:root{--max:980px;--fg:#111;--muted:#555;--bg:#fff;--border:#e5e5e5;--link:#0b57d0;}
*{box-sizing:border-box;}
body{margin:0;font-family:system-ui,-apple-system,Segoe UI,Roboto,Helvetica,Arial,sans-serif;line-height:1.55;color:var(--fg);background:var(--bg);}
header{border-bottom:1px solid var(--border);padding:24px 16px;background:#fafafa;}
header .wrap{max-width:var(--max);margin:0 auto;}
h1{font-size:2rem;line-height:1.2;margin:0 0 8px;}
header .meta{color:var(--muted);font-size:0.95rem;}
main{max-width:var(--max);margin:0 auto;padding:24px 16px 56px;display:grid;grid-template-columns: 280px 1fr;gap:24px;}
@media (max-width: 900px){main{grid-template-columns:1fr;} .toc{position:static;}}
.toc{position:sticky;top:16px;align-self:start;border:1px solid var(--border);border-radius:12px;padding:14px 14px 8px;background:#fff;}
.toc h2{font-size:1rem;margin:0 0 10px;}
.toc ul{list-style:none;padding:0;margin:0;}
.toc li{margin:6px 0;}
.toc li.l1 a{font-weight:700;}
.toc li.l2{padding-left:10px;}
.toc li.l3{padding-left:20px;}
a{color:var(--link);text-decoration:none;}
a:hover{text-decoration:underline;}
article{min-width:0;}
article h1{font-size:1.6rem;margin-top:36px;}
article h2{font-size:1.35rem;margin-top:28px;border-top:1px solid var(--border);padding-top:20px;}
article h3{font-size:1.15rem;margin-top:22px;}
p{margin:10px 0;}
ul,ol{margin:10px 0 10px 22px;}
figure.img{margin:16px 0;padding:10px;border:1px solid var(--border);border-radius:12px;background:#fff;}
figure.img img{max-width:100%;height:auto;display:block;margin:0 auto;}
blockquote{margin:14px 0;padding:10px 14px;border-left:4px solid var(--border);background:#fafafa;border-radius:8px;color:var(--muted);}
hr{border:none;border-top:1px solid var(--border);margin:26px 0;}
.video {
    margin: 24px 0;
}

.video-embed {
    position: relative;
    width: 100%;
    padding-top: 56.25%; /* 16:9 */
    border: 1px solid var(--border, #e5e5e5);
    border-radius: 12px;
    overflow: hidden;
    background: #fff;
}

    .video-embed iframe {
        position: absolute;
        inset: 0;
        width: 100%;
        height: 100%;
        border: 0;
    }