* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
    transition: background-color 0.3s ease, color 0.3s ease, border-color 0.3s ease;
}

:root {
    --bg-primary: #0a0c14;
    --bg-secondary: #141a24;
    --bg-card: #1e2636;
    --bg-hover: #2a3448;
    --text-primary: #e2e8f0;
    --text-secondary: #9aa5b8;
    --text-muted: #6b7a8f;
    --border-color: #2d3f54;
    --accent: #60a5fa;
    --accent-dark: #3b82f6;
    --accent-light: #93c5fd;
    --accent-hover: #3b82f6;
    --success: #10b981;
    --warning: #f59e0b;
    --danger: #ef4444;
    --skill-bg: #1e2a3a;
    --card-bg: #1a212e;
    --shadow: 0 10px 25px -5px rgba(0, 0, 0, 0.5);
    --header-height: 70px;
    --gradient: linear-gradient(135deg, var(--accent), var(--accent-light));
    --border: var(--border-color);
    --transition: all 0.3s ease;
}

[data-theme="light"] {
    --bg-primary: #f8fafc;
    --bg-secondary: #ffffff;
    --bg-card: #f1f5f9;
    --bg-hover: #e2e8f0;
    --text-primary: #0f172a;
    --text-secondary: #334155;
    --text-muted: #64748b;
    --border-color: #cbd5e1;
    --accent: #2563eb;
    --accent-dark: #1d4ed8;
    --accent-light: #3b82f6;
    --accent-hover: #1d4ed8;
    --skill-bg: #e2e8f0;
    --card-bg: #ffffff;
    --shadow: 0 10px 25px -5px rgba(0, 0, 0, 0.1);
    --border: var(--border-color);
}

body {
    background-color: var(--bg-primary);
    color: var(--text-primary);
    font-family: 'Inter', sans-serif;
    font-size: 16px;
    font-weight: 400;
    line-height: 1.6;
    min-height: 100vh;
}

/* Header */
.header {
    background-color: var(--bg-secondary);
    height: var(--header-height);
    padding: 0 2rem;
    display: flex;
    justify-content: space-between;
    align-items: center;
    border-bottom: 2px solid var(--border-color);
    position: sticky;
    top: 0;
    z-index: 1000;
    box-shadow: var(--shadow);
}

.header-left {
    display: flex;
    align-items: center;
    gap: 2rem;
}

.header-logo {
    font-size: 1.5rem;
    font-weight: 800;
    background: linear-gradient(135deg, var(--accent), var(--accent-light));
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    text-decoration: none;
    letter-spacing: -0.5px;
}

.nav-menu {
    display: flex;
    list-style: none;
    gap: 2rem;
    align-items: center;
}

.nav-item a {
    color: var(--text-primary);
    text-decoration: none;
    font-weight: 500;
    transition: color 0.3s;
    position: relative;
    padding: 0.5rem 0;
}

.nav-item a::after {
    content: '';
    position: absolute;
    bottom: 0;
    left: 0;
    width: 0;
    height: 2px;
    background: var(--accent);
    transition: width 0.3s;
}

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

.nav-item a:hover {
    color: var(--accent);
}

/* Header Controls */
.header-controls {
    display: flex;
    align-items: center;
    gap: 1rem;
}

/* Language Switcher */
.lang-switch {
    display: flex;
    background: var(--bg-primary);
    border: 1px solid var(--border-color);
    border-radius: 30px;
    padding: 0.2rem;
}

.lang-btn {
    border: none;
    background: transparent;
    color: var(--text-secondary);
    font-weight: 600;
    font-size: 0.9rem;
    padding: 0.4rem 1rem;
    border-radius: 30px;
    cursor: pointer;
    transition: all 0.3s;
}

.lang-btn.active {
    background: var(--accent);
    color: white;
}

/* Theme Toggle */
.theme-switch-wrapper {
    display: flex;
    align-items: center;
    gap: 0.5rem;
}

.theme-switch {
    display: inline-block;
    height: 34px;
    position: relative;
    width: 60px;
}

.theme-switch input {
    display: none;
}

.slider {
    background-color: var(--bg-primary);
    bottom: 0;
    cursor: pointer;
    left: 0;
    position: absolute;
    right: 0;
    top: 0;
    transition: .4s;
    border: 2px solid var(--border-color);
}

.slider:before {
    background-color: var(--accent);
    bottom: 4px;
    content: "";
    height: 22px;
    left: 4px;
    position: absolute;
    transition: .4s;
    width: 22px;
}

input:checked + .slider:before {
    transform: translateX(26px);
}

.slider.round {
    border-radius: 34px;
}

.slider.round:before {
    border-radius: 50%;
}

.theme-icon {
    color: var(--text-secondary);
    font-size: 1rem;
}

/* Container */
.container {
    max-width: 1300px;
    margin: 0 auto;
    padding: 2rem;
}

/* Back link */
.back-link {
    display: inline-block;
    margin-bottom: 2rem;
    color: var(--text-secondary);
    text-decoration: none;
    font-size: 1rem;
    font-weight: 500;
    transition: color 0.3s;
}

.back-link i {
    margin-right: 0.5rem;
    color: var(--accent);
    transition: transform 0.3s;
}

.back-link:hover {
    color: var(--accent);
}

.back-link:hover i {
    transform: translateX(-5px);
}

/* Page Header */
.page-header {
    background: linear-gradient(135deg, var(--bg-secondary), var(--bg-card));
    border: 1px solid var(--border-color);
    border-radius: 16px;
    padding: 2.5rem;
    margin-bottom: 2rem;
    text-align: center;
    box-shadow: var(--shadow);
}

.page-title {
    font-size: 2.5rem;
    font-weight: 800;
    margin-bottom: 0.5rem;
    background: linear-gradient(135deg, var(--accent), var(--accent-light));
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
}

.page-subtitle {
    color: var(--text-secondary);
    font-size: 1.1rem;
    max-width: 600px;
    margin: 0 auto;
}

/* PDF Links */
.pdf-links {
    display: flex;
    flex-wrap: wrap;
    justify-content: center;
    gap: 1.5rem;
    margin-top: 2rem;
}

.pdf-link {
    display: inline-flex;
    align-items: center;
    gap: 0.8rem;
    padding: 1rem 2rem;
    background-color: var(--bg-card);
    border: 1px solid var(--border-color);
    border-radius: 50px;
    color: var(--text-primary);
    text-decoration: none;
    transition: all 0.3s;
    font-weight: 500;
}

.pdf-link:hover {
    border-color: var(--accent);
    transform: translateY(-3px);
    box-shadow: 0 10px 20px -10px var(--accent);
}

.pdf-link i {
    color: var(--accent);
    font-size: 1.2rem;
}

/* Language Tabs */
.lang-tabs {
    display: flex;
    gap: 0.5rem;
    margin-bottom: 1.5rem;
    border-bottom: 1px solid var(--border-color);
    padding-bottom: 1rem;
}

.tab-btn {
    padding: 0.6rem 1.5rem;
    border: none;
    background: var(--bg-card);
    color: var(--text-secondary);
    font-weight: 600;
    border-radius: 8px;
    cursor: pointer;
    transition: all 0.3s;
    border: 1px solid transparent;
}

.tab-btn.active {
    background: var(--accent);
    color: white;
    border-color: var(--accent);
}

.tab-btn:hover:not(.active) {
    border-color: var(--border-color);
    color: var(--text-primary);
}

/* Content Sections */
.content-section {
    display: none;
}

.content-section.active {
    display: block;
}

/* Info Card */
.info-card {
    background-color: var(--bg-card);
    border: 1px solid var(--border-color);
    border-radius: 16px;
    padding: 2rem;
    margin-bottom: 2rem;
    box-shadow: var(--shadow);
}

.card-title {
    font-size: 1.5rem;
    font-weight: 700;
    margin-bottom: 1.5rem;
    display: flex;
    align-items: center;
    gap: 1rem;
    color: var(--accent);
    border-bottom: 2px solid var(--border-color);
    padding-bottom: 1rem;
}

.card-title i {
    font-size: 1.5rem;
}

/* Course List */
.course-list {
    display: flex;
    flex-direction: column;
    gap: 0.8rem;
    max-height: 600px;
    overflow-y: auto;
    padding-right: 1rem;
}

.course-item {
    display: flex;
    align-items: center;
    gap: 1rem;
    padding: 0.8rem 1.2rem;
    background-color: var(--bg-secondary);
    border: 1px solid var(--border-color);
    border-radius: 8px;
    transition: all 0.3s;
}

.course-item:hover {
    border-color: var(--accent);
    transform: translateX(5px);
    background-color: var(--bg-hover);
}

.course-num {
    min-width: 3rem;
    color: var(--accent);
    font-weight: 700;
    font-family: 'Fira Code', monospace;
}

.course-name {
    flex: 1;
    font-weight: 500;
}

.course-grade {
    background: linear-gradient(135deg, var(--bg-card), var(--bg-secondary));
    color: var(--accent);
    padding: 0.3rem 1rem;
    border-radius: 20px;
    border: 1px solid var(--accent);
    font-size: 0.9rem;
    font-weight: 600;
    font-family: 'Fira Code', monospace;
    min-width: 3rem;
    text-align: center;
}

.course-ects {
    background: linear-gradient(135deg, var(--bg-card), var(--bg-secondary));
    color: var(--success);
    padding: 0.3rem 1rem;
    border-radius: 20px;
    border: 1px solid var(--success);
    font-size: 0.9rem;
    font-weight: 600;
    font-family: 'Fira Code', monospace;
    min-width: 3rem;
    text-align: center;
}

/* Stats Grid */
.stats-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
    gap: 1.5rem;
    margin-top: 2rem;
}

.stat-item {
    background: linear-gradient(135deg, var(--bg-card), var(--bg-secondary));
    border: 1px solid var(--border-color);
    border-radius: 16px;
    padding: 2rem 1rem;
    text-align: center;
    transition: transform 0.3s;
}

.stat-item:hover {
    transform: translateY(-5px);
    border-color: var(--accent);
}

.stat-value {
    font-size: 2.5rem;
    font-weight: 800;
    background: linear-gradient(135deg, var(--accent), var(--accent-light));
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    line-height: 1.2;
}

.stat-label {
    color: var(--text-secondary);
    font-size: 1rem;
    font-weight: 500;
}

/* Footer - професионален */
.footer {
    background-color: var(--bg-secondary);
    border-top: 1px solid var(--border);
    padding: 2.5rem 2rem 2rem;
    text-align: center;
    color: var(--text-muted);
    font-size: 0.9rem;
    margin-top: 3rem;
    position: relative;
    overflow: hidden;
}

.footer::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    height: 2px;
    background: var(--gradient);
}

.footer p {
    margin-bottom: 1.5rem;
}

.footer i {
    color: var(--accent);
    margin: 0 0.2rem;
}

.footer-column {
    width: 100%;
}

/* Social Links - професионални с анимация */
.social-links {
    display: flex;
    justify-content: center;
    gap: 1.2rem;
    margin: 1.5rem 0 0.5rem;
    list-style: none;
    flex-wrap: wrap;
    padding: 0;
}

.social-link a {
    display: flex;
    align-items: center;
    justify-content: center;
    width: 44px;
    height: 44px;
    background-color: var(--bg-primary);
    border: 1px solid var(--border);
    border-radius: 12px;
    color: var(--text-secondary);
    font-size: 1.2rem;
    transition: var(--transition);
    position: relative;
    overflow: hidden;
    text-decoration: none;
}

.social-link a::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: var(--gradient);
    opacity: 0;
    transition: var(--transition);
    z-index: 0;
}

.social-link a i {
    position: relative;
    z-index: 1;
    transition: var(--transition);
}

.social-link a:hover {
    transform: translateY(-5px);
    border-color: transparent;
}

.social-link a:hover::before {
    opacity: 1;
}

.social-link a:hover i {
    color: white;
    transform: scale(1.1);
}

.copyright {
    color: var(--text-secondary);
    font-size: 0.9rem;
}

.copyright i {
    color: var(--accent);
    margin-right: 0.25rem;
}

/* Scrollbar */
.course-list::-webkit-scrollbar {
    width: 8px;
}
.course-list::-webkit-scrollbar-track {
    background: var(--bg-secondary);
    border-radius: 4px;
}
.course-list::-webkit-scrollbar-thumb {
    background: var(--accent);
    border-radius: 4px;
}

/* Responsive */
@media (max-width: 768px) {
    .header {
        flex-direction: column;
        height: auto;
        padding: 1rem;
        gap: 1rem;
    }
    .header-left {
        width: 100%;
        justify-content: space-between;
    }
    .nav-menu {
        flex-wrap: wrap;
        justify-content: center;
        gap: 1rem;
    }
    .header-controls {
        width: 100%;
        justify-content: center;
    }
    .course-item {
        flex-wrap: wrap;
    }
    .pdf-links {
        flex-direction: column;
    }
    .page-title {
        font-size: 2rem;
    }
    .footer {
        padding: 2rem 1rem 1.5rem;
    }
    .social-links {
        gap: 0.8rem;
    }
    .social-link a {
        width: 40px;
        height: 40px;
        font-size: 1.1rem;
    }
}

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

.info-card, .stat-item, .pdf-link {
    animation: fadeIn 0.6s ease forwards;
}

.info-card:nth-child(2) {
    animation-delay: 0.2s;
}
.info-card:nth-child(3) {
    animation-delay: 0.4s;
}