:root{
  --bg:#eef1f8; --bg2:#e7ecf7; --panel:#ffffff; --ink:#151b2c; --muted:#6b7590;
  --line:#e5e9f3; --brand:#2b5ce6; --brand-d:#1f47bd; --brand-soft:#eaf0ff;
  --ok:#128a4f; --ok-bg:#e4f7ec; --err:#c62b45; --err-bg:#fdebef;
  --warn:#8a6a12; --warn-bg:#fff5da; --radius:14px;
  --shadow:0 1px 2px rgba(20,30,60,.05), 0 6px 20px rgba(20,30,60,.06);
  --shadow-lg:0 10px 30px rgba(20,30,60,.12);
}
*{box-sizing:border-box}
html{-webkit-text-size-adjust:100%}
body{margin:0;font:15px/1.6 -apple-system,BlinkMacSystemFont,"Segoe UI",Roboto,Helvetica,Arial,sans-serif;
  color:var(--ink);background:
    radial-gradient(1200px 500px at 100% -8%, var(--brand-soft), transparent 60%),
    linear-gradient(180deg,var(--bg),var(--bg2));
  background-attachment:fixed;min-height:100vh}
a{color:var(--brand);text-decoration:none}
a:hover{text-decoration:underline}

/* ---------- top bar ---------- */
.topbar{background:linear-gradient(100deg,#131a2e,#20304f);color:#fff;padding:0 22px;height:56px;
  display:flex;align-items:center;gap:20px;position:sticky;top:0;z-index:30;
  box-shadow:0 2px 14px rgba(15,22,45,.22)}
.topbar .brand{font-weight:800;letter-spacing:.2px;font-size:16px}
.topbar .brand a{color:#fff}
.topbar>a{color:#c3cee8;font-weight:600;font-size:14px;padding:6px 2px;position:relative}
.topbar>a:hover{color:#fff;text-decoration:none}
.topbar .spacer{flex:1}
.topbar .who{color:#9fb0d8;font-size:13px}

/* ---------- layout ---------- */
.wrap{max-width:1080px;margin:26px auto;padding:0 20px;animation:fade .25s ease}
.wrap.narrow{max-width:520px}
@keyframes fade{from{opacity:0;transform:translateY(4px)}to{opacity:1;transform:none}}
h1{font-size:26px;margin:0 0 6px;letter-spacing:-.2px;font-weight:800}
h2{font-size:19px;margin:26px 0 12px;letter-spacing:-.1px;font-weight:700}
h3{font-size:15px;margin:16px 0 8px;font-weight:700}
.muted{color:var(--muted)}
.small{font-size:13px}
.right{text-align:right}.center{text-align:center}

/* ---------- cards ---------- */
.card{background:var(--panel);border:1px solid var(--line);border-radius:var(--radius);
  box-shadow:var(--shadow);padding:22px;margin-bottom:18px;transition:box-shadow .18s,border-color .18s}
.card:hover{box-shadow:var(--shadow-lg)}
.grid{display:grid;gap:18px}
.grid.cols-2{grid-template-columns:repeat(auto-fill,minmax(300px,1fr))}
.grid.cols-3{grid-template-columns:repeat(auto-fill,minmax(210px,1fr))}
.grid.cols-4{grid-template-columns:repeat(auto-fill,minmax(150px,1fr))}

/* ---------- forms ---------- */
label{display:block;font-weight:600;font-size:13px;margin:14px 0 5px;color:#3a445e}
label{color:#3a445e}
input[type=text],input[type=email],input[type=password],input[type=number],
input[type=datetime-local],input[type=file],input[type=color],select,textarea{
  width:100%;padding:10px 12px;border:1px solid var(--line);border-radius:10px;font:inherit;background:#fff;color:var(--ink);
  transition:border-color .15s,box-shadow .15s}
textarea{min-height:96px;resize:vertical}
input:focus,select:focus,textarea:focus{outline:none;border-color:var(--brand);box-shadow:0 0 0 3px rgba(43,92,230,.14)}
.row{display:flex;gap:14px;flex-wrap:wrap}
.row>*{flex:1;min-width:160px}

/* ---------- buttons ---------- */
.btn{display:inline-flex;align-items:center;gap:6px;background:linear-gradient(180deg,var(--brand),var(--brand-d));
  color:#fff;border:0;border-radius:10px;padding:10px 17px;font:inherit;font-weight:600;cursor:pointer;
  box-shadow:0 1px 2px rgba(20,30,60,.12);transition:transform .08s,box-shadow .15s,filter .15s}
.btn:hover{filter:brightness(1.05);text-decoration:none;box-shadow:0 4px 14px rgba(43,92,230,.28)}
.btn:active{transform:translateY(1px)}
.btn.sm{padding:6px 12px;font-size:13px;border-radius:8px}
.btn.ghost{background:var(--brand-soft);color:var(--brand-d);box-shadow:none}
.btn.ghost:hover{background:#dfe8ff;box-shadow:none;filter:none}
.btn.danger{background:linear-gradient(180deg,#e0435c,var(--err))}
.btn.ok{background:linear-gradient(180deg,#1aa15d,var(--ok))}
.btn.gray{background:linear-gradient(180deg,#6b7488,#525b70)}
.btn:disabled{opacity:.5;cursor:not-allowed;filter:none;box-shadow:none}
.inline{display:inline}

/* ---------- tables ---------- */
table{width:100%;border-collapse:collapse;font-size:14px}
th,td{text-align:left;padding:10px 11px;border-bottom:1px solid var(--line);vertical-align:top}
th{color:var(--muted);font-size:11.5px;text-transform:uppercase;letter-spacing:.5px;font-weight:700}
tbody tr:last-child td{border-bottom:0}
tr:hover td{background:#f7f9ff}

/* ---------- flashes / pills ---------- */
.flash{padding:12px 15px;border-radius:11px;margin-bottom:16px;font-size:14px;font-weight:500;
  border:1px solid transparent;display:flex;align-items:center;gap:8px}
.flash.ok{background:var(--ok-bg);color:var(--ok);border-color:#bfe8cf}
.flash.err{background:var(--err-bg);color:var(--err);border-color:#f5c6d0}
.flash.warn{background:var(--warn-bg);color:var(--warn);border-color:#f0e2ac}
.pill{display:inline-block;padding:2px 10px;border-radius:999px;font-size:12px;font-weight:700;letter-spacing:.2px}
.pill.open{background:var(--ok-bg);color:var(--ok)}
.pill.closed{background:#eef1f6;color:var(--muted)}
.pill.draft{background:var(--warn-bg);color:var(--warn)}

/* ---------- tabs (pill style) ---------- */
.tabs{display:flex;gap:6px;flex-wrap:wrap;margin:10px 0 22px;padding:5px;background:#e9edf7;
  border-radius:12px;box-shadow:inset 0 1px 2px rgba(20,30,60,.05)}
.tabs a{padding:8px 14px;border-radius:8px;color:var(--muted);font-weight:600;font-size:14px;transition:.15s}
.tabs a:hover{color:var(--ink);text-decoration:none;background:#fff}
.tabs a.active{color:var(--brand-d);background:#fff;box-shadow:0 1px 3px rgba(20,30,60,.12)}

/* ---------- course cards / banners ---------- */
.banner-wrap{position:relative;width:100%;height:180px;border-radius:var(--radius);overflow:hidden;margin-bottom:16px;box-shadow:var(--shadow);background-size:cover;background-position:center;isolation:isolate}
.banner-wrap.thumb{height:120px;margin:0;border-radius:0}
.banner-wrap::before{content:'';position:absolute;inset:-20px;background:inherit;background-size:cover;background-position:center;filter:blur(20px) brightness(.8);z-index:0}
.banner-img{position:relative;z-index:1;width:100%;height:100%;object-fit:contain;display:block}
.banner-wrap.fit-cover .banner-img{object-fit:cover}
.banner-wrap.fit-fill  .banner-img{object-fit:fill}
.banner-wrap.fit-cover::before,.banner-wrap.fit-fill::before{display:none}
/* legacy alias, kept in case an old cached template still uses <img class="banner"> */
.banner{width:100%;height:180px;object-fit:cover;background:#eef1f8;border-radius:var(--radius);margin-bottom:16px;box-shadow:var(--shadow)}
.banner.fit-contain{object-fit:contain}
.banner.fit-cover{object-fit:cover}
.banner.fit-fill{object-fit:fill}
.course-card{display:block;border:1px solid var(--line);border-radius:var(--radius);overflow:hidden;background:#fff;
  box-shadow:var(--shadow);transition:transform .12s,box-shadow .18s,border-color .18s;position:relative}
.course-card:before{content:"";position:absolute;left:0;top:0;bottom:0;width:5px;background:linear-gradient(var(--brand),var(--brand-d))}
.course-card .body{padding:16px 16px 16px 20px}
.course-card:hover{text-decoration:none;transform:translateY(-2px);box-shadow:var(--shadow-lg);border-color:#cdd9f6}
.kpi{font-size:30px;font-weight:800;letter-spacing:-.5px;color:var(--brand-d)}
hr{border:0;border-top:1px solid var(--line);margin:20px 0}
code{background:#eef1f6;padding:1px 6px;border-radius:6px;font-size:13px;font-family:ui-monospace,SFMono-Regular,Menlo,monospace}
.help{font-size:12.5px;color:var(--muted);margin-top:4px}

/* ---------- live / results ---------- */
.live-stage{max-width:720px;margin:0 auto;text-align:center}
.count{font-size:64px;font-weight:800;color:var(--brand)}
.bar{height:36px;border-radius:8px;background:linear-gradient(180deg,#ef5c72,var(--err));color:#fff;display:flex;align-items:center;
  padding:0 12px;margin:8px 0;font-weight:700;min-width:44px;transition:width .5s}
.bar.correct{background:linear-gradient(180deg,#26b06c,var(--ok))}
.emoji{font-size:56px}
.prize-box{background:var(--warn-bg);border:1px solid #f0e3b0;border-radius:var(--radius);padding:16px;margin-top:18px}
.prize-box img{max-width:180px;border-radius:9px;margin-top:8px}
.winner{font-size:22px;font-weight:800;color:var(--ok);margin-top:10px}
.explain{background:#f6f8ff;border:1px solid #dde5fb;border-left:4px solid var(--brand);border-radius:10px;
  padding:12px 14px;margin-top:12px}
.explain img{max-width:100%;border-radius:8px;margin-top:8px}

/* ---------- responsive ---------- */
@media (max-width:760px){
  .wrap{margin:14px auto;padding:0 13px}
  .topbar{gap:14px;padding:0 14px;height:auto;min-height:52px;flex-wrap:wrap;padding-top:8px;padding-bottom:8px}
  .topbar .who{display:none}
  h1{font-size:22px}h2{font-size:17px;margin:20px 0 10px}
  .card{padding:16px;margin-bottom:14px}
  .grid.cols-2,.grid.cols-3,.grid.cols-4{grid-template-columns:1fr}
  .row{flex-direction:column;gap:10px}
  .row>*{min-width:0;width:100%}
  .tabs{flex-wrap:nowrap;overflow-x:auto;-webkit-overflow-scrolling:touch;scrollbar-width:thin}
  .tabs a{white-space:nowrap;flex:0 0 auto}
  .card>table,table{display:block;overflow-x:auto;white-space:nowrap;-webkit-overflow-scrolling:touch}
  .banner-wrap{height:130px}
  .banner{height:130px}
  td.right{white-space:normal}
}
@media (max-width:420px){ .btn,.btn.sm{margin:2px 0} h1{font-size:20px} }

/* ---------- discussion respondents (avatar grid + click-to-open) ---------- */
.resp-grid{display:flex;flex-wrap:wrap;gap:16px;margin:12px 0}
.resp-chip{width:82px;text-align:center;color:inherit}
.resp-chip:hover{text-decoration:none}
.resp-chip .av{position:relative;display:inline-block}
.resp-chip .av img,.resp-chip .av .avph{width:52px;height:52px;border-radius:50%;object-fit:cover;
  border:2px solid #fff;box-shadow:0 2px 6px rgba(20,30,60,.18)}
.resp-chip .badge{position:absolute;right:-8px;bottom:-4px;background:#fff;border:1px solid var(--line);
  border-radius:999px;padding:1px 6px;font-size:10.5px;font-weight:700;color:var(--muted);white-space:nowrap;
  box-shadow:0 1px 3px rgba(20,30,60,.15)}
.resp-chip .nm{font-size:12px;margin-top:6px;color:var(--ink);overflow:hidden;text-overflow:ellipsis;white-space:nowrap}
.resp-chip:hover .av img,.resp-chip:hover .av .avph{border-color:var(--brand)}
.dresp{display:none;border:1px solid var(--line);border-radius:12px;padding:14px;margin-top:12px;background:#fbfcff}
.dresp:target{display:block;animation:fade .2s ease}
.avph{display:inline-flex;align-items:center;justify-content:center;background:linear-gradient(180deg,var(--brand),var(--brand-d));
  color:#fff;font-weight:700}

/* ---------- stage-1 polish ---------- */
h2{position:relative;padding-left:12px}
h2::before{content:"";position:absolute;left:0;top:3px;bottom:3px;width:4px;border-radius:3px;
  background:linear-gradient(var(--brand),var(--brand-d))}
.card h2:first-child{padding-left:0}
.card h2:first-child::before{display:none}
thead th,table tr:first-child th{background:#f4f7ff}
.course-card:hover .body{background:linear-gradient(180deg,#fbfcff,transparent)}
.btn.ok{box-shadow:0 2px 10px rgba(18,138,79,.25)}
.btn:focus-visible,input:focus-visible,select:focus-visible,a.btn:focus-visible{outline:2px solid var(--brand);outline-offset:2px}
.pill{box-shadow:inset 0 0 0 1px rgba(20,30,60,.04)}
.flash{box-shadow:var(--shadow)}

/* ---------- Live MCQ list: responsive on all devices ---------- */
.mcq-actions{display:flex;flex-wrap:wrap;gap:6px;justify-content:flex-end;align-items:center}
.btn.icon{padding:6px 10px;font-size:15px;line-height:1;min-width:38px;text-align:center}
.btn:disabled{opacity:.45;cursor:default;filter:saturate(.4)}
.btn:disabled:hover{filter:saturate(.4)}
/* answered = pink, not-answered yet = green (desktop: colour the cells) */
.mcq-table tr.row-answered   > td{background:#fdeef2}
.mcq-table tr.row-unanswered > td{background:#ecf7ee}
@media (max-width:760px){
  .mcq-table thead{display:none}
  .mcq-table, .mcq-table tbody, .mcq-table tr, .mcq-table td{display:block;width:100%}
  .mcq-table tr{border:1px solid var(--line);border-radius:12px;padding:10px 14px;margin-bottom:12px;background:#fff}
  .mcq-table tr.row-answered{background:#fdeef2;border-color:#f4cdd8}
  .mcq-table tr.row-unanswered{background:#ecf7ee;border-color:#cde9d4}
  .mcq-table tr.row-answered > td,
  .mcq-table tr.row-unanswered > td{background:transparent}
  .mcq-table td{border:0;padding:3px 0;text-align:left}
  .mcq-table td[data-label]::before{content:attr(data-label) ": ";color:var(--muted);font-weight:600;font-size:12px}
  .mcq-table td[data-label="Question"]::before{content:""}
  .mcq-table .mcq-actions{justify-content:flex-start;padding-top:8px;margin-top:6px;border-top:1px dashed var(--line)}
}

/* ---------- MathJax on small screens ---------- */
/* keep rendered LaTeX inside the viewport: wide display equations get a
   sideways scroll instead of being clipped off the edge on phones */
mjx-container{max-width:100%}
mjx-container[display="true"]{display:block;overflow-x:auto;overflow-y:hidden;padding:2px 0}
mjx-container svg{max-width:none}
.topbar .brand::before{content:"◆";margin-right:8px;color:#7f9cff;font-size:12px;vertical-align:middle}
.card{background:linear-gradient(180deg,#ffffff, #fdfefe)}
/* subtle section spacing on the student course page */
.wrap>h2{margin-top:30px}

/* ---------- chapter tabs (slanted) + pagination ---------- */
.chapter-header{margin:18px 0 0;overflow-x:auto;overflow-y:hidden;padding-bottom:0}
.chapter-tabs{display:flex;align-items:flex-end;min-width:max-content;padding-left:2px}
.chtab{
  position:relative;
  background:var(--brand);
  color:#fff;
  border:0;
  margin-right:14px;
  padding:15px 30px 14px 22px;
  font-weight:700;
  font-size:14.5px;
  cursor:pointer;
  flex-shrink:0;
  white-space:nowrap;
  display:flex;
  align-items:center;
  gap:9px;
  line-height:1.15;
  border-radius:8px 8px 0 0;
  transition:background .15s,color .15s;
}
/* slanted right edge via a skewed pseudo-element that inherits the tab colour */
.chtab::after{
  content:'';
  position:absolute;
  top:0;right:-13px;
  width:28px;height:100%;
  background:inherit;
  border-radius:0 8px 0 0;
  transform:skewX(20deg);
  transform-origin:bottom left;
  z-index:-1;
}
.chtab .ic{font-size:17px;line-height:1;display:inline-flex}
.chtab .ic svg{width:18px;height:18px;stroke:currentColor;fill:none;stroke-width:2}
.chtab:hover{background:var(--brand-d)}
.chtab.active{background:#fff;color:var(--brand-d);z-index:4}
.chapter-panel{background:#fff;border-radius:0 12px 12px 12px;padding:26px;box-shadow:0 10px 26px rgba(20,30,60,.09);margin:0 0 22px;position:relative;z-index:2}

/* bottom pagination: ← Previous | dots + "n / total" | Next → */
.page-nav-bottom{display:flex;align-items:center;justify-content:space-between;gap:14px;margin:26px 0 4px;padding-top:20px;border-top:1px solid var(--line)}
.pgbtn{display:flex;align-items:center;gap:8px;background:#fff;border:1px solid var(--line);border-radius:11px;padding:11px 20px;font-weight:700;font-size:14px;cursor:pointer;color:var(--ink)}
.pgbtn:hover{border-color:var(--brand);color:var(--brand)}
.pgbtn:disabled{opacity:.4;cursor:default;border-color:var(--line);color:var(--muted)}
.pgcenter{display:flex;flex-direction:column;align-items:center;gap:7px}
.dots{display:flex;gap:10px;align-items:center}
.dot{width:11px;height:11px;border-radius:50%;background:#cfe0cf;border:0;padding:0;cursor:pointer;transition:.15s;font-size:0}
.dot.active{background:var(--brand-d);transform:scale(1.15)}
.dot.locked{background:transparent;box-shadow:inset 0 0 0 2px #cfe0cf}
.dot:hover{background:var(--brand)}
.pgcount{font-size:13px;font-weight:600;color:var(--muted)}

/* ---- locked-page toast + card ---- */
.page-toast{position:fixed;left:50%;bottom:26px;transform:translateX(-50%) translateY(14px);
  background:#1f2a44;color:#fff;padding:13px 22px;border-radius:12px;font-weight:600;font-size:14px;
  box-shadow:0 12px 34px rgba(0,0,0,.30);opacity:0;pointer-events:none;transition:.25s;z-index:200;max-width:90vw;text-align:center}
.page-toast.show{opacity:1;transform:translateX(-50%) translateY(0)}
.locked-card{border:1px dashed var(--line);background:#fbfcff}


/* answered = pink, not-answered yet = green */
.mcq-table tr.row-answered   > td{background:#fdeef2}
.mcq-table tr.row-unanswered > td{background:#ecf7ee}
@media (max-width:760px){
  .mcq-table tr.row-answered{background:#fdeef2;border-color:#f4cdd8}
  .mcq-table tr.row-unanswered{background:#ecf7ee;border-color:#cde9d4}
  .mcq-table tr.row-answered > td,
  .mcq-table tr.row-unanswered > td{background:transparent}
}