {
        display: none;
    }
    
    .vk-platform::before {
        content: 'Наше сообщество в ';
    }
}

@media (max-width: 480px) {
    .vk-button {
        padding: var(--space-sm);
        font-size: var(--font-xs);
    }
    
    .vk-icon {
        width: 20px;
        height: 20px;
    }
}

/* Enhanced accessibility and performance */
@media (prefers-reduced-motion: reduce) {
    *,
    *::before,
    *::after {
        animation-duration: 0.01ms !important;
        animation-iteration-count: 1 !important;
        transition-duration: 0.01ms !important;
        scroll-behavior: auto !important;
    }
    
    .background-animation {
        animation: none;
    }
    
    .background-animation::before {
        animation: none;
    }
}

/* High contrast mode support */
@media (prefers-contrast: high) {
    :root {
        --text-primary: #ffffff;
        --text-secondary: #e5e5e5;
        --bg-primary: #000000;
        --border-color: #ffffff;
        --glass-border: rgba(255, 255, 255, 0.3);
    }
}

/* Print optimizations */
@media print {
    .background-animation,
    .controls,
    .notification,
    .modal-overlay,
    .social-section,
    .header::before,
    .quote-card::before,
    .quote-card::after {
        display: none !important;
    }
    
    .quote-card {
        box-shadow: none;
        border: 2px solid #333;
        background: white;
        color: black;
    }
    
    .quote-text {
        color: black;
    }
    
    .quote-author {
        color: #666;
    }
}

/* Performance optimizations */
.quote-card,
.feature-card,
.btn,
.vk-button {
    contain: layout style paint;
    will-change: transform;
}