/* Core Layout */
body {
    margin: 0;
    padding: 0;
    font-family: "Courier New", Courier, monospace;
    background-color: #ffffff;
    color: #222;
    display: flex;
    min-height: 100vh;
}

/* Sidebar Styling */
#sidebar {
    width: 280px;
    background-color: #1a1a1a;
    color: #00ff00; 
    padding: 20px;
    border-right: 4px solid #000;
    flex-shrink: 0;
    overflow-y: auto;
    height: 100vh;
    position: sticky;
    top: 0;
}

#sidebar h2 {
    font-size: 1.8rem;
    border-bottom: 2px solid #00ff00;
    padding-bottom: 10px;
    text-align: center;
    margin-top: 0;
}

#sidebar ul { list-style: none; padding: 0; }
#sidebar li { margin: 8px 0; line-height: 1.2; }

.section-header {
    font-weight: bold;
    color: #fff;
    display: block;
    margin-top: 25px;
    padding: 5px 0;
    font-size: 0.85rem;
    border-bottom: 1px dashed #555;
}

#sidebar a { color: #00ff00; text-decoration: none; font-size: 0.8rem; }
#sidebar a:hover { background: #00ff00; color: #000; }

.hl-tag { color: #ffcc00; font-weight: bold; }

/* Main Content Area */
#main-content {
    padding: 40px;
    max-width: 800px;
    flex-grow: 1;
}

header { border-bottom: 5px solid #222; margin-bottom: 20px; }
h1 { font-size: 2.5rem; margin: 0; }

/* Boxes and Links */
.box {
    border: 2px solid #222;
    padding: 15px;
    margin: 20px 0;
}

.chapter-grid {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 15px;
    margin: 30px 0;
}

.chapter-link {
    color: #222;
    font-weight: bold;
    text-decoration: underline;
}

footer {
    margin-top: 50px;
    font-size: 0.8rem;
    border-top: 2px solid #222;
    padding-top: 10px;
}

/* Mobile Responsive */
@media (max-width: 800px) {
    body { flex-direction: column; }
    #sidebar { width: 100%; height: auto; position: relative; border-right: none; border-bottom: 4px solid #000; }
    .chapter-grid { grid-template-columns: 1fr; }
}