:root{
  /* palette — kept from original (brand blue + semantic green/amber/red) */
  --bg:#eef1f5; --panel:#fff; --ink:#1d2733; --muted:#5b6b7b;
  --line:#dce3ec; --brand:#0b62c9; --brand-d:#084a99;
  --green:#1f9d55; --green-l:#e8f6ee; --amber:#d98a00; --amber-l:#fbf1d8;
  --red:#d23b3b; --red-l:#fbeaea; --blue-l:#eaf1fb; --grey-l:#f1f4f8;
  /* shape + elevation tokens */
  --radius-sm:10px; --radius:12px; --radius-lg:14px; --radius-pill:999px;
  --shadow-sm:0 1px 2px rgba(20,40,70,.05);
  --shadow:0 1px 3px rgba(20,40,70,.04), 0 12px 28px rgba(20,40,70,.07);
  --ease:cubic-bezier(.4,0,.2,1);
}
[data-theme="dark"]{
  --bg:#0e131a; --panel:#19222e; --ink:#e8eef5; --muted:#9aabbf;
  --line:#283442; --brand:#4d9bff; --brand-d:#2f7fe6;
  --green:#2ec27e; --green-l:#13302a; --amber:#f0b429; --amber-l:#352b12;
  --red:#ef6b6b; --red-l:#3a1f1f; --blue-l:#13273d; --grey-l:#19222e;
  --shadow-sm:0 1px 2px rgba(0,0,0,.35);
  --shadow:0 1px 3px rgba(0,0,0,.3), 0 14px 30px rgba(0,0,0,.35);
}

*{box-sizing:border-box;margin:0;padding:0}
input,select,textarea,button{font-family:inherit}
html{scroll-behavior:smooth}
html,body{height:100%}
body{
  font-family:"JetBrains Mono","Roboto Mono",ui-monospace,SFMono-Regular,Menlo,Consolas,monospace;
  font-size:15px;
  background:var(--bg); color:var(--ink); line-height:1.5;
  -webkit-font-smoothing:antialiased; text-rendering:optimizeLegibility;
  transition:background .25s var(--ease), color .25s var(--ease);
}
::selection{background:var(--blue-l);color:var(--brand)}
.screen{display:none;min-height:100vh}
.screen.active{display:block}

/* ---------- unified button system ---------- */
.btn{display:inline-flex;align-items:center;justify-content:center;gap:8px;
  font:inherit;font-size:14px;font-weight:700;line-height:1.1;cursor:pointer;
  padding:12px 22px;border-radius:var(--radius-sm);border:1.5px solid transparent;
  transition:background .18s var(--ease),border-color .18s var(--ease),color .18s var(--ease),box-shadow .18s var(--ease),transform .05s var(--ease);
  white-space:nowrap;user-select:none;text-align:center}
.btn:active{transform:translateY(1px)}
.btn:focus-visible{outline:3px solid var(--brand);outline-offset:2px}
.btn-primary{background:var(--brand);color:#fff;border-color:var(--brand)}
.btn-primary:hover{background:var(--brand-d);border-color:var(--brand-d)}
.btn-ghost{background:transparent;color:var(--brand);border-color:var(--brand)}
.btn-ghost:hover{background:var(--blue-l)}
.btn-mini{display:inline-flex;align-items:center;justify-content:center;gap:6px;
  font:inherit;font-size:13px;font-weight:700;cursor:pointer;padding:9px 14px;
  border-radius:8px;border:1.5px solid var(--line);background:var(--panel);color:var(--muted);
  transition:all .18s var(--ease);white-space:nowrap}
.btn-mini:hover{border-color:var(--brand);color:var(--brand)}
.btn-ghost:focus-visible,.btn-mini:focus-visible,.btn-end:focus-visible,
.btn-flag:focus-visible,.theme-btn:focus-visible{outline:3px solid var(--brand);outline-offset:2px}

/* ---------- START SCREEN ---------- */
.screen.active#startScreen{display:flex;align-items:flex-start;justify-content:center;min-height:100vh}
#startScreen{background:
  radial-gradient(1100px 520px at 50% -12%, rgba(11,98,201,.10), transparent 62%),
  var(--bg);
  transition:background .2s}
.start-card{width:100%;max-width:540px;margin:6vh auto 0;background:var(--panel);border:1px solid var(--line);
  border-radius:20px;padding:34px 38px 30px;box-shadow:0 14px 44px rgba(20,40,70,.12);text-align:center;
  position:relative;transition:background .2s,border-color .2s}
.start-top{display:flex;justify-content:flex-end;margin:-6px -10px 2px}
.start-hero{display:flex;flex-direction:column;align-items:center;margin-bottom:20px}
.start-card h1{font-size:26px;font-weight:800;letter-spacing:-.4px;line-height:1.15}
.badge{background:var(--brand);color:#fff;font-size:13px;padding:3px 11px;border-radius:20px;
  vertical-align:middle;font-weight:700;letter-spacing:.3px}
.subtitle{color:var(--muted);margin:8px 0 0;font-size:14.5px}

.start-stats{display:grid;grid-template-columns:repeat(4,1fr);gap:10px;margin:0 0 24px}
.start-stats div{background:var(--grey-l);border:1px solid var(--line);border-radius:12px;
  padding:14px 6px;transition:background .2s,border-color .2s}
.start-stats span{display:block;font-size:22px;font-weight:800;color:var(--brand);line-height:1}
.start-stats span .unit{font-size:12px;font-weight:700;color:var(--muted);margin-left:2px}
.start-stats label{display:block;margin-top:6px;font-size:10px;color:var(--muted);
  text-transform:uppercase;letter-spacing:.5px;line-height:1.2}

.start-options{display:flex;flex-direction:column;gap:18px;text-align:left;margin-bottom:24px}
.opt-group{display:flex;flex-direction:column;gap:10px}
.group-title{font-size:12px;font-weight:800;text-transform:uppercase;letter-spacing:.8px;color:var(--muted)}
.chk{display:flex;align-items:center;gap:11px;font-size:14.5px;color:var(--ink);cursor:pointer;
  background:var(--grey-l);border:1px solid var(--line);border-radius:12px;padding:0 14px;min-height:48px;
  transition:border-color .15s,background .15s}
.chk:hover{border-color:var(--brand)}
.chk input{width:18px;height:18px;accent-color:var(--brand);flex:0 0 auto;cursor:pointer}
.chk span{line-height:1.3}

.select-wrap{position:relative}
.select-wrap::after{content:"";position:absolute;right:16px;top:50%;width:9px;height:9px;
  border-right:2px solid var(--muted);border-bottom:2px solid var(--muted);
  transform:translateY(-70%) rotate(45deg);pointer-events:none}
#optMode{width:100%;min-height:48px;padding:0 42px 0 14px;border:1px solid var(--line);border-radius:12px;
  font:inherit;font-size:14.5px;background:var(--panel);color:var(--ink);cursor:pointer;
  appearance:none;-webkit-appearance:none;transition:border-color .15s,background .15s}
#optMode:hover{border-color:var(--brand)}
#optMode:focus-visible{outline:3px solid var(--brand);outline-offset:2px}
.selectlbl{display:block;font-size:12px;font-weight:800;text-transform:uppercase;letter-spacing:.8px;
  color:var(--muted);margin-bottom:8px}
.start-options .domain-picker{margin-top:0}

.btn-block{display:flex;width:100%;min-height:54px;font-size:16px;margin-top:4px;
  box-shadow:0 8px 20px rgba(11,98,201,.22)}
.btn-block:hover{box-shadow:0 10px 26px rgba(11,98,201,.30)}
.btn-block span{transition:transform .15s}
.btn-block:hover span{transform:translateX(3px)}

/* keyboard tutorial */
.kbd-help{position:fixed;inset:0;z-index:900;display:flex;align-items:center;justify-content:center;
  background:rgba(15,23,42,.55);padding:20px}
.kbd-help[hidden]{display:none}
.kbd-help-inner{width:100%;max-width:420px;background:var(--panel);border:1px solid var(--line);
  border-radius:16px;padding:22px 24px;box-shadow:0 18px 50px rgba(20,40,70,.3);text-align:left;
  transition:background .2s,border-color .2s}
.kbd-title{font-size:12px;font-weight:800;text-transform:uppercase;letter-spacing:.6px;color:var(--muted);margin-bottom:12px}
.kbd-grid{display:grid;grid-template-columns:1fr 1fr;gap:10px 20px;margin-bottom:16px}
.kbd-row{display:flex;align-items:center;gap:6px;font-size:12.5px;color:var(--muted);flex-wrap:wrap}
.kbd-row kbd{display:inline-flex;align-items:center;justify-content:center;min-width:22px;height:22px;padding:0 6px;
  font-family:inherit;font-size:12px;font-weight:700;background:var(--panel);border:1px solid var(--line);
  border-bottom-width:2px;border-radius:5px;color:var(--ink)}
.kbd-desc{color:var(--muted)}
.foot{font-size:11px;color:var(--muted);margin-top:18px;line-height:1.5}

/* domain picker chips */
.domain-picker{margin-top:14px}
.domain-chips{display:flex;flex-wrap:wrap;gap:8px;margin-top:8px}
.chip{font:inherit;font-size:13px;cursor:pointer;background:var(--panel);border:1.5px solid var(--line);
  color:var(--ink);padding:7px 11px;border-radius:var(--radius-sm);transition:all .18s var(--ease);display:flex;align-items:center;gap:6px}
.chip b{color:var(--brand)}
.chip .chipcount{font-size:11px;color:var(--muted);background:var(--grey-l);padding:1px 6px;border-radius:var(--radius-pill)}
.chip:hover{border-color:var(--brand)}
.chip.on{border-color:var(--brand);background:var(--blue-l);box-shadow:0 0 0 3px rgba(11,98,201,.10)}
.chip.on .chipcount{background:#dbe9fb;color:var(--brand)}
.chip:focus-visible{outline:3px solid var(--brand);outline-offset:2px}

/* ---------- TOP BAR ---------- */
.topbar{display:flex;justify-content:space-between;align-items:center;background:var(--panel);
  border-bottom:1px solid var(--line);padding:10px 18px;position:sticky;top:0;z-index:10;transition:background .25s var(--ease),border-color .25s var(--ease)}
.top-left{display:flex;align-items:baseline;gap:14px;min-width:0}
.brand{font-weight:800;color:var(--brand);font-size:16px;white-space:nowrap}
.qcounter{color:var(--muted);font-size:14px;font-weight:600;overflow:hidden;text-overflow:ellipsis;white-space:nowrap}
.top-right{display:flex;align-items:center;gap:10px}
.timer{font-variant-numeric:tabular-nums;font-weight:800;font-size:18px;padding:5px 13px;border-radius:var(--radius-sm);
  background:var(--grey-l);letter-spacing:.5px;transition:background .25s var(--ease)}
.timer.warn{background:var(--red-l);color:var(--red)}
.theme-btn{background:var(--panel);border:1px solid var(--line);border-radius:8px;padding:7px 12px;
  font-size:13px;font-weight:700;cursor:pointer;color:var(--ink);transition:all .18s var(--ease)}
.theme-btn:hover{border-color:var(--brand);color:var(--brand)}
.btn-end{background:var(--panel);border:1px solid var(--line);border-radius:8px;padding:8px 14px;font-weight:700;
  font-size:13px;cursor:pointer;color:var(--ink);transition:all .18s var(--ease)}
.btn-end:hover{border-color:var(--red);color:var(--red)}

/* ---------- BODY ---------- */
.body{display:flex;gap:20px;max-width:1100px;margin:0 auto;padding:24px 18px 60px;align-items:flex-start}
.qpanel{flex:1;min-width:0;background:var(--panel);border:1px solid var(--line);border-radius:var(--radius-lg);padding:30px 34px;min-height:60vh;box-shadow:var(--shadow-sm);transition:background .25s var(--ease),border-color .25s var(--ease)}
.flagrow{display:flex;justify-content:space-between;align-items:center;gap:12px;margin-bottom:20px;flex-wrap:wrap}
.btn-flag{background:var(--panel);border:1px solid var(--line);border-radius:var(--radius-pill);padding:7px 14px;font-size:13px;
  cursor:pointer;color:var(--muted);font-weight:600;transition:all .18s var(--ease)}
.btn-flag.on{background:var(--amber-l);border-color:var(--amber);color:var(--amber)}
.btn-flag:focus-visible{outline:3px solid var(--brand);outline-offset:2px}
.multihint{background:var(--blue-l);color:var(--brand);font-size:12px;font-weight:700;padding:5px 12px;border-radius:var(--radius-pill)}
.stem{font-size:15px;line-height:1.55;margin-bottom:22px;white-space:pre-wrap;word-wrap:break-word}
.stem-img{display:block;max-width:100%;height:auto;margin:0 0 22px;border:1px solid var(--line);border-radius:12px;background:var(--bg);padding:10px}
.stem-img[hidden]{display:none}
.options{display:flex;flex-direction:column;gap:12px}
.opt{display:flex;align-items:flex-start;gap:14px;border:1px solid var(--line);border-radius:var(--radius);
  padding:14px 16px;min-height:48px;cursor:pointer;transition:.15s var(--ease);background:var(--panel);outline:none}
.opt:hover{border-color:var(--brand);background:var(--blue-l)}
.opt.sel{border-color:var(--brand);background:var(--blue-l);box-shadow:inset 0 0 0 1px var(--brand)}
.opt:focus-visible{outline:3px solid var(--brand);outline-offset:2px}
.opt .obox{width:24px;height:24px;flex:0 0 24px;border:2px solid var(--line);border-radius:7px;display:flex;
  align-items:center;justify-content:center;font-weight:800;color:var(--brand);margin-top:1px;transition:all .15s var(--ease)}
.opt.sel .obox{background:var(--brand);border-color:var(--brand);color:#fff}
.opt.is-correct{border-color:var(--green);background:var(--green-l)}
.opt.is-correct .obox{background:var(--green);border-color:var(--green);color:#fff}
.opt.is-wrong{border-color:var(--red);background:var(--red-l)}
.opt.is-wrong .obox{background:var(--red);border-color:var(--red);color:#fff}
.opt .otext{font-size:13.5px}
.opt .letter{font-weight:800;margin-right:8px;color:var(--muted)}
.cfg{font-family:var(--mono);font-size:12.5px;line-height:1.5;background:var(--bg);border:1px solid var(--line);border-radius:8px;padding:10px 12px;margin-top:6px;white-space:pre;overflow-x:auto;color:var(--ink)}

.study-feedback{margin-top:16px;padding:12px 16px;border-radius:var(--radius);font-size:14px;font-weight:600;
  border:1.5px solid var(--line);display:none}

/* deep-dive block (why correct / why others wrong / objective) */
.deepdive{margin-top:16px;border:1px solid var(--line);border-radius:var(--radius);background:var(--panel);overflow:hidden}
.deepdive-toggle{cursor:pointer;user-select:none;padding:10px 14px;font-weight:700;font-size:13px;color:var(--brand);
  display:flex;align-items:center;gap:8px;background:var(--blue-l)}
.deepdive-toggle .chev{transition:transform .15s var(--ease)}
.deepdive.open .deepdive-toggle .chev{transform:rotate(90deg)}
.deepdive-body{display:none;padding:12px 16px;white-space:pre-wrap;font-size:13px;line-height:1.6;color:var(--ink)}
.deepdive.open .deepdive-body{display:block}
.deepdive-body b{color:var(--ink)}
.deepdive-body .dd-bullet{display:block;padding-left:18px;text-indent:-15px;margin:2px 0}
.deepdive-body .dd-bullet::before{content:"•";color:var(--muted);margin-right:8px}
.study-feedback.ok{background:var(--green-l);border-color:var(--green);color:var(--green)}
.study-feedback.no{background:var(--red-l);border-color:var(--red);color:var(--red)}
.study-feedback b{font-weight:800}
.study-explain{font-size:13.5px;font-weight:500;color:var(--muted);margin-top:8px;padding-top:8px;border-top:1px dashed var(--line);line-height:1.55}
.study-explain b{color:var(--ink);font-weight:700}
/* nav controls: clear separation from the answer box / study feedback above */
.nav-btns{display:flex;justify-content:space-between;align-items:center;gap:12px;flex-wrap:wrap;margin-top:32px}
.btn-nav{background:var(--panel);border:1px solid var(--line);border-radius:var(--radius-sm);padding:12px 22px;font-weight:700;
  font-size:14px;cursor:pointer;color:var(--ink);transition:all .18s var(--ease)}
.btn-nav:hover:not(:disabled){border-color:var(--brand);color:var(--brand)}
.btn-nav:disabled{opacity:.4;cursor:not-allowed}
.btn-nav:focus-visible{outline:3px solid var(--brand);outline-offset:2px}

/* ---------- NAV PANEL ---------- */
.navpanel{width:230px;flex:0 0 230px;margin-left:20px;background:var(--panel);border:1px solid var(--line);
  border-radius:var(--radius-lg);padding:18px;position:sticky;top:78px;box-shadow:var(--shadow-sm);transition:background .25s var(--ease),border-color .25s var(--ease);min-width:0;overflow:hidden}
.navpanel-head{font-weight:800;font-size:14px;margin-bottom:14px;color:var(--ink)}
.navgrid{display:grid;grid-template-columns:repeat(5,1fr);gap:5px;min-width:0}
.navgrid.big{grid-template-columns:repeat(10,1fr);gap:6px;margin:18px 0}
.navcell{aspect-ratio:1;border:1px solid var(--line);border-radius:7px;display:flex;align-items:center;
  justify-content:center;font-size:11px;font-weight:700;cursor:pointer;background:var(--panel);color:var(--muted);transition:all .15s var(--ease);min-height:36px;min-width:0;overflow:hidden;padding:0 2px}
.navcell:focus-visible{outline:3px solid var(--brand);outline-offset:2px}
.navcell.answered{background:var(--green-l);border-color:var(--green);color:var(--green)}
.navcell.flagged{background:var(--amber-l);border-color:var(--amber);color:var(--amber)}
.navcell.current{border-color:var(--brand);box-shadow:inset 0 0 0 2px var(--brand)}
.navcell.answered.flagged{background:var(--amber-l);border-color:var(--amber);color:var(--amber)}
.navcell.wrong{background:var(--red-l);border-color:var(--red);color:var(--red)}
.legend{margin-top:16px;display:flex;flex-direction:column;gap:6px;font-size:11.5px;color:var(--muted)}
.legend span{display:flex;align-items:center;gap:7px}
.legend .dot{width:11px;height:11px;border-radius:3px;display:inline-block;border:1px solid var(--line)}
.dot.answered{background:var(--green-l);border-color:var(--green)}
.dot.current{box-shadow:inset 0 0 0 2px var(--brand);border-color:var(--brand)}
.dot.flagged{background:var(--amber-l);border-color:var(--amber)}
.dot.blank{background:var(--panel)}
.dot.wrong{background:var(--red-l);border-color:var(--red)}

/* ---------- REVIEW ---------- */
.review-card{max-width:760px;margin:7vh auto 0;background:var(--panel);border:1px solid var(--line);
  border-radius:var(--radius-lg);padding:32px 34px;box-shadow:var(--shadow);transition:background .25s var(--ease),border-color .25s var(--ease)}
.review-card h2{font-size:22px;margin-bottom:8px}
.review-summary{color:var(--muted);font-size:14px;margin-bottom:8px}
.review-actions{display:flex;justify-content:space-between;margin-top:18px;gap:12px}

/* ---------- RESULT ---------- */
.result-card{max-width:620px;margin:6vh auto 0;background:var(--panel);border:1px solid var(--line);
  border-radius:var(--radius-lg);padding:40px;text-align:center;box-shadow:var(--shadow);transition:background .25s var(--ease),border-color .25s var(--ease)}
.score-ring{width:clamp(132px,34vw,160px);aspect-ratio:1;border-radius:50%;margin:0 auto 18px;display:flex;flex-direction:column;
  align-items:center;justify-content:center;border:12px solid var(--green);background:var(--green-l);transition:border-color .25s var(--ease),background .25s var(--ease)}
.score-ring.fail{border-color:var(--red);background:var(--red-l)}
.score-num{font-size:clamp(36px,9vw,46px);font-weight:900;color:var(--green);line-height:1}
.score-ring.fail .score-num{color:var(--red)}
.score-num small{font-size:0.46em}
.score-sub{font-size:12px;color:var(--muted);text-transform:uppercase;letter-spacing:1px;margin-top:2px}
#passMsg{font-size:20px;font-weight:800;margin-bottom:22px}
.result-stats{display:flex;gap:12px;justify-content:center;margin-bottom:22px}
.result-stats div{flex:1;background:var(--grey-l);border-radius:var(--radius);padding:14px 6px;transition:background .25s var(--ease)}
.result-stats span{display:block;font-size:23px;font-weight:800;color:var(--ink)}
.result-stats label{font-size:11px;color:var(--muted);text-transform:uppercase;letter-spacing:.5px}
.breakdown{text-align:left;background:var(--grey-l);border-radius:var(--radius);padding:14px 18px;font-size:13.5px;color:var(--muted);margin-bottom:22px;transition:background .25s var(--ease)}
.breakdown b{color:var(--ink)}
.result-actions{display:flex;justify-content:space-between;gap:12px}

/* ---------- REVIEW INCORRECT ---------- */
.rw-wrap{max-width:820px;margin:5vh auto 60px;padding:0 18px}
.rw-head{display:flex;justify-content:space-between;align-items:center;margin-bottom:18px;flex-wrap:wrap;gap:12px}
.rw-head h2{font-size:22px;font-weight:800}
.rw-count{color:var(--muted);font-weight:600;font-size:15px;margin-left:6px}
.rw-actions{display:flex;gap:10px}
.rw-list{display:flex;flex-direction:column;gap:16px}
.rw-card{background:var(--panel);border:1px solid var(--line);border-radius:var(--radius-lg);padding:20px 22px;box-shadow:var(--shadow-sm);transition:background .25s var(--ease),border-color .25s var(--ease)}
.rw-qhead{display:flex;align-items:center;gap:10px;margin-bottom:10px;flex-wrap:wrap}
.rw-num{font-weight:800;color:var(--brand);font-size:15px}
.rw-dom{font-size:12px;font-weight:700;color:var(--muted);background:var(--grey-l);padding:2px 9px;border-radius:var(--radius-pill)}
.rw-tag{font-size:11px;font-weight:800;text-transform:uppercase;letter-spacing:.5px;padding:2px 9px;border-radius:var(--radius-pill);margin-left:auto}
.rw-tag.correct{background:var(--green-l);color:var(--green)}
.rw-tag.wrong{background:var(--red-l);color:var(--red)}
.rw-tag.blank{background:var(--amber-l);color:var(--amber)}
.rw-stem{font-size:15.5px;line-height:1.6;margin-bottom:14px;white-space:pre-wrap;word-wrap:break-word}
.rw-opts{display:flex;flex-direction:column;gap:8px;margin-bottom:12px}
.rw-opt{display:flex;align-items:flex-start;gap:10px;border:1px solid var(--line);border-radius:var(--radius-sm);padding:11px 13px;min-height:40px;font-size:14.5px;background:var(--panel);transition:background .25s var(--ease),border-color .25s var(--ease)}
.rw-opt .rw-mark{width:16px;font-weight:900;flex:0 0 16px;text-align:center}
.rw-opt .rw-letter{font-weight:800;color:var(--muted)}
.rw-opt.correct{border-color:var(--green);background:var(--green-l)}
.rw-opt.correct .rw-mark{color:var(--green)}
.rw-opt.correct .rw-letter{color:var(--green)}
.rw-opt.yours{border-color:var(--red);background:var(--red-l)}
.rw-opt.yours .rw-mark{color:var(--red)}
.rw-opt.yours .rw-letter{color:var(--red)}
.rw-answer{font-size:14px;background:var(--grey-l);border-radius:var(--radius-sm);padding:10px 14px;transition:background .25s var(--ease)}
.rw-answer .rw-yours{color:var(--red);font-weight:700}

.rw-toolbar{display:flex;justify-content:space-between;align-items:center;gap:12px;margin-bottom:14px;flex-wrap:wrap}
.rw-filter-chips{display:flex;flex-wrap:wrap;gap:6px}
.rw-fchip{font:inherit;font-size:12.5px;cursor:pointer;background:var(--panel);border:1.5px solid var(--line);
  color:var(--muted);padding:5px 11px;border-radius:var(--radius-pill);transition:all .18s var(--ease)}
.rw-fchip:hover{border-color:var(--brand)}
.rw-fchip.on{border-color:var(--brand);background:var(--blue-l);color:var(--brand);font-weight:700}
.rw-fchip:focus-visible{outline:3px solid var(--brand);outline-offset:2px}
.rw-toolbar-right{display:flex;gap:8px}

.rw-jumpnav{display:flex;flex-wrap:wrap;gap:5px;margin-bottom:20px;padding:12px;background:var(--grey-l);border-radius:var(--radius);transition:background .25s var(--ease)}
.rw-jbtn{width:30px;height:30px;border-radius:7px;border:1px solid var(--line);background:var(--panel);font-size:11px;
  font-weight:700;cursor:pointer;color:var(--red);display:flex;align-items:center;justify-content:center;transition:all .15s var(--ease)}
.rw-jbtn.blank{color:var(--amber)}
.rw-jbtn.ok{color:var(--green)}
.rw-jbtn:hover{box-shadow:0 0 0 2px rgba(11,98,201,.25)}
.rw-jbtn:focus-visible{outline:3px solid var(--brand);outline-offset:2px}

.rw-card{cursor:default}
.rw-qhead{cursor:pointer;user-select:none}
.rw-qhead .rw-chev{margin-left:auto;transition:transform .15s var(--ease);color:var(--muted);font-size:13px}
.rw-qhead .rw-tag{margin-left:0}
.rw-qhead .rw-chev{order:99}
.rw-card.collapsed .rw-body{display:none}
.rw-card.collapsed .rw-chev{transform:rotate(-90deg)}
.rw-explain{font-size:13.5px;color:var(--muted);margin-top:6px;padding-left:2px;line-height:1.55}
.rw-explain b{color:var(--ink)}

/* ---------- responsive / mobile ---------- */
@media(max-width:820px){
  .body{flex-direction:column;padding-bottom:104px}
  /* Question is the hero; navigator becomes a scrollable, big-tappable strip docked at the bottom */
  .navpanel{position:fixed;left:0;right:0;bottom:0;top:auto;width:auto;flex:none;margin:0;
    border-radius:14px 14px 0 0;border-bottom:none;padding:10px 12px 12px;z-index:40;
    box-shadow:0 -8px 24px rgba(20,40,70,.16)}
  .navpanel-head{font-size:12px;margin-bottom:8px;color:var(--muted)}
  .navgrid{grid-auto-flow:column;grid-template-columns:none;grid-auto-columns:minmax(46px,1fr);
    overflow-x:auto;padding-bottom:4px;-webkit-overflow-scrolling:touch;scrollbar-width:thin}
  .navcell{aspect-ratio:auto;min-height:46px;min-width:46px;padding:0 4px}
  .legend{flex-direction:row;flex-wrap:wrap;gap:10px;font-size:11px}
  .result-actions,.review-actions,.rw-actions{flex-direction:column-reverse}
  .result-actions .btn,.review-actions .btn,.rw-actions .btn{width:100%}
  /* full-width, tappable navigation controls */
  .nav-btns{flex-direction:column-reverse}
  .nav-btns .btn-nav{width:100%}
  .btn,.btn-nav{min-height:46px;font-size:15px}
  .qpanel{padding:24px 20px}
  .start-card{padding:30px 22px 26px}
  .review-card,.result-card{padding:26px 22px}
  .rw-card{padding:18px 16px}
}
@media(max-width:560px){
  .rw-jumpnav{gap:6px;padding:10px}
  .rw-jbtn{width:36px;height:36px}
}
@media(max-width:480px){
  .topbar{padding:10px 14px;gap:8px}
  .brand{font-size:14px}
  .top-right{gap:8px}
  .qcounter{font-size:12.5px}
  .timer{font-size:16px;padding:4px 10px}
  /* start screen: single-column shortcuts + tighter stats for small phones */
  .kbd-grid{grid-template-columns:1fr}
  .start-stats{grid-template-columns:repeat(2,1fr)}
  .start-stats label{font-size:9.5px}
  .start-card h1{font-size:25px}
}