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

body {
    font-family: 'Inter', sans-serif;
    line-height: 1.7;
    color: #2d3748;
    background: #f4f7fc; /* Matches previous page background */
    min-height: 100vh;
}

.header {
    background: #671473;
    color: white;
    padding: 1rem 0;
    position: sticky;
    top: 0;
    z-index: 1000;
    box-shadow: 0 2px 5px rgba(0, 0, 0, 0.1);
}

.header-content {
    max-width: 1400px;
    margin: 0 auto;
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 0 2rem;
}

.logo {
    color: white;
    text-decoration: none;
}

.logo h1 {
    font-size: 1.8rem;
    font-weight: 800;
    letter-spacing: 1px;
}

.nav-menu {
    display: flex;
    gap: 1.5rem;
}

.nav-menu a {
    color: white;
    text-decoration: none;
    font-weight: 500;
    padding: 0.5rem 1rem;
    border-radius: 6px;
    transition: all 0.3s ease;
}

.nav-menu a:hover {
    background: rgba(255, 255, 255, 0.1);
}

.hamburger {
    display: none;
    flex-direction: column;
    gap: 4px;
    background: none;
    border: none;
    cursor: pointer;
    padding: 0.5rem;
}

.hamburger span {
    width: 25px;
    height: 3px;
    background: white;
    border-radius: 3px;
    transition: all 0.3s ease;
}

.hamburger.active span:nth-child(1) {
    transform: rotate(45deg) translate(5px, 5px);
}

.hamburger.active span:nth-child(2) {
    opacity: 0;
}

.hamburger.active span:nth-child(3) {
    transform: rotate(-45deg) translate(7px, -6px);
}

.main-content {
    max-width: 1200px;
    margin: 0 auto;
    padding: 2rem;
}

.breadcrumb {
    background: white;
    padding: 1rem 2rem;
    margin-bottom: 1.5rem;
    border-radius: 12px;
    box-shadow: 0 2px 10px rgba(0, 0, 0, 0.05);
    border: 1px solid rgba(226, 232, 240, 0.6);
}

.breadcrumb-nav {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    font-size: 0.9rem;
    color: #718096;
}

.breadcrumb-nav a {
    color: #671473; /* C# primary color */
    text-decoration: none;
    font-weight: 500;
    padding: 0.25rem 0.5rem;
    border-radius: 4px;
    transition: all 0.2s ease;
}

.breadcrumb-nav a:hover {
    background: rgba(103, 20, 115, 0.1);
    color: #4b1053; /* Darker shade for hover */
}

.breadcrumb-separator {
    color: #cbd5e0;
    font-weight: 500;
}

.breadcrumb-current {
    color: #2d3748;
    font-weight: 600;
}

.lesson-header {
    background: white;
    padding: 2.5rem;
    border-radius: 16px;
    box-shadow: 0 8px 20px rgba(0, 0, 0, 0.05);
    margin-bottom: 2rem;
    border: 1px solid rgba(226, 232, 240, 0.8);
    position: relative;
}

.lesson-header::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    height: 4px;
    background: #671473; /* C# primary color */
}

.lesson-title {
    color: #671473; /* C# primary color */
    font-size: 2.25rem;
    margin-bottom: 0.75rem;
    font-weight: 700;
}

.lesson-meta {
    color: #718096;
    display: flex;
    gap: 1.5rem;
    margin-bottom: 1.5rem;
    flex-wrap: wrap;
}

.lesson-meta span {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    padding: 0.5rem 1rem;
    background: #f8f9ff;
    border-radius: 20px;
    font-size: 0.9rem;
    font-weight: 500;
}

.lesson-content {
    background: white;
    padding: 2.5rem;
    border-radius: 16px;
    box-shadow: 0 8px 20px rgba(0, 0, 0, 0.05);
    border: 1px solid rgba(226, 232, 240, 0.8);
}

.lesson-content h2 {
    color: #2d3748;
    margin-bottom: 1.5rem;
    margin-top: 2.5rem;
    font-size: 1.75rem;
    font-weight: 600;
    position: relative;
    padding-left: 1rem;
}

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

.lesson-content h2::before {
    content: '';
    position: absolute;
    left: 0;
    top: 50%;
    transform: translateY(-50%);
    width: 4px;
    height: 24px;
    background: #671473; /* C# primary color */
    border-radius: 2px;
}

.lesson-content h3 {
    color: #4a5568;
    margin-bottom: 1rem;
    margin-top: 2rem;
    font-size: 1.3rem;
    font-weight: 600;
}

.lesson-content p {
    margin-bottom: 1.5rem;
    color: #4a5568;
    line-height: 1.8;
}

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

.lesson-content li {
    margin-bottom: 0.75rem;
    color: #4a5568;
    line-height: 1.7;
}

.lesson-content li strong {
    color: #2d3748;
    font-weight: 600;
}

.code-container {
    position: relative;
    margin: 1.5rem 0;
    border-radius: 12px;
    overflow: hidden;
    background: #1e1e1e; /* Matches previous code block */
    box-shadow: 0 8px 20px rgba(0, 0, 0, 0.1);
}

.code-header {
    background: #2d3748;
    padding: 0.75rem 1.5rem;
    display: flex;
    justify-content: space-between;
    align-items: center;
    border-bottom: 1px solid #4a5568;
}

.code-language {
    color: #a0aec0;
    font-size: 0.85rem;
    font-weight: 500;
    text-transform: uppercase;
    letter-spacing: 0.5px;
}

.copy-btn {
    background: #671473; /* C# primary color */
    color: white;
    border: none;
    padding: 0.4rem 0.8rem;
    border-radius: 6px;
    font-size: 0.8rem;
    cursor: pointer;
    transition: all 0.2s ease;
    display: flex;
    align-items: center;
    gap: 0.4rem;
}

.copy-btn:hover {
    background: #4b1053; /* Darker shade for hover */
    transform: translateY(-1px);
}

.copy-btn.copied {
    background: #38a169; /* Green for success, consistent with previous page */
}

.code-block {
    background: #1e1e1e;
    color: #d4d4d4;
    padding: 1.5rem;
    margin: 0;
    overflow-x: auto;
    font-family: 'Consolas', 'Monaco', monospace;
    font-size: 0.95rem;
    line-height: 1.8;
    border: none;
    white-space: pre;
}

.code-block .keyword { color: #569cd6; }
.code-block .string { color: #ce9178; }
.code-block .comment { color: #6a9955; font-style: italic; }
.code-block .type { color: #4ec9b0; }
.code-block .method { color: #dcdcaa; }
.code-block .namespace { color: #4ec9b0; }
.code-block .number { color: #b5cea8; }
.code-block .operator { color: #d4d4d4; }
.code-block .punctuation { color: #d4d4d4; }

.navigation {
    display: flex;
    justify-content: space-between;
    margin-top: 3rem;
    gap: 1rem;
}

.btn {
    display: inline-flex;
    align-items: center;
    gap: 0.5rem;
    padding: 14px 28px;
    background: #671473; /* C# primary color */
    color: white;
    text-decoration: none;
    border-radius: 12px;
    font-weight: 600;
    font-size: 0.95rem;
    transition: all 0.3s ease;
    box-shadow: 0 4px 15px rgba(103, 20, 115, 0.3);
    border: none;
    cursor: pointer;
}

.btn:hover {
    transform: translateY(-2px);
    box-shadow: 0 8px 25px rgba(103, 20, 115, 0.4);
    background: #4b1053; /* Darker shade for hover */
}

.btn-secondary {
    background: #f8f9ff;
    color: #671473; /* C# primary color */
    box-shadow: 0 4px 15px rgba(0, 0, 0, 0.05);
}

.btn-secondary:hover {
    box-shadow: 0 8px 25px rgba(0, 0, 0, 0.1);
    color: #4b1053;
}

.important-note {
    background: #f8f9ff;
    border-left: 4px solid #671473; /* C# primary color */
    padding: 1.5rem;
    margin: 2rem 0;
    border-radius: 8px;
    box-shadow: 0 4px 15px rgba(0, 0, 0, 0.05);
}

.important-note strong {
    color: #671473; /* C# primary color */
    display: block;
    margin-bottom: 0.5rem;
    font-size: 1.05rem;
}

.tip-box {
    background: #f8f9ff;
    border-left: 4px solid #38a169; /* Green for tips, consistent with previous page */
    padding: 1.5rem;
    margin: 2rem 0;
    border-radius: 8px;
    box-shadow: 0 4px 15px rgba(0, 0, 0, 0.05);
}

.warning-box {
    background: #fffaf0;
    border-left: 4px solid #ed8936; /* Orange for warnings, consistent with previous page */
    padding: 1.5rem;
    margin: 2rem 0;
    border-radius: 8px;
    box-shadow: 0 4px 15px rgba(0, 0, 0, 0.05);
}

.scroll-to-top {
    position: fixed;
    bottom: 2rem;
    right: 2rem;
    background: #671473; /* C# primary color */
    color: white;
    border: none;
    border-radius: 50%;
    width: 50px;
    height: 50px;
    cursor: pointer;
    box-shadow: 0 4px 15px rgba(103, 20, 115, 0.3);
    transition: all 0.3s ease;
    opacity: 0;
    visibility: hidden;
}

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

.scroll-to-top:hover {
    transform: translateY(-3px);
    box-shadow: 0 8px 25px rgba(103, 20, 115, 0.4);
}

.dropdown-solution {
    margin: 2rem 0;
    border: 1px solid rgba(226, 232, 240, 0.8);
    border-radius: 12px;
    overflow: hidden;
    background: white;
    box-shadow: 0 4px 15px rgba(0, 0, 0, 0.05);
}

.dropdown-header {
    background: #f8f9ff;
    padding: 1rem 1.5rem;
    cursor: pointer;
    display: flex;
    justify-content: space-between;
    align-items: center;
    transition: all 0.3s ease;
    border: none;
    width: 100%;
    text-align: left;
    font-size: 1rem;
    font-weight: 600;
    color: #2d3748;
}

.dropdown-header:hover {
    background: #e0c3fc; /* Lighter C# purple */
    color: #4b1053;
}

.dropdown-header.active {
    background: #671473; /* C# primary color */
    color: white;
}

.dropdown-icon {
    transition: transform 0.3s ease;
    color: #671473; /* C# primary color */
    font-size: 0.9rem;
}

.dropdown-header.active .dropdown-icon {
    transform: rotate(180deg);
    color: white;
}

.dropdown-content {
    max-height: 0;
    overflow: hidden;
    transition: max-height 0.4s ease-out, padding 0.4s ease-out;
    padding: 0 1.5rem;
}

.dropdown-content.active {
    max-height: 1000px;
    padding: 1.5rem;
    transition: max-height 0.4s ease-in, padding 0.4s ease-in;
}

.solution-label {
    display: inline-flex;
    align-items: center;
    gap: 0.5rem;
    font-size: 0.9rem;
    color: #38a169; /* Green for solutions, consistent with previous page */
    margin-bottom: 1rem;
    font-weight: 500;
}

.solution-label i {
    font-size: 0.8rem;
}

/* Responsive Design */
@media (max-width: 1200px) {
    .main-content {
        max-width: 100%;
        padding: 1.5rem;
    }

    .header-content {
        padding: 0 1.5rem;
    }
}

@media (max-width: 768px) {
    .header-content {
        padding: 0 1rem;
    }

    .nav-menu {
        position: fixed;
        top: 70px;
        right: -100%;
        width: 100%;
        max-width: 300px;
        height: calc(100vh - 70px);
        background: #671473;
        flex-direction: column;
        align-items: flex-start;
        padding: 2rem;
        gap: 1.5rem;
        transition: right 0.3s ease;
        box-shadow: -2px 0 10px rgba(0, 0, 0, 0.2);
        z-index: 999;
    }

    .nav-menu.active {
        right: 0;
    }

    .nav-menu a {
        width: 100%;
        padding: 1rem;
        font-size: 1.1rem;
    }

    .hamburger {
        display: block;
    }

    .main-content {
        padding: 1rem;
    }

    .breadcrumb {
        padding: 1rem;
    }

    .breadcrumb-nav {
        flex-wrap: wrap;
        font-size: 0.85rem;
    }

    .lesson-header {
        padding: 1.5rem;
    }

    .lesson-content {
        padding: 1.5rem;
    }

    .lesson-title {
        font-size: 1.8rem;
    }

    .lesson-meta {
        gap: 0.75rem;
    }

    .lesson-meta span {
        padding: 0.4rem 0.8rem;
        font-size: 0.85rem;
    }

    .lesson-content h2 {
        font-size: 1.5rem;
        padding-left: 0.75rem;
    }

    .lesson-content h2::before {
        height: 20px;
    }

    .lesson-content h3 {
        font-size: 1.2rem;
    }

    .lesson-content ul, .lesson-content ol {
        margin-left: 1.5rem;
    }

    .code-container {
        margin: 1rem 0;
    }

    .code-header {
        padding: 0.6rem 1rem;
    }

    .code-block {
        padding: 1rem;
        font-size: 0.85rem;
    }

    .navigation {
        flex-direction: column;
        gap: 1rem;
        margin-top: 2rem;
    }

    .btn {
        width: 100%;
        text-align: center;
        justify-content: center;
    }

    .scroll-to-top {
        bottom: 1.5rem;
        right: 1.5rem;
        width: 45px;
        height: 45px;
    }
}

@media (max-width: 480px) {
    .logo h1 {
        font-size: 1.4rem;
    }

    .nav-menu a {
        padding: 0.8rem;
        font-size: 1rem;
    }

    .breadcrumb {
        padding: 0.75rem;
    }

    .breadcrumb-nav {
        font-size: 0.8rem;
    }

    .lesson-header {
        padding: 1.25rem;
    }

    .lesson-content {
        padding: 1.25rem;
    }

    .lesson-title {
        font-size: 1.5rem;
    }

    .lesson-header p {
        font-size: 0.9rem;
    }

    .lesson-content h2 {
        font-size: 1.3rem;
    }

    .lesson-content h3 {
        font-size: 1.1rem;
    }

    .lesson-content p, .lesson-content li {
        font-size: 0.95rem;
    }

    .code-block {
        font-size: 0.8rem;
        padding: 0.75rem;
    }

    .code-header {
        padding: 0.5rem 0.75rem;
    }

    .copy-btn {
        padding: 0.3rem 0.6rem;
        font-size: 0.75rem;
    }

    .btn {
        padding: 12px 20px;
        font-size: 0.9rem;
    }

    .important-note, .tip-box, .warning-box {
        padding: 1rem;
        margin: 1.5rem 0;
    }

    .dropdown-header {
        padding: 0.75rem 1rem;
        font-size: 0.9rem;
    }

    .scroll-to-top {
        bottom: 1rem;
        right: 1rem;
        width: 40px;
        height: 40px;
    }
}

@media (max-width: 360px) {
    .logo h1 {
        font-size: 1.2rem;
    }

    .lesson-title {
        font-size: 1.3rem;
    }

    .lesson-content h2 {
        font-size: 1.2rem;
    }

    .lesson-content h3 {
        font-size: 1rem;
    }

    .code-block {
        font-size: 0.75rem;
    }
}

/* Animations */
@keyframes fadeInUp {
    from {
        opacity: 0;
        transform: translateY(30px);
    }
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

body {
    font-family: 'Inter', sans-serif;
    background: #f4f7fc;
    min-height: 100vh;
    color: #333;
}

.container {
    max-width: 1400px;
    margin: 0 auto;
    padding: 2rem;
}

/* Hero Section */
.hero-section {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 3rem;
    align-items: center;
    padding: 3rem 0;
}

.profile-card {
    text-align: center;
}

.profile-img {
    width: 200px;
    height: 200px;
    border-radius: 50%;
    margin-bottom: 1.5rem;
    box-shadow: 0 4px 15px rgba(0,0,0,0.1);
}

.profile-card h1 {
    font-size: 2.5rem;
    color: #1a202c;
    margin-bottom: 1rem;
}

.profile-card p {
    font-size: 1.1rem;
    color: #718096;
}

/* Code Block */
.code-block {
    background: #1e293b;
    border-radius: 12px;
    overflow: hidden;
    box-shadow: 0 8px 30px rgba(0,0,0,0.2);
}

.code-header {
    background: #0f172a;
    padding: 0.75rem 1.25rem;
    display: flex;
    justify-content: space-between;
    align-items: center;
    border-bottom: 1px solid #334155;
}

.code-dots {
    display: flex;
    gap: 0.5rem;
}

.dot {
    width: 12px;
    height: 12px;
    border-radius: 50%;
}

.dot.red { background: #ef4444; }
.dot.yellow { background: #f59e0b; }
.dot.green { background: #10b981; }

.code-lang {
    color: #94a3b8;
    font-size: 0.85rem;
}

.code-content {
    padding: 1.5rem;
}

.code-line {
    display: flex;
    gap: 1.5rem;
    font-family: 'Consolas', monospace;
    font-size: 0.9rem;
    line-height: 1.6;
}

.line-number {
    color: #475569;
    user-select: none;
    min-width: 25px;
    text-align: right;
}

.code-text {
    color: #e2e8f0;
}

.keyword { color: #c792ea; font-weight: 500; }
.class-name { color: #82aaff; }
.method { color: #ffcb6b; }
.string { color: #c3e88d; }
.comment { color: #546e7a; font-style: italic; }

/* Main Content */
main {
    margin-top: 3rem;
}

.main-title {
    font-size: 2rem;
    color: #1a202c;
    margin-bottom: 0.5rem;
    text-align: center;
}

.main-subtitle {
    text-align: center;
    color: #718096;
    margin-bottom: 3rem;
}

/* Courses Grid */
.courses-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: 2rem;
    margin-bottom: 3rem;
}

.course-card {
    background: white;
    padding: 2rem;
    border-radius: 12px;
    box-shadow: 0 2px 10px rgba(0,0,0,0.08);
    transition: transform 0.2s ease, box-shadow 0.2s ease;
}

.course-card:hover {
    transform: translateY(-5px);
    box-shadow: 0 4px 20px rgba(0,0,0,0.12);
}

.course-card h3 {
    color: #1a202c;
    font-size: 1.5rem;
    margin-bottom: 1rem;
}

.course-card h3 i {
    margin-right: 0.5rem;
    color: #667eea;
}

.course-card p {
    color: #718096;
    margin-bottom: 1.5rem;
    line-height: 1.6;
}

.course-lessons {
    list-style: none;
}

.course-lessons li {
    margin-bottom: 0.75rem;
}

.course-lessons a {
    display: flex;
    align-items: center;
    padding: 0.75rem 1rem;
    background: #f7fafc;
    border-radius: 8px;
    text-decoration: none;
    color: #2d3748;
    transition: all 0.2s ease;
    border-left: 3px solid transparent;
}

.course-lessons a:hover {
    background: #edf2f7;
    border-left-color: #667eea;
    transform: translateX(5px);
}

.course-lessons a i {
    color: #667eea;
    margin-right: 0.75rem;
    font-size: 0.9rem;
}

/* Footer */
.footer {
    background: #1a202c;
    color: white;
    text-align: center;
    padding: 2rem;
    margin-top: 4rem;
}

.footer p {
    color: #a0aec0;
}

/* Responsive */
@media (max-width: 768px) {
    .hero-section {
        grid-template-columns: 1fr;
    }

    .courses-grid {
        grid-template-columns: 1fr;
    }

    .container {
        padding: 1rem;
    }
}