:root {
    --bg-color: #ffffff;
    --text-color: #111111;
    --accent-color: #000000;
    --secondary-text: #666666;
    --surface: #ffffff;
    --surface-2: #fafafa;
    --border-color: #eeeeee;
    --shadow-color: rgba(0,0,0,0.25);
    --overlay: rgba(0, 0, 0, 0.35);
    --header-font: 'Playfair Display', serif;
    --body-font: 'Libre Baskerville', serif;
    --sans-font: 'Inter', -apple-system, sans-serif;
}

/* Dark mode defaults (system) */
@media (prefers-color-scheme: dark) {
    :root {
        --bg-color: #0b0e12;
        --surface: #0f141b;
        --surface-2: #0c1117;
        --text-color: #e8eef6;
        --secondary-text: rgba(232, 238, 246, 0.70);
        --accent-color: #ffffff;
        --border-color: rgba(232, 238, 246, 0.10);
        --shadow-color: rgba(0,0,0,0.55);
        --overlay: rgba(0, 0, 0, 0.55);
    }
}

/* Explicit override via JS */
html[data-theme="light"] {
    --bg-color: #ffffff;
    --surface: #ffffff;
    --surface-2: #fafafa;
    --text-color: #111111;
    --secondary-text: #666666;
    --accent-color: #000000;
    --border-color: #eeeeee;
    --shadow-color: rgba(0,0,0,0.25);
    --overlay: rgba(0, 0, 0, 0.35);
}

html[data-theme="dark"] {
    --bg-color: #0b0e12;
    --surface: #0f141b;
    --surface-2: #0c1117;
    --text-color: #e8eef6;
    --secondary-text: rgba(232, 238, 246, 0.70);
    --accent-color: #ffffff;
    --border-color: rgba(232, 238, 246, 0.10);
    --shadow-color: rgba(0,0,0,0.55);
    --overlay: rgba(0, 0, 0, 0.55);
}

body {
    font-family: var(--body-font);
    background-color: var(--bg-color);
    color: var(--text-color);
    line-height: 1.6;
    margin: 0;
    overflow: hidden;
    display: flex;
    flex-direction: column;
    height: 100vh;
}

/* Footer */
.site-footer {
    height: 40px;
    border-top: 1px solid var(--border-color);
    background: var(--surface);
    display: flex;
    align-items: center;
    justify-content: center;
    font-family: var(--sans-font);
    font-size: 0.7rem;
    letter-spacing: 2px;
    text-transform: uppercase;
    color: #999;
}

/* Top Navigation */
.top-nav {
    height: 60px;
    background: var(--surface);
    border-bottom: 1px solid var(--border-color);
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 0 2.5rem;
    z-index: 100;
}

.nav-brand {
    font-family: var(--sans-font);
    font-size: 0.8rem;
    font-weight: 800;
    text-transform: uppercase;
    letter-spacing: 3px;
    cursor: pointer;
    color: var(--text-color);
}

.nav-links {
    display: flex;
    gap: 2rem;
}

.nav-links a {
    text-decoration: none;
    color: var(--secondary-text);
    font-family: var(--sans-font);
    font-size: 0.75rem;
    text-transform: uppercase;
    letter-spacing: 1.5px;
    font-weight: 600;
    transition: color 0.2s;
}

.nav-links a:hover {
    color: var(--text-color);
}

/* Sidebar Styling (Professional & Minimal) */
.treatise-container {
    display: flex;
    flex-grow: 1;
    overflow: hidden;
}

.sidebar {
    width: 280px;
    background-color: var(--surface-2);
    border-right: 1px solid var(--border-color);
    overflow-y: auto;
    padding: 2.5rem 1.5rem;
    display: flex;
    flex-direction: column;
}

.sidebar h2 {
    font-family: var(--sans-font);
    font-size: 0.7rem;
    font-weight: 800;
    text-transform: uppercase;
    letter-spacing: 1.5px;
    margin-bottom: 2rem;
    color: #999;
}

.volume-title {
    font-family: var(--sans-font);
    font-weight: 700;
    font-size: 0.75rem;
    text-transform: uppercase;
    letter-spacing: 1px;
    color: #999;
    margin-bottom: 0.75rem;
    display: block;
}

.chapter-link {
    display: block;
    padding: 0.5rem 0;
    color: var(--secondary-text);
    text-decoration: none;
    font-size: 0.9rem;
    transition: color 0.2s;
}

.chapter-link:hover, .chapter-link.active {
    color: var(--text-color);
}

/* Content Area - The Blank Canvas */
.content-area {
    flex-grow: 1;
    overflow-y: auto;
    padding: 0;
    background: var(--surface);
    display: flex;
    justify-content: center;
    align-items: center;
}

/* Slide Viewer UI */
.slide-viewer {
    max-width: 800px;
    width: 90%;
    padding: 4rem;
    text-align: left;
}

.slide-content {
    min-height: 400px;
    display: flex;
    flex-direction: column;
    justify-content: center;
    animation: fadeIn 0.8s ease-out;
}

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

.slide-content h1 {
    font-family: var(--header-font);
    font-size: 3.5rem;
    margin-bottom: 1.5rem;
    line-height: 1.1;
}

.slide-content p {
    font-size: 1.4rem;
    color: var(--secondary-text);
    margin-bottom: 2rem;
}

.slide-content .highlight {
    color: var(--text-color);
    font-weight: 700;
}

/* Slide Controls */
.slide-nav {
    display: flex;
    align-items: center;
    gap: 2rem;
    margin-top: 4rem;
}

.slide-btn {
    background: none;
    border: 1px solid var(--border-color);
    padding: 0.8rem 2rem;
    font-family: var(--sans-font);
    font-size: 0.8rem;
    text-transform: uppercase;
    letter-spacing: 2px;
    cursor: pointer;
    transition: all 0.3s;
}

.slide-btn:hover {
    background: var(--accent-color);
    color: var(--bg-color);
    border-color: var(--accent-color);
}

.slide-progress {
    font-family: var(--sans-font);
    font-size: 0.7rem;
    letter-spacing: 2px;
    color: #999;
}

/* Treatise Text (Chapters) */
.treatise-text {
    max-width: 800px;
    padding: 6rem 4rem;
    margin: 0 auto;
}

.treatise-text h1 {
    font-family: var(--header-font);
    font-size: 3rem;
    margin-bottom: 3rem;
}

/* Treatises List View */
.treatise-list {
    max-width: 980px;
    width: 92%;
    padding: 4.5rem 2rem;
}

.treatise-list h1 {
    font-family: var(--header-font);
    font-size: 2.6rem;
    margin: 0 0 1rem 0;
}

.treatise-list .lede {
    color: var(--secondary-text);
    margin: 0 0 3rem 0;
    font-size: 1.05rem;
}

.volume-block {
    padding: 1.75rem 0;
    border-top: 1px solid var(--border-color);
}

.volume-block:first-of-type {
    border-top: 0;
}

.volume-block .volume-title {
    color: var(--text-color);
    font-size: 0.85rem;
    letter-spacing: 2px;
    margin-bottom: 0.25rem;
}

.volume-block .volume-subtitle {
    font-family: var(--header-font);
    font-size: 1.6rem;
    margin: 0.3rem 0 1.2rem 0;
}

.chapter-grid {
    display: grid;
    grid-template-columns: repeat(2, minmax(0, 1fr));
    gap: 0.75rem 2.5rem;
}

.chapter-item {
    display: flex;
    justify-content: space-between;
    gap: 1rem;
    padding: 0.65rem 0;
    border-bottom: 1px solid rgba(127,127,127,0.14);
    text-decoration: none;
    color: var(--text-color);
}

.chapter-item:hover {
    background: rgba(127,127,127,0.08);
}

.chapter-item .chapter-title {
    font-size: 1.0rem;
    color: var(--text-color);
}

.chapter-item .chapter-meta {
    font-family: var(--sans-font);
    font-size: 0.7rem;
    letter-spacing: 2px;
    text-transform: uppercase;
    color: #999;
    white-space: nowrap;
    margin-top: 0.15rem;
}

.chapter-topbar {
    max-width: 800px;
    width: 100%;
    margin: 0 auto;
    padding: 2.5rem 4rem 0 4rem;
    box-sizing: border-box;
}

.chapter-topbar a {
    font-family: var(--sans-font);
    font-size: 0.75rem;
    letter-spacing: 2px;
    text-transform: uppercase;
    text-decoration: none;
    color: #999;
}

.chapter-topbar a:hover {
    color: var(--text-color);
}

/* Community Section */
.community-section {
    margin-top: auto;
    padding-top: 2rem;
    border-top: 1px solid var(--border-color);
}

.dedication {
    font-family: var(--sans-font);
    font-size: 0.6rem;
    text-transform: uppercase;
    letter-spacing: 2px;
    margin-bottom: 1rem;
    color: #bbb;
}

.hidden { display: none !important; }

/* Modal */
.modal-overlay {
    position: fixed;
    inset: 0;
    background: var(--overlay);
    backdrop-filter: blur(6px);
    display: flex;
    align-items: center;
    justify-content: center;
    padding: 1.5rem;
    z-index: 1000;
}

.modal {
    width: min(560px, 100%);
    background: var(--surface);
    border: 1px solid var(--border-color);
    box-shadow: 0 30px 80px var(--shadow-color);
    padding: 2rem 2rem 1.75rem 2rem;
    position: relative;
}

.modal-close {
    position: absolute;
    top: 12px;
    right: 12px;
    width: 36px;
    height: 36px;
    border: 1px solid var(--border-color);
    background: var(--surface);
    cursor: pointer;
    font-size: 18px;
    line-height: 1;
    color: var(--text-color);
}

.modal-header {
    margin-bottom: 1.5rem;
}

.modal-kicker {
    font-family: var(--sans-font);
    font-size: 0.7rem;
    letter-spacing: 3px;
    text-transform: uppercase;
    color: #999;
    margin-bottom: 0.75rem;
}

.modal-title {
    font-family: var(--header-font);
    font-size: 2rem;
    margin: 0 0 0.5rem 0;
}

.modal-subtitle {
    margin: 0;
    color: var(--secondary-text);
}

.modal-primary, .modal-secondary {
    width: 100%;
    padding: 0.9rem 1rem;
    font-family: var(--sans-font);
    font-size: 0.8rem;
    letter-spacing: 2px;
    text-transform: uppercase;
    cursor: pointer;
    border: 1px solid var(--border-color);
    background: var(--surface);
    color: var(--text-color);
}

.modal-primary {
    background: var(--accent-color);
    border-color: var(--accent-color);
    color: var(--bg-color);
}

.modal-primary:hover {
    opacity: 0.92;
}

.modal-secondary {
    margin-top: 0.75rem;
}

.modal-fineprint {
    margin: 0.75rem 0 0 0;
    color: #999;
    font-size: 0.85rem;
}

.modal-identity {
    margin: 0 0 1rem 0;
    font-family: var(--sans-font);
    font-size: 0.85rem;
    color: var(--text-color);
    letter-spacing: 0.5px;
}

.modal-link {
    display: inline-block;
    font-family: var(--sans-font);
    font-size: 0.75rem;
    letter-spacing: 2px;
    text-transform: uppercase;
    color: var(--text-color);
    text-decoration: none;
    border-bottom: 1px solid rgba(127,127,127,0.35);
    padding-bottom: 2px;
}

.modal-link:hover {
    border-bottom-color: rgba(127,127,127,0.7);
}

/* Theme toggle */
.theme-toggle {
    border: 1px solid var(--border-color);
    background: var(--surface);
    color: var(--secondary-text);
    font-family: var(--sans-font);
    font-size: 0.75rem;
    text-transform: uppercase;
    letter-spacing: 1.5px;
    font-weight: 700;
    padding: 0.35rem 0.65rem;
    cursor: pointer;
    transition: color 0.2s, border-color 0.2s, background 0.2s;
}

.theme-toggle:hover {
    color: var(--text-color);
}

@media (max-width: 720px) {
    .top-nav {
        padding: 0 1.25rem;
    }
    .nav-links {
        gap: 1.25rem;
    }
    .treatise-text {
        padding: 4rem 1.5rem;
    }
    .slide-viewer {
        padding: 3rem 1.5rem;
    }
    .slide-content h1 {
        font-size: 2.6rem;
    }
    .chapter-grid {
        grid-template-columns: 1fr;
        gap: 0.5rem 0;
    }
    .chapter-topbar {
        padding: 2rem 1.5rem 0 1.5rem;
    }
}