:root{
  --bg-a: #8b5cf6;
  --bg-b: #22c55e;
  --bg-c: #06b6d4;
  --text: #0b1220;
  --muted: rgba(11,18,32,.68);

  --card: rgba(255,255,255,.72);
  --card-2: rgba(255,255,255,.58);
  --border: rgba(255,255,255,.38);
  --shadow: 0 12px 34px rgba(0,0,0,.12);

  --accent: #2563eb;
  --accent-2: #7c3aed;
  --good: #16a34a;
  --bad: #dc2626;

  --radius: 18px;
  --radius-sm: 14px;

  --tap: 0.98;
}

@media (prefers-color-scheme: dark){
  :root{
    --text: rgba(255,255,255,.92);
    --muted: rgba(255,255,255,.66);

    --card: rgba(18,22,33,.62);
    --card-2: rgba(18,22,33,.48);
    --border: rgba(255,255,255,.14);
    --shadow: 0 18px 42px rgba(0,0,0,.42);

    --accent: #60a5fa;
    --accent-2: #a78bfa;
    --good: #22c55e;
    --bad: #fb7185;
  }
}

*{ box-sizing: border-box; }
html,body{ height: 100%; }
body{
  margin: 0;
  font-family: ui-sans-serif, system-ui, -apple-system, "SF Pro Display", "SF Pro Text", Segoe UI, Roboto, Helvetica, Arial, "Apple Color Emoji","Segoe UI Emoji";
  color: var(--text);
  background: radial-gradient(1100px 700px at 15% 10%, rgba(139,92,246,.55), transparent 60%),
              radial-gradient(900px 650px at 85% 20%, rgba(34,197,94,.45), transparent 55%),
              radial-gradient(1000px 700px at 50% 95%, rgba(6,182,212,.45), transparent 60%),
              linear-gradient(180deg, rgba(255,255,255,.55), rgba(255,255,255,.35));
  background-attachment: fixed;
  overflow-x: hidden;
}

@media (prefers-color-scheme: dark){
  body{
    background: radial-gradient(1100px 700px at 15% 10%, rgba(139,92,246,.35), transparent 60%),
                radial-gradient(900px 650px at 85% 20%, rgba(34,197,94,.28), transparent 55%),
                radial-gradient(1000px 700px at 50% 95%, rgba(6,182,212,.28), transparent 60%),
                linear-gradient(180deg, rgba(0,0,0,.55), rgba(0,0,0,.75));
  }
}

.noise{
  position: fixed;
  inset: 0;
  pointer-events: none;
  opacity: .10;
  mix-blend-mode: overlay;
  background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='240' height='240'%3E%3Cfilter id='n'%3E%3CfeTurbulence type='fractalNoise' baseFrequency='.85' numOctaves='3' stitchTiles='stitch'/%3E%3C/filter%3E%3Crect width='240' height='240' filter='url(%23n)' opacity='.65'/%3E%3C/svg%3E");
}

.container{
  width: min(980px, 100%);
  margin: 0 auto;
  padding: 20px 16px 96px;
}

.topbar{
  position: sticky;
  top: 0;
  z-index: 20;
  padding-top: 14px;
  padding-bottom: 12px;
}

.topbar-inner{
  border-radius: 22px;
  border: 1px solid var(--border);
  background: var(--card-2);
  box-shadow: var(--shadow);
  padding: 14px 14px 12px;
  overflow: hidden;
  -webkit-backdrop-filter: blur(18px) saturate(155%);
  backdrop-filter: blur(18px) saturate(155%);
  background-clip: padding-box;
  isolation: isolate;
}

.row{
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 10px;
  flex-wrap: wrap;
}

.h1{
  font-size: 18px;
  font-weight: 750;
  letter-spacing: .2px;
  display: flex;
  align-items: center;
  gap: 10px;
}

.badge{
  font-size: 12px;
  font-weight: 650;
  padding: 6px 10px;
  border-radius: 999px;
  border: 1px solid var(--border);
  background: rgba(255,255,255,.28);
}
@media (prefers-color-scheme: dark){
  .badge{ background: rgba(0,0,0,.22); }
}

.muted{ color: var(--muted); font-size: 13px; }

.actions{
  display: flex;
  align-items: center;
  gap: 10px;
}

.btn{
  border: 1px solid var(--border);
  background: rgba(255,255,255,.28);
  color: var(--text);
  border-radius: 999px;
  padding: 10px 12px;
  font-weight: 700;
  font-size: 13px;
  cursor: pointer;
  user-select: none;
  transition: transform .06s ease, background .2s ease, border-color .2s ease, box-shadow .2s ease;
}
@media (prefers-color-scheme: dark){
  .btn{ background: rgba(0,0,0,.22); }
}
.btn:hover{ background: rgba(255,255,255,.36); }
@media (prefers-color-scheme: dark){
  .btn:hover{ background: rgba(255,255,255,.08); }
}
.btn:active{ transform: scale(var(--tap)); }

.btn.primary{
  border-color: rgba(37,99,235,.55);
  background: linear-gradient(135deg, rgba(37,99,235,.95), rgba(124,58,237,.90));
  color: white;
  box-shadow: 0 12px 30px rgba(37,99,235,.28);
}
.btn.primary[disabled]{
  opacity: .55;
  cursor: not-allowed;
  box-shadow: none;
  background: rgba(148,163,184,.35);
  border-color: rgba(148,163,184,.35);
  color: var(--text);
}

.btn.ghost{
  background: transparent;
}

.progress{
  margin-top: 10px;
  height: 10px;
  width: 100%;
  border-radius: 999px;
  border: 1px solid var(--border);
  overflow: hidden;
  background: rgba(255,255,255,.20);
}
@media (prefers-color-scheme: dark){
  .progress{ background: rgba(0,0,0,.18); }
}
.progress > div{
  height: 100%;
  width: 0%;
  border-radius: 999px;
  background: linear-gradient(90deg, var(--accent), var(--accent-2));
  transition: width .25s ease;
}

.tools{
  display: flex;
  gap: 10px;
  flex-wrap: wrap;
  margin-top: 10px;
}

.input{
  border: 1px solid var(--border);
  background: rgba(255,255,255,.28);
  color: var(--text);
  border-radius: 999px;
  padding: 10px 12px;
  font-weight: 650;
  font-size: 13px;
  outline: none;
  width: 160px;
}
@media (prefers-color-scheme: dark){
  .input{ background: rgba(0,0,0,.22); }
}
.input::placeholder{ color: rgba(127,140,160,.9); }
@media (prefers-color-scheme: dark){
  .input::placeholder{ color: rgba(200,210,230,.55); }
}

.card{
  border-radius: var(--radius);
  border: 1px solid var(--border);
  background: var(--card);
  box-shadow: var(--shadow);
  padding: 14px 14px;
  margin-top: 14px;
  backdrop-filter: blur(16px) saturate(150%);
}

.qhead{
  display: flex;
  align-items: flex-start;
  justify-content: space-between;
  gap: 12px;
}

.qnum{
  font-weight: 850;
  font-size: 13px;
  padding: 6px 10px;
  border-radius: 999px;
  border: 1px solid var(--border);
  background: rgba(255,255,255,.24);
  flex: 0 0 auto;
}
@media (prefers-color-scheme: dark){
  .qnum{ background: rgba(0,0,0,.18); }
}

.qtext{
  font-size: 15px;
  line-height: 1.35;
  font-weight: 720;
}

.opts{
  margin-top: 12px;
  display: grid;
  grid-template-columns: 1fr;
  gap: 10px;
}

.opt{
  display: flex;
  align-items: center;
  gap: 10px;
  padding: 12px 12px;
  border-radius: var(--radius-sm);
  border: 1px solid var(--border);
  background: rgba(255,255,255,.22);
  cursor: pointer;
  transition: transform .06s ease, background .2s ease, border-color .2s ease;
  user-select: none;
}
@media (prefers-color-scheme: dark){
  .opt{ background: rgba(0,0,0,.18); }
}
.opt:active{ transform: scale(var(--tap)); }

.pill{
  width: 28px;
  height: 28px;
  border-radius: 999px;
  display: grid;
  place-items: center;
  font-weight: 900;
  font-size: 13px;
  border: 1px solid var(--border);
  background: rgba(255,255,255,.26);
  flex: 0 0 auto;
}
@media (prefers-color-scheme: dark){
  .pill{ background: rgba(0,0,0,.20); }
}

.opt.selected{
  border-color: rgba(37,99,235,.55);
  background: rgba(37,99,235,.12);
}
.opt.selected .pill{
  border-color: rgba(37,99,235,.55);
  background: linear-gradient(135deg, rgba(37,99,235,.92), rgba(124,58,237,.82));
  color: white;
}

.opt.correct{
  border-color: rgba(22,163,74,.65);
  background: rgba(22,163,74,.14);
}
.opt.correct .pill{
  border-color: rgba(22,163,74,.65);
  background: rgba(22,163,74,.24);
}

.opt.wrong{
  border-color: rgba(220,38,38,.65);
  background: rgba(220,38,38,.12);
}
.opt.wrong .pill{
  border-color: rgba(220,38,38,.65);
  background: rgba(220,38,38,.20);
}

.bottombar{
  position: fixed;
  left: 0;
  right: 0;
  bottom: 0;
  z-index: 25;
  padding: 12px 14px;
}

.bottom-inner{
  width: min(980px, 100%);
  margin: 0 auto;
  border-radius: 22px;
  border: 1px solid var(--border);
  background: var(--card-2);
  box-shadow: var(--shadow);
  padding: 12px 12px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 12px;
  overflow: hidden;
  -webkit-backdrop-filter: blur(18px) saturate(155%);
  backdrop-filter: blur(18px) saturate(155%);
  background-clip: padding-box;
  isolation: isolate;
}

.kpis{
  display: grid;
  gap: 2px;
}
.kpis .big{
  font-weight: 900;
  font-size: 14px;
}
.kpis .small{
  font-size: 12px;
  color: var(--muted);
  font-weight: 650;
}

.modal{
  position: fixed;
  inset: 0;
  z-index: 40;
  display: none;
  align-items: center;
  justify-content: center;
  padding: 18px;
  background: rgba(0,0,0,.38);
}
.modal.show{ display: flex; }
.sheet{
  width: min(940px, 100%);
  max-height: min(82vh, 840px);
  overflow: auto;
  border-radius: 26px;
  border: 1px solid var(--border);
  background: var(--card);
  box-shadow: var(--shadow);
  backdrop-filter: blur(18px) saturate(150%);
  padding: 14px;
}
.sheet-head{
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: 10px;
  margin-bottom: 12px;
}
.sheet-title{
  font-weight: 900;
  font-size: 16px;
}
.grid{
  display: grid;
  grid-template-columns: repeat(10, minmax(0, 1fr));
  gap: 8px;
  padding-bottom: 10px;
}
@media (max-width: 520px){
  .grid{ grid-template-columns: repeat(6, minmax(0, 1fr)); }
}
.pip{
  border-radius: 14px;
  padding: 10px 0;
  text-align: center;
  font-weight: 900;
  font-size: 13px;
  border: 1px solid var(--border);
  background: rgba(255,255,255,.22);
  cursor: pointer;
  transition: transform .06s ease, background .2s ease, border-color .2s ease;

  position: relative;
}
@media (prefers-color-scheme: dark){
  .pip{ background: rgba(0,0,0,.18); }
}
.pip:active{ transform: scale(var(--tap)); }
.pip.ans{ border-color: rgba(37,99,235,.55); background: rgba(37,99,235,.12); }
.pip.good{
  border-color: rgba(22,163,74,.92);
  background: linear-gradient(135deg, rgba(22,163,74,.98), rgba(34,197,94,.86));
  color: rgba(255,255,255,.96);
  text-shadow: 0 1px 0 rgba(0,0,0,.18);
}
.pip.bad{
  border-color: rgba(220,38,38,.92);
  background: linear-gradient(135deg, rgba(220,38,38,.98), rgba(244,63,94,.86));
  color: rgba(255,255,255,.96);
  text-shadow: 0 1px 0 rgba(0,0,0,.18);
}

.result{
  margin-top: 12px;
  display: grid;
  gap: 10px;
}
.result .score{
  font-size: 20px;
  font-weight: 950;
  letter-spacing: .2px;
}
.result .meta{
  display: flex;
  gap: 8px;
  flex-wrap: wrap;
}
.chip{
  padding: 8px 10px;
  border-radius: 999px;
  border: 1px solid var(--border);
  background: rgba(255,255,255,.22);
  font-weight: 800;
  font-size: 12px;
}
@media (prefers-color-scheme: dark){
  .chip{ background: rgba(0,0,0,.18); }
}

hr.sep{
  border: 0;
  height: 1px;
  background: rgba(255,255,255,.22);
  margin: 12px 0;
}
@media (prefers-color-scheme: dark){
  hr.sep{ background: rgba(255,255,255,.10); }
}
/* Desktop polish + list grid */
.listgrid{
  display: grid;
  grid-template-columns: 1fr;
  gap: 14px;
}

#sentinel{
  height: 1px;
}

@media (min-width: 900px){
  .container{
    width: min(1200px, 100%);
    padding: 26px 20px 96px;
  }
  .topbar-inner{
    padding: 16px 16px 14px;
  }
  .h1{
    font-size: 20px;
  }
  .muted{
    font-size: 14px;
  }
  .card{
    padding: 16px 16px;
  }
  .qtext{
    font-size: 16px;
    line-height: 1.42;
  }
  .opt{
    padding: 13px 13px;
  }
  .pill{
    width: 30px;
    height: 30px;
    font-size: 13px;
  }
  .listgrid{
    grid-template-columns: repeat(2, minmax(0, 1fr));
    gap: 16px;
  }
}

@media (min-width: 1280px){
  .listgrid{
    gap: 18px;
  }
}
/* Scroll offset so sticky topbar doesn't cover question when jumping */
.card{
  scroll-margin-top: 140px; /* fallback, JS will handle dynamic offset too */
}

@media (min-width: 900px){
  .card{ scroll-margin-top: 160px; }
}

/* Grid (Bảng câu) clearer states */
.pip.todo{
  opacity: .65;
  background: rgba(255,255,255,.14);
}
@media (prefers-color-scheme: dark){
  .pip.todo{ background: rgba(255,255,255,.06); opacity: .7; }
}

.pip.ans{
  border-color: rgba(37,99,235,.70);
  background: rgba(37,99,235,.18);
}

.pip.good{
  border-color: rgba(22,163,74,.85);
  background: rgba(22,163,74,.22);
}

.pip.bad{
  border-color: rgba(220,38,38,.85);
  background: rgba(220,38,38,.20);
}
/* Top header alignment on desktop: avoid "lệch" when left has 2 lines */
.headrow{
  align-items: flex-start;
}
.headrow .actions{
  margin-top: 2px;
}

/* Tools row: keep it clean & compact */
.tools{
  align-items: center;
}
/* Voice2sub button (soft gradient, clearly a button) */
.brand{
  text-decoration: none;
  font-size: 12.5px;
  font-weight: 900;
  padding: 8px 12px;
  border-radius: 999px;
  border: 1px solid rgba(37,99,235,.32);
  color: rgba(255,255,255,.96);
  background: linear-gradient(135deg, rgba(37,99,235,.86), rgba(124,58,237,.70));
  box-shadow: 0 10px 22px rgba(37,99,235,.18);
  transition: transform .06s ease, filter .2s ease, box-shadow .2s ease;
  display: inline-flex;
  align-items: center;
  gap: 8px;
}
@media (prefers-color-scheme: dark){
  .brand{
    border-color: rgba(96,165,250,.28);
    box-shadow: 0 14px 28px rgba(96,165,250,.14);
  }
}
.brand:hover{
  filter: brightness(1.04);
  box-shadow: 0 14px 30px rgba(37,99,235,.22);
}
.brand:active{ transform: scale(var(--tap)); }


/* Corner marks for grid status */
.pip.good::after,
.pip.bad::after{
  position: absolute;
  top: 4px;
  right: 6px;
  font-size: 12px;
  font-weight: 950;
  opacity: .95;
}
.pip.good::after{ content: "✓"; }
.pip.bad::after{ content: "✕"; }


/* Premium UI upgrade */
:root{
  --hairline: rgba(255,255,255,.34);
  --hairline-dark: rgba(255,255,255,.12);
  --glow: 0 18px 44px rgba(0,0,0,.12);
}
@media (prefers-color-scheme: dark){
  :root{ --glow: 0 22px 52px rgba(0,0,0,.44); }
}

/* Make the main glass blocks look more "iOS" */
.topbar-inner,
.bottom-inner{
  box-shadow: var(--glow);
  border-color: rgba(255,255,255,.34);
}
@media (prefers-color-scheme: dark){
  .topbar-inner,
  .bottom-inner{
    border-color: rgba(255,255,255,.14);
  }
}

/* Question cards: add subtle gradient + crisper border */
.card{
  border-color: rgba(255,255,255,.34);
  background: linear-gradient(180deg, rgba(255,255,255,.76), rgba(255,255,255,.64));
}
@media (prefers-color-scheme: dark){
  .card{
    border-color: rgba(255,255,255,.12);
    background: linear-gradient(180deg, rgba(18,22,33,.68), rgba(18,22,33,.54));
  }
}

.qnum{
  background: linear-gradient(180deg, rgba(255,255,255,.30), rgba(255,255,255,.18));
}
@media (prefers-color-scheme: dark){
  .qnum{ background: rgba(0,0,0,.18); }
}

/* Option tiles: iOS radio look + better separation */
.opt{
  border-color: rgba(255,255,255,.32);
  background: linear-gradient(180deg, rgba(255,255,255,.30), rgba(255,255,255,.18));
  box-shadow: inset 0 1px 0 rgba(255,255,255,.40);
}
@media (prefers-color-scheme: dark){
  .opt{
    border-color: rgba(255,255,255,.14);
    background: linear-gradient(180deg, rgba(255,255,255,.06), rgba(0,0,0,.14));
    box-shadow: inset 0 1px 0 rgba(255,255,255,.08);
  }
}

.opt:hover{
  background: linear-gradient(180deg, rgba(255,255,255,.36), rgba(255,255,255,.20));
}
@media (prefers-color-scheme: dark){
  .opt:hover{
    background: linear-gradient(180deg, rgba(255,255,255,.08), rgba(0,0,0,.10));
  }
}

/* Selected: clearer but still classy */
.opt.selected{
  border-color: rgba(37,99,235,.55);
  background: linear-gradient(180deg, rgba(37,99,235,.14), rgba(124,58,237,.10));
  box-shadow: 0 10px 22px rgba(37,99,235,.10), inset 0 1px 0 rgba(255,255,255,.35);
}
.opt.selected .pill{
  border-color: rgba(37,99,235,.50);
  background: linear-gradient(135deg, rgba(37,99,235,.86), rgba(124,58,237,.72));
}

/* After submit: make correct/wrong pop without being harsh */
.opt.correct{
  border-color: rgba(22,163,74,.70);
  background: linear-gradient(180deg, rgba(22,163,74,.18), rgba(34,197,94,.10));
}
.opt.wrong{
  border-color: rgba(220,38,38,.70);
  background: linear-gradient(180deg, rgba(220,38,38,.16), rgba(244,63,94,.08));
}

/* Make answer tail easier to scan */
.card .muted b{
  font-weight: 950;
}

/* Mobile polish */
@media (max-width: 520px){
  .container{ padding: 16px 14px 110px; }
  .topbar-inner{ padding: 14px 12px 12px; }
  .h1{ font-size: 18px; }
  .card{ padding: 14px 12px; }
  .qtext{ font-size: 15.5px; line-height: 1.42; }
  .opt{ padding: 13px 12px; }
  .pill{ width: 30px; height: 30px; }
  .bottom-inner{ padding: 12px 12px; }
}


/* Compact mobile topbar (more content on screen) */
@media (max-width: 520px){
  .topbar{ padding-top: 10px; padding-bottom: 8px; }
  .topbar-inner{ padding: 10px 10px 10px; border-radius: 18px; }
  .h1{ font-size: 16px; gap: 8px; }
  .brand{ padding: 6px 10px; font-size: 12px; }
  #subTitle{ display: none; }
  .progress{ height: 8px; margin-top: 8px; }
  .tools{ margin-top: 8px; gap: 8px; }
  .tools .input{ width: 130px; padding: 9px 10px; font-size: 13px; }
  .tools .btn{ padding: 9px 11px; font-size: 13px; }
}