:root{
  --brand-1:#7c3aed; --brand-2:#5e48ec; --brand-3:#2563eb;
  --brand-grad:linear-gradient(115deg,#7c3aed 0%,#5e48ec 46%,#2563eb 100%);
  --ink:#151515; --surface:#ffffff; --background:#efeef3; --muted:#5b5b66;
  --border:#e2e2e8; --card:#e9e8ef;
  --r-md:16px; --r-lg:24px; --r-full:9999px; --maxw:820px;
  --font:'Inter',system-ui,-apple-system,Segoe UI,Roboto,sans-serif;
  --display:'Inter Tight','Inter',system-ui,sans-serif;
}
*{box-sizing:border-box}
html{scroll-behavior:smooth}
body{margin:0;background:var(--background);color:var(--ink);font-family:var(--font);font-size:16px;line-height:1.65;letter-spacing:-.01em;-webkit-font-smoothing:antialiased}
a{color:var(--brand-2);text-decoration:none}
a:hover{text-decoration:underline}
img{display:block;max-width:100%}

/* nav */
.lg-nav{position:sticky;top:0;z-index:20;background:rgba(239,238,243,.82);backdrop-filter:saturate(180%) blur(14px);border-bottom:1px solid transparent;transition:border-color .3s}
.lg-nav.stuck{border-bottom-color:var(--border)}
.lg-nav-in{max-width:1100px;margin:0 auto;padding:18px 28px;display:flex;align-items:center;justify-content:space-between;gap:16px}
.lg-nav-in img{height:24px}
.lg-back{display:inline-flex;align-items:center;gap:8px;font-size:14px;font-weight:600;color:var(--ink);border:1px solid var(--border);background:var(--surface);border-radius:var(--r-full);padding:9px 18px;transition:.2s}
.lg-back:hover{border-color:var(--ink);text-decoration:none;transform:translateY(-1px)}

/* hero */
.lg-head{max-width:var(--maxw);margin:0 auto;padding:64px 28px 26px}
.lg-tag{font-size:13px;font-weight:700;letter-spacing:.05em;text-transform:uppercase;color:var(--brand-2)}
.lg-head h1{font-family:var(--display);font-weight:500;letter-spacing:-.04em;line-height:1.02;font-size:clamp(34px,6vw,54px);margin:16px 0 14px;color:var(--ink)}
.lg-meta{color:var(--muted);font-size:15px}
.lg-meta strong{color:var(--ink);font-weight:600}

/* body */
.lg-body{max-width:var(--maxw);margin:0 auto;padding:14px 28px 80px}
.lg-intro{font-size:18px;color:#3a3a44;background:var(--surface);border:1px solid var(--border);border-radius:var(--r-lg);padding:24px 26px;margin-bottom:14px;line-height:1.6}
.lg-toc{background:var(--surface);border:1px solid var(--border);border-radius:var(--r-lg);padding:22px 26px;margin:22px 0 40px}
.lg-toc h2{font-family:var(--display);font-size:14px;text-transform:uppercase;letter-spacing:.04em;color:var(--muted);margin:0 0 14px;font-weight:600}
.lg-toc ol{margin:0;padding-left:20px;columns:2;column-gap:34px}
.lg-toc li{margin-bottom:9px;font-size:14.5px}
.lg-body section{margin:0 0 34px;scroll-margin-top:90px}
.lg-body h2{font-family:var(--display);font-weight:500;letter-spacing:-.03em;font-size:clamp(22px,3vw,29px);margin:36px 0 12px;color:var(--ink)}
.lg-body h3{font-family:var(--display);font-weight:600;letter-spacing:-.02em;font-size:19px;margin:24px 0 8px;color:var(--ink)}
.lg-body p{margin:0 0 14px;color:#33333c}
.lg-body ul,.lg-body ol{margin:0 0 16px;padding-left:22px}
.lg-body li{margin-bottom:9px;color:#33333c}
.lg-body strong{color:var(--ink);font-weight:600}
.lg-body a{font-weight:500}
.lg-body code{font-family:ui-monospace,SFMono-Regular,Menlo,monospace;font-size:.88em;background:rgba(94,72,236,.08);color:#4a37d6;padding:2px 7px;border-radius:6px}
.lg-note{background:var(--card);border:1px solid var(--border);border-left:3px solid var(--brand-2);border-radius:12px;padding:16px 18px;margin:16px 0;font-size:15px}
.lg-contact{background:var(--surface);border:1px solid var(--border);border-radius:var(--r-lg);padding:24px 26px;margin-top:30px}
.lg-contact h3{margin-top:0}
.lg-contact p{margin:4px 0}

/* footer */
.lg-foot{background:var(--ink);color:rgba(255,255,255,.6);padding:48px 28px;text-align:center;font-size:14px}
.lg-foot a{color:rgba(255,255,255,.8)}
.lg-foot .row{display:flex;gap:22px;justify-content:center;flex-wrap:wrap;margin-bottom:18px}
.lg-foot .fine{color:rgba(255,255,255,.45);font-size:13px}
.lg-foot .fine strong{color:rgba(255,255,255,.75);font-weight:600}

@media(max-width:640px){.lg-toc ol{columns:1}}