body { font-family: 'Segoe UI', Arial, sans-serif; margin: 20px; line-height: 1.6; color: #1e293b; background: #f8fafc; }
.chapter { max-width: 900px; margin: auto; background: #fff; padding: 40px; border-radius: 8px; box-shadow: 0 1px 3px rgba(0,0,0,.08); }
h1 { font-size: 2rem; color: #0f172a; border-bottom: 3px solid #3b82f6; padding-bottom: 10px; margin-top: 0; }
h2 { font-size: 1.5rem; color: #1e293b; margin-top: 32px; }
h3 { font-size: 1.15rem; color: #334155; margin-top: 24px; }
.tag { display: inline-block; background: #3b82f6; color: #fff; font-size: .75rem; font-weight: 700; padding: 4px 12px; border-radius: 12px; text-transform: uppercase; letter-spacing: .5px; margin-bottom: 8px; }
pre { background: #1e293b; color: #e2e8f0; padding: 16px; border-radius: 6px; overflow-x: auto; font-size: .9rem; line-height: 1.5; }
code { background: #f1f5f9; padding: 2px 6px; border-radius: 3px; font-size: .9em; }
pre code { background: none; padding: 0; }
.note { background: #eff6ff; border-left: 4px solid #3b82f6; padding: 16px; border-radius: 4px; margin: 16px 0; }
.info { background: #f0fdf4; border-left: 4px solid #22c55e; padding: 16px; border-radius: 4px; margin: 16px 0; }
.exercise { background: #fefce8; border-left: 4px solid #eab308; padding: 16px; border-radius: 4px; margin: 16px 0; }
nav { margin-top: 32px; padding-top: 20px; border-top: 1px solid #e2e8f0; display: flex; justify-content: space-between; flex-wrap: wrap; gap: 8px; }
nav a { color: #3b82f6; text-decoration: none; font-weight: 500; padding: 6px 12px; border-radius: 4px; }
nav a:hover { text-decoration: underline; background: #eff6ff; }
ul.toc { list-style: none; padding: 0; }
ul.toc li { padding: 8px 0; border-bottom: 1px solid #f1f5f9; }
ul.toc li a { color: #3b82f6; text-decoration: none; font-weight: 500; }
ul.toc li a:hover { text-decoration: underline; }
ul.toc li small { color: #64748b; font-weight: 400; display: block; }
img { max-width: 100%; height: auto; display: block; margin: 16px auto; border-radius: 6px; }