:root{
  --fg:#2f3437; --muted:#6b7280; --bg:#fff; --border:#e5e7eb; --primary:#2563eb;
  --bg-soft:#f7f7f8; --bg-soft-2:#f3f4f6; --bg-soft-3:#fafafa;
  --code-bg:#f6f8fa; --code-fg:#111827;
}
*{box-sizing:border-box}
html,body{margin:0;padding:0;background:var(--bg);color:var(--fg)}
body{
  font:16px/1.75 Inter,"Noto Sans SC",-apple-system,BlinkMacSystemFont,"Segoe UI",
       "PingFang SC","Hiragino Sans GB","Microsoft YaHei","Helvetica Neue",Arial,sans-serif;
  -webkit-font-smoothing:antialiased; -moz-osx-font-smoothing:grayscale;
}
main{max-width:1000px;margin:40px auto;padding:0 16px}
h1,h2,h3,h4{letter-spacing:.2px}
h1{font-size:32px;line-height:1.25;margin:0 0 8px}
h2{font-size:24px;line-height:1.35;margin:28px 0 10px}
h3{font-size:20px;line-height:1.45;margin:22px 0 8px}
p{margin:12px 0}
article{max-width:78ch;margin:0 auto}
a{color:var(--primary);text-decoration:none;text-underline-offset:3px}
a:hover{text-decoration:underline}
hr{border:none;border-top:1px solid var(--border);margin:28px 0}

/* Header: title + standard barcode */
.header-flex{display:flex;justify-content:space-between;align-items:flex-start;gap:16px;flex-wrap:wrap}
.header-flex, .downloads, .footer .footer-inner{max-width:78ch;margin:0 auto}
.header-flex h1{margin:0}
.barcode{
  display:block;height:64px;max-width:640px;width:auto;object-fit:contain;flex:0 0 auto;margin-top:6px
}

/* Buttons (downloads) */
.btn{display:inline-block;padding:10px 14px;border-radius:8px;background:#2563eb;color:#fff;
     text-decoration:none;font-weight:600;border:1px solid #1e4fd9;transition:filter .15s;white-space:nowrap}
.btn:hover{filter:brightness(1.05);text-decoration:none}
.btn-xs{padding:6px 10px;font-size:13px}
.btn-outline{background:#fff;color:#2563eb;border-color:#2563eb}
.downloads{margin:12px auto 0; padding:0 2px; display:flex; gap:10px; flex-wrap:wrap}

/* Typography */
article > * + *{margin-top:12px}
article strong{font-weight:700}
article em{font-style:italic}
article code:not(pre code){
  background:var(--code-bg);color:var(--code-fg);
  padding:0 4px;border-radius:4px;border:1px solid #e7e9eb
}

/* Blockquote */
blockquote{margin:14px 0;padding:8px 12px;border-left:4px solid #e1e4e8;background:#fbfbfc;border-radius:6px}
blockquote p{margin:6px 0}

/* Lists */
ul,ol{margin:10px 0 10px 1.25em}
li{margin:6px 0}
li > ul, li > ol{margin-top:6px}

/* Images & captions */
article img{max-width:100%;height:auto;border-radius:8px}
figure{margin:14px 0}
figcaption{color:var(--muted);font-size:13px;margin-top:6px}

/* Tables */
.table-wrap{overflow-x:auto;-webkit-overflow-scrolling:touch;margin:16px 0;padding-bottom:2px}
.table-wrap table{border-collapse:separate;border-spacing:0;width:100%;table-layout:fixed}
@media(min-width:900px){ .table-wrap table{table-layout:auto} }
article th,article td{
  border:1px solid var(--border);padding:8px 10px;text-align:left;vertical-align:top;
  word-break:break-word;white-space:normal
}
article thead th{background:#f6f7f9;font-weight:600}
article tbody tr:nth-child(even) td{background:#fbfbfc}

/* Callout / Toggle / Columns */
.n-callout{display:flex;gap:10px;align-items:flex-start;border-radius:10px;padding:12px 14px;margin:14px 0;background:#f8fafc;border:1px solid #e6e8eb}
.n-callout .icon{font-size:18px;line-height:1.2}
details.n-toggle{border:1px dashed var(--border);border-radius:8px;padding:10px 12px;margin:12px 0;background:#fff}
details.n-toggle > summary{cursor:pointer;font-weight:600;list-style:none}
details.n-toggle > summary::-webkit-details-marker{display:none}
.n-columns{display:grid;gap:16px}
@media(min-width:860px){ .n-columns.cols-2{grid-template-columns:1fr 1fr} .n-columns.cols-3{grid-template-columns:1fr 1fr 1fr} }

/* Code blocks: light Notion-like card */
pre.n-code-notion{
  background:var(--code-bg);color:var(--code-fg);border:1px solid #e5e7eb;border-radius:10px;
  padding:14px 16px;overflow:auto;white-space:pre;word-break:normal;tab-size:2;
  font-family:ui-monospace,SFMono-Regular,Menlo,Monaco,Consolas,"Liberation Mono",monospace;
  font-size:14px;line-height:1.65;
}
pre.n-code-notion code{background:transparent;padding:0;white-space:pre}

/* Math (MathJax) */
.mjx-container{overflow-x:auto}
.math-display{margin:16px 0}

/* Footer with icons */
.footer{margin:48px 0 24px 0;font-size:13px;color:var(--muted)}
.footer-inner{display:flex;align-items:center;gap:12px;flex-wrap:wrap}
.footer-inner .spacer{flex:1 1 auto}
.footer a.icon{
  display:inline-flex;align-items:center;justify-content:center;
  width:28px;height:28px;border-radius:6px;border:1px solid var(--border);
  color:var(--fg);text-decoration:none
}
.footer a.icon:hover{background:var(--bg-soft-2)}

@media print{
  a{color:#000;text-decoration:none}
  .barcode{height:96px}
  pre.n-code-notion{page-break-inside:avoid}
}