:root{
  --ink:#0A2540; --paper:#F5F6F7; --surface:#FFFFFF; --muted:#5B6778; --rule:#D9DEE5;
  --accent:#B8735F; --accent-ink:#8E4F3D; --btn-bg:#0A2540; --btn-ink:#FFFFFF; --contour:#0A254014;
  --serif:"Newsreader",Georgia,"Times New Roman",serif;
  --sans:"Source Sans 3","Segoe UI",system-ui,-apple-system,sans-serif;
  --mono:"IBM Plex Mono",ui-monospace,Menlo,Consolas,monospace;
  --measure:65ch;
}
@media (prefers-color-scheme: dark){
  :root:not([data-theme="light"]){
    --ink:#E4EAF2; --paper:#0B1624; --surface:#112136; --muted:#9AA8BA; --rule:#22344C;
    --accent:#D9967F; --accent-ink:#E7B09C; --btn-bg:#E4EAF2; --btn-ink:#0A2540; --contour:#E4EAF212; color-scheme:dark;
  }
}
:root[data-theme="dark"]{
  --ink:#E4EAF2; --paper:#0B1624; --surface:#112136; --muted:#9AA8BA; --rule:#22344C;
  --accent:#D9967F; --accent-ink:#E7B09C; --btn-bg:#E4EAF2; --btn-ink:#0A2540; --contour:#E4EAF212; color-scheme:dark;
}
*{box-sizing:border-box}
[hidden]{display:none!important}
html{-webkit-text-size-adjust:100%}
body{margin:0;background:var(--paper);color:var(--ink);font-family:var(--sans);font-size:1.0625rem;line-height:1.65}
img,svg{max-width:100%;height:auto}
a{color:inherit;text-decoration-color:var(--accent);text-underline-offset:3px}
a:hover{text-decoration-thickness:2px}
:focus-visible{outline:2px solid var(--accent);outline-offset:3px;border-radius:2px}
h1,h2,h3{font-family:var(--serif);font-weight:400;line-height:1.15;text-wrap:balance;margin:0}
h1{font-size:clamp(2.3rem,5vw,3.6rem);letter-spacing:-.01em}
h2{font-size:clamp(1.6rem,3vw,2.1rem)}
h3{font-size:1.3rem}
p{margin:0}
.label{font-family:var(--mono);font-size:.75rem;letter-spacing:.08em;text-transform:uppercase;color:var(--muted)}
.wrap{max-width:1120px;margin-inline:auto;padding-inline:clamp(16px,4vw,40px)}

/* header */
.site-head{position:sticky;top:env(safe-area-inset-top,0px);z-index:10;background:color-mix(in srgb,var(--paper) 92%,transparent);backdrop-filter:blur(8px);border-bottom:1px solid var(--rule)}
.site-head .wrap{display:flex;align-items:center;justify-content:space-between;gap:24px;min-height:68px}
.brand{font-family:var(--serif);font-size:1.45rem;text-decoration:none;white-space:nowrap}
.brand small{display:block;font-family:var(--mono);font-size:.62rem;letter-spacing:.14em;text-transform:uppercase;color:var(--muted);margin-top:-2px}
.nav>ul{list-style:none;margin:0;padding:0;display:flex;gap:4px;align-items:center}
.nav li{position:relative}
.nav a,.nav .top{display:block;padding:8px 12px;text-decoration:none;font-size:.95rem;border-radius:4px}
.nav a:hover,.nav .top:hover{background:var(--surface)}
.nav a[aria-current="page"]{text-decoration:underline;text-decoration-color:var(--accent)}
.nav .sub{list-style:none;margin:0;padding:6px;position:absolute;left:0;top:100%;min-width:230px;background:var(--surface);border:1px solid var(--rule);border-radius:6px;box-shadow:0 12px 30px #0A25401f;display:none}
.nav li:hover>.sub,.nav li:focus-within>.sub{display:block}
.nav .cta{background:var(--btn-bg);color:var(--btn-ink);margin-left:6px}
.nav .cta:hover{background:var(--btn-bg);opacity:.9}
.menu-toggle{display:none}
@media (max-width:860px){
  .site-head .wrap{flex-wrap:wrap;padding-block:10px}
  .menu-toggle{display:block;font:inherit;background:none;border:1px solid var(--rule);color:var(--ink);border-radius:4px;padding:6px 12px}
  .nav{display:none;width:100%}
  .nav.open{display:block}
  .nav>ul{flex-direction:column;align-items:stretch;padding-bottom:10px}
  .nav .sub{position:static;display:block;border:0;box-shadow:none;background:none;padding:0 0 0 14px;min-width:0}
  .nav .cta{margin:6px 0 0}
}

/* layout pieces */
main{display:block}
.hero{padding-block:clamp(48px,8vw,104px);position:relative;overflow:hidden}
.hero .contours{position:absolute;right:-120px;top:-40px;width:620px;max-width:none;color:var(--contour);pointer-events:none}
.hero-inner{position:relative;display:grid;gap:22px;max-width:760px}
.lede{font-size:1.2rem;color:var(--muted);max-width:var(--measure)}
.btns{display:flex;flex-wrap:wrap;gap:12px;margin-top:6px}
.btn{display:inline-block;padding:12px 20px;border-radius:4px;text-decoration:none;font-weight:600;font-size:.98rem;border:1px solid var(--btn-bg)}
.btn.primary{background:var(--btn-bg);color:var(--btn-ink)}
.btn.ghost{color:var(--ink)}
.page-head{padding-block:clamp(40px,6vw,72px) clamp(20px,3vw,32px);border-bottom:1px solid var(--rule)}
.page-head .wrap{display:grid;gap:14px}
.section{padding-block:clamp(40px,6vw,72px)}
.section+.section{border-top:1px solid var(--rule)}
.prose{max-width:var(--measure);display:grid;gap:1.05em}
.prose h2{margin-top:.8em}
.prose h3{margin-top:.6em}
.prose ul{margin:0;padding-left:1.2em;display:grid;gap:.35em}
.split{display:grid;grid-template-columns:minmax(0,1fr) minmax(0,2fr);gap:clamp(24px,5vw,64px);align-items:start}
@media (max-width:760px){.split{grid-template-columns:1fr}}
.cols{display:grid;grid-template-columns:repeat(auto-fit,minmax(240px,1fr));gap:clamp(20px,3vw,36px)}
.col{display:grid;gap:10px;align-content:start}
.col .more{font-weight:600;margin-top:4px}
.types{display:grid;grid-template-columns:repeat(auto-fit,minmax(200px,1fr));gap:0;border-top:1px solid var(--rule)}
.types div{padding:18px 18px 18px 0;border-bottom:1px solid var(--rule);display:grid;gap:4px}
.types .term{font-family:var(--mono);font-size:.72rem;letter-spacing:.08em;text-transform:uppercase;color:var(--accent-ink)}
.panel{background:var(--surface);border:1px solid var(--rule);border-radius:8px;padding:clamp(20px,3vw,32px);display:grid;gap:12px;align-content:start}
.steps{list-style:none;margin:0;padding:0;display:grid;gap:0;counter-reset:s}
.steps li{display:grid;grid-template-columns:3rem minmax(0,1fr);gap:16px;padding-block:22px;border-top:1px solid var(--rule)}
.steps li::before{counter-increment:s;content:counter(s,decimal-leading-zero);font-family:var(--mono);font-size:.85rem;color:var(--accent-ink);padding-top:6px}
.steps li>div{display:grid;gap:6px;max-width:var(--measure)}
.timeline{list-style:none;margin:0;padding:0;display:grid;gap:0;border-left:1px solid var(--rule)}
.timeline li{position:relative;padding:0 0 22px 24px;display:grid;gap:4px;max-width:var(--measure)}
.timeline li::before{content:"";position:absolute;left:-5px;top:.55em;width:9px;height:9px;border-radius:50%;background:var(--paper);border:1.5px solid var(--accent)}
.timeline .yr{font-family:var(--mono);font-size:.8rem;color:var(--accent-ink)}
details.faq{border-top:1px solid var(--rule);padding-block:6px}
details.faq:last-of-type{border-bottom:1px solid var(--rule)}
details.faq summary{cursor:pointer;list-style:none;padding:14px 32px 14px 0;position:relative;font-family:var(--serif);font-size:1.2rem}
details.faq summary::-webkit-details-marker{display:none}
details.faq summary::after{content:"+";position:absolute;right:4px;top:12px;font-family:var(--sans);color:var(--muted)}
details.faq[open] summary::after{content:"–"}
details.faq .ans{padding-bottom:18px;display:grid;gap:.8em;max-width:var(--measure)}
details.faq .ans h4{margin:.4em 0 0;font-size:.95rem;font-weight:600}
details.faq .ans ul{margin:0;padding-left:1.2em;display:grid;gap:.25em}
.faq-list{max-width:820px}
.hub-grid{display:grid;grid-template-columns:repeat(auto-fit,minmax(250px,1fr));gap:16px}
.hub-card{background:var(--surface);border:1px solid var(--rule);border-radius:8px;padding:22px;display:grid;gap:8px;align-content:start}
.hub-card .q{font-family:var(--serif);font-style:italic;color:var(--muted)}
.hub-card ul{margin:0;padding-left:1.1em;font-size:.95rem;color:var(--muted)}
.status{font-family:var(--mono);font-size:.7rem;letter-spacing:.08em;text-transform:uppercase;color:var(--accent-ink)}
figure{margin:0;display:grid;gap:10px}
figcaption{font-size:.9rem;color:var(--muted);max-width:var(--measure)}
.diagram{background:var(--surface);border:1px solid var(--rule);border-radius:8px;padding:clamp(12px,2vw,24px);overflow-x:auto}
.diagram svg{display:block;width:100%;min-width:560px;height:auto}
.draft{display:inline-block;font-family:var(--mono);font-size:.7rem;letter-spacing:.06em;text-transform:uppercase;border:1px dashed var(--accent);color:var(--accent-ink);padding:3px 8px;border-radius:3px}
.contact-list{display:grid;gap:14px}
.contact-list div{display:grid;gap:2px}
.contact-list .v{font-size:1.15rem;font-variant-numeric:tabular-nums}
.note{font-size:.92rem;color:var(--muted);max-width:var(--measure)}
.site-foot{border-top:1px solid var(--rule);padding-block:40px;margin-top:24px;font-size:.92rem;color:var(--muted)}
.site-foot .wrap{display:grid;grid-template-columns:repeat(auto-fit,minmax(200px,1fr));gap:24px}
.site-foot strong{color:var(--ink);font-family:var(--serif);font-weight:400;font-size:1.15rem}
.site-foot ul{list-style:none;margin:0;padding:0;display:grid;gap:4px}
.site-foot a{text-decoration:none}
@media (prefers-reduced-motion:no-preference){.hero .contours{animation:drift 30s ease-in-out infinite alternate}@keyframes drift{to{transform:translate(-18px,10px)}}}

/* starting-point sorter */
.sorter{max-width:720px;display:grid;gap:22px}
.sorter .progress{display:flex;justify-content:space-between;align-items:center;gap:12px;font-size:.95rem;color:var(--muted)}
.sorter .bar{height:6px;border-radius:3px;background:var(--rule);overflow:hidden}
.sorter .bar span{display:block;height:100%;background:var(--accent);transition:width .25s}
.sorter h2{font-size:clamp(1.6rem,3.4vw,2.2rem)}
.sorter .help{color:var(--muted);font-size:1.05rem}
.opts{display:grid;gap:10px}
.opt{display:block;width:100%;text-align:left;font:inherit;font-size:1.12rem;line-height:1.4;color:var(--ink);background:var(--surface);border:1.5px solid var(--rule);border-radius:8px;padding:18px 20px;cursor:pointer;min-height:60px}
.opt:hover{border-color:var(--ink)}
.opt[aria-pressed="true"]{border-color:var(--accent);box-shadow:inset 0 0 0 1.5px var(--accent)}
.tool-row{display:flex;flex-wrap:wrap;gap:12px;align-items:center}
.linkbtn{font:inherit;font-size:1rem;background:none;border:0;color:var(--ink);text-decoration:underline;text-decoration-color:var(--accent);text-underline-offset:3px;padding:10px 4px;cursor:pointer}
.code-box{background:var(--surface);border:1.5px solid var(--accent);border-radius:8px;padding:clamp(18px,3vw,28px);display:grid;gap:12px}
.code{font-family:var(--mono);font-size:clamp(1.25rem,3.6vw,1.8rem);letter-spacing:.06em;word-break:break-word;font-variant-numeric:tabular-nums}
.summary{display:grid;gap:0;border-top:1px solid var(--rule)}
.summary div{display:grid;grid-template-columns:minmax(0,1fr) minmax(0,1.3fr);gap:16px;padding-block:12px;border-bottom:1px solid var(--rule)}
.summary dt{color:var(--muted);font-size:.95rem}
.summary dd{margin:0}
@media (max-width:560px){.summary div{grid-template-columns:1fr;gap:2px}}
.bigger{font-size:1.18rem}
.bigger .opt{font-size:1.28rem}
.sorter [data-view]{display:grid;gap:20px}
.decoder textarea,.decoder input{font:inherit;font-family:var(--mono);font-size:1.1rem;width:100%;padding:12px;border:1.5px solid var(--rule);border-radius:6px;background:var(--surface);color:var(--ink)}
/* BCX2 sorter additions */
.sorter .expect{margin:0;padding:14px 18px;border-left:3px solid var(--accent);background:var(--surface);border-radius:0 8px 8px 0;display:grid;gap:4px;font-size:1.02rem}
.sorter .expect .label{color:var(--accent-ink)}
.sorter .zip{display:grid;gap:10px}
.sorter .zip-row{display:flex;gap:10px;align-items:stretch;flex-wrap:wrap}
.sorter .zip-row input{font:inherit;font-family:var(--mono);font-size:1.4rem;letter-spacing:.2em;width:7ch;padding:10px 12px;border:1.5px solid var(--rule);border-radius:8px;background:var(--surface);color:var(--ink)}
.sorter .zip-row input:focus-visible{border-color:var(--accent)}
.bigger .expect{font-size:1.15rem}
/* Old Masters placeholder gallery (education page) */
.m-area{display:grid;gap:16px;padding-top:24px;border-top:1px solid var(--rule)}
.m-head{display:grid;gap:6px;max-width:var(--measure)}
.m-head h3{font-size:1.5rem}
.m-head p{margin:0;color:var(--muted)}
.m-grid{display:grid;grid-template-columns:repeat(auto-fill,minmax(min(230px,100%),1fr));gap:20px;align-items:start}
.m-fig{display:grid;gap:10px;min-width:0}
.m-img{background:var(--surface);border:1px solid var(--rule);border-radius:8px;display:grid;place-items:center;padding:12px;aspect-ratio:4/5;max-width:100%;min-width:0;overflow:hidden}
.m-img img{width:100%;height:100%;object-fit:contain;min-width:0}
.m-fig figcaption{display:grid;gap:4px;font-size:.92rem}
.m-fig figcaption strong{font-family:var(--serif);font-weight:500;font-size:1.08rem;color:var(--ink)}
.m-by{color:var(--muted)}
.m-note{color:var(--ink)}
.m-credit{font-size:.78rem;color:var(--muted)}

.panels-2{display:grid;grid-template-columns:repeat(auto-fit,minmax(min(220px,100%),1fr));gap:16px;margin-top:8px}
.panels-2 .panel h3{font-size:1.25rem}
.types.two{grid-template-columns:repeat(auto-fit,minmax(min(260px,100%),1fr))}
.prose .panels-2{max-width:none}
.cols-4{grid-template-columns:repeat(auto-fit,minmax(min(210px,100%),1fr))}