:root{
  --ink:#1b2333; --muted:#5b6578; --line:#dfe3ea; --bg:#f5f6f9; --card:#fff;
  --brand:#1f3c88; --brand-2:#e39b2d; --brand-soft:#eaf0fb; --danger:#c0392b; --ok:#1e8e4e; --warn:#b7791f;
  --radius:10px; --shadow:0 1px 2px rgba(20,30,60,.06),0 4px 14px rgba(20,30,60,.06);
}
*{box-sizing:border-box}
html,body{margin:0;height:100%}
body{font-family:"Segoe UI",system-ui,-apple-system,Roboto,sans-serif;color:var(--ink);background:var(--bg);font-size:14px}
button,input,select,textarea{font:inherit;color:inherit}
a{color:var(--brand)}
.app{display:grid;grid-template-columns:220px 1fr;height:100vh}
nav.side{background:#13234f;color:#dfe6f7;display:flex;flex-direction:column;padding:16px 10px;gap:2px}
nav.side .logo{padding:6px 10px 18px;border-bottom:1px solid rgba(255,255,255,.12);margin-bottom:10px}
nav.side .logo b{display:block;font-family:"Times New Roman",serif;font-size:21px;letter-spacing:.5px;color:#fff}
nav.side .logo span{font-family:"Times New Roman",serif;font-style:italic;color:var(--brand-2);font-size:14px}
nav.side button{all:unset;cursor:pointer;padding:9px 12px;border-radius:8px;display:flex;gap:10px;align-items:center}
nav.side button:hover{background:rgba(255,255,255,.08)}
nav.side button.active{background:#fff;color:#13234f;font-weight:600}
nav.side .foot{margin-top:auto;font-size:12px;opacity:.7;padding:10px}
main{overflow:auto;padding:22px 28px 60px}
h1{font-size:22px;margin:0 0 4px}
h2{font-size:17px;margin:18px 0 8px}
.sub{color:var(--muted);margin:0 0 16px}
.row{display:flex;gap:10px;align-items:center;flex-wrap:wrap}
.grow{flex:1}
.btn{border:1px solid var(--line);background:#fff;border-radius:8px;padding:7px 13px;cursor:pointer;white-space:nowrap}
.btn:hover{border-color:#b9c2d3}
.btn.primary{background:var(--brand);border-color:var(--brand);color:#fff}
.btn.primary:hover{filter:brightness(1.1)}
.btn.accent{background:var(--brand-2);border-color:var(--brand-2);color:#fff}
.btn.danger{color:var(--danger);border-color:#f0c7c2}
.btn.danger.solid{background:var(--danger);color:#fff;border-color:var(--danger)}
.btn.sm{padding:4px 9px;font-size:12.5px}
.btn:disabled{opacity:.5;cursor:default}
.card{background:var(--card);border:1px solid var(--line);border-radius:var(--radius);box-shadow:var(--shadow);padding:16px}
input[type=text],input[type=number],input[type=password],input[type=date],select,textarea{
  border:1px solid var(--line);border-radius:7px;padding:7px 9px;background:#fff;width:100%}
textarea{resize:vertical;min-height:60px}
input:focus,select:focus,textarea:focus{outline:2px solid #b7c8f0;border-color:#8ea6dd}
label.f{display:flex;flex-direction:column;gap:4px;font-size:12.5px;color:var(--muted);font-weight:600}
label.f > *{font-weight:400;color:var(--ink);font-size:14px}
.grid2{display:grid;grid-template-columns:1fr 1fr;gap:12px}
.grid3{display:grid;grid-template-columns:repeat(3,1fr);gap:12px}
.grid4{display:grid;grid-template-columns:repeat(4,1fr);gap:12px}
.chk{display:flex;gap:6px;align-items:center;font-size:13.5px;cursor:pointer}
.pill{display:inline-block;padding:2px 8px;border-radius:20px;font-size:11.5px;background:#eef1f6;color:#3d4a63;margin-right:4px}
.pill.Easy{background:#e3f5ea;color:#1e7a43}.pill.Medium{background:#fdf2dc;color:#8a5a06}.pill.Hard{background:#fbe4e1;color:#a2291b}
.pill.pyq{background:var(--brand-soft);color:var(--brand);font-weight:600}
.pill.type{background:#efe9fb;color:#5b3aa6}
.muted{color:var(--muted)}
.small{font-size:12.5px}
/* bank layout */
.bank{display:grid;grid-template-columns:250px 1fr;gap:18px;align-items:start}
.filters{position:sticky;top:0;display:flex;flex-direction:column;gap:10px;max-height:calc(100vh - 44px);overflow-y:auto;overscroll-behavior:contain;padding-right:4px}
.filters > *{flex-shrink:0}  /* lists keep their height; the panel scrolls instead of squashing them */
.filters .ms{min-height:64px;max-height:150px;overflow:auto;border:1px solid var(--line);border-radius:7px;padding:6px;background:#fff}
.filters .ms label{display:flex;gap:6px;font-size:12.5px;padding:2px 0;cursor:pointer}
.qcard{background:#fff;border:1px solid var(--line);border-radius:var(--radius);padding:12px 14px;margin-bottom:10px;display:grid;grid-template-columns:24px 1fr;gap:8px}
.qcard.sel{border-color:var(--brand);box-shadow:0 0 0 2px #c8d6f5}
.qcard .meta{display:flex;flex-wrap:wrap;gap:4px;align-items:center;margin-bottom:6px}
.qcard .acts{display:flex;gap:6px;margin-top:8px;flex-wrap:wrap}
.qbody{font-family:"Times New Roman",Times,serif;font-size:16.5px;line-height:1.45}
.qbody .lab{font-weight:700}
.qbody .opts{display:grid;grid-template-columns:1fr 1fr;gap:2px 18px;margin-top:4px}
.qbody .opts div{padding:1px 0}
.qbody .opts .correct{color:var(--ok);font-weight:600}
.qbody table.match{border-collapse:collapse;margin:6px 0}
.qbody table.match td,.qbody table.match th{border:1px solid #c6ccd8;padding:3px 8px;text-align:left}
.qbody table.match.wide th{text-align:center;background:#f2f4f8}
.qbody table.match.wide td:nth-child(odd){white-space:nowrap;color:#333}
.qbody img.fig{max-width:340px;max-height:240px;display:block;margin:6px 0;border:1px solid #eee}
.qbody .ans{margin-top:6px;font-family:"Segoe UI",system-ui,sans-serif;font-size:13px;color:var(--ok)}
.qbody .sol{margin-top:4px;font-size:15px;color:#333;background:#f7f8fb;border-left:3px solid var(--brand-2);padding:4px 8px}
.toolbar{position:sticky;top:-22px;z-index:5;background:var(--bg);padding:10px 0;display:flex;gap:8px;align-items:center;flex-wrap:wrap}
.pager{display:flex;gap:6px;align-items:center;justify-content:center;margin:14px 0}
/* modal */
.modal-bg{position:fixed;inset:0;background:rgba(15,22,40,.45);display:flex;align-items:flex-start;justify-content:center;z-index:50;padding:30px 16px;overflow:auto}
.modal{background:#fff;border-radius:12px;width:min(1100px,100%);box-shadow:0 20px 60px rgba(0,0,0,.25)}
.modal.narrow{width:min(620px,100%)}
.modal header{display:flex;align-items:center;padding:14px 18px;border-bottom:1px solid var(--line)}
.modal header h3{margin:0;font-size:17px;flex:1}
.modal .body{padding:16px 18px}
.modal footer{padding:12px 18px;border-top:1px solid var(--line);display:flex;gap:8px;justify-content:flex-end;flex-wrap:wrap}
.x{all:unset;cursor:pointer;font-size:22px;line-height:1;padding:0 6px;color:var(--muted)}
.editor{display:grid;grid-template-columns:1.15fr .85fr;gap:18px}
.preview{border:1px dashed #c9d1e0;border-radius:10px;padding:12px;background:#fcfcfe;position:sticky;top:0}
.snips{display:flex;flex-wrap:wrap;gap:4px;margin:4px 0 8px}
.snips button{border:1px solid var(--line);background:#f8f9fc;border-radius:6px;padding:2px 7px;font-size:12px;cursor:pointer}
.opt-row{display:grid;grid-template-columns:34px 1fr 34px 30px;gap:6px;align-items:center;margin-bottom:5px}
.toast{position:fixed;bottom:18px;right:18px;background:#13234f;color:#fff;padding:10px 16px;border-radius:9px;z-index:99;box-shadow:var(--shadow);max-width:420px}
.toast.err{background:var(--danger)}
.notice{background:#fff8e6;border:1px solid #f1d58a;padding:10px 12px;border-radius:8px;margin:8px 0}
.notice.blue{background:var(--brand-soft);border-color:#c4d3f3}
.dz{border:2px dashed #b8c3da;border-radius:12px;padding:26px;text-align:center;background:#fff;cursor:pointer}
.dz.over{background:var(--brand-soft);border-color:var(--brand)}
.progress{height:6px;background:#e3e7ef;border-radius:4px;overflow:hidden}
.progress div{height:100%;background:var(--brand);width:40%;animation:slide 1.4s infinite ease-in-out}
@keyframes slide{0%{margin-left:-40%}100%{margin-left:100%}}
.state-approved{opacity:.6;border-left:4px solid var(--ok)}
.state-rejected{opacity:.45;border-left:4px solid var(--danger)}
.paper-sec{margin-bottom:18px}
.paper-sec > header{display:flex;gap:8px;align-items:center;background:var(--brand-soft);padding:8px 12px;border-radius:8px;margin-bottom:8px}
.pq{display:grid;grid-template-columns:44px 1fr auto;gap:10px;background:#fff;border:1px solid var(--line);border-radius:9px;padding:10px;margin-bottom:8px}
.pq .num{font-weight:700;color:var(--brand);font-family:"Times New Roman",serif;font-size:17px}
.pq .tools{display:flex;flex-direction:column;gap:4px}
.split{display:grid;grid-template-columns:1fr 330px;gap:18px;align-items:start}
.sticky{position:sticky;top:0;max-height:calc(100vh - 44px);overflow-y:auto;overscroll-behavior:contain;padding-right:4px}  /* side panel scrolls on its own */
.tabs{display:flex;gap:4px;border-bottom:1px solid var(--line);margin-bottom:12px}
.tabs button{all:unset;cursor:pointer;padding:8px 12px;border-bottom:2px solid transparent;color:var(--muted)}
.tabs button.active{border-color:var(--brand);color:var(--brand);font-weight:600}
table.list{width:100%;border-collapse:collapse;background:#fff;border-radius:10px;overflow:hidden}
table.list th,table.list td{padding:9px 10px;border-bottom:1px solid var(--line);text-align:left;vertical-align:top}
table.list th{background:#f0f2f7;font-size:12.5px;color:var(--muted)}
.crop-wrap{position:relative;display:inline-block;max-width:100%;user-select:none;cursor:crosshair}
.crop-wrap canvas,.crop-wrap img{max-width:100%;display:block}
.crop-box{position:absolute;border:2px solid #e8590c;background:rgba(232,89,12,.12)}
.stat{background:#fff;border:1px solid var(--line);border-radius:10px;padding:12px 14px}
.stat b{font-size:24px;display:block;color:var(--brand)}
.dupgroup{background:#fff;border:1px solid var(--line);border-radius:10px;padding:12px;margin-bottom:12px}
.dupgroup .members{display:grid;grid-template-columns:repeat(auto-fit,minmax(320px,1fr));gap:10px}
.dupgroup .m{border:1px solid var(--line);border-radius:8px;padding:10px}
.kbd{font-family:monospace;background:#eef1f6;border-radius:4px;padding:0 4px}
@media (max-width:1000px){.bank,.split,.editor{grid-template-columns:1fr}.app{grid-template-columns:70px 1fr}nav.side .lbl,nav.side .logo span{display:none}nav.side{padding:16px 6px}nav.side .logo{padding:6px 2px 14px}nav.side .logo b{font-size:13px;letter-spacing:0;text-align:center;line-height:1.15}}
.row select,.toolbar select{width:auto}
.opt-row textarea{min-height:36px}
.pill.crumb{background:#eef6f3;color:#185c47}
.pill.src{background:#fff1e0;color:#8a4b00}
.tagf{margin-top:4px}
/* house style: no italics in previews either */
.qbody, .qbody i, .qbody em { font-style: normal !important; }
.katex .mathnormal, .katex .mathit, .katex .boldsymbol { font-family: KaTeX_Main, "Times New Roman", serif !important; font-style: normal !important; }
.used-hint{flex-basis:100%;font-size:12px;color:#8a4b00;background:#fff4e0;border-left:3px solid var(--brand-2);padding:2px 8px;margin-top:3px;border-radius:4px}
table.rules td,table.rules th{padding:4px 5px;white-space:nowrap}
table.rules select,table.rules input{padding:4px 5px;font-size:12.5px}
.qbody{text-align:justify}

.figcmp{border:1px dashed #c4d3f3;border-radius:8px;padding:8px 10px;margin:8px 0;background:#fafcff}
.figcmp.low{border-color:#f1d58a;background:#fffdf5}
.figcmp img{max-width:340px;max-height:200px;display:block;margin:6px 0;border:1px solid #eee;background:#fff}
.sol img.struct[src*="/images/fig_"],.sol img.struct[src*="/images/gpt"],.sol img.struct[src*="/images/nb_"]{display:block;margin:6px 0;max-height:220px !important}

.modal.wide{max-width:1150px;width:96vw}
.ct-tiles{display:flex;gap:10px;flex-wrap:wrap;margin:14px 0}
.ct-tile{display:flex;flex-direction:column;min-width:120px;padding:10px 14px;border:1px solid var(--line);border-radius:10px;background:#fff;text-decoration:none;color:inherit}
.ct-tile span{font-size:12.5px;color:var(--muted)}.ct-tile b{font-size:24px;color:var(--brand)}
.ct-grid{display:grid;grid-template-columns:minmax(0,1.6fr) minmax(0,1fr);gap:14px;align-items:start}
.ct-side{display:grid;gap:14px}
.ct-row{display:flex;align-items:center;gap:6px;padding:5px 4px;border-bottom:1px solid #f0f2f6}
.ct-row:hover{background:#f7f9fc}
.ct-tog{width:16px;cursor:pointer;color:var(--muted);text-align:center}
.ct-name.b{font-weight:600}
.ct-n{min-width:38px;text-align:right;font-weight:600}
.ct-bar{height:8px;background:#eef1f6;border-radius:4px;overflow:hidden}.ct-bar span{display:block;height:100%;background:var(--brand)}
.ct-cross td,.ct-cross th{padding:6px 8px}
@media (max-width:1000px){.ct-grid{grid-template-columns:1fr}}
.export-bar{position:fixed;right:18px;bottom:18px;z-index:60;display:flex;gap:8px;align-items:center;background:#fff;border:1px solid var(--line);border-radius:12px;box-shadow:0 10px 30px rgba(0,0,0,.18);padding:10px 12px;font-size:13.5px;max-width:92vw}

/* option pictures cut from the page (import review) */
.optcrops { display: flex; flex-wrap: wrap; gap: 6px 12px; align-items: center; margin: 6px 0; }
.optcrop { display: inline-flex; align-items: center; gap: 4px; }
.optcrop img { max-height: 46px; max-width: 110px; border: 1px solid var(--line, #ddd); background: #fff; border-radius: 4px; }

/* online version: what a teacher does not see (the admin keeps the question bank) */
body.role-teacher nav.side [data-view=import], body.role-teacher nav.side [data-view=imports], body.role-teacher nav.side [data-view=dups],
body.role-teacher button[onclick*="openEditor"], body.role-teacher button[onclick*="go('import')"],
body.role-teacher button[onclick*="go('dups')"], body.role-teacher .qcard [data-act=edit],
body.role-teacher .qcard [data-act=copy], body.role-teacher .qcard [data-act=json], body.role-teacher .qcard [data-act=del],
body.role-teacher #b-edit, body.role-teacher #b-dups, body.role-teacher #b-del, body.role-teacher [data-edit], body.role-teacher [data-edq],
body.role-teacher #mimp, body.role-teacher [data-ai] { display: none !important; }
.tbl th, .tbl td { text-align: left; padding: 6px 8px; border-bottom: 1px solid var(--line); font-size: 13.5px; vertical-align: middle; }
/* reaction arrows: the same small gap to the formula / letter on each side as in the exports (teacher, Oct 2026) */
.katex .mspace:has(+ .mrel.x-arrow), .katex .mrel.x-arrow + .mspace { margin-right: 0.17em !important; }
/* credits & plans panel (teachers' My account, students' home) */
.bill{max-width:880px}.bill-top{display:flex;gap:18px;align-items:center;flex-wrap:wrap}
.bill-n{font-size:30px;font-weight:700;color:var(--brand,#14214a);line-height:1.1}.bill-rule{flex:1;min-width:220px}
.bill-h{font-weight:600;margin:16px 0 8px}.bill-grid{display:grid;grid-template-columns:repeat(auto-fill,minmax(170px,1fr));gap:10px}
.bill-card{border:1px solid var(--line,#dde2ee);border-radius:10px;padding:12px;display:flex;flex-direction:column;gap:4px;background:#fff}
.bill-price{font-size:20px;font-weight:700}.bill-card .btn,.bill-card .b{margin-top:6px;align-self:flex-start}
.bill-soon{background:#fff4e0;color:#8a4b00;padding:6px 10px;border-radius:8px}.bill-msg{margin-top:10px;font-weight:600}
.bill-log table{width:100%;border-collapse:collapse;font-size:13px}.bill-log td{padding:4px 6px;border-bottom:1px solid var(--line,#dde2ee)}
html[data-theme=dark] .bill-card{background:var(--card)}
.bill-card{position:relative}.bill-card.best{border-color:#e39b2d;box-shadow:0 0 0 1px #e39b2d inset}
.bill-badge{position:absolute;top:-9px;right:10px;background:#e39b2d;color:#14214a;font-size:11px;font-weight:700;padding:2px 8px;border-radius:20px}
@media (max-width:600px){.bill-grid{grid-template-columns:1fr 1fr;gap:8px}.bill-card{padding:10px}.bill-price{font-size:18px}.bill-n{font-size:26px}}

/* a little air between statements A. B. C. / Statement-I, II / Assertion, Reason (teacher, Oct 2026) */
.q-st { margin-top: .4em; }
.q-st + .q-closing, .q-st + .opts { margin-top: .5em; }