:root{--bg:#e4e6e1;--panel:#eef0ec;--ink:#16201c;--muted:#4b5853;--accent:#2a4bff;--line:#c3c8c0;--line2:#8a948d;color-scheme:light dark}
@media (prefers-color-scheme:dark){:root{--bg:#101514;--panel:#171d1b;--ink:#e8ece7;--muted:#9aa59f;--accent:#8aa0ff;--line:#2a322f;--line2:#56625c}}
*{box-sizing:border-box}
html{scroll-padding-top:env(safe-area-inset-top,0);scroll-behavior:smooth}
body{margin:0;background:var(--bg);color:var(--ink);font:18px/1.7 "Segoe UI",system-ui,-apple-system,Roboto,sans-serif;padding:env(safe-area-inset-top,0) 0 env(safe-area-inset-bottom,0)}
a{color:var(--accent);text-underline-offset:3px}
a:focus-visible,button:focus-visible,input:focus-visible{outline:3px solid var(--accent);outline-offset:3px}
.wrap{max-width:46rem;margin:0 auto;padding:0 1.5rem}
.wide{max-width:72rem;margin:0 auto;padding:0 1.5rem}
header{border-bottom:1px solid var(--line);position:sticky;top:0;background:var(--bg);z-index:5;padding-top:env(safe-area-inset-top,0)}
header .wide{display:flex;flex-wrap:wrap;gap:.4rem 2rem;align-items:baseline;justify-content:space-between;padding-top:1rem;padding-bottom:1rem}
.brand{font-weight:800;letter-spacing:-.02em;color:var(--ink);text-decoration:none;font-size:1.15rem}
nav{display:flex;flex-wrap:wrap;gap:.2rem 1.25rem;font-size:.97rem}
nav a{color:var(--muted);text-decoration:none}
nav a:hover,nav a[aria-current]{color:var(--ink);text-decoration:underline;text-decoration-color:var(--accent);text-decoration-thickness:2px}
main{padding:3rem 0 4rem}
h1{font-size:clamp(2.1rem,6vw,3.4rem);line-height:1.08;letter-spacing:-.03em;margin:0 0 1.2rem;font-weight:800}
h2{font-size:1.5rem;line-height:1.25;margin:2.4rem 0 .6rem;letter-spacing:-.01em}
h3{font-size:1.1rem;margin:1.4rem 0 .3rem}
p,li{max-width:40rem}
ul.plain{padding-left:1.2rem}
.lead{font-size:1.25rem;color:var(--muted)}
.bar{width:4rem;height:6px;background:var(--accent);margin:0 0 1.5rem}
.note{background:var(--panel);border-left:4px solid var(--accent);padding:.9rem 1.1rem;margin:1.5rem 0}
.links{list-style:none;padding:0;margin:1.5rem 0}
.links li{border-top:1px solid var(--line);padding:.7rem 0}
.links li:last-child{border-bottom:1px solid var(--line)}
.crumbs{font-size:.92rem;color:var(--muted);margin-bottom:1.2rem}
.crumbs a{color:var(--muted)}
.meta{font-size:.92rem;color:var(--muted);margin:-.4rem 0 1.4rem}
.hero{display:grid;gap:2.5rem;align-items:center;padding:3.5rem 0 2.5rem}
@media(min-width:56rem){.hero{grid-template-columns:1.05fr .95fr}}
.hero h1{font-size:clamp(2.4rem,6.5vw,4.2rem)}
.btns{display:flex;flex-wrap:wrap;gap:.8rem;margin-top:1.6rem}
.btn{display:inline-block;padding:.75rem 1.3rem;font-weight:700;text-decoration:none;border:2px solid var(--accent);color:var(--ink);transition:background .2s,color .2s}
.btn.pri{background:var(--accent);color:#fff}
@media (prefers-color-scheme:dark){.btn.pri{color:#0b0f14}}
.btn:hover{background:var(--ink);border-color:var(--ink);color:var(--bg)}
.bracket{width:100%;height:auto;max-height:22rem}
.bracket path{fill:none;stroke:var(--line2);stroke-width:2;stroke-linecap:square}
.bracket .fin{stroke:var(--accent);stroke-width:3}
.bracket circle{fill:var(--accent);opacity:0;animation:pop .5s ease 2.1s forwards}
.dr{stroke-dasharray:1;stroke-dashoffset:1;animation:draw .6s ease forwards;animation-delay:var(--d)}
@keyframes draw{to{stroke-dashoffset:0}}
@keyframes pop{from{opacity:0;transform:scale(.4)}to{opacity:1;transform:scale(1)}}
.bracket circle{transform-box:fill-box;transform-origin:center}
.grid{display:grid;gap:1rem;grid-template-columns:repeat(auto-fill,minmax(16rem,1fr));margin:1.2rem 0 2.5rem}
.card{display:block;background:var(--panel);border:1px solid var(--line);padding:1.2rem 1.3rem;text-decoration:none;color:var(--ink);transition:transform .2s,border-color .2s}
.card:hover{transform:translateY(-3px);border-color:var(--accent)}
.card strong{display:block;font-size:1.08rem;line-height:1.3;margin-bottom:.4rem}
.card span{color:var(--muted);font-size:.95rem;line-height:1.5;display:block}
.js .rv{opacity:0;transform:translateY(14px);transition:opacity .6s ease,transform .6s ease}
.js .rv.in{opacity:1;transform:none}
@media (prefers-reduced-motion:reduce){.js .rv{opacity:1;transform:none;transition:none}.dr{animation:none;stroke-dashoffset:0}.bracket circle{animation:none;opacity:1}html{scroll-behavior:auto}}
.calc{background:var(--panel);border:1px solid var(--line);padding:1.3rem;margin:1.5rem 0}
.calc label{font-weight:700;display:block;margin-bottom:.4rem}
.calc input{font:inherit;padding:.6rem .8rem;width:9rem;border:2px solid var(--line2);background:var(--bg);color:var(--ink)}
table{border-collapse:collapse;width:100%;margin-top:1rem;font-size:.97rem}
th,td{text-align:left;padding:.6rem .5rem;border-bottom:1px solid var(--line);vertical-align:top}
.tw{overflow-x:auto}
footer{border-top:1px solid var(--line);padding:1.6rem 0 2.2rem;font-size:.92rem;color:var(--muted)}
footer ul{list-style:none;display:flex;flex-wrap:wrap;gap:.3rem 1.25rem;padding:0;margin:0 0 1rem}
footer a{color:var(--muted)}
.toc{background:var(--panel);border:1px solid var(--line);padding:1rem 1.3rem;margin:1.5rem 0}
.toc ol{margin:.5rem 0 0;padding-left:1.2rem}
.toc li{margin:.15rem 0}
section[id]{scroll-margin-top:5rem}