* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

:root {
    --primary-color: #0069b4;
    --primary-dark: #005a9a;
    --primary-light: #0080d6;
    --secondary-color: #64748b;
    --accent-color: #0069b4;
    --accent-dark: #005a9a;
    --background: #f8fafc;
    --background-gradient: linear-gradient(135deg, #0069b4 0%, #005a9a 100%);
    --card-background: #ffffff;
    --text-primary: #1e293b;
    --text-secondary: #64748b;
    --border-color: #e2e8f0;
    --shadow: 0 1px 3px rgba(0, 0, 0, 0.08), 0 1px 2px rgba(0, 0, 0, 0.06);
    --shadow-md: 0 4px 12px rgba(0, 0, 0, 0.08), 0 2px 4px rgba(0, 0, 0, 0.04);
    --shadow-lg: 0 10px 25px rgba(0, 0, 0, 0.08);
    --shadow-xl: 0 20px 40px rgba(0, 0, 0, 0.1);
    --gradient-primary: linear-gradient(135deg, #0069b4 0%, #005a9a 100%);
    --gradient-accent: linear-gradient(135deg, #0069b4 0%, #005a9a 100%);
    --gradient-purple: linear-gradient(135deg, #0080d6 0%, #0069b4 100%);
    --card-gradient-soft: #ffffff;
}

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;
    line-height: 1.7;
    color: var(--text-primary);
    background: var(--background);
    min-height: 100vh;
    display: flex;
    flex-direction: column;
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
}

/* Прогресс-бар чтения */
.reading-progress-bar {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 6px;
    background: rgba(0, 0, 0, 0.1);
    z-index: 9999;
    transition: opacity 0.3s ease;
}

.reading-progress-fill {
    height: 100%;
    background: linear-gradient(90deg, #0069b4 0%, #005a9a 100%);
    width: 0%;
    transition: width 0.1s ease-out;
}

.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 20px;
    width: 100%;
}

/* Обертка для страницы урока с боковой панелью */
.lesson-page-wrapper {
    display: flex;
    min-height: calc(100vh - 200px);
}

/* Боковая панель с уроками */
.lessons-sidebar {
    width: 320px;
    background: var(--card-background);
    border-right: 1px solid var(--border-color);
    padding: 1.5rem 0;
    position: sticky;
    top: 0;
    height: calc(100vh - 6px);
    overflow-y: auto;
    overflow-x: hidden;
    flex-shrink: 0;
    scrollbar-width: thin;
    scrollbar-color: var(--border-color) transparent;
    box-shadow: 2px 0 8px rgba(0, 0, 0, 0.04);
}

/* Кастомный скроллбар для WebKit браузеров */
.lessons-sidebar::-webkit-scrollbar {
    width: 8px;
}

.lessons-sidebar::-webkit-scrollbar-track {
    background: transparent;
}

.lessons-sidebar::-webkit-scrollbar-thumb {
    background: var(--border-color);
    border-radius: 4px;
}

.lessons-sidebar::-webkit-scrollbar-thumb:hover {
    background: var(--text-secondary);
}

.sidebar-header {
    padding: 0 1.5rem 1.5rem 1.5rem;
    border-bottom: 2px solid var(--border-color);
    margin-bottom: 1.5rem;
    background: linear-gradient(135deg, rgba(0, 105, 180, 0.05) 0%, rgba(0, 90, 154, 0.05) 100%);
    margin: 0 1rem 1.5rem 1rem;
    padding: 1.25rem 1.5rem;
    border-radius: 12px;
}

.sidebar-header h3 {
    color: var(--text-primary);
    font-size: 1.2rem;
    font-weight: 700;
    margin: 0;
    background: var(--gradient-primary);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.lessons-nav {
    display: flex;
    flex-direction: column;
    gap: 0.5rem;
    padding: 0 1rem;
}

.chapter-section {
    margin-bottom: 0.75rem;
    border: 1px solid var(--border-color);
    border-radius: 12px;
    overflow: hidden;
    background: var(--card-background);
    box-shadow: var(--shadow);
    transition: all 0.3s ease;
}

.chapter-section:hover {
    box-shadow: var(--shadow-md);
    border-color: var(--primary-light);
}

.chapter-header {
    padding: 1.25rem 1.5rem;
    cursor: pointer;
    user-select: none;
    transition: all 0.3s ease;
    display: flex;
    flex-direction: column;
    gap: 0.5rem;
    background: linear-gradient(135deg, rgba(0, 105, 180, 0.03) 0%, rgba(0, 90, 154, 0.03) 100%);
}

.chapter-header:hover {
    background: linear-gradient(135deg, rgba(0, 105, 180, 0.08) 0%, rgba(0, 90, 154, 0.08) 100%);
    transform: translateX(2px);
}

.chapter-header-content {
    display: flex;
    align-items: center;
    gap: 0.5rem;
}

.chapter-number {
    font-weight: 800;
    background: var(--gradient-primary);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
    font-size: 1rem;
}

.chapter-name {
    font-weight: 700;
    color: var(--text-primary);
    font-size: 1rem;
    flex: 1;
}

.chapter-progress {
    font-size: 0.75rem;
    color: var(--text-secondary);
    margin-left: 1.5rem;
}

.chapter-toggle {
    position: absolute;
    right: 1.5rem;
    top: 50%;
    transform: translateY(-50%);
    font-size: 0.875rem;
    color: var(--primary-color);
    transition: all 0.3s ease;
    font-weight: 700;
}

.chapter-header:hover .chapter-toggle {
    color: var(--accent-color);
    transform: translateY(-50%) scale(1.2);
}

.chapter-header {
    position: relative;
}

.chapter-lessons {
    max-height: 0;
    overflow: hidden;
    transition: max-height 0.3s ease-out;
    padding: 0;
}

.chapter-section.expanded .chapter-lessons {
    max-height: 2000px;
    transition: max-height 0.5s ease-in;
    padding: 0.5rem 0;
}

.chapter-section:not(.expanded) .chapter-lessons {
    display: none;
}

.chapter-section.expanded .chapter-lessons .lesson-nav-item {
    display: flex;
}

.lesson-nav-item {
    display: flex;
    align-items: center;
    gap: 0.75rem;
    padding: 0.875rem 1.25rem;
    border-radius: 10px;
    text-decoration: none;
    color: var(--text-primary);
    transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
    opacity: 0.7;
    margin: 0.25rem 0.5rem;
    position: relative;
}

.lesson-nav-item::before {
    content: '';
    position: absolute;
    left: 0;
    top: 50%;
    transform: translateY(-50%);
    width: 3px;
    height: 0;
    background: #0069b4;
    border-radius: 0 3px 3px 0;
    transition: height 0.3s ease;
}

.lesson-nav-item:hover {
    background: linear-gradient(90deg, rgba(0, 105, 180, 0.08) 0%, rgba(0, 90, 154, 0.04) 100%);
    opacity: 1;
    transform: translateX(6px);
    box-shadow: var(--shadow);
}

.lesson-nav-item:hover::before {
    height: 60%;
}

.lesson-nav-item.active {
    background: linear-gradient(90deg, rgba(0, 105, 180, 0.15) 0%, rgba(0, 90, 154, 0.08) 100%);
    border-left: 4px solid #0069b4;
    opacity: 1;
    font-weight: 600;
    box-shadow: var(--shadow);
}

.lesson-nav-item.active::before {
    height: 100%;
    width: 4px;
}

.lesson-nav-number {
    display: flex;
    align-items: center;
    justify-content: center;
    width: 32px;
    height: 32px;
    border-radius: 8px;
    background: linear-gradient(135deg, #f1f5f9 0%, #e2e8f0 100%);
    color: var(--text-secondary);
    font-size: 0.875rem;
    font-weight: 700;
    flex-shrink: 0;
    transition: all 0.3s ease;
    box-shadow: 0 2px 4px rgba(0, 0, 0, 0.05);
}

.lesson-nav-item:hover .lesson-nav-number {
    transform: scale(1.1);
    box-shadow: 0 4px 8px rgba(0, 0, 0, 0.1);
}

.lesson-nav-item.active .lesson-nav-number {
    background: var(--gradient-accent);
    color: white;
    box-shadow: 0 4px 12px rgba(0, 105, 180, 0.4);
    transform: scale(1.1);
}

.lesson-nav-title {
    flex: 1;
    font-size: 0.95rem;
    line-height: 1.5;
    font-weight: 500;
}

.lesson-nav-item.active .lesson-nav-title {
    font-weight: 600;
}

.lesson-main-content {
    flex: 1;
    padding-left: 3rem;
    padding-right: 2rem;
}

header {
    background: var(--gradient-primary);
    color: white;
    padding: 3rem 0 3.5rem 0;
    box-shadow: var(--shadow-md);
    position: relative;
    overflow: hidden;
    border-radius: 0 0 1.5rem 1.5rem;
}

header::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: url('data:image/svg+xml,<svg width="100" height="100" xmlns="http://www.w3.org/2000/svg"><defs><pattern id="grid" width="100" height="100" patternUnits="userSpaceOnUse"><path d="M 100 0 L 0 0 0 100" fill="none" stroke="rgba(255,255,255,0.06)" stroke-width="1"/></pattern></defs><rect width="100" height="100" fill="url(%23grid)"/></svg>');
    opacity: 0.5;
}

header .container {
    position: relative;
    z-index: 1;
}

header h1 {
    font-size: 2.75rem;
    margin-bottom: 0.75rem;
    font-weight: 700;
    text-shadow: 0 2px 10px rgba(0, 0, 0, 0.2);
    letter-spacing: -0.02em;
}

.subtitle {
    font-size: 1.2rem;
    opacity: 0.95;
    font-weight: 400;
    text-shadow: 0 1px 3px rgba(0, 0, 0, 0.1);
    line-height: 1.6;
}

.back-link {
    color: white;
    text-decoration: none;
    display: inline-flex;
    align-items: center;
    gap: 0.5rem;
    margin-bottom: 1.5rem;
    opacity: 0.95;
    transition: all 0.3s ease;
    font-weight: 500;
    padding: 0.5rem 1rem;
    border-radius: 8px;
    background: rgba(255, 255, 255, 0.1);
    backdrop-filter: blur(10px);
}

.back-link:hover {
    opacity: 1;
    background: rgba(255, 255, 255, 0.2);
    transform: translateX(-4px);
}

main {
    flex: 1;
    padding: 4rem 0;
}

/* Категории */
.categories-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: 2rem;
    margin-top: 2rem;
}

.category-card {
    background: var(--card-background);
    border-radius: 20px;
    padding: 2.5rem;
    box-shadow: var(--shadow-md);
    transition: all 0.4s cubic-bezier(0.4, 0, 0.2, 1);
    cursor: pointer;
    position: relative;
    border: 1px solid var(--border-color);
    overflow: hidden;
}

.category-card::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    height: 4px;
    background: var(--gradient-primary);
    transform: scaleX(0);
    transform-origin: left;
    transition: transform 0.4s ease;
}

.category-card:hover {
    transform: translateY(-8px) scale(1.02);
    box-shadow: var(--shadow-xl);
    border-color: var(--primary-light);
}

.category-card:hover::before {
    transform: scaleX(1);
}

.category-icon {
    font-size: 4rem;
    margin-bottom: 1.5rem;
    display: inline-block;
    transition: transform 0.4s cubic-bezier(0.68, -0.55, 0.265, 1.55);
    filter: drop-shadow(0 4px 6px rgba(0, 0, 0, 0.1));
}

.category-card:hover .category-icon {
    transform: scale(1.15) rotate(5deg);
}

.category-card h2 {
    color: var(--text-primary);
    margin-bottom: 0.75rem;
    font-size: 1.75rem;
    font-weight: 700;
    background: var(--gradient-primary);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.category-card p {
    color: var(--text-secondary);
    line-height: 1.7;
    font-size: 1rem;
}

.card-arrow {
    position: absolute;
    top: 2rem;
    right: 2rem;
    font-size: 1.5rem;
    color: var(--primary-color);
    opacity: 0;
    transition: opacity 0.3s;
}

.category-card:hover .card-arrow {
    opacity: 1;
}

/* Бейдж NEW на карточке (например, Arduino) */
.category-badge {
    position: absolute;
    z-index: 5;
    font-size: 1rem;
    font-weight: 800;
    letter-spacing: 0.2em;
    padding: 0.5rem 1.1rem;
    border-radius: 6px;
    box-shadow: 0 2px 8px rgba(0, 0, 0, 0.2);
    pointer-events: none;
}

.category-badge-new {
    top: 1rem;
    right: 1rem;
    background: linear-gradient(135deg, #10b981 0%, #059669 100%);
    color: #fff;
    transform: rotate(12deg);
    text-shadow: 0 1px 2px rgba(0, 0, 0, 0.2);
}

.category-card:hover .category-badge-new {
    transform: rotate(12deg) scale(1.05);
    box-shadow: 0 3px 12px rgba(16, 185, 129, 0.4);
}

/* Метка Soon на карточках (переход по клику доступен) */
.category-badge-soon {
    top: 1rem;
    right: 1rem;
    background: linear-gradient(135deg, #64748b 0%, #475569 100%);
    color: #fff;
    transform: rotate(-12deg);
    text-shadow: 0 1px 2px rgba(0, 0, 0, 0.2);
}

/* Список уроков */
.lessons-list {
    display: flex;
    flex-direction: column;
    gap: 1rem;
    margin-top: 2rem;
}

.chapter-group {
    margin-bottom: 2.5rem;
}

.chapter-title {
    color: var(--text-primary);
    font-size: 1.75rem;
    font-weight: 700;
    margin-bottom: 0.75rem;
    padding-bottom: 0.75rem;
    border-bottom: 3px solid;
    border-image: var(--gradient-primary) 1;
    background: var(--gradient-primary);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.chapter-description {
    color: var(--text-secondary);
    font-size: 0.95rem;
    margin-bottom: 1rem;
    line-height: 1.5;
}

.lesson-card {
    background: var(--card-background);
    border-radius: 16px;
    padding: 1.75rem;
    box-shadow: var(--shadow-md);
    transition: all 0.4s cubic-bezier(0.4, 0, 0.2, 1);
    cursor: pointer;
    display: flex;
    align-items: center;
    gap: 1.5rem;
    border: 1px solid var(--border-color);
    position: relative;
    margin-bottom: 1rem;
    overflow: hidden;
}

a.lesson-card--link {
    text-decoration: none;
    color: inherit;
}

.lesson-card::before {
    content: '';
    position: absolute;
    left: 0;
    top: 0;
    bottom: 0;
    width: 4px;
    background: var(--gradient-primary);
    transform: scaleY(0);
    transform-origin: top;
    transition: transform 0.4s ease;
}

.lesson-card:hover {
    transform: translateX(8px) scale(1.01);
    box-shadow: var(--shadow-xl);
    border-color: var(--primary-light);
}

.lesson-card:hover::before {
    transform: scaleY(1);
}

.lesson-number {
    background: var(--gradient-primary);
    color: white;
    width: 56px;
    height: 56px;
    border-radius: 16px;
    display: flex;
    align-items: center;
    justify-content: center;
    font-weight: 700;
    font-size: 1.3rem;
    flex-shrink: 0;
    box-shadow: 0 4px 12px rgba(99, 102, 241, 0.3);
    transition: all 0.3s ease;
}

.lesson-card:hover .lesson-number {
    transform: scale(1.1) rotate(5deg);
    box-shadow: 0 6px 20px rgba(99, 102, 241, 0.4);
}

.lesson-content {
    flex: 1;
}

/* Баннер «Урок в видеоформате» с вылетающей анимацией (золотой) */
.lesson-video-banner {
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: 1rem;
    padding: 1rem 1.25rem;
    margin-bottom: 1.5rem;
    background: linear-gradient(135deg, rgba(212, 175, 55, 0.18) 0%, rgba(184, 134, 11, 0.12) 100%);
    border: 1px solid rgba(218, 165, 32, 0.4);
    border-radius: 16px;
    animation: videoBannerSlideIn 0.6s cubic-bezier(0.34, 1.56, 0.64, 1) forwards;
    transform-origin: right center;
    opacity: 0;
}

@keyframes videoBannerSlideIn {
    from {
        opacity: 0;
        transform: translateX(40px) scale(0.92);
    }
    to {
        opacity: 1;
        transform: translateX(0) scale(1);
    }
}

.lesson-video-banner__text {
    display: flex;
    align-items: center;
    gap: 0.75rem;
    color: var(--text-primary);
    font-weight: 500;
}

.lesson-video-banner__text::before {
    content: '';
    display: inline-block;
    width: 40px;
    height: 40px;
    flex-shrink: 0;
    background: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 24 24' fill='%23b8860b'%3E%3Cpath d='M8 5v14l11-7z'/%3E%3Cpath d='M4 3h16a1 1 0 011 1v16a1 1 0 01-1 1H4a1 1 0 01-1-1V4a1 1 0 011-1z' fill='none' stroke='%23b8860b' stroke-width='2'/%3E%3C/svg%3E") center/contain no-repeat;
}

.lesson-video-banner__btn {
    display: inline-flex;
    align-items: center;
    gap: 0.5rem;
    padding: 0.6rem 1.25rem;
    background: linear-gradient(135deg, #d4af37 0%, #b8860b 100%);
    color: #1a1a1a;
    font-weight: 600;
    font-size: 0.95rem;
    border: none;
    border-radius: 12px;
    cursor: pointer;
    text-decoration: none;
    box-shadow: 0 4px 14px rgba(184, 134, 11, 0.4);
    transition: transform 0.2s ease, box-shadow 0.2s ease;
}

.lesson-video-banner__btn:hover {
    transform: translateY(-2px);
    box-shadow: 0 6px 20px rgba(184, 134, 11, 0.5);
}

.lesson-video-banner__btn:active {
    transform: translateY(0);
}

.lesson-content h2 {
    color: var(--text-primary);
    margin-bottom: 0.5rem;
    font-size: 1.3rem;
}

.lesson-content p {
    color: var(--text-secondary);
}

.lesson-card .card-arrow {
    position: static;
    opacity: 0.5;
}

.lesson-card:hover .card-arrow {
    opacity: 1;
}

.lesson-card--disabled {
    cursor: default;
    opacity: 0.85;
    pointer-events: none;
}
.lesson-card--disabled:hover {
    transform: none;
    box-shadow: var(--shadow-md);
    border-color: var(--border-color);
}
.lesson-card--disabled:hover::before {
    transform: scaleY(0);
}
.lesson-card--disabled:hover .lesson-number {
    transform: none;
    box-shadow: 0 4px 12px rgba(99, 102, 241, 0.2);
}
.lesson-card--disabled:hover .card-arrow {
    opacity: 0.5;
}

/* Roadmap — уроки как путь */
.roadmap {
    position: relative;
    padding-left: 2.5rem;
    margin-top: 2.5rem;
    padding-bottom: 2rem;
}

.roadmap-track {
    position: absolute;
    left: 0.6875rem;
    top: 0.5rem;
    bottom: 0.5rem;
    width: 3px;
    background: linear-gradient(180deg, var(--primary-color) 0%, var(--primary-light) 50%, var(--primary-dark) 100%);
    border-radius: 3px;
    box-shadow: 0 0 12px rgba(0, 105, 180, 0.2);
}

.roadmap-chapter {
    position: relative;
    margin-bottom: 2.5rem;
}

.roadmap-chapter:last-of-type {
    margin-bottom: 0;
}

.roadmap-chapter-milestone {
    display: flex;
    align-items: flex-start;
    gap: 1.25rem;
    margin-bottom: 1rem;
}

.roadmap-dot {
    flex-shrink: 0;
    border-radius: 50%;
    background: var(--card-background);
    border: 3px solid var(--primary-color);
    box-shadow: 0 0 0 2px var(--background), 0 2px 8px rgba(0, 105, 180, 0.15);
    z-index: 1;
}

.roadmap-dot--chapter {
    width: 24px;
    height: 24px;
    margin-top: 0.35rem;
    background: var(--gradient-primary);
    border-color: var(--primary-dark);
}

.roadmap-dot--lesson {
    width: 2.25rem;
    height: 2.25rem;
    border-radius: 50%;
    background: var(--card-background);
    border: 2px solid var(--primary-color);
    display: flex;
    align-items: center;
    justify-content: center;
    box-shadow: 0 2px 8px rgba(0, 105, 180, 0.15);
}

.roadmap-chapter-heading {
    flex: 1;
    min-width: 0;
}

.roadmap-chapter-title {
    color: var(--text-primary);
    font-size: 1.5rem;
    font-weight: 700;
    margin: 0 0 0.25rem 0;
    background: var(--gradient-primary);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.roadmap-chapter-description {
    color: var(--text-secondary);
    font-size: 0.9rem;
    margin: 0;
    line-height: 1.5;
}

.roadmap-lessons {
    display: flex;
    flex-direction: column;
    gap: 0.5rem;
    margin-left: 0.5rem;
}

.roadmap-node {
    display: flex;
    align-items: center;
    gap: 1rem;
    padding: 0.875rem 1.25rem;
    border-radius: 14px;
    background: var(--card-background);
    border: 1px solid var(--border-color);
    box-shadow: var(--shadow);
    transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
    position: relative;
    text-decoration: none;
    color: inherit;
}

a.roadmap-node--link:hover {
    border-color: var(--primary-light);
    box-shadow: var(--shadow-md);
    transform: translateX(6px);
}

a.roadmap-node--link:hover .roadmap-dot--lesson {
    background: var(--gradient-primary);
    border-color: var(--primary-dark);
    color: white;
}

a.roadmap-node--link:hover .roadmap-node-arrow {
    opacity: 1;
    transform: translateX(4px);
}

.roadmap-node--disabled {
    cursor: default;
    opacity: 0.85;
    pointer-events: none;
}

.roadmap-node-num {
    font-weight: 700;
    font-size: 0.85rem;
    color: var(--primary-color);
}

a.roadmap-node--link:hover .roadmap-node-num {
    color: white;
}

.roadmap-node-content {
    flex: 1;
    min-width: 0;
}

.roadmap-node-title {
    font-size: 1.05rem;
    font-weight: 600;
    margin: 0;
    color: var(--text-primary);
}

.roadmap-node-arrow {
    opacity: 0.4;
    font-size: 1.25rem;
    transition: opacity 0.3s ease, transform 0.3s ease;
}

@media (max-width: 768px) {
    .roadmap {
        padding-left: 2rem;
    }

    .roadmap-track {
        left: 0.5rem;
    }

    .roadmap-dot--chapter {
        width: 20px;
        height: 20px;
    }

    .roadmap-dot--lesson {
        width: 2rem;
        height: 2rem;
        font-size: 0.8rem;
    }

    .roadmap-node {
        padding: 0.75rem 1rem;
    }

    .roadmap-chapter-title {
        font-size: 1.25rem;
    }
}

/* Контент урока */
article.lesson-content {
    background: var(--card-background);
    border-radius: 24px;
    padding: 3.5rem;
    box-shadow: var(--shadow-lg);
    margin-bottom: 2rem;
    line-height: 1.9;
    border: 1px solid rgba(99, 102, 241, 0.1);
    position: relative;
    overflow: hidden;
}

article.lesson-content::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    height: 4px;
    background: var(--gradient-primary);
}

article.lesson-content h2 {
    color: var(--text-primary);
    margin-top: 2.5rem;
    margin-bottom: 1.25rem;
    font-size: 2rem;
    font-weight: 700;
    background: var(--gradient-primary);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
    line-height: 1.3;
}

article.lesson-content h2:first-child {
    margin-top: 0;
}

article.lesson-content h3 {
    color: var(--text-primary);
    margin-top: 2rem;
    margin-bottom: 1rem;
    font-size: 1.5rem;
    font-weight: 600;
    color: var(--primary-dark);
}

article.lesson-content p {
    margin-bottom: 1rem;
    color: var(--text-primary);
}

article.lesson-content ul,
article.lesson-content ol {
    margin-left: 2rem;
    margin-bottom: 1.5rem;
    padding-left: 1rem;
}

article.lesson-content li {
    margin-bottom: 0.75rem;
    color: var(--text-primary);
    line-height: 1.8;
    position: relative;
    padding-left: 0.5rem;
}

article.lesson-content ul li::marker {
    color: var(--primary-color);
    font-weight: 700;
}

article.lesson-content ol li::marker {
    color: var(--primary-color);
    font-weight: 700;
}

/* Картинки в уроках — скруглённые углы, по центру */
article.lesson-content .lesson-figure {
    margin: 1.5rem auto;
    text-align: center;
}

article.lesson-content .lesson-figure img {
    display: block;
    max-width: 100%;
    height: auto;
    margin: 0 auto;
    border-radius: 16px;
    box-shadow: 0 2px 12px rgba(0, 0, 0, 0.08);
}

/* Таблицы сравнения в уроках */
article.lesson-content .lesson-table {
    width: 100%;
    max-width: 100%;
    border-collapse: separate;
    border-spacing: 0;
    margin: 1.75rem 0;
    font-size: 0.95rem;
    border-radius: 16px;
    overflow: hidden;
    box-shadow: 0 4px 20px rgba(0, 105, 180, 0.08), 0 1px 3px rgba(0, 0, 0, 0.06);
    background: var(--card-background);
    border: 1px solid var(--border-color);
}

article.lesson-content .lesson-table thead {
    background: var(--gradient-primary);
}

article.lesson-content .lesson-table thead th {
    padding: 1rem 1.25rem;
    text-align: left;
    font-weight: 700;
    color: #fff;
    font-size: 0.9rem;
    letter-spacing: 0.02em;
    border: none;
}

article.lesson-content .lesson-table thead th:first-child {
    border-radius: 16px 0 0 0;
}

article.lesson-content .lesson-table thead th:last-child {
    border-radius: 0 16px 0 0;
}

article.lesson-content .lesson-table tbody tr {
    transition: background 0.2s ease;
}

article.lesson-content .lesson-table tbody tr:hover {
    background: rgba(0, 105, 180, 0.04);
}

article.lesson-content .lesson-table tbody tr:last-child td:first-child {
    border-radius: 0 0 0 16px;
}

article.lesson-content .lesson-table tbody tr:last-child td:last-child {
    border-radius: 0 0 16px 0;
}

article.lesson-content .lesson-table td {
    padding: 1rem 1.25rem;
    border: none;
    border-bottom: 1px solid var(--border-color);
    text-align: left;
    vertical-align: top;
}

article.lesson-content .lesson-table tbody tr:last-child td {
    border-bottom: none;
}

article.lesson-content .lesson-table td:first-child {
    font-weight: 600;
    color: var(--text-primary);
    background: rgba(0, 105, 180, 0.03);
    width: 22%;
}

article.lesson-content .lesson-table td:nth-child(2),
article.lesson-content .lesson-table td:nth-child(3) {
    color: var(--text-secondary);
}

article.lesson-content .lesson-table tbody tr:nth-child(even) td:first-child {
    background: rgba(0, 105, 180, 0.05);
}

/* Обертка для блока кода с кнопкой копирования */
.code-block-wrapper {
    position: relative;
    margin: 2rem 0;
}

article.lesson-content pre {
    background: #fafafa !important;
    color: #242424 !important;
    padding: 2rem;
    border-radius: 16px;
    overflow-x: auto;
    margin: 0;
    font-family: 'Fira Code', 'Consolas', 'Courier New', monospace;
    font-size: 0.95rem;
    line-height: 1.7;
    border: 1px solid #e5e7eb;
    outline: none !important;
    position: relative;
    box-shadow: 0 1px 3px rgba(0, 0, 0, 0.06);
}

/* Кнопка копирования кода */
.copy-code-button {
    position: absolute;
    top: 1rem;
    right: 1rem;
    background: #0069b4;
    color: white;
    border: none;
    border-radius: 8px;
    padding: 0.625rem 1.25rem;
    font-size: 0.875rem;
    cursor: pointer;
    transition: all 0.3s ease;
    z-index: 10;
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
    display: flex;
    align-items: center;
    gap: 0.5rem;
    font-weight: 600;
    box-shadow: 0 2px 8px rgba(0, 105, 180, 0.3);
}

.copy-code-button:hover {
    background: #005a9a;
    transform: translateY(-2px);
    box-shadow: 0 4px 12px rgba(0, 105, 180, 0.4);
}

.copy-code-button:active {
    transform: translateY(0);
}

.copy-code-button.copied {
    background: #10b981;
    box-shadow: 0 4px 12px rgba(16, 185, 129, 0.4);
}

.copy-code-button::before {
    content: "📋";
    margin-right: 0.25rem;
}

.copy-code-button::after {
    content: "Копировать";
}

.copy-code-button.copied::before {
    content: "✓";
}

.copy-code-button.copied::after {
    content: "Скопировано!";
}

article.lesson-content code {
    background: linear-gradient(135deg, #e6e6e6 0%, #d9d9d9 100%);
    padding: 0.25rem 0.5rem;
    border-radius: 6px;
    font-family: 'Courier New', 'Fira Code', 'Consolas', monospace;
    font-size: 0.95em;
    color: #555;
    border: none !important;
    outline: none !important;
    font-weight: 500;
    box-shadow: inset 0 1px 3px rgba(0, 0, 0, 0.05);
}

article.lesson-content pre code {
    background: transparent;
    padding: 0;
    color: inherit;
    border: none !important;
    outline: none !important;
}


/* Подсветка синтаксиса в стиле VS Code (светлая тема) */
article.lesson-content pre code.hljs,
article.lesson-content pre.hljs,
article.lesson-content pre code[class*="hljs"],
article.lesson-content pre[class*="hljs"] {
    background: transparent !important;
    background-color: transparent !important;
    padding: 0;
    color: #242424 !important;
    border: none !important;
    outline: none !important;
}

.hljs {
    background: transparent !important;
    color: #242424 !important;
    border: none !important;
    outline: none !important;
}

article.lesson-content pre *,
article.lesson-content pre code *,
article.lesson-content .hljs * {
    border: none !important;
    outline: none !important;
    box-shadow: none !important;
}

/* Токены в стиле VS Code Light+ */
article.lesson-content .hljs-keyword {
    color: #0000ff;
    font-weight: 600;
}

article.lesson-content .hljs-string {
    color: #a31515;
}

article.lesson-content .hljs-comment {
    color: #008000;
    font-style: italic;
}

article.lesson-content .hljs-number {
    color: #098658;
}

article.lesson-content .hljs-function,
article.lesson-content .hljs-title.function_ {
    color: #795e26;
}

article.lesson-content .hljs-variable,
article.lesson-content .hljs-title {
    color: #267f99;
}

article.lesson-content .hljs-type {
    color: #267f99;
}

article.lesson-content .hljs-meta {
    color: #808080;
}

article.lesson-content .hljs-built_in {
    color: #795e26;
}

article.lesson-content .hljs-params {
    color: #242424;
}

article.lesson-content .hljs-literal {
    color: #0000ff;
}

article.lesson-content .hljs-attr,
article.lesson-content .hljs-attribute {
    color: #267f99;
}

article.lesson-content .hljs-regexp {
    color: #a31515;
}

article.lesson-content .hljs-doctag {
    color: #008000;
}

article.lesson-content .hljs-symbol {
    color: #0000ff;
}

/* Навигация между уроками */
.lesson-navigation {
    display: flex;
    justify-content: space-between;
    gap: 1.5rem;
    margin-top: 3rem;
}

.nav-button {
    flex: 1;
    padding: 1.25rem 2rem;
    background: var(--card-background);
    border: 1px solid var(--border-color);
    border-radius: 16px;
    text-decoration: none;
    color: var(--text-primary);
    transition: all 0.4s cubic-bezier(0.4, 0, 0.2, 1);
    text-align: center;
    font-weight: 600;
    position: relative;
    overflow: hidden;
    box-shadow: var(--shadow-md);
    display: flex;
    align-items: center;
    justify-content: center;
}

.nav-button::before {
    content: '';
    position: absolute;
    top: 0;
    left: -100%;
    width: 100%;
    height: 100%;
    background: var(--gradient-primary);
    transition: left 0.4s ease;
    z-index: 0;
}

.nav-button span {
    position: relative;
    z-index: 1;
}

.nav-button:hover {
    border-color: var(--primary-light);
    color: white;
    transform: translateY(-4px);
    box-shadow: var(--shadow-xl);
}

.nav-button:hover::before {
    left: 0;
}

.nav-button.prev {
    text-align: left;
    justify-content: flex-start;
}

.nav-button.next {
    text-align: right;
    justify-content: flex-end;
}

footer {
    background: var(--card-background);
    border-top: 1px solid var(--border-color);
    padding: 2.5rem 0;
    margin-top: auto;
    text-align: center;
    color: var(--text-secondary);
}

/* Адаптивность */
@media (max-width: 768px) {
    header h1 {
        font-size: 1.8rem;
    }
    
    .subtitle {
        font-size: 1rem;
    }
    
    .categories-grid {
        grid-template-columns: 1fr;
    }
    
    .lesson-navigation {
        flex-direction: column;
    }
    
    article.lesson-content {
        padding: 1.5rem;
    }
    
    .lesson-card {
        flex-direction: column;
        text-align: center;
    }
    
    /* Адаптивность для боковой панели */
    .lesson-page-wrapper {
        flex-direction: column;
    }
    
    .lessons-sidebar {
        width: 100%;
        height: auto;
        position: relative;
        border-right: none;
        border-bottom: 1px solid var(--border-color);
        max-height: 300px;
    }
    
    .lesson-main-content {
        padding-left: 0;
    }
    
    /* Адаптивность для кнопки копирования */
    .copy-code-button {
        padding: 0.5rem 1rem;
        font-size: 0.75rem;
        top: 0.75rem;
        right: 0.75rem;
    }
    
    .copy-code-button::after {
        content: "";
    }
    
    .copy-code-button.copied::after {
        content: "";
    }
}

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

@keyframes fadeIn {
    from {
        opacity: 0;
    }
    to {
        opacity: 1;
    }
}

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

@keyframes scaleIn {
    from {
        opacity: 0;
        transform: scale(0.9);
    }
    to {
        opacity: 1;
        transform: scale(1);
    }
}

/* Классы для анимаций */
.category-card,
.lesson-card,
.roadmap-node,
.roadmap-chapter-milestone {
    opacity: 0;
    transform: translateY(30px);
    transition: all 0.3s ease;
}

.category-card.animate-in,
.lesson-card.animate-in,
.roadmap-node.animate-in,
.roadmap-chapter-milestone.animate-in {
    animation: fadeInUp 0.6s ease-out forwards;
}

/* Улучшенные transitions */
.category-card,
.lesson-card,
.nav-button {
    will-change: transform;
}

/* Анимация для контента урока */
article.lesson-content {
    animation: fadeIn 0.5s ease-out;
}

article.lesson-content h2,
article.lesson-content h3,
article.lesson-content p,
article.lesson-content ul,
article.lesson-content ol,
article.lesson-content pre {
    transition: all 0.5s ease-out;
}

/* Пульсирующая анимация для иконок */
@keyframes pulse {
    0%, 100% {
        transform: scale(1);
    }
    50% {
        transform: scale(1.1);
    }
}

.category-icon:hover {
    animation: pulse 0.6s ease-in-out;
}

/* Анимация для стрелок */
.card-arrow {
    transition: all 0.3s ease;
}

.category-card:hover .card-arrow,
.lesson-card:hover .card-arrow {
    transform: translateX(5px);
}

.lesson-card--disabled:hover .card-arrow {
    transform: none;
}

/* Формы авторизации */
.auth-container {
    display: flex;
    justify-content: center;
    align-items: center;
    min-height: 60vh;
    padding: 2rem 0;
}

.auth-card {
    background: var(--card-background);
    border-radius: 12px;
    padding: 2.5rem;
    box-shadow: var(--shadow-lg);
    width: 100%;
    max-width: 400px;
    border: 1px solid var(--border-color);
}

.auth-card h2 {
    color: var(--text-primary);
    margin-bottom: 1.5rem;
    font-size: 1.8rem;
    text-align: center;
}

.auth-form {
    display: flex;
    flex-direction: column;
    gap: 1.5rem;
}

.form-group {
    display: flex;
    flex-direction: column;
    gap: 0.5rem;
}

.form-group label {
    color: var(--text-primary);
    font-weight: 500;
    font-size: 0.95rem;
}

.form-group input {
    padding: 0.75rem;
    border: 2px solid var(--border-color);
    border-radius: 8px;
    font-size: 1rem;
    transition: all 0.3s ease;
    font-family: inherit;
}

.form-group input:focus {
    outline: none;
    border-color: var(--primary-color);
    box-shadow: 0 0 0 3px rgba(37, 99, 235, 0.1);
}

.form-group small {
    color: var(--text-secondary);
    font-size: 0.85rem;
}

.auth-button {
    padding: 0.75rem 1.5rem;
    background: var(--primary-color);
    color: white;
    border: none;
    border-radius: 8px;
    font-size: 1rem;
    font-weight: 500;
    cursor: pointer;
    transition: all 0.3s ease;
    margin-top: 0.5rem;
}

.auth-button:hover {
    background: var(--primary-dark);
    transform: translateY(-2px);
    box-shadow: var(--shadow);
}

.auth-link {
    text-align: center;
    margin-top: 1.5rem;
    color: var(--text-secondary);
}

.auth-link a {
    color: var(--primary-color);
    text-decoration: none;
    font-weight: 500;
}

.auth-link a:hover {
    text-decoration: underline;
}

.error-message {
    background: #fee2e2;
    color: #dc2626;
    padding: 0.75rem;
    border-radius: 8px;
    margin-bottom: 1rem;
    border: 1px solid #fecaca;
    text-align: center;
}

/* Информация о пользователе */
.user-info {
    display: flex;
    align-items: center;
    gap: 1rem;
    margin-top: 1rem;
}

.user-info span {
    color: white;
    opacity: 0.9;
}

.logout-button {
    background: rgba(255, 255, 255, 0.2);
    color: white;
    border: 1px solid rgba(255, 255, 255, 0.3);
    padding: 0.5rem 1rem;
    border-radius: 6px;
    text-decoration: none;
    font-size: 0.9rem;
    transition: all 0.3s ease;
}

.logout-button:hover {
    background: rgba(255, 255, 255, 0.3);
    border-color: rgba(255, 255, 255, 0.5);
}