/* ============================================================
   SUTRA — design tokens
   ============================================================ */
:root{
  --font-display:'Newsreader',serif;
  --font-body:'IBM Plex Sans',sans-serif;
  --font-mono:'IBM Plex Mono',monospace;

  --gold:#E8B34E;   /* Mathematics */
  --teal:#5FC3B8;   /* Physics */
  --coral:#E2796D;  /* Chemistry */
  --sage:#8FBF74;   /* Biology */

  --radius-s:6px;
  --radius-m:12px;
  --radius-l:20px;
  --shadow-card:0 1px 2px rgba(0,0,0,.24), 0 8px 24px -12px rgba(0,0,0,.4);
  --dur:180ms;
}

html[data-theme="dark"]{
  --paper:#121C19;
  --paper-alt:#182420;
  --paper-raised:#1D2B26;
  --ink:#EDEAE0;
  --ink-soft:#A9B6B0;
  --ink-faint:#6F7C77;
  --rule:#2A3A35;
  --rule-strong:#3C4E48;
  --gold-ink:#F0C267; --teal-ink:#79D2C8; --coral-ink:#EC9187; --sage-ink:#A2D183;
  --overlay:rgba(8,14,12,.72);
  --focus:#F0C267;
}
html[data-theme="light"]{
  --paper:#EEF1EF;
  --paper-alt:#FFFFFF;
  --paper-raised:#FBFCFB;
  --ink:#152420;
  --ink-soft:#48564F;
  --ink-faint:#829088;
  --rule:#D3DAD6;
  --rule-strong:#BEC8C3;
  --gold-ink:#8A5D19; --teal-ink:#1B756B; --coral-ink:#A73F32; --sage-ink:#3F6B2C;
  --overlay:rgba(20,28,25,.45);
  --focus:#8A5D19;
}

*,*::before,*::after{box-sizing:border-box;}
html{scroll-behavior:smooth;}
body{
  margin:0;
  background:var(--paper);
  color:var(--ink);
  font-family:var(--font-body);
  font-size:16px;
  line-height:1.5;
  transition:background var(--dur),color var(--dur);
}
img,svg{display:block;max-width:100%;}
a{color:inherit;}
button{font-family:inherit;}
::selection{background:var(--gold);color:#16231F;}

.visually-hidden{position:absolute;width:1px;height:1px;overflow:hidden;clip:rect(0 0 0 0);white-space:nowrap;}

:focus-visible{outline:2px solid var(--focus);outline-offset:2px;border-radius:4px;}

/* background texture: faint graph grid, subject-appropriate (ledger/graph paper) */
.grid-bg{
  position:fixed;inset:0;z-index:-1;pointer-events:none;
  background-image:
    linear-gradient(var(--rule) 1px, transparent 1px),
    linear-gradient(90deg, var(--rule) 1px, transparent 1px);
  background-size:44px 44px;
  opacity:.35;
  mask-image:radial-gradient(ellipse 80% 60% at 50% 0%, black 40%, transparent 85%);
}

.wrap{max-width:1280px;margin:0 auto;padding:0 28px;}

/* ============================================================
   HEADER
   ============================================================ */
header.site{
  position:sticky;top:0;z-index:40;
  background:color-mix(in srgb, var(--paper) 88%, transparent);
  backdrop-filter:blur(10px);
  border-bottom:1px solid var(--rule);
}
.site-bar{
  display:flex;align-items:center;gap:20px;
  padding:14px 28px;max-width:1280px;margin:0 auto;
}
.brand{
  display:flex;align-items:baseline;gap:10px;text-decoration:none;margin-right:auto;
}
.brand .mark{
  font-family:var(--font-display);font-style:italic;font-weight:600;
  font-size:1.5rem;letter-spacing:.01em;color:var(--ink);
}
.brand .devanagari{font-family:var(--font-display);font-size:1.5rem;color:var(--gold-ink);}
.brand small{
  font-family:var(--font-mono);font-size:.62rem;letter-spacing:.14em;text-transform:uppercase;color:var(--ink-faint);
}
nav.site-nav{display:flex;gap:4px;}
nav.site-nav a{
  font-size:.88rem;font-weight:500;text-decoration:none;color:var(--ink-soft);
  padding:8px 12px;border-radius:var(--radius-s);transition:color var(--dur),background var(--dur);
}
nav.site-nav a:hover{color:var(--ink);background:var(--paper-alt);}

.icon-btn{
  display:inline-flex;align-items:center;justify-content:center;
  width:38px;height:38px;border-radius:var(--radius-s);
  background:transparent;border:1px solid transparent;color:var(--ink-soft);
  cursor:pointer;transition:background var(--dur),color var(--dur),border-color var(--dur);
  position:relative;
}
.icon-btn:hover{background:var(--paper-alt);color:var(--ink);border-color:var(--rule);}
.icon-btn svg{width:18px;height:18px;stroke:currentColor;fill:none;stroke-width:1.7;stroke-linecap:round;stroke-linejoin:round;}
.icon-btn .badge{
  position:absolute;top:-4px;right:-4px;min-width:16px;height:16px;padding:0 3px;
  border-radius:8px;background:var(--gold);color:#16231F;font-family:var(--font-mono);
  font-size:.62rem;font-weight:600;display:flex;align-items:center;justify-content:center;
}

.search-trigger{
  display:flex;align-items:center;gap:10px;
  border:1px solid var(--rule);background:var(--paper-alt);
  border-radius:var(--radius-m);padding:9px 12px 9px 14px;
  color:var(--ink-faint);cursor:pointer;min-width:200px;
  transition:border-color var(--dur);
}
.search-trigger:hover{border-color:var(--rule-strong);}
.search-trigger svg{width:16px;height:16px;stroke:currentColor;fill:none;stroke-width:1.8;flex-shrink:0;}
.search-trigger span{font-size:.86rem;flex:1;text-align:left;}
.search-trigger kbd{
  font-family:var(--font-mono);font-size:.68rem;background:var(--paper);
  border:1px solid var(--rule);border-radius:4px;padding:2px 6px;color:var(--ink-faint);
}
.header-controls{display:flex;align-items:center;gap:6px;}

/* ============================================================
   HERO
   ============================================================ */
.hero{padding:68px 28px 40px;position:relative;}
.hero-inner{max-width:1280px;margin:0 auto;}
.hero-eyebrow{
  font-family:var(--font-mono);font-size:.72rem;letter-spacing:.16em;text-transform:uppercase;
  color:var(--gold-ink);margin:0 0 14px;
}
.hero h1{
  font-family:var(--font-display);font-weight:600;
  font-size:clamp(2.4rem,5.2vw,4.4rem);line-height:1.02;letter-spacing:-.01em;
  margin:0 0 18px;max-width:16ch;
}
.hero h1 em{font-style:italic;color:var(--gold-ink);font-weight:500;}
.hero p.lede{
  font-size:1.08rem;color:var(--ink-soft);max-width:52ch;margin:0 0 32px;line-height:1.6;
}

.hero-search{
  position:relative;max-width:640px;margin-bottom:22px;
}
.hero-search input{
  width:100%;font-family:var(--font-body);font-size:1.02rem;
  padding:17px 20px 17px 50px;border-radius:var(--radius-m);
  border:1.5px solid var(--rule-strong);background:var(--paper-alt);color:var(--ink);
  transition:border-color var(--dur), box-shadow var(--dur);
}
.hero-search input:focus{outline:none;border-color:var(--gold-ink);box-shadow:0 0 0 4px color-mix(in srgb, var(--gold) 22%, transparent);}
.hero-search svg{
  position:absolute;left:18px;top:50%;transform:translateY(-50%);
  width:19px;height:19px;stroke:var(--ink-faint);fill:none;stroke-width:1.8;
}
.hero-search .count{
  position:absolute;right:16px;top:50%;transform:translateY(-50%);
  font-family:var(--font-mono);font-size:.72rem;color:var(--ink-faint);
  background:var(--paper);border:1px solid var(--rule);padding:4px 9px;border-radius:20px;
}

.chip-row{display:flex;flex-wrap:wrap;gap:8px;margin-bottom:10px;}
.chip-row .row-label{
  font-family:var(--font-mono);font-size:.68rem;letter-spacing:.1em;text-transform:uppercase;
  color:var(--ink-faint);align-self:center;margin-right:4px;min-width:58px;
}
.chip{
  font-size:.84rem;font-weight:500;padding:7px 14px;border-radius:20px;
  border:1px solid var(--rule);background:var(--paper-alt);color:var(--ink-soft);
  cursor:pointer;transition:all var(--dur);white-space:nowrap;
}
.chip:hover{border-color:var(--rule-strong);color:var(--ink);}
.chip.active{background:var(--ink);color:var(--paper);border-color:var(--ink);}
.chip.active[data-subj="Mathematics"]{background:var(--gold);border-color:var(--gold);color:#20160a;}
.chip.active[data-subj="Physics"]{background:var(--teal);border-color:var(--teal);color:#0c211e;}
.chip.active[data-subj="Chemistry"]{background:var(--coral);border-color:var(--coral);color:#26100c;}
.chip.active[data-subj="Biology"]{background:var(--sage);border-color:var(--sage);color:#132009;}

/* ============================================================
   CATALOG LAYOUT
   ============================================================ */
.catalog-section{padding:20px 28px 90px;}
.catalog-inner{max-width:1280px;margin:0 auto;display:grid;grid-template-columns:230px 1fr;gap:32px;align-items:start;}
.sidebar{
  position:sticky;top:88px;background:var(--paper-alt);border:1px solid var(--rule);
  border-radius:var(--radius-m);padding:20px;display:flex;flex-direction:column;gap:18px;
}
.sidebar h3{font-size:.7rem;letter-spacing:.12em;text-transform:uppercase;color:var(--ink-faint);margin:0 0 8px;font-family:var(--font-mono);font-weight:600;}
.select-field select{
  width:100%;font-family:var(--font-body);font-size:.86rem;padding:9px 10px;border-radius:var(--radius-s);
  border:1px solid var(--rule);background:var(--paper);color:var(--ink);
}
.check-row{display:flex;align-items:center;gap:8px;font-size:.86rem;color:var(--ink-soft);cursor:pointer;}
.check-row input{accent-color:var(--gold-ink);width:15px;height:15px;}
.clear-btn{
  font-size:.8rem;font-weight:500;color:var(--coral-ink);background:none;border:none;
  text-align:left;padding:0;cursor:pointer;text-decoration:underline;text-underline-offset:3px;
}
.result-count{font-family:var(--font-mono);font-size:.78rem;color:var(--ink-faint);padding-top:6px;border-top:1px solid var(--rule);}
.sidebar-actions{display:flex;flex-direction:column;gap:8px;}
.btn-line{
  display:flex;align-items:center;gap:8px;font-size:.82rem;font-weight:500;color:var(--ink-soft);
  background:var(--paper);border:1px solid var(--rule);border-radius:var(--radius-s);padding:9px 10px;
  cursor:pointer;transition:all var(--dur);
}
.btn-line:hover{border-color:var(--rule-strong);color:var(--ink);}
.btn-line svg{width:15px;height:15px;stroke:currentColor;fill:none;stroke-width:1.8;flex-shrink:0;}

.grid{display:grid;grid-template-columns:repeat(auto-fill,minmax(340px,1fr));gap:20px;}

/* ============================================================
   FORMULA CARD (signature: library catalog tab + call number)
   ============================================================ */
.card{
  background:var(--paper-alt);border:1px solid var(--rule);border-radius:var(--radius-m);
  position:relative;overflow:hidden;box-shadow:var(--shadow-card);
  display:flex;flex-direction:column;scroll-margin-top:100px;
  transition:transform var(--dur), border-color var(--dur);
}
.card::before{
  content:"";position:absolute;left:0;top:0;bottom:0;width:5px;background:var(--tab,var(--gold));
}
.card.pulse{animation:pulseCard 1.1s ease;}
@keyframes pulseCard{0%{box-shadow:0 0 0 0 color-mix(in srgb, var(--tab,var(--gold)) 55%, transparent);}70%{box-shadow:0 0 0 14px transparent;}100%{box-shadow:var(--shadow-card);}}

.card-tab{
  display:flex;align-items:center;justify-content:space-between;gap:8px;
  padding:11px 16px 11px 20px;border-bottom:1px dashed var(--rule);
}
.call-number{
  font-family:var(--font-mono);font-size:.66rem;letter-spacing:.06em;color:var(--ink-faint);
  text-transform:uppercase;
}
.call-number b{color:var(--tab,var(--gold));}
.star-btn{background:none;border:none;cursor:pointer;color:var(--ink-faint);padding:2px;display:flex;}
.star-btn svg{width:17px;height:17px;stroke:currentColor;fill:none;stroke-width:1.7;}
.star-btn.active{color:var(--gold-ink);}
.star-btn.active svg{fill:var(--gold-ink);}

.card-body{padding:6px 20px 18px;flex:1;display:flex;flex-direction:column;gap:14px;}
.card-title{font-family:var(--font-display);font-size:1.22rem;font-weight:600;margin:6px 0 0;line-height:1.25;}
.card-topic{font-size:.76rem;color:var(--ink-faint);margin:-8px 0 0;}

.tex-display{padding:14px 4px;overflow-x:auto;}
.tex-display .katex{font-size:1.12em;}

.diagram{
  background:var(--paper);border:1px solid var(--rule);border-radius:var(--radius-s);
  padding:6px 8px;color:var(--tab,var(--ink-soft));
}
.diagram svg{width:100%;height:auto;display:block;}
.diagram .dlabel{
  font-family:var(--font-mono);font-size:11px;fill:currentColor;stroke:none;
}
.diagram .dlabel.small{font-size:9px;}

.tip-block{
  display:flex;gap:9px;background:var(--paper);border:1px solid var(--rule);border-radius:var(--radius-s);
  padding:10px 12px;font-size:.82rem;color:var(--ink-soft);line-height:1.45;
}
.tip-block svg{width:15px;height:15px;stroke:var(--tab,var(--gold-ink));fill:none;stroke-width:1.8;flex-shrink:0;margin-top:2px;}

.var-grid{border:1px solid var(--rule);border-radius:var(--radius-s);overflow:hidden;}
.var-row{display:grid;grid-template-columns:44px 1fr auto;gap:10px;align-items:center;padding:7px 12px;font-size:.8rem;}
.var-row + .var-row{border-top:1px solid var(--rule);}
.var-row .sym{font-family:var(--font-mono);font-weight:600;color:var(--tab,var(--gold-ink));}
.var-row .meaning{color:var(--ink-soft);}
.var-row .unit{font-family:var(--font-mono);font-size:.72rem;color:var(--ink-faint);white-space:nowrap;}

.accordion{border:1px solid var(--rule);border-radius:var(--radius-s);overflow:hidden;}
.accordion summary{
  list-style:none;cursor:pointer;padding:9px 12px;font-size:.8rem;font-weight:600;
  display:flex;align-items:center;justify-content:space-between;color:var(--ink-soft);
  background:var(--paper);
}
.accordion summary::-webkit-details-marker{display:none;}
.accordion summary .chevron{width:14px;height:14px;stroke:currentColor;fill:none;stroke-width:2;transition:transform var(--dur);}
.accordion[open] summary .chevron{transform:rotate(90deg);}
.accordion .steps{padding:10px 14px 12px;margin:0;font-size:.8rem;color:var(--ink-soft);line-height:1.7;}
.accordion .steps li{margin-bottom:4px;}

.card-actions{display:flex;gap:8px;margin-top:auto;padding-top:2px;}
.action-btn{
  flex:1;display:flex;align-items:center;justify-content:center;gap:7px;
  font-size:.78rem;font-weight:500;padding:9px;border-radius:var(--radius-s);
  border:1px solid var(--rule);background:var(--paper);color:var(--ink-soft);cursor:pointer;
  transition:all var(--dur);
}
.action-btn:hover{border-color:var(--tab,var(--gold-ink));color:var(--ink);}
.action-btn svg{width:14px;height:14px;stroke:currentColor;fill:none;stroke-width:1.8;}

.empty-state{
  grid-column:1/-1;text-align:center;padding:70px 20px;color:var(--ink-faint);
}
.empty-state svg{width:40px;height:40px;stroke:var(--ink-faint);fill:none;stroke-width:1.4;margin:0 auto 14px;}
.empty-state h3{font-family:var(--font-display);font-size:1.3rem;color:var(--ink-soft);margin:0 0 6px;}

/* ============================================================
   SEARCH MODAL
   ============================================================ */
.modal-overlay{
  position:fixed;inset:0;background:var(--overlay);z-index:100;
  display:none;align-items:flex-start;justify-content:center;padding:12vh 20px 20px;
  backdrop-filter:blur(3px);
}
.modal-overlay.open{display:flex;}
.search-modal{
  width:100%;max-width:620px;background:var(--paper-alt);border:1px solid var(--rule-strong);
  border-radius:var(--radius-l);box-shadow:0 30px 70px -20px rgba(0,0,0,.5);overflow:hidden;
}
.search-modal .field{display:flex;align-items:center;gap:12px;padding:16px 20px;border-bottom:1px solid var(--rule);}
.search-modal .field svg{width:19px;height:19px;stroke:var(--ink-faint);fill:none;stroke-width:1.8;flex-shrink:0;}
.search-modal input{flex:1;border:none;background:none;font-size:1.05rem;color:var(--ink);font-family:var(--font-body);}
.search-modal input:focus{outline:none;}
.search-modal .esc{font-family:var(--font-mono);font-size:.68rem;color:var(--ink-faint);border:1px solid var(--rule);padding:2px 7px;border-radius:4px;}
.results-list{max-height:56vh;overflow-y:auto;padding:8px;}
.result-item{
  display:flex;align-items:center;gap:12px;padding:11px 12px;border-radius:var(--radius-s);cursor:pointer;
}
.result-item.hover, .result-item:hover{background:var(--paper);}
.result-item .rt{width:4px;align-self:stretch;border-radius:2px;background:var(--tab,var(--gold));flex-shrink:0;}
.result-item .rc{flex:1;min-width:0;}
.result-item .rc .rtitle{font-size:.92rem;font-weight:500;}
.result-item .rc .rmeta{font-family:var(--font-mono);font-size:.68rem;color:var(--ink-faint);text-transform:uppercase;letter-spacing:.04em;}
.results-empty{padding:30px 20px;text-align:center;color:var(--ink-faint);font-size:.88rem;}

/* ============================================================
   FAVORITES DRAWER
   ============================================================ */
.drawer-overlay{position:fixed;inset:0;background:var(--overlay);z-index:90;display:none;}
.drawer-overlay.open{display:block;}
.drawer{
  position:fixed;top:0;right:0;bottom:0;width:min(400px,92vw);background:var(--paper-alt);
  border-left:1px solid var(--rule-strong);z-index:91;transform:translateX(100%);
  transition:transform 260ms ease;display:flex;flex-direction:column;
}
.drawer.open{transform:translateX(0);}
.drawer-head{display:flex;align-items:center;justify-content:space-between;padding:18px 20px;border-bottom:1px solid var(--rule);}
.drawer-head h3{font-family:var(--font-display);font-size:1.2rem;margin:0;}
.drawer-body{flex:1;overflow-y:auto;padding:14px 20px;display:flex;flex-direction:column;gap:10px;}
.drawer-foot{padding:14px 20px;border-top:1px solid var(--rule);display:flex;gap:8px;}
.fav-row{
  display:flex;align-items:center;gap:10px;padding:10px 12px;border:1px solid var(--rule);border-radius:var(--radius-s);
  background:var(--paper);
}
.fav-row .ft{width:4px;align-self:stretch;border-radius:2px;background:var(--tab,var(--gold));flex-shrink:0;}
.fav-row .fc{flex:1;min-width:0;}
.fav-row .fc .ftitle{font-size:.86rem;font-weight:500;}
.fav-row .fc .fmeta{font-family:var(--font-mono);font-size:.66rem;color:var(--ink-faint);}
.fav-row button{background:none;border:none;color:var(--ink-faint);cursor:pointer;padding:4px;}
.fav-row button svg{width:15px;height:15px;stroke:currentColor;fill:none;stroke-width:1.8;}
.drawer-empty{color:var(--ink-faint);font-size:.86rem;text-align:center;padding:40px 10px;}

/* ============================================================
   TOAST
   ============================================================ */
.toast{
  position:fixed;bottom:26px;left:50%;transform:translateX(-50%) translateY(20px);
  background:var(--ink);color:var(--paper);font-size:.86rem;font-weight:500;
  padding:12px 20px;border-radius:var(--radius-m);box-shadow:0 12px 30px rgba(0,0,0,.3);
  z-index:200;opacity:0;pointer-events:none;transition:all 220ms ease;display:flex;align-items:center;gap:8px;
}
.toast.show{opacity:1;transform:translateX(-50%) translateY(0);}
.toast svg{width:15px;height:15px;stroke:currentColor;fill:none;stroke-width:2;}

/* ============================================================
   INFO / LEGAL MODALS (About, Privacy, Terms)
   ============================================================ */
.info-overlay{
  position:fixed;inset:0;background:var(--overlay);z-index:120;display:none;
  align-items:center;justify-content:center;padding:6vh 20px;backdrop-filter:blur(3px);
}
.info-overlay.open{display:flex;}
.info-modal{
  width:100%;max-width:680px;max-height:88vh;background:var(--paper-alt);border:1px solid var(--rule-strong);
  border-radius:var(--radius-l);box-shadow:0 30px 70px -20px rgba(0,0,0,.5);
  display:flex;flex-direction:column;overflow:hidden;
}
.info-head{display:flex;align-items:center;justify-content:space-between;padding:20px 26px;border-bottom:1px solid var(--rule);}
.info-head h2{font-family:var(--font-display);font-size:1.5rem;margin:0;}
.info-body{padding:22px 26px 28px;overflow-y:auto;font-size:.92rem;color:var(--ink-soft);line-height:1.7;}
.info-body h3{font-family:var(--font-body);font-size:.95rem;color:var(--ink);margin:20px 0 6px;}
.info-body h3:first-child{margin-top:0;}
.info-body p{margin:0 0 10px;}
.info-body ul{margin:0 0 10px;padding-left:20px;}
.info-body .updated{font-family:var(--font-mono);font-size:.7rem;color:var(--ink-faint);text-transform:uppercase;letter-spacing:.06em;margin-bottom:18px;display:block;}

/* ============================================================
   FOOTER
   ============================================================ */
footer.site{border-top:1px solid var(--rule);background:var(--paper-alt);padding:64px 28px 30px;margin-top:40px;}
.footer-inner{max-width:1280px;margin:0 auto;}
.footer-top{display:grid;grid-template-columns:1.3fr 1fr;gap:60px;margin-bottom:52px;}
.footer-about h2{font-family:var(--font-display);font-size:1.9rem;font-weight:600;margin:0 0 14px;max-width:20ch;}
.footer-about p{color:var(--ink-soft);max-width:48ch;line-height:1.65;margin:0 0 20px;}
.footer-links{display:flex;gap:10px;flex-wrap:wrap;}
.footer-links a{
  display:inline-flex;align-items:center;gap:7px;font-size:.82rem;font-weight:500;
  border:1px solid var(--rule);padding:8px 14px;border-radius:20px;text-decoration:none;color:var(--ink-soft);
  transition:all var(--dur);
}
.footer-links a:hover{border-color:var(--rule-strong);color:var(--ink);}
.footer-links a svg{width:14px;height:14px;stroke:currentColor;fill:none;stroke-width:1.8;}

.projects h3, .footer-nav h3{
  font-family:var(--font-mono);font-size:.7rem;letter-spacing:.12em;text-transform:uppercase;
  color:var(--ink-faint);margin:0 0 16px;
}
.project-grid{display:grid;grid-template-columns:1fr 1fr;gap:10px;}
.project-card{
  border:1px solid var(--rule);border-radius:var(--radius-s);padding:12px 14px;background:var(--paper);
}
.project-card .pname{font-size:.86rem;font-weight:600;margin:0 0 3px;}
.project-card .pdesc{font-size:.74rem;color:var(--ink-faint);line-height:1.4;margin:0;}

.footer-bottom{
  display:flex;align-items:center;justify-content:space-between;flex-wrap:wrap;gap:14px;
  padding-top:26px;border-top:1px solid var(--rule);
}
.footer-nav-list{display:flex;gap:20px;flex-wrap:wrap;}
.footer-nav-list a, .footer-nav-list button{
  background:none;border:none;font-size:.82rem;color:var(--ink-soft);text-decoration:none;cursor:pointer;
  font-family:inherit;padding:0;
}
.footer-nav-list a:hover, .footer-nav-list button:hover{color:var(--ink);text-decoration:underline;text-underline-offset:3px;}
.copyright{font-size:.78rem;color:var(--ink-faint);font-family:var(--font-mono);}

/* ============================================================
   RESPONSIVE
   ============================================================ */
@media (max-width:980px){
  .catalog-inner{grid-template-columns:1fr;}
  .sidebar{position:static;}
  .footer-top{grid-template-columns:1fr;gap:40px;}
}
@media (max-width:640px){
  .site-bar{padding:12px 16px;gap:10px;}
  .search-trigger{min-width:0;flex:1;}
  .search-trigger span{display:none;}
  nav.site-nav{display:none;}
  .hero{padding:40px 16px 30px;}
  .catalog-section{padding:10px 16px 60px;}
  .grid{grid-template-columns:1fr;}
  footer.site{padding:44px 16px 24px;}
  .project-grid{grid-template-columns:1fr;}
}

/* ============================================================
   PRINT — cheat sheet mode
   ============================================================ */
@media print{
  body{background:#fff !important;color:#000 !important;}
  header.site,.hero,.sidebar,.modal-overlay,.drawer,.drawer-overlay,.toast,footer.site,.card-actions,.info-overlay,.grid-bg{display:none !important;}
  .catalog-inner{display:block !important;}
  .grid{display:block !important;}
  .card{
    border:1px solid #999 !important;box-shadow:none !important;break-inside:avoid;
    margin-bottom:10px;background:#fff !important;
  }
  .card::before{background:#000 !important;width:3px;}
  .card-title,.call-number,.var-row .sym,.var-row .meaning,.var-row .unit,.card-topic,.tip-block{color:#000 !important;}
  .accordion{display:none !important;}
  .tex-display{color:#000 !important;}
  .star-btn{display:none !important;}
}
/* ============================================================
   SIMPLE PAGE (feedback.html) — shares header/footer, adds its own content well
   ============================================================ */
.page-hero{padding:56px 28px 20px;max-width:760px;margin:0 auto;}
.page-hero .hero-eyebrow{margin-bottom:12px;}
.page-hero h1{font-family:var(--font-display);font-weight:600;font-size:clamp(2rem,4.5vw,3rem);margin:0 0 14px;}
.page-hero p.lede{color:var(--ink-soft);max-width:56ch;line-height:1.6;margin:0;}

.page-section{padding:20px 28px 100px;max-width:760px;margin:0 auto;}
.feedback-form{
  background:var(--paper-alt);border:1px solid var(--rule);border-radius:var(--radius-l);
  padding:32px;display:flex;flex-direction:column;gap:20px;
}
.form-row{display:flex;flex-direction:column;gap:7px;}
.form-row label{font-size:.84rem;font-weight:600;color:var(--ink);}
.form-row .hint{font-size:.76rem;color:var(--ink-faint);font-weight:400;}
.form-row input, .form-row select, .form-row textarea{
  font-family:var(--font-body);font-size:.95rem;padding:11px 14px;border-radius:var(--radius-s);
  border:1px solid var(--rule);background:var(--paper);color:var(--ink);resize:vertical;
}
.form-row input:focus, .form-row select:focus, .form-row textarea:focus{
  outline:none;border-color:var(--gold-ink);box-shadow:0 0 0 4px color-mix(in srgb, var(--gold) 18%, transparent);
}
.chip-select{display:flex;gap:8px;flex-wrap:wrap;}
.chip-select .chip{margin:0;}
.form-submit{
  align-self:flex-start;display:inline-flex;align-items:center;gap:10px;
  background:var(--gold);color:#20160a;border:none;font-weight:600;font-size:.92rem;
  padding:13px 24px;border-radius:var(--radius-m);cursor:pointer;transition:transform var(--dur), opacity var(--dur);
}
.form-submit:hover{transform:translateY(-1px);}
.form-submit svg{width:16px;height:16px;stroke:currentColor;fill:none;stroke-width:2;}
.form-note{font-size:.78rem;color:var(--ink-faint);line-height:1.6;}
.form-success{
  display:none;align-items:center;gap:10px;background:color-mix(in srgb, var(--sage) 16%, var(--paper));
  border:1px solid var(--sage);color:var(--sage-ink);padding:12px 16px;border-radius:var(--radius-s);font-size:.86rem;font-weight:500;
}
.form-success.show{display:flex;}
.form-success svg{width:16px;height:16px;stroke:currentColor;fill:none;stroke-width:2;flex-shrink:0;}
.back-link{
  display:inline-flex;align-items:center;gap:6px;font-size:.86rem;color:var(--ink-soft);text-decoration:none;
  margin-bottom:22px;
}
.back-link:hover{color:var(--ink);}
.back-link svg{width:15px;height:15px;stroke:currentColor;fill:none;stroke-width:2;}