/* ─── RESET & UNIVERSAL TOKENS ─── */
:root {
    --bg-app: #f7f3e9;         /* Very soft linen warm grey */
    --bg-sidebar: #e9e3d4;     /* Deepened linen sidebar */
    --bg-paper: #fefdfa;       /* Pure matte book-paper ivory background */
    --border: #ded7c6;         /* Clay border */
    --border-hover: #c9beaa;   /* Focus hover border */
    
    --text: #2c2c2c;           /* Charcoal ink readability color */
    --muted: #625d52;          /* Warm slate-brown secondary label */
    
    --accent: #a33b26;         /* Terracotta / Crimson accent */
    --accent-teal: #3b6b6c;    /* Deep Teal */
    
    --sans: "Outfit", -apple-system, system-ui, sans-serif;
    --serif: "Crimson Pro", Georgia, serif;
    --mono: "JetBrains Mono", ui-monospace, monospace;
}

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

html, body {
    height: 100%;
    background-color: var(--bg-app);
    color: var(--text);
    font-family: var(--sans);
    overflow: hidden;
}

/* ─── APP SCREEN LAYOUT ─── */
.app-container {
    display: flex;
    width: 100vw;
    height: 100vh;
}

/* ─── SIDEBAR NAVIGATION (LEFT PANEL) ─── */
.sidebar {
    width: 320px;
    background-color: var(--bg-sidebar);
    border-right: 1px solid var(--border);
    display: flex;
    flex-direction: column;
    flex-shrink: 0;
    height: 100%;
    padding: 35px 24px;
}

.sidebar-header {
    margin-bottom: 25px;
    border-bottom: 1.5px solid var(--border);
    padding-bottom: 20px;
}

.badge {
    display: inline-block;
    background: rgba(163, 59, 38, 0.08);
    border: 1px solid rgba(163, 59, 38, 0.25);
    color: var(--accent);
    padding: 4px 10px;
    border-radius: 12px;
    font-size: 10px;
    font-weight: 700;
    text-transform: uppercase;
    letter-spacing: 1px;
    margin-bottom: 12px;
}

.sidebar h1 {
    font-size: 24px;
    font-weight: 800;
    letter-spacing: -0.5px;
    line-height: 1.1;
    color: #1e1e1e;
}

.sidebar .subtitle {
    font-size: 12.5px;
    color: var(--muted);
    font-weight: 600;
    margin-top: 4px;
    text-transform: uppercase;
    letter-spacing: 0.5px;
}

.nav-sections {
    flex: 1;
    overflow-y: auto;
    padding-right: 4px;
}

.nav-sections::-webkit-scrollbar {
    width: 5px;
}
.nav-sections::-webkit-scrollbar-thumb {
    background: var(--border);
    border-radius: 3px;
}

.nav-group {
    margin-bottom: 25px;
}

.nav-group h3 {
    font-size: 11px;
    text-transform: uppercase;
    letter-spacing: 1px;
    font-weight: 750;
    color: var(--muted);
    margin-bottom: 10px;
    padding-left: 8px;
}

.nav-item {
    display: flex;
    align-items: center;
    gap: 12px;
    color: var(--muted);
    text-decoration: none;
    font-size: 13.5px;
    font-weight: 500;
    padding: 8px 12px;
    border-radius: 8px;
    transition: all 0.15s ease;
    margin-bottom: 4px;
    border: 1px solid transparent;
}

.nav-item:hover {
    background: rgba(254, 253, 250, 0.4);
    color: var(--text);
}

.nav-item.active {
    background: var(--bg-paper);
    color: var(--accent);
    border-color: var(--border);
    font-weight: 600;
    box-shadow: 0 2px 6px rgba(0, 0, 0, 0.02);
}

.nav-item .num {
    font-family: var(--mono);
    font-size: 11px;
    opacity: 0.7;
}

/* ─── MONOGRAPH READER VIEWPORT ─── */
.viewer-container {
    flex: 1;
    display: flex;
    flex-direction: column;
    height: 100%;
    padding: 40px 60px 30px;
    position: relative;
    overflow: hidden;
}

/* THE READING WELL CONTAINER */
.reading-well {
    flex: 1;
    background-color: var(--bg-paper);
    border: 1px solid var(--border);
    border-radius: 12px;
    box-shadow: 0 4px 20px rgba(42, 42, 42, 0.03);
    overflow-y: auto;
    padding: 60px 80px;
    width: 100%;
}

.reading-well::-webkit-scrollbar {
    width: 8px;
}
.reading-well::-webkit-scrollbar-thumb {
    background: var(--border);
    border-radius: 4px;
}

/* ─── PREMIUM EDITORIAL TYPOGRAPHY ─── */
.page-content {
    font-family: var(--serif);
    font-size: 18.5px;
    line-height: 1.85;
    color: var(--text);
    max-width: 820px; /* Optimal readability line width (~75 characters) */
    margin: 0 auto;
    opacity: 1;
    transition: opacity 0.22s ease-in-out;
}

.page-content.loading {
    opacity: 0;
}

.page-content h1 {
    font-family: var(--sans);
    font-size: 34px;
    font-weight: 800;
    letter-spacing: -0.8px;
    margin-bottom: 25px;
    color: #1a1a1a;
    border-bottom: 1.5px solid var(--border);
    padding-bottom: 15px;
    line-height: 1.2;
}

.page-content h2 {
    font-family: var(--sans);
    font-size: 21px;
    font-weight: 750;
    margin-top: 40px;
    margin-bottom: 16px;
    color: var(--accent);
    letter-spacing: -0.3px;
}

.page-content h3 {
    font-family: var(--sans);
    font-size: 15px;
    font-weight: 700;
    margin-top: 28px;
    margin-bottom: 12px;
    text-transform: uppercase;
    letter-spacing: 0.5px;
    color: var(--accent-teal);
}

.page-content p {
    margin-bottom: 20px;
    text-align: justify;
}

.page-content strong {
    font-weight: 600;
    color: #000;
}

.page-content code {
    font-family: var(--mono);
    font-size: 14.5px;
    background: rgba(163, 59, 38, 0.05);
    border: 1px solid rgba(163, 59, 38, 0.12);
    color: var(--accent);
    padding: 2px 6px;
    border-radius: 4px;
}

/* Bullet list grids */
.page-content ul, .page-content ol {
    margin-left: 28px;
    margin-bottom: 25px;
}

.page-content li {
    margin-bottom: 10px;
}

/* Elegant research tables */
.page-content table {
    width: 100%;
    border-collapse: collapse;
    font-family: var(--sans);
    font-size: 13.5px;
    margin: 30px 0;
    border: 1px solid var(--border);
    box-shadow: 0 2px 8px rgba(0,0,0,0.01);
}

.page-content th, .page-content td {
    padding: 14px 16px;
    border: 1px solid var(--border);
    text-align: left;
}

.page-content th {
    background: #f7f3e9;
    color: #000;
    font-weight: 650;
}

.page-content td {
    background: #fdfdfb;
}

/* ─── ACTION BUTTONS FOOTER ─── */
.reader-footer {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-top: 25px;
    padding-top: 15px;
    border-top: 1.5px solid var(--border);
}

.progress-indicator {
    font-size: 13px;
    color: var(--muted);
    font-weight: 600;
}

.progress-indicator strong {
    color: var(--text);
    font-family: var(--mono);
    background: var(--bg-sidebar);
    padding: 3px 8px;
    border-radius: 5px;
    font-size: 12px;
    border: 1px solid var(--border);
}

.btn {
    background: var(--bg-sidebar);
    border: 1px solid var(--border);
    color: var(--text);
    border-radius: 8px;
    padding: 9px 18px;
    font-size: 13.5px;
    font-weight: 600;
    cursor: pointer;
    display: inline-flex;
    align-items: center;
    gap: 8px;
    transition: all 0.15s ease;
}

.btn:hover {
    background: #ffffff;
    border-color: var(--accent);
    color: var(--accent);
    box-shadow: 0 4px 12px rgba(163, 59, 38, 0.05);
}

.btn:disabled {
    opacity: 0.4;
    cursor: not-allowed;
    background: transparent;
    border-color: var(--border);
    color: var(--muted);
}

/* ─── MOBILE RESPONSIVE STRUCTURE ─── */
.mobile-header {
    display: none;
}

.sidebar-backdrop {
    position: fixed;
    top: 0;
    left: 0;
    width: 100vw;
    height: 100vh;
    background: rgba(0, 0, 0, 0.35);
    z-index: 95;
    opacity: 0;
    pointer-events: none;
    transition: opacity 0.25s ease;
}

.sidebar-backdrop.active {
    opacity: 1;
    pointer-events: auto;
}

@media (max-width: 768px) {
    .app-container {
        flex-direction: column;
    }
    
    /* Off-canvas sidebar overlay drawer */
    .sidebar {
        position: fixed;
        left: -320px;
        top: 0;
        bottom: 0;
        z-index: 100;
        transition: left 0.28s cubic-bezier(0.4, 0, 0.2, 1);
        box-shadow: 10px 0 30px rgba(42, 42, 42, 0.12);
    }
    
    .sidebar.open {
        left: 0;
    }
    
    /* Mobile Header Layout */
    .mobile-header {
        display: flex;
        align-items: center;
        gap: 15px;
        background: var(--bg-sidebar);
        border: 1px solid var(--border);
        border-radius: 10px;
        padding: 10px 16px;
        margin-bottom: 12px;
        width: 100%;
        box-shadow: 0 2px 4px rgba(0,0,0,0.01);
    }
    
    .menu-btn {
        background: transparent;
        border: none;
        color: var(--text);
        cursor: pointer;
        display: flex;
        align-items: center;
        justify-content: center;
        padding: 4px;
        border-radius: 6px;
        transition: background 0.15s ease;
    }
    
    .menu-btn:hover {
        background: var(--border);
    }
    
    .mobile-title {
        font-family: var(--sans);
        font-size: 14.5px;
        font-weight: 800;
        letter-spacing: 0.8px;
        color: var(--accent);
    }
    
    .viewer-container {
        padding: 12px 12px 18px;
    }
    
    .reading-well {
        padding: 28px 20px;
        border-radius: 8px;
    }
    
    .page-content {
        font-size: 16.5px;
    }
    
    .page-content h1 {
        font-size: 26px;
        margin-bottom: 18px;
        padding-bottom: 10px;
    }
    
    .reader-footer {
        margin-top: 15px;
        padding-top: 10px;
    }
    
    .btn {
        padding: 8px 12px;
        font-size: 12px;
    }
    
    .progress-indicator {
        font-size: 11px;
    }
}