/* Reset and Base Styles */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

body {
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
    font-size: 16px;
    line-height: 1.6;
    color: #333;
    background-color: #ffffff;
}

/* Header and Logo */
header {
    background-color: #ffffff;
    /* border-bottom: 1px solid #e0e0e0; */
    padding: 20px 0;
    position: sticky;
    top: 0;
    z-index: 100;
    background-color: rgba(255, 255, 255, 0.98);
    backdrop-filter: blur(10px);
}

.header-container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 20px;
    display: flex;
    justify-content: center;
    align-items: center;
}

.logo-link {
    display: inline-block;
    text-decoration: none;
    transition: opacity 0.3s ease;
}

.logo-link:hover {
    opacity: 0.8;
}

.logo-img {
    max-height: 150px;
    width: auto;
    display: block;
}

/* Navigation Bar */
.navbar {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 20px;
    margin-top: 15px;
    padding-top: 15px;
}

.nav-list {
    list-style: none;
    display: flex;
    justify-content: center;
    gap: 40px;
    flex-wrap: wrap;
}

.nav-list li {
    margin: 0;
}

.nav-list a {
    color: #333;
    text-decoration: none;
    font-size: 16px;
    font-weight: 500;
    padding: 8px 0;
    position: relative;
    transition: color 0.3s ease;
    letter-spacing: 0.5px;
}

.nav-list a::after {
    content: '';
    position: absolute;
    bottom: 0;
    left: 0;
    width: 0;
    height: 2px;
    background-color: #2563eb;
    transition: width 0.3s ease;
}

.nav-list a:hover {
    color: #2563eb;
    text-decoration: none;
}

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

.nav-list a.active {
    color: #2563eb;
}

.nav-list a.active::after {
    width: 100%;
}

/* Main Content */
.main-content {
    max-width: 1200px;
    margin: 0 auto;
    padding: 40px 20px;
    min-height: calc(100vh - 200px);
}

.content-container {
    max-width: 800px;
    margin: 0 auto;
}

.content-container.wide-container {
    max-width: 1200px;
}

h1 {
    font-size: 48px;
    font-weight: 700;
    color: #1e293b;
    margin-bottom: 10px;
    text-align: center;
}

h2 {
    font-size: 24px;
    font-weight: 400;
    color: #64748b;
    margin-bottom: 40px;
    text-align: center;
}

h3 {
    font-size: 28px;
    font-weight: 600;
    color: #1e293b;
    margin-top: 40px;
    margin-bottom: 20px;
}

p {
    margin-bottom: 20px;
    color: #475569;
}

ul {
    margin-left: 20px;
    margin-bottom: 20px;
}

li {
    margin-bottom: 10px;
    color: #475569;
}

a {
    color: #2563eb;
    text-decoration: none;
    transition: color 0.3s ease;
}

a:hover {
    color: #1d4ed8;
    text-decoration: underline;
}

/* Responsive Design */
@media (max-width: 768px) {
    .header-container {
        padding: 15px 20px;
    }

    .logo-img {
        max-height: 50px;
    }

    .navbar {
        padding: 10px 20px;
        margin-top: 10px;
        padding-top: 10px;
    }

    .nav-list {
        gap: 25px;
        justify-content: center;
    }

    .nav-list a {
        font-size: 15px;
    }

    .main-content {
        padding: 30px 15px;
    }

    h1 {
        font-size: 36px;
    }

    h2 {
        font-size: 20px;
    }

    h3 {
        font-size: 24px;
    }

    body {
        font-size: 15px;
    }
}

@media (max-width: 480px) {
    .header-container {
        padding: 12px 15px;
    }

    .logo-img {
        max-height: 45px;
    }

    .navbar {
        padding: 8px 15px;
        margin-top: 8px;
        padding-top: 8px;
    }

    .nav-list {
        gap: 20px;
    }

    .nav-list a {
        font-size: 14px;
    }

    .main-content {
        padding: 25px 12px;
    }

    h1 {
        font-size: 32px;
    }

    h2 {
        font-size: 18px;
    }

    h3 {
        font-size: 22px;
    }
}

/* Utility Classes */
.centered-body {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 20px;
}

hr {
    border: none;
    border-top: 1px solid #e0e0e0;
    margin: 30px 0;
}

/* Page Description */
.page-description {
    text-align: center;
    color: #64748b;
    margin-bottom: 40px;
    font-size: 18px;
}

/* Filter Component */
.filter-container {
    display: flex;
    justify-content: center;
    gap: 12px;
    margin-bottom: 40px;
    flex-wrap: wrap;
}

.filter-btn {
    padding: 10px 24px;
    border: 2px solid #e0e0e0;
    background-color: #ffffff;
    color: #475569;
    font-size: 15px;
    font-weight: 500;
    border-radius: 25px;
    cursor: pointer;
    transition: all 0.3s ease;
    font-family: inherit;
}

.filter-btn:hover {
    border-color: #2563eb;
    color: #2563eb;
    background-color: #eff6ff;
}

.filter-btn.active {
    background-color: #2563eb;
    color: #ffffff;
    border-color: #2563eb;
}

/* Cards Container */
.cards-container {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(300px, 1fr));
    gap: 24px;
    margin-top: 30px;
}

/* Lesson Card */
.lesson-card {
    background-color: #ffffff;
    border: 1px solid #e0e0e0;
    border-radius: 8px;
    padding: 24px;
    transition: all 0.3s ease;
    opacity: 1;
    display: block;
    text-decoration: none;
    color: inherit;
    cursor: pointer;
}

.lesson-card:hover {
    box-shadow: 0 4px 12px rgba(37, 99, 235, 0.1);
    border-color: #2563eb;
    transform: translateY(-2px);
    text-decoration: none;
    color: inherit;
}

.card-header {
    display: flex;
    justify-content: space-between;
    align-items: flex-start;
    margin-bottom: 16px;
    gap: 12px;
}

.lesson-title {
    font-size: 20px;
    font-weight: 600;
    color: #1e293b;
    margin: 0;
    flex: 1;
    line-height: 1.4;
}

.lesson-description {
    color: #64748b;
    line-height: 1.6;
    margin-bottom: 20px;
    font-size: 15px;
}

.card-footer {
    display: flex;
    align-items: center;
    padding-top: 16px;
    border-top: 1px solid #f1f5f9;
}

.duration {
    color: #64748b;
    font-size: 14px;
    font-weight: 500;
}

/* Tags */
.tag {
    display: inline-block;
    padding: 4px 12px;
    border-radius: 12px;
    font-size: 12px;
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 0.5px;
    white-space: nowrap;
    flex-shrink: 0;
}

.technical-tag {
    background-color: #dbeafe;
    color: #1e40af;
}

.socio-ethical-tag {
    background-color: #fce7f3;
    color: #9f1239;
}

.career-tag {
    background-color: #dcfce7;
    color: #166534;
}

/* Responsive adjustments for cards */
@media (max-width: 768px) {
    .cards-container {
        grid-template-columns: 1fr;
        gap: 20px;
    }

    .filter-container {
        gap: 8px;
    }

    .filter-btn {
        padding: 8px 20px;
        font-size: 14px;
    }

    .lesson-card {
        padding: 20px;
    }

    .lesson-title {
        font-size: 18px;
    }

    .page-description {
        font-size: 16px;
    }
}

@media (max-width: 480px) {
    .filter-container {
        gap: 6px;
    }

    .filter-btn {
        padding: 8px 16px;
        font-size: 13px;
    }

    .lesson-card {
        padding: 16px;
    }

    .card-header {
        flex-direction: column;
        align-items: flex-start;
    }

    .tag {
        margin-top: 8px;
    }
}

/* Loading and Error States */
.loading-indicator {
    text-align: center;
    padding: 40px 20px;
    color: #64748b;
}

.loading-indicator p {
    margin: 0;
    font-size: 18px;
}

.error-message {
    text-align: center;
    padding: 40px 20px;
    color: #dc2626;
    background-color: #fef2f2;
    border: 1px solid #fecaca;
    border-radius: 8px;
    margin-top: 20px;
}

.error-message p {
    margin: 0;
    font-size: 16px;
}

/* Lesson Page Styles */
.back-link {
    display: inline-block;
    color: #2563eb;
    text-decoration: none;
    margin-bottom: 20px;
    font-weight: 500;
    transition: color 0.3s ease;
}

.back-link:hover {
    color: #1d4ed8;
    text-decoration: underline;
}

.lesson-header {
    margin-bottom: 40px;
    padding-bottom: 30px;
    border-bottom: 2px solid #e0e0e0;
}

.lesson-header h1 {
    text-align: left;
    margin-bottom: 20px;
    font-size: 42px;
}

.lesson-meta {
    display: flex;
    flex-wrap: wrap;
    gap: 15px;
    margin-bottom: 20px;
    align-items: center;
}

.meta-item {
    color: #64748b;
    font-size: 15px;
}

.lesson-overview {
    font-size: 18px;
    line-height: 1.8;
    color: #475569;
    margin-top: 20px;
}

.lesson-section {
    margin-bottom: 50px;
}

.lesson-section h2 {
    font-size: 32px;
    margin-bottom: 25px;
    color: #1e293b;
    border-bottom: 2px solid #2563eb;
    padding-bottom: 10px;
}

.objectives-list {
    list-style: none;
    padding-left: 0;
}

.objectives-list li {
    padding: 12px 0 12px 30px;
    position: relative;
    color: #475569;
    font-size: 16px;
    line-height: 1.7;
}

.objectives-list li::before {
    content: "✓";
    position: absolute;
    left: 0;
    color: #2563eb;
    font-weight: bold;
    font-size: 18px;
}

/* --- Clean Lesson Outline --- */

.outline-container {
    display: flex;
    flex-direction: column;
    gap: 22px;
}

.outline-section {
    background: none;
    border: none;
    padding: 0;
}

/* Header row: title + duration */
.outline-section-header {
    display: flex;
    justify-content: space-between;
    align-items: baseline;
    margin-bottom: 6px;
    gap: 10px;
}

.outline-section-header h3 {
    font-size: 18px;
    font-weight: 600;
    color: #1e293b;
    margin: 0;
}

/* Subtle duration styling */
.outline-duration {
    font-size: 13px;
    color: #64748b;
    font-weight: 400;
    background: none;
    padding: 0;
}

/* Topics list */
.outline-topics {
    list-style: none;
    padding-left: 0;
    margin: 6px 0 0 0;
}

.outline-topics li {
    padding-left: 14px;
    position: relative;
    font-size: 15px;
    color: #475569;
    line-height: 1.6;
}

/* Simple dot marker */
.outline-topics li::before {
    content: "–";
    position: absolute;
    left: 0;
    color: #94a3b8;
}


.download-section {
    background-color: #f8fafc;
    padding: 30px;
    border-radius: 8px;
    border: 1px solid #e0e0e0;
}

.download-buttons {
    display: flex;
    gap: 15px;
    flex-wrap: wrap;
    justify-content: center;
}

.download-btn {
    display: inline-block;
    padding: 12px 24px;
    background-color: #2563eb;
    color: #ffffff;
    text-decoration: none;
    border-radius: 6px;
    font-weight: 500;
    transition: all 0.3s ease;
    border: 2px solid #2563eb;
}

.download-btn:hover {
    background-color: #1d4ed8;
    border-color: #1d4ed8;
    transform: translateY(-2px);
    box-shadow: 0 4px 8px rgba(37, 99, 235, 0.2);
    text-decoration: none;
    color: #ffffff;
}

.download-btn-guide {
    background-color: #2563eb;
    border-color: #2563eb;
}

.download-btn-slides {
    background-color: #059669;
    border-color: #059669;
}

.download-btn-slides:hover {
    background-color: #047857;
    border-color: #047857;
    box-shadow: 0 4px 8px rgba(5, 150, 105, 0.2);
}

.download-btn-worksheets {
    background-color: #dc2626;
    border-color: #dc2626;
}

.download-btn-worksheets:hover {
    background-color: #b91c1c;
    border-color: #b91c1c;
    box-shadow: 0 4px 8px rgba(220, 38, 38, 0.2);
}

/* Responsive adjustments for lesson page */
@media (max-width: 768px) {
    .lesson-header h1 {
        font-size: 32px;
    }

    .lesson-section h2 {
        font-size: 26px;
    }

    .lesson-meta {
        flex-direction: column;
        align-items: flex-start;
    }

    .outline-section {
        padding: 20px;
    }

    .download-section {
        padding: 20px;
    }

    .download-buttons {
        flex-direction: column;
    }

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

/* --- Lesson condensed layout --- */
.lesson-grid {
    display: grid;
    grid-template-columns: 1fr 1.25fr; /* objectives slightly narrower than outline */
    gap: 28px;
    margin-bottom: 50px;
}

.lesson-panel {
    background-color: #ffffff;
    border: 1px solid #e0e0e0;
    border-radius: 8px;
    padding: 24px;
}

.lesson-panel h2 {
    text-align: left;
    margin-bottom: 18px;
}

/* Put download section under overview, visually integrated */
.lesson-download-under-overview {
    margin-top: 22px;
}

/* Responsive: stack into one column */
@media (max-width: 768px) {
    .lesson-grid {
        grid-template-columns: 1fr;
    }

    .lesson-panel {
        padding: 20px;
    }
}