:root {
    --primary: #00d2ff;
    --primary-dark: #00adff;
    --bg-dark: #0a192f;
    --bg-card: rgba(16, 33, 65, 0.7);
    --text-primary: #e6f1ff;
    --text-secondary: #8892b0;
    --border: rgba(100, 255, 218, 0.1);
    --accent: #64ffda;
}

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

body {
    background-color: var(--bg-dark);
    color: var(--text-primary);
    font-family: 'Inter', -apple-system, sans-serif;
    display: flex;
    min-height: 100vh;
    overflow: hidden;
}

/* Sidebar */
aside {
    width: 300px;
    background: rgba(2, 12, 27, 0.95);
    border-right: 1px solid var(--border);
    display: flex;
    flex-direction: column;
    z-index: 10;
}

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

.sidebar-logo {
    display: flex;
    align-items: center;
    gap: 1rem;
    text-decoration: none;
    color: var(--accent);
    font-weight: 800;
    font-size: 1.2rem;
}

.logo-icon {
    width: 40px;
    height: 40px;
    background: var(--accent);
    color: var(--bg-dark);
    display: flex;
    align-items: center;
    justify-content: center;
    border-radius: 8px;
    font-size: 1rem;
}

.nav-content {
    flex: 1;
    overflow-y: auto;
    padding: 1.5rem;
}

.chapter {
    margin-bottom: 2rem;
}

.chapter-title {
    font-size: 0.75rem;
    text-transform: uppercase;
    letter-spacing: 0.1em;
    color: var(--accent);
    margin-bottom: 1rem;
    opacity: 0.7;
}

.page-link {
    display: block;
    padding: 0.75rem 1rem;
    color: var(--text-secondary);
    text-decoration: none;
    border-radius: 6px;
    margin-bottom: 0.25rem;
    transition: all 0.2s;
    font-size: 0.9rem;
}

.page-link:hover {
    background: rgba(100, 255, 218, 0.1);
    color: var(--accent);
}

.page-link.active {
    background: rgba(100, 255, 218, 0.1);
    color: var(--accent);
    border-left: 3px solid var(--accent);
}

/* Main Content */
main {
    flex: 1;
    overflow-y: auto;
    padding: 4rem;
    scroll-behavior: smooth;
    background-image: 
        radial-gradient(at 0% 0%, rgba(100, 255, 218, 0.05) 0px, transparent 50%),
        radial-gradient(at 100% 100%, rgba(0, 210, 255, 0.05) 0px, transparent 50%);
}

.content-header {
    margin-bottom: 3rem;
    max-width: 800px;
}

.label {
    display: inline-block;
    padding: 0.25rem 0.75rem;
    background: rgba(100, 255, 218, 0.1);
    color: var(--accent);
    border-radius: 20px;
    font-size: 0.75rem;
    font-weight: 600;
    margin-bottom: 1rem;
}

h1 {
    font-size: 3rem;
    font-weight: 800;
    margin-bottom: 1rem;
    letter-spacing: -0.02em;
}

.book-page {
    display: none;
    max-width: 800px;
    animation: fadeIn 0.4s ease-out;
}

.book-page.active {
    display: block;
}

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

.content-body {
    font-size: 1.1rem;
    line-height: 1.7;
    color: var(--text-secondary);
}

.content-body h3 {
    color: var(--text-primary);
    margin: 2.5rem 0 1.25rem;
    font-size: 1.5rem;
}

.content-body p {
    margin-bottom: 1.5rem;
}

.content-body code {
    background: rgba(2, 12, 27, 0.5);
    padding: 0.2rem 0.4rem;
    border-radius: 4px;
    font-family: 'Fira Code', monospace;
    color: var(--accent);
    font-size: 0.9em;
}

.content-body pre {
    background: #020c1b;
    padding: 1.5rem;
    border-radius: 12px;
    overflow-x: auto;
    margin: 1.5rem 0;
    border: 1px solid var(--border);
}

.content-body blockquote {
    border-left: 4px solid var(--accent);
    background: rgba(100, 255, 218, 0.05);
    padding: 1rem 1.5rem;
    margin: 1.5rem 0;
    font-style: italic;
}

/* Footer Nav */
.page-nav {
    margin-top: 5rem;
    display: flex;
    justify-content: space-between;
    max-width: 800px;
}

.nav-btn {
    display: flex;
    flex-direction: column;
    text-decoration: none;
    padding: 1.5rem;
    border: 1px solid var(--border);
    border-radius: 12px;
    width: 48%;
    transition: all 0.3s;
}

.nav-btn:hover {
    border-color: var(--accent);
    background: rgba(100, 255, 218, 0.05);
}

.nav-btn .dir {
    font-size: 0.75rem;
    color: var(--accent);
    margin-bottom: 0.5rem;
    text-transform: uppercase;
}

.nav-btn .title {
    font-weight: 700;
    color: var(--text-primary);
}