/* Static lesson pages — self-contained, no build step, no external fonts. */
:root{
  --navy:#1A2330; --orange:#D4875A; --orange-deep:#C4703F;
  --line:#E5DFD8; --gray:#5C6672; --bg:#FAF8F5; --ink:#232323;
}
*{margin:0;padding:0;box-sizing:border-box}
html{-webkit-text-size-adjust:100%}
body{
  font-family:-apple-system,BlinkMacSystemFont,"Segoe UI",Roboto,"PingFang SC","Microsoft YaHei",sans-serif;
  color:var(--ink);line-height:1.75;background:#fff;
}
.top{background:#141B26;color:#9AA5B4;font-size:13px}
.top .wrap{max-width:860px;margin:0 auto;padding:0 24px;display:flex;align-items:center;gap:14px;height:48px}
.top .brand{color:var(--orange);font-weight:800;text-decoration:none;font-size:14px;white-space:nowrap}
.top .crumb{flex:1;overflow:hidden;text-overflow:ellipsis;white-space:nowrap}
.langs{display:flex;gap:6px}
.langs button{background:transparent;border:1px solid #3A4658;color:#B8C1CC;border-radius:20px;padding:3px 12px;font-size:12px;font-weight:600;cursor:pointer}
.langs button.on{background:var(--orange);border-color:var(--orange);color:#fff}

main.wrap{max-width:860px;margin:0 auto;padding:36px 24px 60px}
h1{font-size:30px;line-height:1.3;margin-bottom:8px;letter-spacing:-.01em}
.meta{color:var(--gray);font-size:13.5px;margin-bottom:24px}

video{width:100%;border-radius:12px;border:1px solid var(--line);background:#0E1622;margin-bottom:26px;display:block}

article h1{font-size:24px;margin:30px 0 10px}
article h2{font-size:20px;margin:32px 0 10px;padding-bottom:6px;border-bottom:1px solid var(--line)}
article h3{font-size:16.5px;margin:24px 0 8px;color:var(--navy)}
article p{font-size:15.5px;color:#3A4149;margin:12px 0}
article ul{padding-left:22px;margin:12px 0}
article li{font-size:15.5px;color:#3A4149;margin:6px 0}
article strong{color:var(--navy)}
article a{color:var(--orange-deep)}
article code{background:var(--bg);border:1px solid var(--line);padding:1px 6px;border-radius:4px;font-size:.9em;font-family:ui-monospace,Menlo,Consolas,monospace}
article pre{background:#141B26;color:#E6EDF3;border-radius:10px;padding:16px 18px;overflow-x:auto;margin:14px 0}
article pre code{background:none;border:0;padding:0;color:inherit;font-size:13px;line-height:1.6}
article blockquote{border-left:3px solid var(--orange);background:var(--bg);padding:10px 16px;margin:14px 0;color:#4A5460;font-size:15px;border-radius:0 8px 8px 0}
.mdline{font-family:ui-monospace,Menlo,monospace;font-size:13px;color:#5C6672;padding:2px 8px;background:var(--bg);border-radius:4px;margin:2px 0;overflow-x:auto;white-space:pre}

.codecard{border:1px solid var(--line);border-radius:12px;overflow:hidden;margin:22px 0;background:#fff}
.codecard .head{display:flex;justify-content:space-between;gap:12px;align-items:center;background:var(--bg);border-bottom:1px solid var(--line);padding:9px 14px;font-size:13px;font-weight:700;color:var(--navy)}
.codecard .head .k{color:var(--gray);font-weight:500;font-size:11.5px;overflow:hidden;text-overflow:ellipsis;white-space:nowrap}
.codecard pre{margin:0;padding:16px 18px;overflow-x:auto;background:#141B26;color:#E6EDF3}
.codecard pre code{font-size:12.8px;line-height:1.62;font-family:ui-monospace,Menlo,Consolas,monospace}
.codecard.sol{border-color:#BFD8C0;background:#FBFDFB}
.codecard.sol .head{background:#EFF7EF;color:#2F6B36}

.pager{display:flex;gap:12px;align-items:center;justify-content:space-between;margin:40px 0 0;padding-top:24px;border-top:1px solid var(--line);flex-wrap:wrap}
.pager .pg{flex:1;min-width:180px;text-decoration:none;color:var(--gray);font-size:12.5px;border:1px solid var(--line);border-radius:10px;padding:10px 14px;line-height:1.45}
.pager .pg:hover{border-color:var(--orange)}
.pager .pg span{display:block;color:var(--navy);font-weight:700;font-size:13.5px;margin-top:2px}
.pager .pg.right{text-align:right}
.pager button{background:var(--bg);border:1px solid var(--line);border-radius:10px;padding:10px 18px;font-size:13.5px;font-weight:700;color:var(--navy);cursor:pointer;font-family:inherit}
.pager button.on{background:#EFF7EF;border-color:#BFD8C0;color:#2F6B36}

footer.wrap{max-width:860px;margin:0 auto;padding:0 24px 60px;color:var(--gray);font-size:13px}
footer a{color:var(--gray)}

@media (max-width:640px){
  h1{font-size:24px}
  main.wrap{padding:24px 18px 40px}
  .top .crumb{display:none}
}