/* Layout: graph-paper hero with title + search, sticky category jump bar, then category sections of cards.
   Edit mode adds a sticky teacher bar, per-section and per-card tool rows, and a dialog editor. */
@font-face{font-family:"Barlow";font-weight:400;font-display:swap;src:url(fonts/barlow-latin-400-normal.woff2) format("woff2")}
@font-face{font-family:"Barlow";font-weight:500;font-display:swap;src:url(fonts/barlow-latin-500-normal.woff2) format("woff2")}
@font-face{font-family:"Barlow";font-weight:600;font-display:swap;src:url(fonts/barlow-latin-600-normal.woff2) format("woff2")}
@font-face{font-family:"Barlow Condensed";font-weight:600;font-display:swap;src:url(fonts/barlow-condensed-latin-600-normal.woff2) format("woff2")}
@font-face{font-family:"Barlow Condensed";font-weight:700;font-display:swap;src:url(fonts/barlow-condensed-latin-700-normal.woff2) format("woff2")}

:root{
  --bg:#f3f5f7; --surface:#ffffff; --surface-2:#eef1f4; --line:#d6dce3; --ink:#17202a; --muted:#5a6876;
  --grid:#dbe3ec; --hero:#e8eef5;
  --accent:#1f5fbf; --accent-ink:#ffffff; --focus:#1f5fbf;
  --edit:#7a4fd6; --edit-soft:#efe9fb; --danger:#b3261e; --danger-soft:#fbe9e7;
  --blue:#1f5fbf; --blue-soft:#e1ebf9;
  --orange:#c25a0a; --orange-soft:#fbeadc;
  --green:#1d7f45; --green-soft:#ddf1e5;
  --purple:#6b45c4; --purple-soft:#ece6fa;
  --red:#b8323a; --red-soft:#f9e3e4;
  --teal:#0f7c80; --teal-soft:#d9f0f0;
  --f-display:"Barlow Condensed","Arial Narrow",system-ui,sans-serif;
  --f-body:"Barlow",system-ui,-apple-system,"Segoe UI","PingFang SC","Microsoft YaHei",sans-serif;
  --r:12px;
  color-scheme:light;
}
@media (prefers-color-scheme: dark){:root{
  --bg:#11161c; --surface:#19212a; --surface-2:#202934; --line:#2e3946; --ink:#e8edf2; --muted:#9aa8b6;
  --grid:#1f2833; --hero:#151c24;
  --accent:#6fa6f2; --accent-ink:#0b1320; --focus:#6fa6f2;
  --edit:#a98cf2; --edit-soft:#2a2340; --danger:#f08a80; --danger-soft:#3a1d1b;
  --blue:#6fa6f2; --blue-soft:#1b2c44;
  --orange:#f0a35e; --orange-soft:#3a2614;
  --green:#5cc98a; --green-soft:#16301f;
  --purple:#ad92f2; --purple-soft:#2a2340;
  --red:#ef8a90; --red-soft:#3a1d20;
  --teal:#5cc7c9; --teal-soft:#123032;
  color-scheme:dark}}

*{box-sizing:border-box}
html,body{margin:0}
body{background:var(--bg);color:var(--ink);font-family:var(--f-body);font-size:16px;line-height:1.5;-webkit-text-size-adjust:100%}
.wrap{max-width:1120px;margin:0 auto;padding-left:max(16px,env(safe-area-inset-left,0px));padding-right:max(16px,env(safe-area-inset-right,0px))}
button,input,select,textarea{font:inherit;color:inherit}
button{cursor:pointer}
:focus-visible{outline:2px solid var(--focus);outline-offset:2px}
.sr{position:absolute;width:1px;height:1px;overflow:hidden;clip:rect(0 0 0 0)}
[hidden]{display:none!important}

/* hero on engineering graph paper */
.hero{background-color:var(--hero);
  background-image:linear-gradient(var(--grid) 1px,transparent 1px),linear-gradient(90deg,var(--grid) 1px,transparent 1px);
  background-size:24px 24px;border-bottom:1px solid var(--line)}
.hero-in{padding-block:44px 28px;display:flex;flex-direction:column;gap:10px}
h1{font-family:var(--f-display);font-weight:700;font-size:clamp(34px,6vw,56px);line-height:.95;letter-spacing:.005em;margin:0;text-wrap:balance}
.intro{margin:0;color:var(--muted);font-size:17px;max-width:62ch}
.search{margin-top:10px;max-width:520px}
.search input{width:100%;border:1px solid var(--line);background:var(--surface);border-radius:999px;padding:11px 18px;font-size:16px}

/* category jump bar */
.jump{position:sticky;top:env(safe-area-inset-top,0px);z-index:20;background:var(--bg);border-bottom:1px solid var(--line)}
.jump-in{display:flex;gap:8px;overflow-x:auto;padding-block:10px;scrollbar-width:none}
.jump-in::-webkit-scrollbar{display:none}
.chip{flex:none;display:inline-flex;align-items:center;gap:8px;border:1px solid var(--line);background:var(--surface);border-radius:999px;padding:6px 14px;font-weight:600;font-size:14.5px;text-decoration:none;color:var(--ink);white-space:nowrap}
.chip i{width:9px;height:9px;border-radius:3px;background:var(--c)}
.chip:hover{border-color:var(--c)}

/* sections */
main{padding-block:12px 24px}
.cat{padding-block:26px 6px;scroll-margin-top:64px}
body.editing .cat{scroll-margin-top:calc(64px + var(--abh,50px))}
.cat-head{display:flex;align-items:flex-end;justify-content:space-between;gap:12px;flex-wrap:wrap;margin-bottom:14px}
.cat-title{display:flex;flex-direction:column;gap:2px;min-width:0}
.cat h2{font-family:var(--f-display);font-weight:700;font-size:30px;line-height:1;margin:0;letter-spacing:.01em;display:flex;align-items:center;gap:10px}
.cat h2::before{content:"";width:14px;height:14px;border-radius:4px;background:var(--c);flex:none}
.cat-blurb{margin:0;color:var(--muted);font-size:15px;padding-left:24px}
.grid{display:grid;grid-template-columns:repeat(auto-fill,minmax(270px,1fr));gap:14px}

/* cards */
.card{position:relative;display:flex;flex-direction:column;background:var(--surface);border:1px solid var(--line);border-radius:var(--r);overflow:hidden;min-width:0}
.card.linky:hover{border-color:var(--c);box-shadow:0 0 0 3px var(--cs)}
.card .img{aspect-ratio:16/9;background:var(--surface-2);border-bottom:1px solid var(--line);overflow:hidden}
.card .img img{width:100%;height:100%;object-fit:cover;display:block}
.card .body{padding:16px 18px 18px;display:flex;flex-direction:column;gap:8px;flex:1;min-width:0}
.tag{align-self:flex-start;font-size:12px;font-weight:600;letter-spacing:.04em;color:var(--c);background:var(--cs);border-radius:999px;padding:2px 10px}
.card h3{margin:0;font-family:var(--f-display);font-weight:600;font-size:23px;line-height:1.1;letter-spacing:.01em;overflow-wrap:anywhere}
.card p{margin:0;color:var(--muted);font-size:15px;overflow-wrap:anywhere}
.card .text{color:var(--ink);font-size:15.5px;display:flex;flex-direction:column;gap:8px}
.card .text p{color:inherit}
.card .text a{color:var(--c);overflow-wrap:anywhere}
.card.note{border-left:4px solid var(--c)}
.act{margin-top:auto;padding-top:6px;display:flex;align-items:center;gap:10px;flex-wrap:wrap}
.go{display:inline-flex;align-items:center;gap:6px;font-weight:600;font-size:15px;color:var(--accent-ink);background:var(--c);border-radius:8px;padding:8px 14px;text-decoration:none}
.go:hover{filter:brightness(1.08)}
.fmeta{font-size:13px;color:var(--muted);font-variant-numeric:tabular-nums}
.stretch::after{content:"";position:absolute;inset:0}
.empty{color:var(--muted);padding:40px 0;text-align:center}
.foot-in{display:flex;justify-content:space-between;align-items:center;gap:12px;padding-block:24px calc(36px + env(safe-area-inset-bottom,0px));color:var(--muted);font-size:13.5px}
.foot-in>div{border-top:1px solid var(--line)}
footer{margin-top:12px}
.foot-line{border-top:1px solid var(--line);display:flex;justify-content:space-between;align-items:center;gap:12px;width:100%;padding-top:20px}
.linkbtn{border:0;background:none;padding:0;color:var(--muted);font-size:13.5px;text-decoration:underline;text-underline-offset:3px}

/* category colour hooks */
.c-blue{--c:var(--blue);--cs:var(--blue-soft)}
.c-orange{--c:var(--orange);--cs:var(--orange-soft)}
.c-green{--c:var(--green);--cs:var(--green-soft)}
.c-purple{--c:var(--purple);--cs:var(--purple-soft)}
.c-red{--c:var(--red);--cs:var(--red-soft)}
.c-teal{--c:var(--teal);--cs:var(--teal-soft)}

/* ---------- edit mode ---------- */
#adminbar{position:sticky;top:env(safe-area-inset-top,0px);z-index:30;background:var(--edit);color:#fff}
.ab-in{display:flex;align-items:center;gap:8px 14px;flex-wrap:wrap;padding-block:8px}
.ab-in b{font-weight:600}
.ab-in .sp{flex:1}
.ab-btn{border:1px solid rgba(255,255,255,.55);background:transparent;color:#fff;border-radius:8px;padding:5px 11px;font-weight:600;font-size:14px}
.ab-btn.solid{background:#fff;color:#3b2470;border-color:#fff}
body.editing .jump{top:calc(env(safe-area-inset-top,0px) + var(--abh,50px))}
.tools{display:flex;gap:4px;flex-wrap:wrap;align-items:center}
.tb{border:1px solid var(--line);background:var(--surface);border-radius:7px;padding:3px 9px;font-size:13px;font-weight:600;color:var(--ink);line-height:1.6}
.tb:hover{border-color:var(--edit);color:var(--edit)}
.tb.danger{color:var(--danger)}
.tb.danger:hover{border-color:var(--danger)}
.tb[disabled]{opacity:.35;cursor:default}
.card .tools{position:relative;z-index:2;padding:8px 10px;border-top:1px dashed var(--line);background:var(--surface-2)}
.hiddenbadge{align-self:flex-start;font-size:12px;font-weight:600;color:var(--edit);background:var(--edit-soft);border-radius:999px;padding:2px 9px}
.is-hidden{opacity:.62}
.is-hidden:hover{opacity:1}
.card.add{border:2px dashed var(--line);background:transparent;align-items:center;justify-content:center;min-height:150px;color:var(--muted);font-weight:600;gap:6px}
.card.add:hover{border-color:var(--edit);color:var(--edit)}
.card.add span{font-size:30px;line-height:1}
.confirmrow{display:flex;gap:6px;align-items:center;flex-wrap:wrap;font-size:13.5px;font-weight:600;color:var(--danger)}

/* dialog */
dialog{border:1px solid var(--line);border-radius:14px;padding:0;background:var(--surface);color:var(--ink);width:min(560px,calc(100vw - 32px));max-height:calc(100dvh - 40px)}
dialog::backdrop{background:rgba(10,15,22,.5)}
dialog form{display:flex;flex-direction:column;max-height:calc(100dvh - 42px)}
.dl-head{padding:18px 20px 6px}
.dl-head h2{font-family:var(--f-display);font-size:26px;margin:0}
.dl-body{padding:8px 20px 4px;display:flex;flex-direction:column;gap:14px;overflow:auto}
.dl-foot{padding:14px 20px 18px;display:flex;gap:8px;justify-content:flex-end;align-items:center;border-top:1px solid var(--line);margin-top:10px}
.dl-foot .err{margin-right:auto;color:var(--danger);font-size:14px}
.fld{display:flex;flex-direction:column;gap:5px}
.fld>span{font-size:13.5px;font-weight:600}
.fld small{color:var(--muted);font-size:12.5px}
.fld input[type=text],.fld input[type=url],.fld input[type=password],.fld select,.fld textarea{border:1px solid var(--line);background:var(--bg);border-radius:8px;padding:9px 11px;width:100%}
.fld textarea{min-height:110px;resize:vertical}
.row2{display:grid;grid-template-columns:1fr 1fr;gap:12px}
.seg{display:flex;border:1px solid var(--line);border-radius:9px;overflow:hidden}
.seg label{flex:1;text-align:center;padding:8px 6px;font-weight:600;font-size:14px;cursor:pointer;border-left:1px solid var(--line)}
.seg label:first-child{border-left:0}
.seg input{position:absolute;opacity:0;pointer-events:none}
.seg label:has(input:checked){background:var(--ink);color:var(--bg)}
.seg label:has(input:focus-visible){outline:2px solid var(--focus);outline-offset:-2px}
.swatches{display:flex;gap:8px;flex-wrap:wrap}
.swatches label{width:34px;height:34px;border-radius:9px;background:var(--c);cursor:pointer;border:3px solid transparent;position:relative}
.swatches label:has(input:checked){border-color:var(--ink)}
.swatches input{position:absolute;opacity:0}
.upl{display:flex;gap:10px;align-items:center;flex-wrap:wrap}
.upl .thumb{width:96px;aspect-ratio:16/9;border-radius:6px;object-fit:cover;border:1px solid var(--line);background:var(--surface-2)}
.upl .fname{font-size:14px;overflow-wrap:anywhere}
.btn{border:1px solid var(--line);background:var(--surface-2);border-radius:8px;padding:8px 14px;font-weight:600;font-size:14.5px}
.btn.primary{background:var(--accent);border-color:var(--accent);color:var(--accent-ink)}
.btn.editc{background:var(--edit);border-color:var(--edit);color:#fff}
.toast{position:fixed;left:50%;bottom:calc(20px + env(safe-area-inset-bottom,0px));transform:translateX(-50%);background:var(--ink);color:var(--bg);padding:9px 16px;border-radius:9px;font-size:14.5px;font-weight:600;z-index:50}

@media (max-width:560px){
  .hero-in{padding-block:30px 22px}
  .grid{grid-template-columns:1fr}
  .row2{grid-template-columns:1fr}
}
@media (prefers-reduced-motion:no-preference){.card{transition:border-color .15s,box-shadow .15s}}