:root{--fg:#1d2329;--muted:#55606b;--bg:#fff;--alt:#f4f6f8;--accent:#0b6e4f;--b:#d5dbe1}
*{box-sizing:border-box}body{margin:0;font:16px/1.6 system-ui,-apple-system,Segoe UI,Roboto,sans-serif;color:var(--fg);background:var(--bg)}
a{color:var(--accent)}.wrap{max-width:860px;margin:0 auto;padding:0 1rem}
header{border-bottom:1px solid var(--b)}header .wrap{display:flex;flex-wrap:wrap;gap:.5rem 1rem;align-items:center;justify-content:space-between;padding:.75rem 1rem}
html{overflow-x:clip}.logo{font-weight:800;font-size:1.25rem;text-decoration:none;color:var(--fg)}
header nav{display:flex;flex-wrap:wrap;gap:.15rem .25rem;min-width:0}header nav a{text-decoration:none;padding:.35rem .45rem;border-radius:6px;min-height:36px;display:inline-flex;align-items:center}header nav a[aria-current]{background:var(--alt);font-weight:700}
@media(max-width:600px){header .wrap{padding:.5rem .75rem}header nav{width:100%;margin:0 -.45rem}header nav a{padding:.4rem .45rem;min-height:40px}}
main{overflow-wrap:break-word}img{max-width:100%}
.skip{position:absolute;left:-999px}.skip:focus{left:1rem;top:1rem;background:#fff;padding:.5rem;z-index:9}
h1{font-size:1.75rem;line-height:1.25}main{padding:1rem 0 2rem}
.cards{display:grid;gap:1rem;grid-template-columns:repeat(auto-fit,minmax(220px,1fr));padding:0;list-style:none}
.cards a{display:block;padding:1rem;border:1px solid var(--b);border-radius:10px;text-decoration:none;color:var(--fg);background:var(--alt)}.cards a:hover,.cards a:focus{border-color:var(--accent)}
.calc{background:var(--alt);border:1px solid var(--b);border-radius:10px;padding:1rem;margin:1rem 0}
.grid{display:grid;gap:.75rem;grid-template-columns:repeat(auto-fit,minmax(150px,1fr))}
label{display:block;font-weight:600;font-size:.9rem}input,select{width:100%;padding:.55rem;font-size:1rem;border:1px solid #9aa5b1;border-radius:6px;margin-top:.2rem}
input:focus,select:focus,button:focus{outline:3px solid #f2b705;outline-offset:1px}
.units{margin-bottom:.75rem}.units label{display:inline;font-weight:400;margin-right:1rem}.units input{width:auto}
.result{margin-top:1rem;padding:1rem;background:#fff;border-left:4px solid var(--accent);border-radius:6px}.result strong{font-size:1.2rem}
.ad-slot[hidden],.ad-slot:empty{display:none}.ad-slot{margin:1.25rem 0}
footer{border-top:1px solid var(--b);color:var(--muted);font-size:.9rem;padding:1rem 0}.small{color:var(--muted);font-size:.9rem}
details{border-bottom:1px solid var(--b);padding:.5rem 0}summary{cursor:pointer;font-weight:600}
.ws-card img{width:100%;height:auto;border:1px solid var(--b);border-radius:6px;background:#fff;display:block;margin-bottom:.5rem}
.ws-card .meta,.meta{color:var(--muted);font-size:.85rem}
.ws-layout{display:grid;gap:1.25rem;grid-template-columns:minmax(0,320px) 1fr;align-items:start}@media(max-width:700px){.ws-layout{grid-template-columns:1fr}}
.preview{margin:0;border:1px solid var(--b);border-radius:8px;padding:.5rem;background:#fff}.preview img{width:100%;height:auto;display:block}.preview figcaption{font-size:.8rem;color:var(--muted);text-align:center}
.btn{display:inline-block;padding:.7rem 1.1rem;border-radius:8px;background:var(--accent);color:#fff;text-decoration:none;font-weight:700;margin:.25rem .5rem .25rem 0}.btn.secondary{background:#fff;color:var(--accent);border:2px solid var(--accent)}
.tags span{display:inline-block;background:var(--alt);border:1px solid var(--b);border-radius:99px;padding:.1rem .6rem;font-size:.8rem;margin:0 .3rem .3rem 0}
.crumbs{font-size:.85rem;color:var(--muted)}
@media print{header,footer,.ad-slot,nav,.btn{display:none!important}}
.versions{grid-template-columns:repeat(auto-fill,minmax(150px,1fr))}.versions .ws-card{display:block;padding:.6rem;border:1px solid var(--b);border-radius:10px;background:var(--alt);font-size:.9rem}
.cards.versions .ws-card a{display:inline;padding:0;border:0;background:none;text-decoration:underline}

/* compact listing cards on phones: small thumbnail + title, 1 column */
.ws-card .ws-text{display:block}.ws-card .ws-text .meta{display:block}
@media(max-width:600px){.cards{grid-template-columns:1fr;gap:.5rem}.cards a.ws-card{display:flex;gap:.75rem;align-items:center;padding:.5rem}.cards a.ws-card img{width:64px;flex:0 0 64px;margin:0}h1{font-size:1.45rem}}
.see-all{margin-top:-.25rem}.new-list ul{padding-left:1.1rem}.new-list li{margin:.2rem 0}
/* worksheet page: actions first in DOM (above the preview on phones); preview on the left on wide screens */
.ws-layout .preview{grid-column:1;grid-row:1}.ws-layout .ws-info{grid-column:2;grid-row:1}
@media(max-width:700px){.ws-layout .preview,.ws-layout .ws-info{grid-column:1;grid-row:auto}.ws-layout .preview{max-width:260px}}
.actions .btn{min-height:44px}@media(max-width:600px){.actions .btn{display:block;text-align:center;margin:.4rem 0}}
/* version tiles */
.vgrid{list-style:none;margin:1rem 0;padding:0;display:grid;gap:.5rem;grid-template-columns:repeat(auto-fill,minmax(150px,1fr))}
.vgrid li{list-style:none;border:1px solid var(--b);border-radius:10px;background:var(--alt);padding:.4rem;display:grid;grid-template-columns:1fr;gap:.3rem;align-items:center}
@media(max-width:520px){.vgrid{grid-template-columns:1fr;gap:.35rem}.vgrid li{grid-template-columns:auto 1fr auto}.vgrid .vprev{grid-column:auto;padding:0 .6rem;min-height:44px;margin:0 0 0 .2rem}}
.vgrid li[aria-current]{border-color:var(--accent);box-shadow:0 0 0 2px var(--accent) inset}
.vnum{font-weight:800;font-size:1rem;color:var(--accent)}.vsep{display:none}
.vlinks{display:flex;gap:.4rem}.vlinks a{flex:1;min-width:0;min-height:44px;padding:0 .4rem;display:flex;align-items:center;justify-content:center;border:1.5px solid var(--accent);border-radius:999px;background:#fff;font-size:.85rem;font-weight:600;text-decoration:none}
.vprev{grid-column:1/-1;min-height:44px;margin-top:.15rem;border:1px dashed var(--b);background:none;border-radius:6px;font:inherit;font-size:.85rem;color:var(--fg);cursor:pointer}
/* grade page filter + topic jump links */
.filter{margin:1rem 0;max-width:420px}.filter[hidden],[data-group][hidden],li[hidden]{display:none}
.toc{display:flex;flex-wrap:wrap;gap:.35rem;margin:.75rem 0}.toc a{font-size:.85rem;padding:.3rem .6rem;border:1px solid var(--b);border-radius:99px;text-decoration:none;min-height:32px;display:inline-flex;align-items:center}
h3{margin:1.25rem 0 .4rem;font-size:1.05rem;color:var(--muted)}
.prevnext{display:grid;grid-template-columns:1fr 1fr;gap:.75rem;margin:1.5rem 0}.prevnext a{display:block;padding:.75rem;border:1px solid var(--b);border-radius:10px;text-decoration:none;background:var(--alt)}.prevnext a[rel=next],.prevnext a:last-child{text-align:right}.prevnext .meta{display:block}
@media(max-width:480px){.prevnext{grid-template-columns:1fr}.prevnext a:last-child{text-align:left}}
@media print{.vgrid,.prevnext,.filter,.toc{display:none!important}}
.toc[hidden]{display:none}

/* "Make a new one" randomizer panel (math pages, shown only when JS runs) */
.rand{margin:1.5rem 0;padding:1rem;border:2px dashed var(--accent);border-radius:12px;background:#f3faf7}.rand h2{margin-top:0}.rand[hidden]{display:none}
.rand .btn[disabled]{opacity:.7;cursor:progress}.rand-title{font-weight:700;margin:.75rem 0 0}.rand input{font-size:.85rem;margin-top:.35rem}.rand-note{color:var(--fg)}
@media print{.rand{display:none!important}}
.rand button.btn{font:inherit;font-weight:700;border:0;cursor:pointer;min-height:44px}

/* tap targets: small inline nav-type links get at least 24px of height (WCAG 2.5.8) */
.crumbs a,footer a,.see-all a,.home-browse a,.ws-info .small a{display:inline-block;min-height:24px;line-height:24px}
.search-results,.new-list ul{list-style:none;padding-left:0;margin:.25rem 0 0}.search-results li,.new-list li{padding:.3rem 0;border-bottom:1px solid var(--b);margin:0}.search-results a,.new-list a{display:block;min-height:24px}.search-results .meta,.new-list .meta{display:block}.site-search{max-width:520px}
[data-site-search][hidden]{display:none}