:root{
  --bg:#f3f5f9; --panel:#ffffff; --ink:#1b2330; --muted:#5b6677;
  --line:#e3e8f0; --blue:#0a5fd6; --blue-d:#0848a3; --green:#1aa45a;
  --green-bg:#e7f7ee; --red:#d23b3b; --red-bg:#fdeaea; --amber:#e0a416;
  --shadow:0 1px 3px rgba(20,30,50,.08),0 6px 24px rgba(20,30,50,.06);
  --radius:12px;
}
*{box-sizing:border-box}
html,body{margin:0;padding:0}
body{font-family:-apple-system,BlinkMacSystemFont,"Segoe UI",Roboto,Helvetica,Arial,sans-serif;
  background:var(--bg);color:var(--ink);line-height:1.55;font-size:15px}
.hidden{display:none !important}
a{color:var(--blue)}
button{font-family:inherit}

/* ---- top bar ---- */
#topbar{position:sticky;top:0;z-index:30;display:flex;align-items:center;justify-content:space-between;
  gap:12px;padding:10px 18px;background:#fff;border-bottom:1px solid var(--line);box-shadow:var(--shadow)}
.tb-left,.tb-right{display:flex;align-items:center;gap:10px}
.logo{font-weight:800;font-size:20px;letter-spacing:-.5px}
.logo-blue{color:var(--blue)}
.mode-label{font-size:12px;font-weight:700;text-transform:uppercase;letter-spacing:.5px;color:#fff;
  background:var(--blue);padding:3px 10px;border-radius:20px}
#progress-text{font-weight:600;color:var(--muted)}
.timer{font-variant-numeric:tabular-nums;font-weight:700;background:#eef3fb;color:var(--blue-d);
  padding:5px 12px;border-radius:8px}
.timer.danger{background:var(--red-bg);color:var(--red)}
.score-live{font-weight:700;color:var(--green)}

/* ---- buttons ---- */
.btn{border:1px solid var(--line);background:#fff;color:var(--ink);padding:9px 16px;border-radius:9px;
  cursor:pointer;font-weight:600;font-size:14px;transition:.15s;white-space:nowrap}
.btn:hover{background:#f6f8fc;border-color:#cdd6e4}
.btn:active{transform:translateY(1px)}
.btn.primary{background:var(--blue);border-color:var(--blue);color:#fff}
.btn.primary:hover{background:var(--blue-d)}
.btn.success{background:var(--green);border-color:var(--green);color:#fff}
.btn.warn{color:var(--amber);border-color:#f0dca6}
.btn.warn.on{background:var(--amber);color:#fff;border-color:var(--amber)}
.btn.ghost{border-color:transparent;background:transparent;color:var(--muted)}
.btn.ghost:hover{background:#eef1f6}
.btn.block{display:block;width:100%;margin-bottom:8px}
.btn.big{width:100%;margin-top:8px;padding:12px;font-size:15px}
.btn.danger-ghost{color:var(--red);border-color:#f0c9c9}
.btn:disabled{opacity:.45;cursor:not-allowed}

/* ---- screens ---- */
.screen{max-width:1000px;margin:0 auto;padding:26px 18px 80px}

/* ---- home ---- */
.hero{text-align:center;padding:26px 0 8px}
.hero h1{font-size:34px;margin:0 0 8px;letter-spacing:-1px}
.accent{color:var(--blue)}
.hero .sub{color:var(--muted);font-size:16px;margin:0 auto;max-width:640px}
.stat-row{display:flex;gap:12px;justify-content:center;flex-wrap:wrap;margin:20px 0 6px}
.stat{background:#fff;border:1px solid var(--line);border-radius:12px;padding:12px 20px;min-width:110px;text-align:center;box-shadow:var(--shadow)}
.stat b{display:block;font-size:26px;color:var(--blue)}
.stat span{font-size:12px;color:var(--muted);text-transform:uppercase;letter-spacing:.5px}
.cards{display:grid;grid-template-columns:repeat(3,1fr);gap:18px;margin-top:24px}
.card{background:#fff;border:1px solid var(--line);border-radius:var(--radius);padding:20px;box-shadow:var(--shadow);display:flex;flex-direction:column}
.card h3{margin:0 0 6px;font-size:18px}
.card p{margin:0 0 14px;color:var(--muted);font-size:14px}
.card label{display:block;font-size:13px;font-weight:600;color:var(--muted);margin-bottom:10px}
.card label.chk{display:flex;align-items:center;gap:8px;font-weight:500}
.card select,.card input[type=text]{width:100%;margin-top:4px;padding:8px 10px;border:1px solid var(--line);
  border-radius:8px;font-size:14px;background:#fbfcfe}
.card label.chk input{margin-top:0;width:auto}
.foot{text-align:center;color:var(--muted);font-size:13px;margin-top:30px}

/* ---- quiz card ---- */
#quiz{max-width:1000px;margin:0 auto;padding:22px 18px 110px}
#qcard{background:#fff;border:1px solid var(--line);border-radius:var(--radius);padding:26px 28px;box-shadow:var(--shadow)}
.q-head{display:flex;align-items:center;gap:10px;margin-bottom:16px}
.q-num{font-weight:800;font-size:18px}
.badge{font-size:11px;font-weight:700;text-transform:uppercase;letter-spacing:.5px;padding:3px 9px;border-radius:20px}
.badge.mcq{background:#eaf1fd;color:var(--blue-d)}
.badge.hotspot{background:#fdf0e1;color:#a96a10}
.badge.dragdrop{background:#eee6fb;color:#6b3fb0}
.badge.multi{background:#e7f7ee;color:var(--green)}
.badge.flagcnt{background:#fff5db;color:#9a7400}
.q-stem{font-size:16px;white-space:pre-wrap;margin-bottom:18px}
.q-img{max-width:100%;border:1px solid var(--line);border-radius:8px;margin:6px 0;display:block}
.img-note{font-size:13px;color:var(--muted);font-style:italic;margin:4px 0 12px}

/* options */
.opts{display:flex;flex-direction:column;gap:10px;margin-top:6px}
.opt{display:flex;gap:12px;align-items:flex-start;border:1.5px solid var(--line);border-radius:10px;
  padding:12px 14px;cursor:pointer;transition:.12s;background:#fff}
.opt:hover{border-color:#b9c6dc;background:#f9fbff}
.opt.sel{border-color:var(--blue);background:#f0f6ff}
.opt .mark{flex:0 0 26px;height:26px;border:2px solid #c3cddd;border-radius:50%;display:flex;
  align-items:center;justify-content:center;font-weight:700;color:var(--muted);font-size:13px}
.opt.multi .mark{border-radius:7px}
.opt.sel .mark{border-color:var(--blue);background:var(--blue);color:#fff}
.opt .otext{flex:1;padding-top:2px}
.opt .letter{font-weight:700;margin-right:2px}
.opt.correct{border-color:var(--green);background:var(--green-bg)}
.opt.correct .mark{border-color:var(--green);background:var(--green);color:#fff}
.opt.wrong{border-color:var(--red);background:var(--red-bg)}
.opt.wrong .mark{border-color:var(--red);background:var(--red);color:#fff}
.opt.locked{cursor:default}
.opt-tag{margin-left:auto;font-size:11px;font-weight:700;padding:2px 8px;border-radius:12px;align-self:center}
.opt.correct .opt-tag{background:var(--green);color:#fff}
.opt.wrong .opt-tag{background:var(--red);color:#fff}

/* case study panel */
.badge.cs-badge{background:#e8eefc;color:#33489c}
.cs{border:1px solid #cdd9f0;border-radius:10px;background:#f7faff;margin:0 0 16px;padding:4px 14px}
.cs summary{cursor:pointer;font-size:14px;padding:9px 0;color:#23407a;list-style:none}
.cs summary::-webkit-details-marker{display:none}
.cs summary::before{content:"▸ ";color:#7a90c0}
.cs[open] summary::before{content:"▾ "}
.cs-open{font-size:12px;color:#8aa0c8;font-weight:600}
.cs-warn{background:#fff7e6;border:1px solid #f0d99a;color:#8a6400;padding:9px 12px;border-radius:8px;font-size:13px;margin:6px 0}
.cs-ok{background:var(--green-bg);border:1px solid #b6e3c8;color:#136b3c;padding:9px 12px;border-radius:8px;font-size:13px;margin:6px 0}
.cs-body{white-space:normal;font-size:14px;line-height:1.6;margin:10px 0;color:#243}
.cs-exh-t{font-weight:700;font-size:12px;text-transform:uppercase;letter-spacing:.5px;color:var(--muted);margin-top:8px}
.cs-src{font-size:12.5px;color:var(--muted);margin-top:8px}
.cs-nav{margin:10px 0 6px;font-size:13px;color:var(--muted)}
.cs-jump{display:inline-block;margin:2px 3px;padding:2px 8px;border:1px solid var(--line);border-radius:12px;background:#fff;text-decoration:none;font-weight:600}
.cs-jump.cur{background:var(--blue);color:#fff;border-color:var(--blue)}
.cs-jump.off{color:#b6c0d0;cursor:default}

/* context image toggle */
.ctx{margin:10px 0;border:1px solid var(--line);border-radius:8px;padding:6px 10px;background:#fafbfe}
.ctx summary{cursor:pointer;font-size:13px;font-weight:600;color:var(--blue-d)}
.ctx .q-img{margin-top:10px}

/* hotspot interactive */
.hs{display:flex;flex-direction:column;gap:12px;margin-top:8px}
.hs-row{display:flex;align-items:center;gap:14px;border:1px solid var(--line);border-radius:10px;padding:12px 14px;background:#fff}
.hs-row.col{flex-direction:column;align-items:flex-start;gap:8px}
.hs-label{flex:1;font-size:15px}
.hs-opts{display:flex;gap:8px;flex-shrink:0}
.yn{border:1.5px solid var(--line);background:#fff;border-radius:8px;padding:8px 18px;font-weight:700;cursor:pointer;color:var(--muted);min-width:64px}
.yn:hover{border-color:#b9c6dc}
.yn.on{border-color:var(--blue);background:var(--blue);color:#fff}
.yn.correct{border-color:var(--green);background:var(--green);color:#fff}
.yn.wrong{border-color:var(--red);background:var(--red);color:#fff}
.yn:disabled{cursor:default;opacity:1}
.hs-select{width:100%;padding:10px 12px;border:1.5px solid var(--line);border-radius:8px;font-size:14px;background:#fbfcfe}
.hs-select.correct{border-color:var(--green);background:var(--green-bg)}
.hs-select.wrong{border-color:var(--red);background:var(--red-bg)}
.slot-correct{color:var(--green);font-weight:700;font-size:13px;margin-top:2px}

/* drag-drop interactive */
.dd{display:grid;grid-template-columns:1fr 1fr;gap:16px;margin-top:8px}
.dd-title{font-size:12px;font-weight:700;text-transform:uppercase;letter-spacing:.5px;color:var(--muted);margin-bottom:8px}
.dd-pool,.dd-slots{display:flex;flex-direction:column;gap:8px;min-height:60px}
.chip{border:1.5px solid #b9c6dc;background:#f0f6ff;border-radius:9px;padding:10px 12px;font-weight:600;cursor:grab;text-align:center;user-select:none}
.chip:hover{border-color:var(--blue)}
.chip.pick{border-color:var(--blue);background:var(--blue);color:#fff}
.chip.placed{opacity:.4;text-decoration:line-through;cursor:default}
.slot{border:1.5px dashed #c3cddd;border-radius:9px;padding:10px 12px;min-height:44px;display:flex;flex-direction:column;justify-content:center;cursor:pointer;background:#fafbff}
.slot:hover{border-color:var(--blue)}
.slot-label{font-size:12px;color:var(--muted);font-weight:700}
.slot-val{font-weight:600}
.slot.correct{border-style:solid;border-color:var(--green);background:var(--green-bg)}
.slot.wrong{border-style:solid;border-color:var(--red);background:var(--red-bg)}
@media(max-width:760px){.dd{grid-template-columns:1fr}.hs-row{flex-direction:column;align-items:flex-start}}

/* self-grade for image questions */
.selfgrade{margin-top:14px;padding:14px;border:1px dashed var(--line);border-radius:10px;background:#fafbfe}
.selfgrade p{margin:0 0 10px;font-weight:600}
.selfgrade .btn{margin-right:8px}

/* explanation */
#explanation{background:#fff;border:1px solid var(--line);border-radius:var(--radius);padding:22px 26px;
  box-shadow:var(--shadow);margin-top:16px}
.exp-verdict{font-size:18px;font-weight:800;margin-bottom:6px}
.exp-verdict.ok{color:var(--green)}
.exp-verdict.no{color:var(--red)}
.exp-ans{font-size:15px;margin-bottom:14px}
.exp-ans b{color:var(--blue-d)}
.disputed{background:#fff7e6;border:1px solid #f0d99a;color:#8a6400;padding:10px 14px;border-radius:8px;
  font-size:13.5px;margin:10px 0}
.verified{background:var(--green-bg);border:1px solid #b6e3c8;color:#136b3c;padding:10px 14px;border-radius:8px;
  font-size:13.5px;margin:10px 0}
.exp-sec-title{font-weight:700;margin:16px 0 8px;font-size:13px;text-transform:uppercase;letter-spacing:.5px;color:var(--muted)}
.votes{display:flex;gap:8px;flex-wrap:wrap;margin-bottom:6px}
.vote{background:#eef2f8;border-radius:20px;padding:3px 12px;font-size:13px;font-weight:600}
.vote.top{background:var(--blue);color:#fff}
.comment{border-top:1px solid var(--line);padding:10px 0}
.comment:first-child{border-top:none}
.cmt-head{font-size:13px;color:var(--muted);margin-bottom:3px}
.cmt-head b{color:var(--ink)}
.cmt-pts{background:#eef2f8;border-radius:10px;padding:1px 8px;font-weight:700;font-size:12px}
.cmt-body{white-space:pre-wrap;font-size:14px}
.ms-link{display:inline-block;margin-top:12px;font-weight:600}

/* nav */
#qnav{position:fixed;bottom:0;left:0;right:0;background:#fff;border-top:1px solid var(--line);
  display:flex;gap:10px;justify-content:center;padding:12px 18px;z-index:20;box-shadow:0 -2px 12px rgba(20,30,50,.05)}
#qnav .btn{min-width:96px}

/* palette */
.modal{position:fixed;inset:0;background:rgba(15,22,35,.45);display:flex;align-items:center;justify-content:center;z-index:50}
.modal-box{background:#fff;border-radius:14px;max-width:680px;width:92%;max-height:80vh;overflow:auto;padding:18px 20px;box-shadow:var(--shadow)}
.modal-head{display:flex;justify-content:space-between;align-items:center;margin-bottom:12px}
.modal-head h3{margin:0}
.palette-grid{display:grid;grid-template-columns:repeat(auto-fill,minmax(44px,1fr));gap:8px}
.pcell{aspect-ratio:1;border:1px solid var(--line);border-radius:8px;display:flex;align-items:center;
  justify-content:center;font-weight:700;font-size:13px;cursor:pointer;background:#fff;position:relative}
.pcell:hover{border-color:var(--blue)}
.pcell.cur{outline:3px solid var(--blue);outline-offset:-1px}
.pcell.ans{background:#eaf1fd;border-color:#b9d0f5}
.pcell.correct{background:var(--green-bg);border-color:#b6e3c8;color:#136b3c}
.pcell.wrong{background:var(--red-bg);border-color:#eeb6b6;color:#a12626}
.pcell.flag::after{content:"⚑";position:absolute;top:-6px;right:-2px;font-size:12px;color:var(--amber)}
.palette-legend{display:flex;gap:14px;flex-wrap:wrap;margin-top:14px;font-size:12px;color:var(--muted)}
.palette-legend i{display:inline-block;width:14px;height:14px;border-radius:4px;margin-right:5px;vertical-align:-2px;border:1px solid var(--line)}
.lg.cur{outline:2px solid var(--blue);background:#fff}
.lg.ans{background:#eaf1fd}
.lg.correct{background:var(--green-bg)}
.lg.wrong{background:var(--red-bg)}
.lg.flag{background:#fff5db}

/* results */
#results{max-width:820px}
.res-hero{text-align:center;background:#fff;border:1px solid var(--line);border-radius:var(--radius);padding:30px;box-shadow:var(--shadow)}
.res-score{font-size:60px;font-weight:800;line-height:1}
.res-score.pass{color:var(--green)}
.res-score.fail{color:var(--red)}
.res-verdict{font-size:22px;font-weight:700;margin:6px 0}
.res-sub{color:var(--muted)}
.res-bars{margin-top:18px;text-align:left}
.res-bar-row{display:flex;align-items:center;gap:10px;margin:8px 0}
.res-bar-row .lab{width:120px;font-size:13px;font-weight:600}
.res-bar{flex:1;height:14px;background:#eef2f8;border-radius:8px;overflow:hidden}
.res-bar i{display:block;height:100%;background:var(--blue)}
.res-actions{display:flex;gap:10px;justify-content:center;margin-top:22px;flex-wrap:wrap}

@media(max-width:760px){
  .cards{grid-template-columns:1fr}
  .hero h1{font-size:26px}
  #qcard{padding:18px}
  .tb-center{display:none}
  #qnav .btn{min-width:auto;padding:9px 11px}
}

/* ---- standalone home sections (Yes/No + Case Study) ---- */
.section-block{margin-top:34px;background:#fff;border:1px solid var(--line);border-radius:var(--radius);
  padding:22px 24px;box-shadow:var(--shadow)}
.section-block .section-head{margin-bottom:14px}
.section-block .section-head h2{margin:0 0 6px;font-size:20px;letter-spacing:-.3px}
.section-block .section-head p{margin:0;color:var(--muted);font-size:14px}
.section-block .section-card{display:grid;grid-template-columns:1fr 1fr auto;gap:14px;align-items:end}
.section-block .section-card label{display:block;font-size:13px;font-weight:600;color:var(--muted);margin:0}
.section-block .section-card label.chk{display:flex;align-items:center;gap:8px;font-weight:500;align-self:center}
.section-block .section-card select,
.section-block .section-card input[type=text]{width:100%;margin-top:4px;padding:8px 10px;
  border:1px solid var(--line);border-radius:8px;font-size:14px;background:#fbfcfe}
.section-block .section-card .btn.big{margin-top:0;width:auto;min-width:240px}
.count-pill{display:inline-block;background:#eaf1fd;color:var(--blue-d);padding:1px 10px;border-radius:20px;
  font-weight:700;font-size:13px;margin:0 2px}
.yesno-block{border-left:4px solid var(--green)}
.yesno-block .section-head h2{color:#136b3c}
.yesno-block .count-pill{background:var(--green-bg);color:#136b3c}
.cs-block{border-left:4px solid #6b3fb0}
.cs-block .section-head h2{color:#4b2a85}
.cs-block .count-pill{background:#eee6fb;color:#4b2a85}

@media(max-width:760px){
  .section-block .section-card{grid-template-columns:1fr}
  .section-block .section-card .btn.big{width:100%}
}