:root{
  --paper:#f5fbfa;--card:#ffffff;--ink:#102a26;--muted:#4b635e;--line:#d6e7e3;
  --blue:#0f766e;--red:#6d28d9;--blue-soft:#d7f3ee;--red-soft:#ede5fb;--gold:#e6f6f2;
  --link:#0f766e;--focus:#6d28d9;--btn:#0f766e;--btn-ink:#ffffff;
  --head:system-ui,-apple-system,BlinkMacSystemFont,"Segoe UI",Roboto,"Noto Sans","Helvetica Neue",Arial,sans-serif;--body:system-ui,-apple-system,BlinkMacSystemFont,"Segoe UI",Roboto,"Noto Sans","Helvetica Neue",Arial,sans-serif;
  color-scheme:light;
}
@media (prefers-color-scheme:dark){:root:not([data-theme="light"]){
  --paper:#0e1716;--card:#16221f;--ink:#e6f2ef;--muted:#a2b8b2;--line:#2a3b37;
  --blue:#5eead4;--red:#c4b5fd;--blue-soft:#123029;--red-soft:#261f3d;--gold:#15302a;--link:#7fe0d2;--focus:#c4b5fd;--btn:#2dd4bf;--btn-ink:#06201c;color-scheme:dark}}
:root[data-theme="dark"]{
  --paper:#0e1716;--card:#16221f;--ink:#e6f2ef;--muted:#a2b8b2;--line:#2a3b37;
  --blue:#5eead4;--red:#c4b5fd;--blue-soft:#123029;--red-soft:#261f3d;--gold:#15302a;--link:#7fe0d2;--focus:#c4b5fd;--btn:#2dd4bf;--btn-ink:#06201c;color-scheme:dark}

*{box-sizing:border-box}
html{-webkit-text-size-adjust:100%}
body{margin:0;background:var(--paper);color:var(--ink);font:400 1.0625rem/1.65 var(--body)}
img,svg{max-width:100%}
a{color:var(--link);text-underline-offset:.18em;text-decoration-thickness:1px}
a:hover{text-decoration-thickness:2px}
:focus-visible{outline:3px solid var(--focus);outline-offset:2px;border-radius:3px}
.skip{position:absolute;left:-999px;top:0;background:var(--ink);color:var(--paper);padding:.6rem 1rem;z-index:9}
.skip:focus{left:1rem;top:1rem}
.sr{position:absolute;width:1px;height:1px;overflow:hidden;clip:rect(0 0 0 0);white-space:nowrap}

/* airmail band */
.band{height:4px;background:linear-gradient(90deg,var(--blue),var(--red))}

.top{display:flex;align-items:center;gap:1rem;max-width:1120px;margin:0 auto;padding:.9rem 16px;flex-wrap:wrap}
.brand{display:flex;align-items:center;gap:.55rem;color:var(--ink);text-decoration:none;font:700 1.35rem/1 var(--head);letter-spacing:-.01em}
.brand b{color:var(--red);font-weight:800}
.nav{display:flex;gap:.25rem 1.1rem;margin-left:auto;flex-wrap:wrap}
.nav a{color:var(--ink);text-decoration:none;font-weight:700;font-size:.97rem;padding:.25rem 0;border-bottom:2px solid transparent}
.nav a:hover,.nav a[aria-current="page"]{border-color:var(--red)}
.theme-btn{background:none;border:1px solid var(--line);color:var(--ink);border-radius:999px;padding:.3rem .7rem;font:inherit;font-size:.85rem;cursor:pointer}
@media (max-width:640px){.nav{order:3;width:100%;margin:0;gap:.2rem 1rem}.theme-btn{margin-left:auto}}

main{display:block}
.wrap{max-width:1120px;margin:0 auto;padding:0 16px}
.read{max-width:720px;margin:0 auto;padding:0 16px}

/* home */
.hero{max-width:1120px;margin:0 auto;padding:3rem 16px 2rem;display:grid;grid-template-columns:1.2fr .8fr;gap:2.5rem;align-items:center}
.hero h1{font:700 clamp(2.3rem,6vw,3.9rem)/1.02 var(--head);letter-spacing:-.015em;margin:0 0 1rem}
.hero h1 em{font-style:normal;color:var(--red)}
.hero p{font-size:1.18rem;color:var(--muted);margin:0 0 1.4rem;max-width:34rem}
.stamp{border:1px solid var(--line);border-radius:18px;padding:1.4rem;background:var(--card)}
.stamp h2{font:700 1.05rem/1.2 var(--head);margin:0 0 .6rem}
.stamp ol{margin:0;padding-left:1.2rem}
.stamp li{margin:.35rem 0}
@media (max-width:820px){.hero{grid-template-columns:1fr;padding-top:2rem}}
.search{display:flex;gap:.5rem;max-width:34rem}
.search input{flex:1;min-width:0;font:inherit;padding:.75rem 1rem;border:2px solid var(--blue);border-radius:14px;background:var(--card);color:var(--ink)}
.count{color:var(--muted);font-size:.9rem;margin:.5rem 0 0}

.sect{max-width:1120px;margin:0 auto;padding:1.5rem 16px 2.5rem}
.sect>h2{font:700 1.7rem/1.15 var(--head);margin:0 0 .3rem;letter-spacing:-.01em}
.sect>p{color:var(--muted);margin:0 0 1.2rem}
.grid{display:grid;grid-template-columns:repeat(auto-fill,minmax(250px,1fr));gap:14px;list-style:none;padding:0;margin:0}
.card{display:block;height:100%;background:var(--card);border:1px solid var(--line);border-radius:18px;padding:1rem 1.1rem;text-decoration:none;color:var(--ink);transition:transform .12s,border-color .12s}
.card:hover{border-color:var(--ink);transform:translateY(-2px)}
.card .k{display:inline-block;font-size:.72rem;font-weight:700;letter-spacing:.06em;text-transform:uppercase;padding:.12rem .5rem;border-radius:999px;margin-bottom:.5rem}
.k.help{background:var(--blue-soft);color:var(--blue)}
.k.send{background:var(--red-soft);color:var(--red)}
.card h3{font:700 1.08rem/1.25 var(--head);margin:0 0 .35rem}
.card p{margin:0;color:var(--muted);font-size:.95rem;line-height:1.5}

/* article */
.crumbs{font-size:.88rem;color:var(--muted);padding-top:1.6rem}
.crumbs a{color:var(--muted)}
article h1{font:700 clamp(1.9rem,4.6vw,2.7rem)/1.1 var(--head);letter-spacing:-.01em;margin:.6rem 0 .8rem}
.lede{font-size:1.2rem;color:var(--muted);margin:0 0 .8rem}
.meta{font-size:.88rem;color:var(--muted);margin:0 0 1.4rem;padding-bottom:1rem;border-bottom:1px solid var(--line)}
.answer{background:var(--gold);border-radius:12px;padding:1rem 1.2rem;margin:0 0 1.6rem}
.answer strong:first-child{display:block;font:700 .8rem/1 var(--head);letter-spacing:.08em;text-transform:uppercase;margin-bottom:.45rem}
.answer p{margin:.3rem 0}
.toc{border-left:3px solid var(--blue);padding:.2rem 0 .2rem 1rem;margin:0 0 1.8rem}
.toc h2{font:700 .82rem/1 var(--head);letter-spacing:.08em;text-transform:uppercase;margin:0 0 .5rem;color:var(--muted)}
.toc ol{margin:0;padding-left:1.1rem}
.toc li{margin:.2rem 0}
article h2{font:700 1.55rem/1.2 var(--head);margin:2.2rem 0 .7rem;letter-spacing:-.01em;scroll-margin-top:1rem}
article h3{font:700 1.18rem/1.3 var(--head);margin:1.6rem 0 .5rem}
article p,article li{max-width:68ch}
article ol li,article ul li{margin:.35rem 0}
article table{border-collapse:collapse;width:100%;margin:1rem 0 1.4rem;font-size:.95rem;display:block;overflow-x:auto}
article th,article td{border-bottom:1px solid var(--line);padding:.55rem .6rem;text-align:left;vertical-align:top}
article th{font-family:var(--head);background:var(--card)}
kbd,code{font:600 .88em/1 ui-monospace,Consolas,monospace;background:var(--card);border:1px solid var(--line);border-radius:5px;padding:.12em .38em}
.note{border:1px solid var(--line);background:var(--card);border-radius:10px;padding:.9rem 1.1rem;margin:1.2rem 0}
.note.warn{border-color:var(--red);background:var(--red-soft)}
.example{border:1px solid var(--line);border-radius:10px;padding:.9rem 1.1rem;margin:1rem 0;background:var(--card);white-space:pre-line}
.faq dt{font:700 1.05rem/1.35 var(--head);margin-top:1.1rem}
.faq dd{margin:.35rem 0 0}
.cta{margin:2.2rem 0;border-radius:14px;padding:1.3rem 1.4rem;background:var(--ink);color:var(--paper);position:relative;overflow:hidden}
.cta::before{content:"";position:absolute;inset:0 0 auto 0;height:6px;background:linear-gradient(90deg,#2dd4bf,#a78bfa)}
.cta h2{font:700 1.3rem/1.2 var(--head);margin:.4rem 0 .4rem;color:var(--paper)}
.cta p{margin:.3rem 0 .9rem;color:var(--paper);opacity:.88}
.btn{display:inline-block;background:var(--btn);color:var(--btn-ink);text-decoration:none;font-weight:700;padding:.65rem 1.1rem;border-radius:10px}
.btn:hover{filter:brightness(1.08)}
.cta small{display:block;margin-top:.8rem;opacity:.75;font-size:.82rem}
.related{margin:2.4rem 0 3rem}
.related h2{font:700 1.3rem/1.2 var(--head);margin:0 0 .8rem}
.related .grid{grid-template-columns:repeat(auto-fill,minmax(210px,1fr))}
.sources{font-size:.88rem;color:var(--muted);border-top:1px solid var(--line);margin-top:2.2rem;padding-top:.8rem}
.sources ul{padding-left:1.1rem}

/* forms */
.form label{display:block;font-weight:700;margin:1rem 0 .3rem}
.form input,.form textarea{width:100%;font:inherit;padding:.7rem .8rem;border:1px solid var(--muted);border-radius:8px;background:var(--card);color:var(--ink)}
.form textarea{min-height:9rem}
.form button{margin-top:1rem;font:inherit;font-weight:700;border:0;background:var(--btn);color:var(--btn-ink);padding:.7rem 1.2rem;border-radius:10px;cursor:pointer}

.foot{margin-top:3rem;border-top:1px solid var(--line);background:var(--card)}
.foot .cols{max-width:1120px;margin:0 auto;padding:2rem 16px 1rem;display:grid;grid-template-columns:repeat(auto-fit,minmax(200px,1fr));gap:1.5rem}
.foot h2{font:700 .82rem/1 var(--head);letter-spacing:.08em;text-transform:uppercase;color:var(--muted);margin:0 0 .7rem}
.foot ul{list-style:none;margin:0;padding:0}
.foot li{margin:.3rem 0;font-size:.95rem}
.foot .small{max-width:1120px;margin:0 auto;padding:0 16px 2rem;color:var(--muted);font-size:.85rem}
@media (prefers-reduced-motion:reduce){*{transition:none!important}}
@media print{.top,.foot,.cta,.related,.band{display:none}}
.form .sr{width:1px;height:1px;padding:0;margin:0}
article,.card{overflow-wrap:break-word}
/* tools */
.tool{background:var(--card);border:2px solid var(--ink);border-radius:14px;padding:1.2rem;margin:0 0 1.6rem}
.tool label{display:block;font-weight:700;margin:0 0 .35rem}
.tool textarea,.tool input{width:100%;font:inherit;padding:.7rem .8rem;border:1px solid var(--muted);border-radius:8px;background:var(--paper);color:var(--ink)}
.tool textarea{min-height:7rem;font-family:ui-monospace,Consolas,monospace;font-size:.95rem}
.tool .row{display:grid;grid-template-columns:1fr 1fr;gap:.8rem}
@media (max-width:560px){.tool .row{grid-template-columns:1fr}}
.tool .hint{font-size:.88rem;color:var(--muted);margin:.35rem 0 0}
.tool button[type=submit]{margin-top:.9rem;font:inherit;font-weight:700;border:0;background:var(--btn);color:var(--btn-ink);padding:.7rem 1.3rem;border-radius:10px;cursor:pointer}
.tool button[disabled]{opacity:.7;cursor:wait}
.tool .privacy{font-size:.85rem;color:var(--muted);margin:.8rem 0 0}
.out{outline:none}
.out:empty{display:none}
.result{border:1px solid var(--line);border-left:6px solid var(--muted);border-radius:10px;padding:.8rem 1rem;margin:.8rem 0;background:var(--card)}
.result h3{margin:0 0 .4rem;font:700 1.08rem/1.3 var(--head)}
.result p{margin:.35rem 0}
.result.ok{border-left-color:#1d7a46}.result.warn{border-left-color:#b7791f}.result.bad{border-left-color:#b42a23}.result.unk{border-left-color:var(--muted)}
.rlabel{font:700 1.3rem/1.2 var(--head);margin:0}
.raddr{font-family:ui-monospace,Consolas,monospace;overflow-wrap:anywhere}
.result pre,.tool pre{white-space:pre-wrap;overflow-wrap:anywhere;font:.85rem/1.45 ui-monospace,Consolas,monospace;background:var(--paper);border:1px solid var(--line);border-radius:8px;padding:.6rem .7rem;margin:.4rem 0}
.pill{display:inline-block;font-size:.78rem;font-weight:700;padding:.12rem .55rem;border-radius:999px;white-space:nowrap}
.pill.ok{background:#e3f3ea;color:#145a33}.pill.warn{background:#fbf0d9;color:#7a4e0c}.pill.bad{background:#fbe4e2;color:#8f1f19}.pill.unk{background:var(--line);color:var(--ink)}
.summary{font-size:1.05rem}
.tablewrap{overflow-x:auto;border:1px solid var(--line);border-radius:10px;margin:.6rem 0}
.rtable{width:100%;border-collapse:collapse;font-size:.92rem;display:table!important;margin:0!important}
.rtable td,.rtable th{padding:.5rem .6rem;border-bottom:1px solid var(--line);text-align:left;vertical-align:top}
.rtable td:first-child{font-family:ui-monospace,Consolas,monospace;overflow-wrap:anywhere;min-width:12rem}
.btn.ghost{background:none;color:var(--ink);border:1px solid var(--ink);font:inherit;font-weight:700;padding:.5rem .9rem;border-radius:10px;cursor:pointer}
.nextstep{background:var(--blue-soft);border-radius:10px;padding:.8rem 1rem;margin:1rem 0}
.nextstep p{margin:0}
.toolcards .card h3::before{content:"⚙ ";color:var(--red)}
/* diagrams */
figure.diagram{margin:1.4rem 0;padding:1rem;background:var(--card);border:1px solid var(--line);border-radius:12px}
figure.diagram svg{display:block;width:100%;height:auto}
figure.diagram figcaption{font-size:.88rem;color:var(--muted);margin-top:.6rem}