/* CSS Variables for theming */
:root {
    --bg-primary: #1a1a2e;
    --bg-secondary: #16213e;
    --bg-tertiary: #0f3460;
    --text-primary: #eaeaea;
    --text-secondary: #a0a0a0;
    --accent: #e94560;
    --accent-hover: #ff6b6b;
    --success: #4ecca3;
    --warning: #ffc107;
    --error: #ff4757;
    --code-bg: #0d1117;
    --border: #2d3748;
    --shadow: rgba(0, 0, 0, 0.3);
}

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

html {
    scroll-behavior: smooth;
}

body {
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    background-color: var(--bg-primary);
    color: var(--text-primary);
    line-height: 1.6;
    min-height: 100vh;
}

/* Typography */
h1, h2, h3, h4 {
    margin-bottom: 1rem;
    font-weight: 600;
}

h1 { font-size: 2.5rem; }
h2 { font-size: 2rem; }
h3 { font-size: 1.5rem; }
h4 { font-size: 1.25rem; }

p {
    margin-bottom: 1rem;
    color: var(--text-secondary);
}

a {
    color: var(--accent);
    text-decoration: none;
    transition: color 0.3s ease;
}

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

/* Container */
.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 20px;
}

/* Header & Navigation */
header {
    background-color: var(--bg-secondary);
    padding: 1rem 0;
    position: sticky;
    top: 0;
    z-index: 1000;
    box-shadow: 0 2px 10px var(--shadow);
}

nav {
    display: flex;
    justify-content: space-between;
    align-items: center;
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 20px;
}

.logo {
    font-size: 1.5rem;
    font-weight: 700;
    color: var(--text-primary);
    display: flex;
    align-items: center;
    gap: 0.5rem;
}

.logo span {
    color: var(--accent);
}

.nav-links {
    display: flex;
    list-style: none;
    gap: 2rem;
}

.nav-links a {
    color: var(--text-primary);
    font-weight: 500;
    padding: 0.5rem 1rem;
    border-radius: 5px;
    transition: background-color 0.3s ease;
}

.nav-links a:hover {
    background-color: var(--bg-tertiary);
}

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

/* Hero Section */
.hero {
    text-align: center;
    padding: 4rem 0;
    background: linear-gradient(135deg, var(--bg-secondary), var(--bg-tertiary));
}

.hero h1 {
    font-size: 3rem;
    margin-bottom: 1rem;
}

.hero p {
    font-size: 1.25rem;
    max-width: 600px;
    margin: 0 auto 2rem;
}

/* Progress Bar */
.progress-container {
    background-color: var(--bg-secondary);
    padding: 1.5rem;
    border-radius: 10px;
    margin: 2rem 0;
}

.progress-bar {
    background-color: var(--bg-tertiary);
    border-radius: 10px;
    height: 20px;
    overflow: hidden;
    margin-top: 0.5rem;
}

.progress-fill {
    background: linear-gradient(90deg, var(--accent), var(--accent-hover));
    height: 100%;
    border-radius: 10px;
    transition: width 0.5s ease;
}

.progress-text {
    display: flex;
    justify-content: space-between;
    margin-top: 0.5rem;
    font-size: 0.9rem;
    color: var(--text-secondary);
}

/* Topic Cards */
.topics-section {
    padding: 3rem 0;
}

.topics-section h2 {
    margin-bottom: 2rem;
}

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

.topic-card {
    background-color: var(--bg-secondary);
    border-radius: 10px;
    padding: 1.5rem;
    transition: transform 0.3s ease, box-shadow 0.3s ease;
    border: 1px solid var(--border);
    position: relative;
    overflow: hidden;
}

.topic-card:hover {
    transform: translateY(-5px);
    box-shadow: 0 10px 30px var(--shadow);
}

.topic-card.completed::after {
    content: '✓';
    position: absolute;
    top: 10px;
    right: 10px;
    background-color: var(--success);
    color: white;
    width: 25px;
    height: 25px;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 0.8rem;
}

.topic-card h3 {
    color: var(--text-primary);
    margin-bottom: 0.5rem;
}

.topic-card p {
    font-size: 0.9rem;
    margin-bottom: 1rem;
}

.topic-card .difficulty {
    display: inline-block;
    padding: 0.25rem 0.75rem;
    border-radius: 15px;
    font-size: 0.75rem;
    font-weight: 600;
    text-transform: uppercase;
}

.difficulty.beginner {
    background-color: var(--success);
    color: var(--bg-primary);
}

.difficulty.intermediate {
    background-color: var(--warning);
    color: var(--bg-primary);
}

/* Lesson Content */
.lesson-container {
    max-width: 900px;
    margin: 0 auto;
    padding: 2rem 20px;
}

.lesson-header {
    margin-bottom: 2rem;
    padding-bottom: 1rem;
    border-bottom: 1px solid var(--border);
}

.lesson-header h1 {
    margin-bottom: 0.5rem;
}

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

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

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

.lesson-content section {
    margin-bottom: 3rem;
}

.lesson-content h2 {
    color: var(--accent);
    margin-bottom: 1rem;
}

.lesson-content ul, .lesson-content ol {
    margin-left: 1.5rem;
    margin-bottom: 1rem;
    color: var(--text-secondary);
}

.lesson-content li {
    margin-bottom: 0.5rem;
}

/* Code Blocks */
.code-block {
    background-color: var(--code-bg);
    border-radius: 8px;
    margin: 1rem 0;
    overflow: hidden;
    border: 1px solid var(--border);
}

.code-header {
    background-color: var(--bg-tertiary);
    padding: 0.5rem 1rem;
    display: flex;
    justify-content: space-between;
    align-items: center;
    font-size: 0.85rem;
    color: var(--text-secondary);
}

.code-header .language {
    font-weight: 600;
}

pre {
    padding: 1rem;
    overflow-x: auto;
    font-family: 'Fira Code', 'Consolas', monospace;
    font-size: 0.9rem;
    line-height: 1.5;
}

code {
    font-family: 'Fira Code', 'Consolas', monospace;
}

/* Inline code */
p code, li code {
    background-color: var(--code-bg);
    padding: 0.2rem 0.5rem;
    border-radius: 4px;
    font-size: 0.85em;
    color: var(--accent);
}

/* Syntax Highlighting */
.keyword { color: #c678dd; }
.string { color: #98c379; }
.number { color: #d19a66; }
.comment { color: #5c6370; font-style: italic; }
.function { color: #61afef; }
.operator { color: #56b6c2; }
.variable { color: #e06c75; }
.property { color: #e5c07b; }

/* Interactive Code Editor */
.code-editor {
    background-color: var(--code-bg);
    border-radius: 8px;
    margin: 1.5rem 0;
    border: 1px solid var(--border);
    overflow: hidden;
}

.editor-header {
    background-color: var(--bg-tertiary);
    padding: 0.75rem 1rem;
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.editor-header span {
    font-weight: 600;
    color: var(--text-secondary);
}

.editor-textarea {
    width: 100%;
    min-height: 150px;
    padding: 1rem;
    background-color: var(--code-bg);
    color: var(--text-primary);
    border: none;
    font-family: 'Fira Code', 'Consolas', monospace;
    font-size: 0.9rem;
    line-height: 1.5;
    resize: vertical;
    outline: none;
}

.editor-textarea:focus {
    box-shadow: inset 0 0 0 2px var(--accent);
}

.editor-output {
    border-top: 1px solid var(--border);
    padding: 1rem;
    background-color: #0a0e14;
    min-height: 60px;
    font-family: 'Fira Code', 'Consolas', monospace;
    font-size: 0.85rem;
}

.output-label {
    color: var(--text-secondary);
    font-size: 0.75rem;
    text-transform: uppercase;
    margin-bottom: 0.5rem;
}

.output-content {
    color: var(--success);
    white-space: pre-wrap;
}

.output-content.error {
    color: var(--error);
}

/* Buttons */
.btn {
    display: inline-block;
    padding: 0.75rem 1.5rem;
    border: none;
    border-radius: 5px;
    font-size: 1rem;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.3s ease;
    text-align: center;
}

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

.btn-primary:hover {
    background-color: var(--accent-hover);
}

.btn-secondary {
    background-color: var(--bg-tertiary);
    color: var(--text-primary);
}

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

.btn-success {
    background-color: var(--success);
    color: var(--bg-primary);
}

.btn-success:hover {
    background-color: #3db892;
}

.btn-small {
    padding: 0.5rem 1rem;
    font-size: 0.85rem;
}

/* Challenge Box */
.challenge-box {
    background-color: var(--bg-tertiary);
    border-left: 4px solid var(--accent);
    border-radius: 0 8px 8px 0;
    padding: 1.5rem;
    margin: 2rem 0;
}

.challenge-box h4 {
    color: var(--accent);
    margin-bottom: 0.5rem;
}

/* Info Box */
.info-box {
    background-color: var(--bg-secondary);
    border-left: 4px solid var(--success);
    border-radius: 0 8px 8px 0;
    padding: 1rem 1.5rem;
    margin: 1rem 0;
}

.info-box.warning {
    border-left-color: var(--warning);
}

/* Lesson Navigation */
.lesson-nav {
    display: flex;
    justify-content: space-between;
    margin-top: 3rem;
    padding-top: 2rem;
    border-top: 1px solid var(--border);
}

.lesson-nav a {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    padding: 0.75rem 1.5rem;
    background-color: var(--bg-secondary);
    border-radius: 5px;
    transition: background-color 0.3s ease;
}

.lesson-nav a:hover {
    background-color: var(--bg-tertiary);
}

.lesson-nav .next {
    margin-left: auto;
}

/* Quiz Styles */
.quiz-container {
    max-width: 800px;
    margin: 0 auto;
    padding: 2rem 20px;
}

.quiz-header {
    text-align: center;
    margin-bottom: 2rem;
}

.quiz-progress {
    display: flex;
    justify-content: center;
    gap: 0.5rem;
    margin-bottom: 2rem;
}

.quiz-progress .dot {
    width: 12px;
    height: 12px;
    border-radius: 50%;
    background-color: var(--bg-tertiary);
    transition: background-color 0.3s ease;
}

.quiz-progress .dot.active {
    background-color: var(--accent);
}

.quiz-progress .dot.correct {
    background-color: var(--success);
}

.quiz-progress .dot.incorrect {
    background-color: var(--error);
}

.question-card {
    background-color: var(--bg-secondary);
    border-radius: 10px;
    padding: 2rem;
    margin-bottom: 1.5rem;
}

.question-number {
    color: var(--accent);
    font-size: 0.9rem;
    margin-bottom: 0.5rem;
}

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

.options-list {
    list-style: none;
}

.option {
    background-color: var(--bg-tertiary);
    border: 2px solid var(--border);
    border-radius: 8px;
    padding: 1rem 1.5rem;
    margin-bottom: 0.75rem;
    cursor: pointer;
    transition: all 0.3s ease;
    display: flex;
    align-items: center;
    gap: 1rem;
}

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

.option.selected {
    border-color: var(--accent);
    background-color: rgba(233, 69, 96, 0.1);
}

.option.correct {
    border-color: var(--success);
    background-color: rgba(78, 204, 163, 0.1);
}

.option.incorrect {
    border-color: var(--error);
    background-color: rgba(255, 71, 87, 0.1);
}

.option-marker {
    width: 30px;
    height: 30px;
    border-radius: 50%;
    background-color: var(--bg-secondary);
    display: flex;
    align-items: center;
    justify-content: center;
    font-weight: 600;
    flex-shrink: 0;
}

.feedback {
    padding: 1rem;
    border-radius: 8px;
    margin-top: 1rem;
    display: none;
}

.feedback.show {
    display: block;
}

.feedback.correct {
    background-color: rgba(78, 204, 163, 0.1);
    border: 1px solid var(--success);
    color: var(--success);
}

.feedback.incorrect {
    background-color: rgba(255, 71, 87, 0.1);
    border: 1px solid var(--error);
    color: var(--error);
}

.quiz-actions {
    display: flex;
    justify-content: center;
    gap: 1rem;
    margin-top: 1.5rem;
}

/* Results */
.results-container {
    text-align: center;
    padding: 3rem;
    background-color: var(--bg-secondary);
    border-radius: 10px;
}

.results-score {
    font-size: 4rem;
    font-weight: 700;
    color: var(--accent);
    margin-bottom: 1rem;
}

.results-message {
    font-size: 1.5rem;
    margin-bottom: 2rem;
}

/* Footer */
footer {
    background-color: var(--bg-secondary);
    padding: 2rem 0;
    margin-top: 4rem;
    text-align: center;
    border-top: 1px solid var(--border);
}

footer p {
    color: var(--text-secondary);
    margin: 0;
}

/* Responsive Design */
@media (max-width: 768px) {
    .nav-links {
        display: none;
        position: absolute;
        top: 100%;
        left: 0;
        right: 0;
        background-color: var(--bg-secondary);
        flex-direction: column;
        padding: 1rem;
        gap: 0.5rem;
    }

    .nav-links.active {
        display: flex;
    }

    .mobile-menu {
        display: block;
    }

    .hero h1 {
        font-size: 2rem;
    }

    .hero p {
        font-size: 1rem;
    }

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

    .lesson-nav {
        flex-direction: column;
        gap: 1rem;
    }

    .lesson-nav a {
        justify-content: center;
    }

    h1 { font-size: 2rem; }
    h2 { font-size: 1.5rem; }
}

@media (max-width: 480px) {
    .container {
        padding: 0 15px;
    }

    .question-card {
        padding: 1.5rem;
    }

    .option {
        padding: 0.75rem 1rem;
    }
}

/* Animations */
@keyframes fadeIn {
    from { opacity: 0; transform: translateY(10px); }
    to { opacity: 1; transform: translateY(0); }
}

.fade-in {
    animation: fadeIn 0.3s ease forwards;
}

/* Mark Complete Button */
.mark-complete {
    display: flex;
    justify-content: center;
    margin: 2rem 0;
}

.mark-complete .btn {
    display: flex;
    align-items: center;
    gap: 0.5rem;
}

/* Complete Status */
.complete-status {
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 0.5rem;
    color: var(--success);
    font-weight: 600;
    margin: 2rem 0;
}