/* ============================================
   EDEXCEL GCSE COMPUTER SCIENCE - MAIN STYLES
   ============================================ */

/* CSS Variables */
:root {
    --primary-color: #2563eb;
    --primary-dark: #1d4ed8;
    --primary-light: #3b82f6;
    --secondary-color: #7c3aed;
    --accent-color: #06b6d4;
    --success-color: #10b981;
    --warning-color: #f59e0b;
    --danger-color: #ef4444;

    --text-primary: #1f2937;
    --text-secondary: #4b5563;
    --text-light: #9ca3af;

    --bg-primary: #ffffff;
    --bg-secondary: #f3f4f6;
    --bg-dark: #111827;

    --border-color: #e5e7eb;
    --shadow-sm: 0 1px 2px rgba(0, 0, 0, 0.05);
    --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.1);
    --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.1);
    --shadow-xl: 0 20px 25px -5px rgba(0, 0, 0, 0.1);

    --radius-sm: 0.375rem;
    --radius-md: 0.5rem;
    --radius-lg: 0.75rem;
    --radius-xl: 1rem;

    --transition: all 0.3s ease;

    /* Topic Colors */
    --topic1-color: #8b5cf6;
    --topic2-color: #06b6d4;
    --topic3-color: #10b981;
    --topic4-color: #f59e0b;
    --topic5-color: #ef4444;
    --topic6-color: #ec4899;
}

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

html {
    scroll-behavior: smooth;
}

body {
    font-family: 'Segoe UI', system-ui, -apple-system, sans-serif;
    font-size: 16px;
    line-height: 1.6;
    color: var(--text-primary);
    background-color: var(--bg-primary);
}

a {
    text-decoration: none;
    color: inherit;
}

ul {
    list-style: none;
}

img {
    max-width: 100%;
    height: auto;
}

.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 1.5rem;
}

/* ============================================
   NAVIGATION
   ============================================ */

.navbar {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    z-index: 1000;
    background: rgba(255, 255, 255, 0.95);
    backdrop-filter: blur(10px);
    border-bottom: 1px solid var(--border-color);
    padding: 0 1.5rem;
    display: flex;
    justify-content: space-between;
    align-items: center;
    height: 70px;
}

.nav-brand a {
    display: flex;
    align-items: center;
    gap: 0.75rem;
    font-size: 1.5rem;
    font-weight: 700;
    color: var(--primary-color);
}

.nav-brand i {
    font-size: 1.75rem;
}

.nav-toggle {
    display: none;
    background: none;
    border: none;
    font-size: 1.5rem;
    color: var(--text-primary);
    cursor: pointer;
}

.nav-menu {
    display: flex;
    align-items: center;
    gap: 0.5rem;
}

.nav-item {
    position: relative;
}

.nav-link {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    padding: 0.75rem 1rem;
    font-weight: 500;
    color: var(--text-secondary);
    border-radius: var(--radius-md);
    transition: var(--transition);
}

.nav-link:hover {
    color: var(--primary-color);
    background: var(--bg-secondary);
}

.nav-link i.fa-chevron-down {
    font-size: 0.75rem;
    transition: transform 0.3s ease;
}

.dropdown:hover .fa-chevron-down {
    transform: rotate(180deg);
}

.dropdown-menu {
    position: absolute;
    top: 100%;
    left: 0;
    min-width: 250px;
    background: var(--bg-primary);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow-lg);
    opacity: 0;
    visibility: hidden;
    transform: translateY(10px);
    transition: var(--transition);
}

.dropdown:hover .dropdown-menu {
    opacity: 1;
    visibility: visible;
    transform: translateY(0);
}

.dropdown-menu li a {
    display: block;
    padding: 0.75rem 1rem;
    color: var(--text-secondary);
    transition: var(--transition);
}

.dropdown-menu li a:hover {
    background: var(--bg-secondary);
    color: var(--primary-color);
}

.dropdown-menu li:first-child a {
    border-radius: var(--radius-lg) var(--radius-lg) 0 0;
}

.dropdown-menu li:last-child a {
    border-radius: 0 0 var(--radius-lg) var(--radius-lg);
}

/* ============================================
   HERO SECTION
   ============================================ */

.hero {
    position: relative;
    min-height: 100vh;
    display: flex;
    align-items: center;
    padding: 100px 1.5rem 60px;
    background: linear-gradient(135deg, var(--bg-primary) 0%, var(--bg-secondary) 100%);
    overflow: hidden;
}

.hero::before {
    content: '';
    position: absolute;
    top: -50%;
    right: -20%;
    width: 80%;
    height: 150%;
    background: linear-gradient(135deg, rgba(37, 99, 235, 0.05) 0%, rgba(124, 58, 237, 0.05) 100%);
    border-radius: 50%;
    z-index: 0;
}

.hero-content {
    position: relative;
    z-index: 1;
    max-width: 700px;
}

.hero h1 {
    font-size: clamp(2.5rem, 5vw, 4rem);
    font-weight: 800;
    line-height: 1.1;
    margin-bottom: 1rem;
    background: linear-gradient(135deg, var(--primary-color) 0%, var(--secondary-color) 100%);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.hero-subtitle {
    font-size: 1.5rem;
    font-weight: 600;
    color: var(--text-secondary);
    margin-bottom: 0.75rem;
}

.hero-description {
    font-size: 1.125rem;
    color: var(--text-light);
    margin-bottom: 2rem;
}

.hero-buttons {
    display: flex;
    gap: 1rem;
    flex-wrap: wrap;
}

/* Buttons */
.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: 0.5rem;
    padding: 0.875rem 1.75rem;
    font-size: 1rem;
    font-weight: 600;
    border-radius: var(--radius-lg);
    border: none;
    cursor: pointer;
    transition: var(--transition);
}

.btn-primary {
    background: linear-gradient(135deg, var(--primary-color) 0%, var(--secondary-color) 100%);
    color: white;
    box-shadow: 0 4px 15px rgba(37, 99, 235, 0.3);
}

.btn-primary:hover {
    transform: translateY(-2px);
    box-shadow: 0 6px 20px rgba(37, 99, 235, 0.4);
}

.btn-secondary {
    background: var(--bg-primary);
    color: var(--text-primary);
    border: 2px solid var(--border-color);
}

.btn-secondary:hover {
    border-color: var(--primary-color);
    color: var(--primary-color);
}

/* Circuit Pattern Animation */
.hero-graphic {
    position: absolute;
    top: 0;
    right: 0;
    width: 50%;
    height: 100%;
    z-index: 0;
    opacity: 0.1;
}

.circuit-pattern {
    width: 100%;
    height: 100%;
    background-image:
        linear-gradient(var(--primary-color) 1px, transparent 1px),
        linear-gradient(90deg, var(--primary-color) 1px, transparent 1px);
    background-size: 50px 50px;
    animation: circuitPulse 4s ease-in-out infinite;
}

@keyframes circuitPulse {
    0%, 100% { opacity: 0.1; }
    50% { opacity: 0.2; }
}

/* ============================================
   SECTIONS
   ============================================ */

section {
    padding: 5rem 0;
}

.section-title {
    font-size: 2.5rem;
    font-weight: 700;
    text-align: center;
    margin-bottom: 0.75rem;
    color: var(--text-primary);
}

.section-subtitle {
    font-size: 1.125rem;
    text-align: center;
    color: var(--text-secondary);
    margin-bottom: 3rem;
}

/* ============================================
   TOPICS SECTION
   ============================================ */

.topics-section {
    background: var(--bg-secondary);
}

.topics-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(320px, 1fr));
    gap: 1.5rem;
}

.topic-card {
    display: flex;
    gap: 1.25rem;
    padding: 1.5rem;
    background: var(--bg-primary);
    border-radius: var(--radius-xl);
    box-shadow: var(--shadow-md);
    transition: var(--transition);
    border: 2px solid transparent;
}

.topic-card:hover {
    transform: translateY(-5px);
    box-shadow: var(--shadow-xl);
}

.topic-card[data-topic="1"] { border-color: var(--topic1-color); }
.topic-card[data-topic="1"] .topic-icon { background: var(--topic1-color); }

.topic-card[data-topic="2"] { border-color: var(--topic2-color); }
.topic-card[data-topic="2"] .topic-icon { background: var(--topic2-color); }

.topic-card[data-topic="3"] { border-color: var(--topic3-color); }
.topic-card[data-topic="3"] .topic-icon { background: var(--topic3-color); }

.topic-card[data-topic="4"] { border-color: var(--topic4-color); }
.topic-card[data-topic="4"] .topic-icon { background: var(--topic4-color); }

.topic-card[data-topic="5"] { border-color: var(--topic5-color); }
.topic-card[data-topic="5"] .topic-icon { background: var(--topic5-color); }

.topic-card[data-topic="6"] { border-color: var(--topic6-color); }
.topic-card[data-topic="6"] .topic-icon { background: var(--topic6-color); }

.topic-icon {
    flex-shrink: 0;
    width: 60px;
    height: 60px;
    display: flex;
    align-items: center;
    justify-content: center;
    border-radius: var(--radius-lg);
    color: white;
    font-size: 1.5rem;
}

.topic-content h3 {
    font-size: 0.875rem;
    font-weight: 600;
    color: var(--text-light);
    text-transform: uppercase;
    letter-spacing: 0.05em;
    margin-bottom: 0.25rem;
}

.topic-content h4 {
    font-size: 1.25rem;
    font-weight: 700;
    color: var(--text-primary);
    margin-bottom: 0.75rem;
}

.topic-content ul {
    margin-bottom: 0.75rem;
}

.topic-content li {
    font-size: 0.875rem;
    color: var(--text-secondary);
    padding: 0.25rem 0;
    padding-left: 1rem;
    position: relative;
}

.topic-content li::before {
    content: '';
    position: absolute;
    left: 0;
    top: 50%;
    transform: translateY(-50%);
    width: 6px;
    height: 6px;
    border-radius: 50%;
    background: var(--primary-light);
}

.topic-papers {
    display: inline-block;
    font-size: 0.75rem;
    font-weight: 600;
    padding: 0.25rem 0.75rem;
    background: var(--bg-secondary);
    border-radius: var(--radius-sm);
    color: var(--text-secondary);
}

/* ============================================
   ACTIVITIES SECTION
   ============================================ */

.activities-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
    gap: 1.5rem;
}

.activity-card {
    display: flex;
    flex-direction: column;
    align-items: center;
    text-align: center;
    padding: 2rem 1.5rem;
    background: var(--bg-primary);
    border-radius: var(--radius-xl);
    box-shadow: var(--shadow-md);
    transition: var(--transition);
    border: 2px solid var(--border-color);
}

.activity-card:hover {
    transform: translateY(-5px);
    box-shadow: var(--shadow-xl);
    border-color: var(--primary-color);
}

.activity-icon {
    width: 70px;
    height: 70px;
    display: flex;
    align-items: center;
    justify-content: center;
    background: linear-gradient(135deg, var(--primary-color) 0%, var(--secondary-color) 100%);
    border-radius: 50%;
    color: white;
    font-size: 1.75rem;
    margin-bottom: 1rem;
}

.activity-card h3 {
    font-size: 1.125rem;
    font-weight: 700;
    color: var(--text-primary);
    margin-bottom: 0.5rem;
}

.activity-card p {
    font-size: 0.875rem;
    color: var(--text-secondary);
}

/* ============================================
   RESOURCES SECTION
   ============================================ */

.resources-section {
    background: var(--bg-secondary);
}

.resources-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
    gap: 1.5rem;
}

.resource-card {
    display: flex;
    flex-direction: column;
    align-items: center;
    text-align: center;
    padding: 2.5rem 2rem;
    background: var(--bg-primary);
    border-radius: var(--radius-xl);
    box-shadow: var(--shadow-md);
    transition: var(--transition);
}

.resource-card:hover {
    transform: translateY(-5px);
    box-shadow: var(--shadow-xl);
}

.resource-card i {
    font-size: 3rem;
    color: var(--primary-color);
    margin-bottom: 1rem;
}

.resource-card h3 {
    font-size: 1.25rem;
    font-weight: 700;
    color: var(--text-primary);
    margin-bottom: 0.5rem;
}

.resource-card p {
    font-size: 0.95rem;
    color: var(--text-secondary);
}

/* ============================================
   ASSESSMENT INFO
   ============================================ */

.assessment-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(350px, 1fr));
    gap: 2rem;
}

.assessment-card {
    padding: 2rem;
    background: var(--bg-primary);
    border-radius: var(--radius-xl);
    box-shadow: var(--shadow-md);
    border-top: 4px solid;
}

.assessment-card.paper1 {
    border-color: var(--primary-color);
}

.assessment-card.paper2 {
    border-color: var(--secondary-color);
}

.assessment-card h3 {
    display: flex;
    align-items: center;
    gap: 0.75rem;
    font-size: 1.5rem;
    font-weight: 700;
    color: var(--text-primary);
    margin-bottom: 0.25rem;
}

.assessment-card h3 i {
    color: var(--primary-color);
}

.assessment-card.paper2 h3 i {
    color: var(--secondary-color);
}

.assessment-card h4 {
    font-size: 1rem;
    font-weight: 500;
    color: var(--text-secondary);
    margin-bottom: 1.5rem;
}

.assessment-card ul {
    display: flex;
    flex-direction: column;
    gap: 0.75rem;
}

.assessment-card li {
    font-size: 0.95rem;
    color: var(--text-secondary);
}

.assessment-card li strong {
    color: var(--text-primary);
}

/* ============================================
   FOOTER
   ============================================ */

.footer {
    background: var(--bg-dark);
    color: white;
    padding: 4rem 1.5rem 2rem;
}

.footer-content {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
    gap: 2rem;
    margin-bottom: 3rem;
}

.footer-section h4 {
    font-size: 1.125rem;
    font-weight: 600;
    margin-bottom: 1rem;
    color: white;
}

.footer-section p {
    font-size: 0.875rem;
    color: var(--text-light);
    line-height: 1.7;
}

.footer-section ul {
    display: flex;
    flex-direction: column;
    gap: 0.5rem;
}

.footer-section li a {
    font-size: 0.875rem;
    color: var(--text-light);
    transition: var(--transition);
}

.footer-section li a:hover {
    color: white;
}

.footer-bottom {
    text-align: center;
    padding-top: 2rem;
    border-top: 1px solid rgba(255, 255, 255, 0.1);
}

.footer-bottom p {
    font-size: 0.875rem;
    color: var(--text-light);
}

/* ============================================
   TOPIC PAGE STYLES
   ============================================ */

.topic-header {
    padding: 120px 0 60px;
    background: linear-gradient(135deg, var(--bg-secondary) 0%, var(--bg-primary) 100%);
}

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

.topic-header-icon {
    width: 100px;
    height: 100px;
    display: flex;
    align-items: center;
    justify-content: center;
    border-radius: var(--radius-xl);
    color: white;
    font-size: 2.5rem;
}

.topic-header h1 {
    font-size: 2.5rem;
    font-weight: 700;
    margin-bottom: 0.5rem;
}

.topic-header p {
    font-size: 1.125rem;
    color: var(--text-secondary);
}

.breadcrumb {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    font-size: 0.875rem;
    color: var(--text-light);
    margin-bottom: 1rem;
}

.breadcrumb a {
    color: var(--primary-color);
}

.breadcrumb a:hover {
    text-decoration: underline;
}

/* Subtopic Navigation */
.subtopic-nav {
    background: var(--bg-primary);
    border-bottom: 1px solid var(--border-color);
    padding: 1rem 0;
    position: sticky;
    top: 70px;
    z-index: 100;
}

.subtopic-tabs {
    display: flex;
    gap: 0.5rem;
    overflow-x: auto;
    padding-bottom: 0.5rem;
}

.subtopic-tab {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    padding: 0.75rem 1.25rem;
    font-weight: 500;
    color: var(--text-secondary);
    background: var(--bg-secondary);
    border-radius: var(--radius-md);
    white-space: nowrap;
    transition: var(--transition);
}

.subtopic-tab:hover,
.subtopic-tab.active {
    background: var(--primary-color);
    color: white;
}

/* Content Sections */
.content-section {
    padding: 3rem 0;
    border-bottom: 1px solid var(--border-color);
}

.content-section:last-child {
    border-bottom: none;
}

.content-section h2 {
    font-size: 1.75rem;
    font-weight: 700;
    margin-bottom: 1.5rem;
    color: var(--text-primary);
}

.content-section h3 {
    font-size: 1.25rem;
    font-weight: 600;
    margin: 1.5rem 0 1rem;
    color: var(--text-primary);
}

.content-section p {
    font-size: 1rem;
    color: var(--text-secondary);
    margin-bottom: 1rem;
    line-height: 1.8;
}

.content-section ul,
.content-section ol {
    margin: 1rem 0;
    padding-left: 1.5rem;
}

.content-section li {
    font-size: 1rem;
    color: var(--text-secondary);
    margin-bottom: 0.5rem;
    line-height: 1.7;
    list-style: disc;
}

.content-section ol li {
    list-style: decimal;
}

/* Info Boxes */
.info-box {
    padding: 1.5rem;
    border-radius: var(--radius-lg);
    margin: 1.5rem 0;
}

.info-box.definition {
    background: rgba(37, 99, 235, 0.1);
    border-left: 4px solid var(--primary-color);
}

.info-box.tip {
    background: rgba(16, 185, 129, 0.1);
    border-left: 4px solid var(--success-color);
}

.info-box.warning {
    background: rgba(245, 158, 11, 0.1);
    border-left: 4px solid var(--warning-color);
}

.info-box.exam {
    background: rgba(124, 58, 237, 0.1);
    border-left: 4px solid var(--secondary-color);
}

.info-box h4 {
    font-size: 1rem;
    font-weight: 600;
    margin-bottom: 0.5rem;
    display: flex;
    align-items: center;
    gap: 0.5rem;
}

.info-box p {
    margin-bottom: 0;
}

/* Code Blocks */
.code-block {
    background: var(--bg-dark);
    border-radius: var(--radius-lg);
    padding: 1.5rem;
    margin: 1rem 0;
    overflow-x: auto;
}

.code-block pre {
    font-family: 'Fira Code', 'Consolas', monospace;
    font-size: 0.9rem;
    color: #e5e7eb;
    line-height: 1.6;
    margin: 0;
}

.code-block code {
    font-family: inherit;
}

/* Video Embed */
.video-container {
    position: relative;
    padding-bottom: 56.25%;
    height: 0;
    overflow: hidden;
    border-radius: var(--radius-lg);
    margin: 1.5rem 0;
    background: var(--bg-dark);
}

.video-container iframe {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
}

.video-link {
    display: flex;
    align-items: center;
    gap: 1rem;
    padding: 1rem 1.5rem;
    background: var(--bg-secondary);
    border-radius: var(--radius-lg);
    margin: 1rem 0;
    transition: var(--transition);
}

.video-link:hover {
    background: var(--bg-primary);
    box-shadow: var(--shadow-md);
}

.video-link i {
    font-size: 2rem;
    color: #ff0000;
}

.video-link-content h4 {
    font-size: 1rem;
    font-weight: 600;
    margin-bottom: 0.25rem;
}

.video-link-content p {
    font-size: 0.875rem;
    color: var(--text-light);
    margin: 0;
}

/* Activity Links in Topics */
.activity-links {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
    gap: 1rem;
    margin: 1.5rem 0;
}

.activity-link {
    display: flex;
    align-items: center;
    gap: 0.75rem;
    padding: 1rem;
    background: var(--bg-secondary);
    border-radius: var(--radius-md);
    transition: var(--transition);
}

.activity-link:hover {
    background: var(--primary-color);
    color: white;
}

.activity-link i {
    font-size: 1.25rem;
}

/* Past Paper Questions */
.past-paper-question {
    background: var(--bg-secondary);
    border-radius: var(--radius-lg);
    padding: 1.5rem;
    margin: 1.5rem 0;
}

.past-paper-question .question-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 1rem;
    padding-bottom: 0.75rem;
    border-bottom: 1px solid var(--border-color);
}

.past-paper-question .paper-ref {
    font-size: 0.875rem;
    font-weight: 600;
    color: var(--primary-color);
}

.past-paper-question .marks {
    font-size: 0.875rem;
    font-weight: 600;
    padding: 0.25rem 0.75rem;
    background: var(--primary-color);
    color: white;
    border-radius: var(--radius-sm);
}

.past-paper-question .question-text {
    font-size: 1rem;
    color: var(--text-primary);
    margin-bottom: 1rem;
}

.answer-reveal {
    margin-top: 1rem;
}

.answer-reveal summary {
    cursor: pointer;
    font-weight: 600;
    color: var(--primary-color);
    padding: 0.5rem;
    border-radius: var(--radius-sm);
    transition: var(--transition);
}

.answer-reveal summary:hover {
    background: rgba(37, 99, 235, 0.1);
}

.answer-content {
    padding: 1rem;
    margin-top: 0.5rem;
    background: var(--bg-primary);
    border-radius: var(--radius-md);
    border-left: 3px solid var(--success-color);
}

/* ============================================
   ACTIVITY PAGE STYLES
   ============================================ */

.activity-header {
    padding: 120px 0 40px;
    background: linear-gradient(135deg, var(--primary-color) 0%, var(--secondary-color) 100%);
    color: white;
    text-align: center;
}

.activity-header h1 {
    font-size: 2.5rem;
    font-weight: 700;
    margin-bottom: 0.5rem;
}

.activity-header p {
    font-size: 1.125rem;
    opacity: 0.9;
}

.activity-controls {
    display: flex;
    justify-content: center;
    gap: 1rem;
    padding: 1.5rem;
    background: var(--bg-secondary);
    flex-wrap: wrap;
}

.topic-select,
.difficulty-select {
    padding: 0.75rem 1.25rem;
    border: 2px solid var(--border-color);
    border-radius: var(--radius-md);
    font-size: 1rem;
    background: var(--bg-primary);
    cursor: pointer;
}

.activity-area {
    min-height: 60vh;
    padding: 2rem;
    display: flex;
    flex-direction: column;
    align-items: center;
}

.game-stats {
    display: flex;
    gap: 2rem;
    margin-bottom: 2rem;
}

.stat {
    text-align: center;
}

.stat-value {
    font-size: 2rem;
    font-weight: 700;
    color: var(--primary-color);
}

.stat-label {
    font-size: 0.875rem;
    color: var(--text-light);
}

/* Memory Match Specific */
.memory-grid {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 1rem;
    max-width: 600px;
    margin: 0 auto;
}

.memory-card {
    aspect-ratio: 1;
    min-height: 100px;
    perspective: 1000px;
    cursor: pointer;
}

.memory-card-inner {
    position: relative;
    width: 100%;
    height: 100%;
    transition: transform 0.6s;
    transform-style: preserve-3d;
}

.memory-card.flipped .memory-card-inner {
    transform: rotateY(180deg);
}

.memory-card-front,
.memory-card-back {
    position: absolute;
    width: 100%;
    height: 100%;
    backface-visibility: hidden;
    border-radius: var(--radius-lg);
    display: flex;
    align-items: center;
    justify-content: center;
    padding: 1rem;
    text-align: center;
}

.memory-card-front {
    background: linear-gradient(135deg, var(--primary-color) 0%, var(--secondary-color) 100%);
    color: white;
    font-size: 2rem;
}

.memory-card-back {
    background: var(--bg-primary);
    border: 2px solid var(--border-color);
    transform: rotateY(180deg);
    font-size: 0.9rem;
    color: var(--text-primary);
    overflow: hidden;
}

.memory-card.matched .memory-card-back {
    background: rgba(16, 185, 129, 0.1);
    border-color: var(--success-color);
}

/* Connection Wall Specific */
.connection-grid {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 0.75rem;
    max-width: 800px;
    margin: 0 auto 2rem;
}

.connection-item {
    padding: 1.25rem;
    background: var(--bg-primary);
    border: 2px solid var(--border-color);
    border-radius: var(--radius-md);
    text-align: center;
    font-weight: 500;
    cursor: pointer;
    transition: var(--transition);
}

.connection-item:hover {
    border-color: var(--primary-color);
}

.connection-item.selected {
    background: var(--primary-color);
    color: white;
    border-color: var(--primary-color);
}

.connection-item.solved {
    cursor: default;
}

.connection-item.solved.group-1 { background: var(--topic1-color); color: white; }
.connection-item.solved.group-2 { background: var(--topic2-color); color: white; }
.connection-item.solved.group-3 { background: var(--topic3-color); color: white; }
.connection-item.solved.group-4 { background: var(--topic4-color); color: white; }

.solved-groups {
    width: 100%;
    max-width: 800px;
}

.solved-group {
    padding: 1rem;
    border-radius: var(--radius-md);
    margin-bottom: 0.75rem;
    color: white;
}

.solved-group h4 {
    font-size: 1rem;
    margin-bottom: 0.5rem;
}

.solved-group p {
    font-size: 0.875rem;
    opacity: 0.9;
    margin: 0;
}

/* Sequence Builder */
.sequence-container {
    max-width: 600px;
    margin: 0 auto;
}

.sequence-item {
    display: flex;
    align-items: center;
    gap: 1rem;
    padding: 1rem 1.5rem;
    background: var(--bg-primary);
    border: 2px solid var(--border-color);
    border-radius: var(--radius-md);
    margin-bottom: 0.75rem;
    cursor: grab;
    transition: var(--transition);
}

.sequence-item:hover {
    border-color: var(--primary-color);
}

.sequence-item.dragging {
    opacity: 0.5;
    cursor: grabbing;
}

.sequence-item .step-number {
    width: 30px;
    height: 30px;
    display: flex;
    align-items: center;
    justify-content: center;
    background: var(--bg-secondary);
    border-radius: 50%;
    font-weight: 600;
    color: var(--text-secondary);
}

.sequence-item.correct {
    border-color: var(--success-color);
    background: rgba(16, 185, 129, 0.05);
}

.sequence-item.correct .step-number {
    background: var(--success-color);
    color: white;
}

.sequence-item.incorrect {
    border-color: var(--danger-color);
    background: rgba(239, 68, 68, 0.05);
}

/* Code Breaker */
.code-challenge {
    max-width: 700px;
    width: 100%;
    margin: 0 auto;
}

.code-editor {
    background: var(--bg-dark);
    border-radius: var(--radius-lg);
    overflow: hidden;
}

.code-editor-header {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    padding: 0.75rem 1rem;
    background: rgba(0, 0, 0, 0.2);
}

.code-editor-header span {
    width: 12px;
    height: 12px;
    border-radius: 50%;
}

.code-editor-header span:nth-child(1) { background: #ef4444; }
.code-editor-header span:nth-child(2) { background: #f59e0b; }
.code-editor-header span:nth-child(3) { background: #10b981; }

.code-editor textarea {
    width: 100%;
    min-height: 200px;
    padding: 1.5rem;
    background: transparent;
    border: none;
    color: #e5e7eb;
    font-family: 'Fira Code', 'Consolas', monospace;
    font-size: 0.95rem;
    line-height: 1.6;
    resize: vertical;
}

.code-editor textarea:focus {
    outline: none;
}

.code-output {
    padding: 1rem 1.5rem;
    background: rgba(0, 0, 0, 0.3);
    border-top: 1px solid rgba(255, 255, 255, 0.1);
}

.code-output h4 {
    font-size: 0.875rem;
    color: var(--text-light);
    margin-bottom: 0.5rem;
}

.code-output pre {
    font-family: 'Fira Code', 'Consolas', monospace;
    font-size: 0.875rem;
    color: #10b981;
}

.code-output.error pre {
    color: #ef4444;
}

/* Logic Gates */
.logic-workspace {
    display: flex;
    gap: 2rem;
    max-width: 1000px;
    width: 100%;
}

.gate-palette {
    width: 150px;
    background: var(--bg-secondary);
    border-radius: var(--radius-lg);
    padding: 1rem;
}

.gate-palette h3 {
    font-size: 0.875rem;
    font-weight: 600;
    color: var(--text-secondary);
    margin-bottom: 1rem;
}

.gate-item {
    display: flex;
    flex-direction: column;
    align-items: center;
    padding: 0.75rem;
    background: var(--bg-primary);
    border-radius: var(--radius-md);
    margin-bottom: 0.5rem;
    cursor: grab;
    transition: var(--transition);
}

.gate-item:hover {
    box-shadow: var(--shadow-md);
}

.gate-item svg {
    width: 40px;
    height: 40px;
}

.gate-item span {
    font-size: 0.75rem;
    font-weight: 600;
    margin-top: 0.25rem;
}

.logic-canvas {
    flex: 1;
    min-height: 400px;
    background: var(--bg-primary);
    border: 2px dashed var(--border-color);
    border-radius: var(--radius-lg);
    position: relative;
}

.truth-table {
    margin-top: 2rem;
    overflow-x: auto;
}

.truth-table table {
    width: 100%;
    border-collapse: collapse;
    background: var(--bg-primary);
    border-radius: var(--radius-lg);
    overflow: hidden;
}

.truth-table th,
.truth-table td {
    padding: 0.75rem 1rem;
    text-align: center;
    border-bottom: 1px solid var(--border-color);
}

.truth-table th {
    background: var(--bg-secondary);
    font-weight: 600;
}

.truth-table input[type="text"] {
    width: 40px;
    padding: 0.25rem;
    text-align: center;
    border: 2px solid var(--border-color);
    border-radius: var(--radius-sm);
}

.truth-table input.correct {
    border-color: var(--success-color);
    background: rgba(16, 185, 129, 0.1);
}

.truth-table input.incorrect {
    border-color: var(--danger-color);
    background: rgba(239, 68, 68, 0.1);
}

/* Cookie Quizzer */
.quiz-container {
    max-width: 700px;
    width: 100%;
}

.quiz-progress {
    display: flex;
    align-items: center;
    gap: 1rem;
    margin-bottom: 2rem;
}

.progress-bar {
    flex: 1;
    height: 8px;
    background: var(--bg-secondary);
    border-radius: 4px;
    overflow: hidden;
}

.progress-fill {
    height: 100%;
    background: linear-gradient(90deg, var(--primary-color) 0%, var(--secondary-color) 100%);
    transition: width 0.3s ease;
}

.progress-text {
    font-size: 0.875rem;
    font-weight: 600;
    color: var(--text-secondary);
}

.quiz-question {
    background: var(--bg-primary);
    border-radius: var(--radius-xl);
    padding: 2rem;
    box-shadow: var(--shadow-md);
}

.quiz-question h3 {
    font-size: 1.25rem;
    margin-bottom: 1.5rem;
    color: var(--text-primary);
}

.quiz-options {
    display: flex;
    flex-direction: column;
    gap: 0.75rem;
}

.quiz-option {
    display: flex;
    align-items: center;
    gap: 1rem;
    padding: 1rem 1.25rem;
    background: var(--bg-secondary);
    border: 2px solid var(--border-color);
    border-radius: var(--radius-md);
    cursor: pointer;
    transition: var(--transition);
}

.quiz-option:hover {
    border-color: var(--primary-color);
}

.quiz-option.selected {
    border-color: var(--primary-color);
    background: rgba(37, 99, 235, 0.1);
}

.quiz-option.correct {
    border-color: var(--success-color);
    background: rgba(16, 185, 129, 0.1);
}

.quiz-option.incorrect {
    border-color: var(--danger-color);
    background: rgba(239, 68, 68, 0.1);
}

.option-letter {
    width: 30px;
    height: 30px;
    display: flex;
    align-items: center;
    justify-content: center;
    background: var(--bg-primary);
    border-radius: 50%;
    font-weight: 600;
    color: var(--text-secondary);
}

.quiz-option.selected .option-letter {
    background: var(--primary-color);
    color: white;
}

.quiz-option.correct .option-letter {
    background: var(--success-color);
    color: white;
}

.quiz-option.incorrect .option-letter {
    background: var(--danger-color);
    color: white;
}

/* Category Sort */
.category-sort-container {
    max-width: 900px;
    width: 100%;
}

.items-pool {
    display: flex;
    flex-wrap: wrap;
    gap: 0.75rem;
    padding: 1.5rem;
    background: var(--bg-secondary);
    border-radius: var(--radius-lg);
    margin-bottom: 2rem;
    min-height: 80px;
}

.sort-item {
    padding: 0.75rem 1.25rem;
    background: var(--bg-primary);
    border: 2px solid var(--border-color);
    border-radius: var(--radius-md);
    cursor: grab;
    transition: var(--transition);
    font-weight: 500;
}

.sort-item:hover {
    border-color: var(--primary-color);
    box-shadow: var(--shadow-sm);
}

.sort-item.dragging {
    opacity: 0.5;
}

.categories-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
    gap: 1rem;
}

.category-box {
    background: var(--bg-primary);
    border: 2px dashed var(--border-color);
    border-radius: var(--radius-lg);
    min-height: 200px;
    transition: var(--transition);
}

.category-box.drag-over {
    border-color: var(--primary-color);
    background: rgba(37, 99, 235, 0.05);
}

.category-box h4 {
    padding: 1rem;
    background: var(--bg-secondary);
    border-radius: var(--radius-lg) var(--radius-lg) 0 0;
    font-size: 1rem;
    font-weight: 600;
    text-align: center;
}

.category-items {
    padding: 1rem;
    display: flex;
    flex-direction: column;
    gap: 0.5rem;
    min-height: 150px;
}

/* ============================================
   PAST PAPERS PAGE
   ============================================ */

.papers-filter {
    display: flex;
    gap: 1rem;
    justify-content: center;
    flex-wrap: wrap;
    margin-bottom: 2rem;
}

.filter-btn {
    padding: 0.75rem 1.5rem;
    background: var(--bg-secondary);
    border: 2px solid var(--border-color);
    border-radius: var(--radius-md);
    font-weight: 500;
    cursor: pointer;
    transition: var(--transition);
}

.filter-btn:hover,
.filter-btn.active {
    background: var(--primary-color);
    border-color: var(--primary-color);
    color: white;
}

.papers-list {
    display: flex;
    flex-direction: column;
    gap: 1rem;
    max-width: 800px;
    margin: 0 auto;
}

.paper-item {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 1.5rem;
    background: var(--bg-primary);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-lg);
    transition: var(--transition);
}

.paper-item:hover {
    box-shadow: var(--shadow-md);
}

.paper-info h4 {
    font-size: 1.125rem;
    font-weight: 600;
    margin-bottom: 0.25rem;
}

.paper-info p {
    font-size: 0.875rem;
    color: var(--text-secondary);
}

.paper-links {
    display: flex;
    gap: 0.75rem;
}

.paper-link {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    padding: 0.5rem 1rem;
    background: var(--bg-secondary);
    border-radius: var(--radius-md);
    font-size: 0.875rem;
    font-weight: 500;
    transition: var(--transition);
}

.paper-link:hover {
    background: var(--primary-color);
    color: white;
}

/* ============================================
   RESPONSIVE DESIGN
   ============================================ */

@media (max-width: 768px) {
    .nav-toggle {
        display: block;
    }

    .nav-menu {
        position: fixed;
        top: 70px;
        left: 0;
        right: 0;
        background: var(--bg-primary);
        flex-direction: column;
        padding: 1rem;
        border-bottom: 1px solid var(--border-color);
        transform: translateY(-100%);
        opacity: 0;
        visibility: hidden;
        transition: var(--transition);
    }

    .nav-menu.active {
        transform: translateY(0);
        opacity: 1;
        visibility: visible;
    }

    .dropdown-menu {
        position: static;
        opacity: 1;
        visibility: visible;
        transform: none;
        box-shadow: none;
        border: none;
        background: var(--bg-secondary);
        margin-top: 0.5rem;
        display: none;
    }

    .dropdown.active .dropdown-menu {
        display: block;
    }

    .hero {
        padding-top: 100px;
    }

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

    .topic-card {
        flex-direction: column;
        text-align: center;
    }

    .activities-grid {
        grid-template-columns: repeat(2, 1fr);
    }

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

    .memory-grid {
        grid-template-columns: repeat(3, 1fr);
    }

    .connection-grid {
        grid-template-columns: repeat(2, 1fr);
    }

    .logic-workspace {
        flex-direction: column;
    }

    .gate-palette {
        width: 100%;
        display: flex;
        flex-wrap: wrap;
        gap: 0.5rem;
    }

    .gate-palette h3 {
        width: 100%;
    }

    .gate-item {
        flex: 1;
        min-width: 80px;
    }
}

@media (max-width: 480px) {
    .activities-grid {
        grid-template-columns: 1fr;
    }

    .memory-grid {
        grid-template-columns: repeat(2, 1fr);
    }

    .game-stats {
        flex-wrap: wrap;
        justify-content: center;
    }
}

/* Print Styles */
@media print {
    .navbar,
    .hero-buttons,
    .activity-controls,
    footer {
        display: none;
    }

    .hero {
        min-height: auto;
        padding: 2rem 0;
    }

    section {
        padding: 2rem 0;
    }
}