:root {
    --bg-main: #fafafa;
    --bg-sidebar: #ffffff;
    --bg-glossary: #f5f5f5;
    --bg-card: #ffffff;
    --text-primary: #1a1a1a;
    --text-secondary: #555555;
    --text-muted: #888888;
    --accent: #2563eb;
    --accent-light: #3b82f6;
    --border: #e5e5e5;
    --border-light: #f0f0f0;
    --code-bg: #f8f8f8;
    --shadow: 0 1px 3px rgba(0,0,0,0.08);
}

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

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', sans-serif;
    background: var(--bg-main);
    color: var(--text-primary);
    display: flex;
    min-height: 100vh;
    line-height: 1.7;
    font-size: 15px;
}

/* Left Navigation Sidebar */
.sidebar {
    width: 220px;
    background: var(--bg-sidebar);
    padding: 1.5rem 1rem;
    position: fixed;
    left: 0;
    height: 100vh;
    overflow-y: auto;
    border-right: 1px solid var(--border);
    z-index: 100;
}

.book-title {
    font-size: 1.1rem;
    font-weight: 600;
    color: var(--text-primary);
    margin-bottom: 1.5rem;
    padding-bottom: 1rem;
    border-bottom: 1px solid var(--border);
}

.sidebar ul {
    list-style: none;
}

.sidebar li {
    margin-bottom: 0.2rem;
}

.sidebar a {
    color: var(--text-secondary);
    text-decoration: none;
    display: block;
    padding: 0.4rem 0.75rem;
    border-radius: 4px;
    font-size: 0.875rem;
    transition: all 0.15s ease;
}

.sidebar a:hover {
    background: var(--bg-main);
    color: var(--text-primary);
}

.sidebar a.active {
    background: var(--accent);
    color: white;
}

/* Main Content Area */
.content {
    margin-left: 220px;
    margin-right: 260px;
    padding: 2.5rem 3rem;
    max-width: 750px;
    flex: 1;
}

/* Right Glossary Sidebar */
.glossary-sidebar {
    width: 260px;
    background: var(--bg-glossary);
    padding: 1.5rem;
    position: fixed;
    right: 0;
    height: 100vh;
    overflow-y: auto;
    border-left: 1px solid var(--border);
}

.glossary-title {
    font-size: 0.875rem;
    font-weight: 600;
    color: var(--text-muted);
    text-transform: uppercase;
    letter-spacing: 0.5px;
    margin-bottom: 1rem;
    padding-bottom: 0.5rem;
    border-bottom: 1px solid var(--border);
    display: flex;
    align-items: center;
    gap: 0.5rem;
}

.glossary-item {
    margin-bottom: 0.875rem;
    padding-bottom: 0.75rem;
    border-bottom: 1px solid var(--border-light);
}

.glossary-term {
    font-weight: 600;
    color: var(--text-primary);
    font-size: 0.8rem;
    font-family: 'SF Mono', 'Monaco', 'Consolas', monospace;
}

.glossary-def {
    color: var(--text-secondary);
    font-size: 0.75rem;
    margin-top: 0.2rem;
    line-height: 1.5;
}

/* Typography */
h1 {
    font-size: 2rem;
    font-weight: 700;
    margin-bottom: 0.5rem;
    color: var(--text-primary);
    letter-spacing: -0.5px;
}

.subtitle {
    color: var(--text-muted);
    font-size: 1rem;
    margin-bottom: 2rem;
    font-weight: 400;
}

h2 {
    font-size: 1.35rem;
    font-weight: 600;
    margin: 2.5rem 0 1rem;
    color: var(--text-primary);
    padding-bottom: 0.5rem;
    border-bottom: 1px solid var(--border);
}

h3 {
    font-size: 1.1rem;
    font-weight: 600;
    margin: 1.5rem 0 0.75rem;
    color: var(--text-primary);
}

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

ul, ol {
    margin: 1rem 0 1rem 1.5rem;
    color: var(--text-secondary);
}

li {
    margin-bottom: 0.4rem;
}

/* Head First Special Boxes - Minimalist Style */
.brain-power,
.no-dumb-questions,
.watch-it,
.fireside-chat,
.bullet-points,
.exercise,
.code-magnet,
.analogy-box,
.remember-this,
.mnemonic,
.trivia {
    background: var(--bg-card);
    border: 1px solid var(--border);
    border-radius: 6px;
    padding: 1.25rem 1.5rem;
    margin: 1.5rem 0;
    position: relative;
}

.brain-power { border-left: 3px solid #3b82f6; }
.no-dumb-questions { border-left: 3px solid #8b5cf6; }
.watch-it { border-left: 3px solid #f59e0b; }
.fireside-chat { border-left: 3px solid #ef4444; }
.bullet-points { border-left: 3px solid #10b981; }
.exercise { border-left: 3px solid #6366f1; }
.code-magnet { border-left: 3px solid #eab308; }
.analogy-box { border-left: 3px solid #06b6d4; }
.remember-this { border-left: 3px solid #a855f7; }
.mnemonic { border-left: 3px solid #22c55e; }
.trivia { border-left: 3px solid #f97316; }

.brain-power::before,
.no-dumb-questions::before,
.watch-it::before,
.fireside-chat::before,
.bullet-points::before,
.exercise::before,
.code-magnet::before,
.analogy-box::before,
.remember-this::before,
.mnemonic::before,
.trivia::before {
    position: absolute;
    top: -10px;
    left: 12px;
    background: var(--bg-main);
    padding: 0 8px;
    font-weight: 600;
    font-size: 0.7rem;
    text-transform: uppercase;
    letter-spacing: 0.5px;
}

.brain-power::before { content: "🧠 Brain Power"; color: #3b82f6; }
.no-dumb-questions::before { content: "❓ No Dumb Questions"; color: #8b5cf6; }
.watch-it::before { content: "⚠️ Watch It"; color: #f59e0b; }
.fireside-chat::before { content: "🔥 Fireside Chat"; color: #ef4444; }
.bullet-points::before { content: "🎯 Key Points"; color: #10b981; }
.exercise::before { content: "✏️ Exercise"; color: #6366f1; }
.code-magnet::before { content: "🧲 Code Magnets"; color: #eab308; }
.analogy-box::before { content: "🎭 Analogy"; color: #06b6d4; }
.remember-this::before { content: "💡 Remember"; color: #a855f7; }
.mnemonic::before { content: "🎵 Memory Trick"; color: #22c55e; }
.trivia::before { content: "🎲 Fun Fact"; color: #f97316; }

/* Fireside Chat Messages */
.chat-message {
    margin: 0.6rem 0;
    padding-left: 1rem;
    border-left: 2px solid var(--border);
}

.chat-speaker {
    font-weight: 600;
    color: var(--text-primary);
}

/* Mnemonic Text */
.mnemonic-text {
    font-size: 1.2rem;
    font-weight: 600;
    color: var(--text-primary);
    text-align: center;
    letter-spacing: 0.5px;
}

/* Diagram Box */
.diagram {
    background: var(--code-bg);
    padding: 1.25rem;
    border-radius: 6px;
    text-align: left;
    margin: 1.5rem 0;
    font-family: 'SF Mono', 'Monaco', 'Consolas', monospace;
    font-size: 0.8rem;
    white-space: pre;
    overflow-x: auto;
    border: 1px solid var(--border);
    line-height: 1.5;
    color: var(--text-secondary);
}

/* Code Blocks */
pre {
    background: var(--code-bg);
    padding: 1rem 1.25rem;
    border-radius: 6px;
    overflow-x: auto;
    margin: 1rem 0;
    border: 1px solid var(--border);
}

code {
    font-family: 'SF Mono', 'Monaco', 'Consolas', monospace;
    font-size: 0.85rem;
    color: var(--accent);
}

pre code {
    color: var(--text-secondary);
}

/* Tables */
table {
    width: 100%;
    border-collapse: collapse;
    margin: 1.5rem 0;
    font-size: 0.9rem;
}

th, td {
    padding: 0.65rem 1rem;
    text-align: left;
    border: 1px solid var(--border);
}

th {
    background: var(--bg-glossary);
    color: var(--text-primary);
    font-weight: 600;
}

td {
    color: var(--text-secondary);
}

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

.navigation a {
    color: var(--accent);
    text-decoration: none;
    padding: 0.6rem 1.25rem;
    background: var(--bg-card);
    border: 1px solid var(--border);
    border-radius: 4px;
    font-size: 0.875rem;
    transition: all 0.15s ease;
}

.navigation a:hover {
    background: var(--accent);
    color: white;
    border-color: var(--accent);
}

/* Paper Info Box */
.paper-info {
    background: var(--bg-card);
    padding: 1.25rem 1.5rem;
    border-radius: 6px;
    margin: 1.5rem 0;
    border: 1px solid var(--border);
    border-left: 3px solid var(--accent);
}

.paper-info p {
    margin-bottom: 0.4rem;
    font-size: 0.9rem;
}

/* Feature Grid */
.feature-grid {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: 1rem;
    margin: 1.5rem 0;
}

.feature {
    background: var(--bg-card);
    padding: 1.25rem;
    border-radius: 6px;
    border: 1px solid var(--border);
}

.feature h3 {
    margin-top: 0;
    margin-bottom: 0.5rem;
    color: var(--text-primary);
    font-size: 1rem;
}

.feature p {
    margin: 0;
    font-size: 0.875rem;
}

/* Quiz styling */
.quiz-option {
    background: var(--bg-glossary);
    padding: 0.6rem 1rem;
    margin: 0.4rem 0;
    border-radius: 4px;
    cursor: pointer;
    border: 1px solid var(--border);
    transition: all 0.15s ease;
    font-size: 0.9rem;
}

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

.answer-reveal {
    background: var(--bg-glossary);
    padding: 1rem;
    border-radius: 4px;
    margin-top: 1rem;
    border-left: 3px solid #10b981;
    font-size: 0.875rem;
}

/* Responsive */
@media (max-width: 1200px) {
    .glossary-sidebar {
        display: none;
    }
    .content {
        margin-right: 0;
        max-width: 100%;
    }
}

@media (max-width: 900px) {
    .sidebar {
        width: 100%;
        height: auto;
        position: relative;
    }
    .content {
        margin-left: 0;
        padding: 1.5rem;
    }
    .feature-grid {
        grid-template-columns: 1fr;
    }
}

/* Links */
a {
    color: var(--accent);
    text-decoration: none;
}

a:hover {
    text-decoration: underline;
}

/* Strong/Bold */
strong {
    color: var(--text-primary);
    font-weight: 600;
}