:root {
  font-family: system-ui, -apple-system, "Segoe UI", sans-serif;
  line-height: 1.75;
  --bg: #0c1019;
  --panel: #121926;
  --card: #182232;
  --text: #e8edf7;
  --muted: #a4b2c8;
  --line: #2a384e;
  --accent: #9dafff;
  --green: #6ee7c0;
  --code: #0b1322;
  color-scheme: dark;
}
:root[data-theme="light"] {
  --bg: #f9fafc;
  --panel: #fff;
  --card: #edf2fb;
  --text: #182438;
  --muted: #526179;
  --line: #ccd5e4;
  --accent: #354bc0;
  --green: #086c50;
  --code: #edf1f8;
  color-scheme: light;
}
* { box-sizing: border-box; }
[hidden] { display: none !important; }
body { margin: 0; background: var(--bg); color: var(--text); }
a { color: var(--accent); text-underline-offset: 3px; }
button, input { font: inherit; }
button, summary, input[type="checkbox"] { cursor: pointer; }
button { background: var(--card); color: var(--text); border: 1px solid var(--line); border-radius: 8px; padding: 7px 12px; }
button:hover { border-color: var(--accent); }
a:focus-visible, button:focus-visible, input:focus-visible, summary:focus-visible { outline: 3px solid var(--accent); outline-offset: 3px; }
.skip-link { position: fixed; top: -80px; left: 16px; background: var(--panel); padding: 10px; z-index: 20; }
.skip-link:focus { top: 10px; }
#reading-progress { position: fixed; top: 0; left: 0; height: 3px; width: 0; background: var(--green); z-index: 15; }
#sidebar { position: fixed; inset: 0 auto 0 0; width: 300px; padding: 28px 20px 20px; background: var(--panel); border-right: 1px solid var(--line); overflow-y: auto; z-index: 10; }
.brand { display: flex; align-items: center; gap: 12px; text-decoration: none; color: var(--text); font-weight: 750; line-height: 1.4; }
.brand-mark { color: var(--green); font: bold 27px ui-monospace, monospace; }
.brand small { display: block; font-size: 9px; color: var(--muted); letter-spacing: 1.5px; margin-top: 6px; }
.search-label { display: flex; justify-content: space-between; font-size: 12px; color: var(--muted); margin: 30px 0 8px; }
kbd { border: 1px solid var(--line); padding: 0 6px; border-radius: 4px; }
#search { width: 100%; background: var(--bg); color: var(--text); border: 1px solid var(--line); padding: 10px; border-radius: 8px; font-size: 13px; }
#search-status { font-size: 12px; min-height: 20px; margin: 6px 0; }
.nav-group { margin: 18px 0; }
.nav-group summary { font-size: 13px; font-weight: 750; color: var(--green); padding: 6px 0; }
.nav-link { display: block; padding: 7px 10px; margin: 3px 0; text-decoration: none; font-size: 12px; color: var(--muted); border-radius: 6px; border-left: 2px solid transparent; }
.nav-link:hover, .nav-link[aria-current="page"] { color: var(--text); background: var(--card); border-left-color: var(--accent); }
.nav-link.reviewed::after { content: " [reviewed]"; color: var(--green); font-size: 10px; }
.sidebar-bottom { border-top: 1px solid var(--line); margin-top: 26px; padding-top: 14px; font-size: 12px; }
.sidebar-bottom a { display: inline-block; margin: 12px 0 0 8px; }
#study-progress { color: var(--muted); }
#main { margin-left: 300px; max-width: 1320px; padding: 54px 64px 20px; min-height: 100vh; }
.eyebrow { color: var(--green); text-transform: uppercase; letter-spacing: 2px; font-size: 11px; font-weight: 750; }
.hero h1 { font-size: clamp(36px, 5vw, 64px); letter-spacing: -2px; line-height: 1.12; max-width: 820px; margin: 20px 0; }
.hero h1 span { color: var(--accent); }
.hero p { color: var(--muted); max-width: 680px; font-size: 17px; }
.pill-row { display: flex; gap: 10px; flex-wrap: wrap; margin: 28px 0 40px; }
.pill { border: 1px solid var(--line); border-radius: 30px; padding: 6px 14px; font-size: 12px; color: var(--muted); }
.path { background: var(--card); border: 1px solid var(--line); border-radius: 14px; padding: 22px 26px; margin-bottom: 36px; }
.path h2 { margin: 0 0 8px; font-size: 18px; }
.path p { margin: 0; color: var(--muted); font-size: 14px; }
.track { margin: 38px 0; }
.track-header { display: flex; align-items: baseline; gap: 16px; }
.track-header h2 { font-size: 28px; margin: 0; }
.track-header span { font-size: 12px; color: var(--green); }
.track > p { color: var(--muted); font-size: 14px; margin: 8px 0 20px; }
.topic-grid { display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); gap: 12px; }
.topic-card { display: block; background: var(--panel); border: 1px solid var(--line); border-radius: 12px; padding: 20px; text-decoration: none; transition: border-color .15s, transform .15s; }
.topic-card:hover { border-color: var(--accent); transform: translateY(-2px); }
.topic-card .number { font-size: 11px; color: var(--green); letter-spacing: 1px; }
.topic-card h3 { font-size: 16px; margin: 8px 0; color: var(--text); }
.topic-card p { color: var(--muted); font-size: 12px; margin: 0; }
.reader-toolbar { display: flex; justify-content: space-between; gap: 16px; font-size: 12px; margin-bottom: 32px; flex-wrap: wrap; }
.reader-toolbar label { color: var(--muted); }
#complete { accent-color: var(--green); }
.contents { margin: 24px 0; padding: 14px 18px; border: 1px solid var(--line); border-radius: 10px; font-size: 13px; }
#page-toc { display: grid; margin-top: 10px; gap: 5px; }
article { overflow-wrap: anywhere; }
article h1 { font-size: clamp(30px, 4vw, 44px); letter-spacing: -1px; line-height: 1.2; margin: 20px 0 26px; }
article h2 { font-size: 25px; margin: 42px 0 16px; padding-bottom: 8px; border-bottom: 1px solid var(--line); scroll-margin-top: 70px; }
article h3 { font-size: 19px; margin-top: 28px; scroll-margin-top: 70px; }
article p, article li { font-size: 15px; }
article li { margin: 8px 0; }
article ul, article ol { padding-left: 24px; }
article blockquote { margin: 24px 0; border-left: 3px solid var(--green); background: var(--card); padding: 14px 20px; color: var(--text); }
article blockquote p { margin: 4px 0; }
code { font: .88em ui-monospace, "Cascadia Code", Consolas, monospace; background: var(--code); padding: 2px 5px; border-radius: 4px; }
pre { background: var(--code); padding: 45px 20px 20px; border: 1px solid var(--line); border-radius: 10px; overflow-x: auto; position: relative; line-height: 1.65; }
pre code { padding: 0; font-size: 13px; white-space: pre; }
.copy-code { position: absolute; top: 7px; right: 8px; font-size: 11px; padding: 3px 9px; }
.table-wrap { overflow-x: auto; margin: 24px 0; }
table { border-collapse: collapse; width: 100%; font-size: 13px; }
th, td { padding: 12px; border: 1px solid var(--line); text-align: left; min-width: 110px; }
th { background: var(--card); }
article details { border: 1px solid var(--line); border-radius: 9px; padding: 14px 18px; margin: 14px 0; }
article summary { font-weight: 650; color: var(--accent); }
#chapter-pagination { display: flex; justify-content: space-between; gap: 20px; border-top: 1px solid var(--line); margin-top: 40px; padding-top: 24px; font-size: 14px; }
#chapter-pagination a { max-width: 48%; }
footer { margin-top: 60px; padding: 24px 0; border-top: 1px solid var(--line); color: var(--muted); font-size: 11px; }
#announcement:not(:empty) { border: 1px solid var(--accent); padding: 12px; border-radius: 8px; margin-bottom: 20px; font-size: 13px; }
.muted { color: var(--muted); }
.mobile-header { display: none; }
@media (min-width: 1600px) { #main { margin-right: auto; } }
@media (max-width: 1050px) { #main { padding: 40px 30px 20px; } .topic-grid { grid-template-columns: 1fr; } }
@media (max-width: 760px) {
  .mobile-header { display: flex; align-items: center; gap: 18px; background: var(--panel); border-bottom: 1px solid var(--line); position: sticky; top: 0; padding: 10px 16px; z-index: 8; font-size: 13px; }
  .mobile-header a { text-decoration: none; color: var(--text); font-weight: 650; }
  #sidebar { transform: translateX(-100%); width: min(300px, 87vw); }
  #sidebar.open { transform: translateX(0); }
  #overlay { position: fixed; inset: 0; background: #0009; border: 0; border-radius: 0; z-index: 9; }
  #main { margin-left: 0; padding: 32px 20px 16px; }
  .track-header { display: block; }
  .hero h1 { letter-spacing: -1px; }
}
@media (prefers-reduced-motion: reduce) { * { transition: none !important; scroll-behavior: auto !important; } }
@media print {
  #sidebar, .mobile-header, .reader-toolbar, .contents, #chapter-pagination, .copy-code, footer { display: none; }
  #main { margin: 0; padding: 0; max-width: none; }
  :root { --bg: white; --text: black; --code: #eee; --line: #aaa; --muted: #333; --card: #eee; --green: #333; --accent: #333; color-scheme: light; }
  pre { white-space: pre-wrap; } pre code { white-space: pre-wrap; }
}