/* ============================================================================
   LUYEN GIAI TOAN VAO 10 — dung chung mau + font voi thuchanh-style.css / dethi-style.css
   de dong bo giao dien toan site. Tat ca class dat tien to "lg10-" va nam trong
   .lg10-scope de khong dam vao CSS san co cua theme.
   ============================================================================ */
.lg10-scope{
  --lg10-ink:#20242b;
  --lg10-ink-soft:#5b6472;
  --lg10-line:#e7e9ee;
  --lg10-bg:#f5f6f9;
  --lg10-card:#ffffff;
  --lg10-red:#ae1f2b;
  --lg10-red-dark:#7d1620;
  --lg10-orange:#f96511;
  --lg10-gold:#ffd304;
  --lg10-green:#2e9e5b;
  --lg10-blue:#2b5fd9;
  --lg10-blue-dark:#1c3f96;
  --lg10-purple:#7a4fd6;
  --lg10-purple-dark:#5a34b0;
  --lg10-radius:16px;
  --lg10-shadow:0 6px 24px rgba(20,24,34,.08);
  --lg10-shadow-lg:0 18px 40px rgba(20,24,34,.14);
  font-family:'Noto Sans','Segoe UI',Roboto,Helvetica,Arial,sans-serif;
  color:var(--lg10-ink);
  background:var(--lg10-bg);
  line-height:1.5;
  -webkit-font-smoothing:antialiased;
}
.lg10-scope *{ box-sizing:border-box; }
.lg10-scope a{ text-decoration:none; }
.lg10-scope .lg10-container{ max-width:1180px; margin:0 auto; padding:0 16px; }
.lg10-scope h1, .lg10-scope h2, .lg10-scope h3, .lg10-scope h4, .lg10-scope h5, .lg10-scope h6{
  /* FIX: css/style-menu.css dat rieng font-family cho the h1..h6 (Arial/Open Sans) bang
     selector khong lop (h1,h2,...) - selector nay du specificity thap hon .lg10-scope
     nhung lai KHOP TRUC TIEP voi the h, nen ghi de mat gia tri font ke thua tu .lg10-scope
     (quy tac CSS: gia tri khop truc tiep luon thang gia tri ke thua, bat ke specificity).
     Ep lai font-family:inherit de cac tieu de dung dung font Noto Sans nhu phan noi dung. */
  font-family:inherit;
}
.lg10-scope h1, .lg10-scope h2, .lg10-scope h3, .lg10-scope h4,
.lg10-scope h1 *, .lg10-scope h2 *, .lg10-scope h3 *, .lg10-scope h4 *{
  text-shadow:none !important; -webkit-text-fill-color:currentColor !important;
  background:none !important; -webkit-background-clip:initial !important; background-clip:initial !important;
}

.lg10-scope .breadcrumb{ display:none; }
.lg10-crumb{ display:flex; align-items:center; gap:8px; font-size:13.5px; color:var(--lg10-ink-soft); margin:0 0 16px; }
.lg10-crumb a, .lg10-crumb-home{ color:var(--lg10-blue); font-weight:600; }
.lg10-crumb-home{ display:inline-flex; align-items:center; }
.lg10-crumb i{ font-size:11px; color:var(--lg10-ink-soft); }
.lg10-page{ padding-bottom:36px; }

.lg10-hub-hero{ display:flex; align-items:center; justify-content:space-between; gap:24px; margin:6px 0 22px; }
.lg10-hub-head{ margin:0; }
.lg10-hub-head h1{ font-size:27px; font-weight:800; margin:0 0 8px; color:var(--lg10-ink); }
.lg10-hub-head h1 span{ color:var(--lg10-red); }
.lg10-hub-head p{ margin:0; color:var(--lg10-ink-soft); font-size:14px; max-width:560px; }

.lg10-hub-illus{ position:relative; flex:none; width:190px; height:150px; display:none; }
@media (min-width:860px){ .lg10-hub-illus{ display:block; } }
.lg10-hub-illus-blob{
  position:absolute; inset:6px; border-radius:46% 54% 55% 45% / 45% 45% 55% 55%;
  background:linear-gradient(135deg,#eaf1ff,#dfeaff);
}
.lg10-hub-illus-book{
  position:absolute; left:50%; top:56%; transform:translate(-50%,-50%); width:86px; height:86px; border-radius:22px;
  background:#fff; box-shadow:var(--lg10-shadow-lg); display:flex; align-items:center; justify-content:center;
  font-size:34px; color:var(--lg10-blue);
}
.lg10-hub-illus-pencil{
  position:absolute; right:10px; top:2px; width:42px; height:42px; border-radius:50%;
  background:linear-gradient(135deg,var(--lg10-blue),var(--lg10-blue-dark)); color:#fff; display:flex;
  align-items:center; justify-content:center; font-size:17px; transform:rotate(18deg);
  box-shadow:0 10px 18px -8px var(--lg10-blue);
}
.lg10-hub-illus-badge{
  position:absolute; width:34px; height:34px; border-radius:50%; background:#fff; box-shadow:var(--lg10-shadow);
  display:flex; align-items:center; justify-content:center; font-weight:800; font-size:12.5px; color:var(--lg10-blue);
}
.lg10-hub-illus-badge-1{ left:0; top:14px; }
.lg10-hub-illus-badge-2{ right:18px; bottom:6px; color:var(--lg10-red); }

.lg10-chuong-list{ display:flex; flex-direction:column; gap:14px; }
.lg10-chuong-card{
  display:flex; flex-direction:column; align-items:stretch; text-decoration:none; background:var(--lg10-card);
  border:1px solid var(--lg10-line); border-radius:16px; box-shadow:var(--lg10-shadow); overflow:hidden;
  transition:box-shadow .15s ease, transform .1s ease;
}
.lg10-chuong-card:hover{ transform:translateY(-1px); box-shadow:var(--lg10-shadow-lg); }
.lg10-chuong-card .lg10-dang-card-meta{ display:flex; align-items:center; gap:6px; }
.lg10-chuong-top{ display:flex; align-items:stretch; min-height:82px; }
.lg10-chuong-top .lg10-dang-ribbon{ border-radius:0; }
.lg10-chuong-stats{
  display:grid; grid-template-columns:repeat(4,1fr); gap:10px; border-top:1px solid var(--lg10-line);
  padding:14px 18px 16px 18px;
}
.lg10-stat-item{ display:flex; align-items:center; gap:10px; min-width:0; }
.lg10-stat-icon{
  flex:none; width:36px; height:36px; border-radius:50%; display:flex; align-items:center; justify-content:center;
  font-size:14px;
}
.lg10-stat-item div{ display:flex; flex-direction:column; min-width:0; }
.lg10-stat-item b{ font-size:14px; font-weight:800; color:var(--lg10-ink); line-height:1.3; }
.lg10-stat-item span{ font-size:11px; color:var(--lg10-ink-soft); line-height:1.3; white-space:nowrap; overflow:hidden; text-overflow:ellipsis; }

.lg10-empty{
  text-align:center; padding:52px 20px; background:var(--lg10-card); border:1px dashed var(--lg10-line);
  border-radius:var(--lg10-radius); color:var(--lg10-ink-soft);
}

.lg10-detail-head{ margin:6px 0 22px; }
.lg10-detail-head h1{ font-size:24px; font-weight:800; margin:0 0 8px; color:var(--lg10-ink); }

.lg10-pdf-bar{ display:flex; flex-wrap:wrap; gap:10px; margin-top:4px; }
.lg10-pdf-btn{
  display:inline-flex; align-items:center; gap:6px; font-size:12.5px; font-weight:700; color:var(--lg10-ink);
  background:#fff; border:1.5px solid var(--lg10-line); padding:8px 14px; border-radius:999px; cursor:pointer;
  white-space:nowrap;
}
.lg10-pdf-btn:hover{ border-color:var(--lg10-red); color:var(--lg10-red); }
.lg10-pdf-btn-alt{ background:#fff8f2; border-color:#ffd9bd; color:var(--lg10-orange); }
.lg10-pdf-btn-alt:hover{ border-color:var(--lg10-orange); color:var(--lg10-orange); }
.lg10-pdf-btn-sm{ padding:8px 12px; font-size:12px; }

.lg10-method-box{
  background:var(--lg10-card); border:1px solid var(--lg10-line); border-left:4px solid var(--lg10-red);
  border-radius:var(--lg10-radius); box-shadow:var(--lg10-shadow); padding:22px 24px; font-size:14.5px; line-height:1.8;
  margin-bottom:30px;
}
.lg10-method-box h4{ color:var(--lg10-ink); font-weight:800; margin:18px 0 10px; }
.lg10-method-box h4:first-child{ margin-top:0; }
.lg10-method-box p{ margin:0 0 12px; }
.lg10-method-box ol, .lg10-method-box ul{ margin:0 0 14px; padding-left:22px; }
.lg10-method-box li{ margin-bottom:10px; }
.lg10-method-box strong{ color:var(--lg10-red); }
.lg10-method-box .katex-display{ margin:10px 0; padding:10px 12px; background:var(--lg10-bg); border-radius:10px; overflow-x:auto; }
.lg10-note{
  background:#fff8f2; border:1.5px dashed var(--lg10-orange); border-radius:12px; padding:14px 16px;
  font-size:13.5px; color:var(--lg10-ink-soft); margin-top:16px;
}
.lg10-note b{ color:var(--lg10-orange); }

/* ---------- Lý thuyết: khoi kien thuc co ban (badge + cong thuc dang hang) ---------- */
.lg10-mk-head{ display:flex; align-items:center; gap:12px; margin:22px 0 14px; }
.lg10-mk-head:first-child{ margin-top:0; }
.lg10-mk-badge{
  flex:none; width:32px; height:32px; border-radius:9px; background:var(--lg10-red); color:#fff;
  display:flex; align-items:center; justify-content:center; font-weight:900; font-size:15px;
  box-shadow:0 8px 16px -8px var(--lg10-red);
}
.lg10-mk-head h4{ margin:0; font-size:17px; font-weight:800; color:var(--lg10-ink); }
.lg10-mk-sub{
  display:flex; align-items:center; gap:8px; margin:0 0 12px; font-size:13px; font-weight:700;
  color:var(--lg10-ink-soft); text-transform:uppercase; letter-spacing:.2px;
}
.lg10-mk-sub i{ color:var(--lg10-red); font-size:13px; }
.lg10-formula-list{ display:flex; flex-direction:column; gap:8px; margin-bottom:16px; }
.lg10-formula-row{ display:flex; align-items:flex-start; gap:14px; background:#fdf5f6; border-radius:12px; padding:13px 16px; }
.lg10-formula-num{
  flex:none; width:26px; height:26px; border-radius:50%; background:#f8d9dc; color:var(--lg10-red-dark);
  display:flex; align-items:center; justify-content:center; font-weight:800; font-size:12.5px; margin-top:1px;
}
.lg10-formula-body{ flex:1; min-width:0; display:flex; gap:18px; align-items:flex-start; }
.lg10-formula-label{
  flex:0 0 190px; font-weight:800; font-size:13.5px; color:var(--lg10-red-dark); line-height:1.5;
  padding-right:16px; border-right:1px solid #f0d3d6;
}
.lg10-formula-eq{ flex:1; min-width:0; font-size:14.5px; line-height:1.7; }
.lg10-formula-bullets{ flex:1; min-width:0; list-style:none; margin:0; padding:0; display:flex; flex-direction:column; gap:8px; font-size:14px; line-height:1.6; }
.lg10-chu-y{
  display:flex; align-items:flex-start; gap:12px; background:#fef1f2; border:1px solid #fbd7db;
  border-radius:12px; padding:15px 18px; margin:6px 0 22px; font-size:13.5px; line-height:1.75; color:var(--lg10-ink);
}
.lg10-chu-y i{ flex:none; color:var(--lg10-red); font-size:18px; margin-top:2px; }
.lg10-chu-y b{ color:var(--lg10-red); }
.lg10-simple-list{ list-style:none; margin:0 0 4px; padding:0; counter-reset:lg10mk; }
.lg10-simple-list li{ counter-increment:lg10mk; margin-bottom:10px; padding-left:26px; position:relative; }
.lg10-simple-list li::before{
  content:counter(lg10mk)"."; position:absolute; left:0; top:0; color:var(--lg10-red); font-weight:800;
}

/* ---------- Chon dang / chon chuong: header khoi + hang ribbon mau xoay vong ---------- */
.lg10-dselect-head{ display:flex; align-items:center; gap:14px; margin-bottom:18px; }
.lg10-dselect-icon{
  flex:none; width:50px; height:50px; border-radius:50%; background:#e8f0ff; color:var(--lg10-blue);
  display:flex; align-items:center; justify-content:center; font-size:21px;
}
.lg10-dselect-head.lg10-collapsible{ cursor:pointer; user-select:none; }
.lg10-dselect-chev{ margin-left:auto; flex:none; color:var(--lg10-ink-soft); font-size:16px; transition:transform .2s ease; }
.lg10-dselect-head.collapsed .lg10-dselect-chev{ transform:rotate(180deg); }
.lg10-dang-select{ margin-bottom:28px; }
.lg10-dang-select-title{ font-size:18px; font-weight:900; letter-spacing:.3px; text-transform:uppercase; color:#12213d; margin:0 0 2px; }
.lg10-dselect-sub{ margin:0; font-size:12.5px; color:var(--lg10-ink-soft); }
.lg10-dang-cards{ display:flex; flex-direction:column; gap:14px; }
.lg10-dang-card{
  display:flex; align-items:stretch; gap:0; text-align:left; background:var(--lg10-card); border:1px solid var(--lg10-line);
  border-radius:16px; padding:0; cursor:pointer; box-shadow:var(--lg10-shadow); font-family:inherit; overflow:hidden;
  min-height:82px; transition:box-shadow .15s ease, transform .1s ease;
}
.lg10-dang-card:hover{ transform:translateY(-1px); box-shadow:var(--lg10-shadow-lg); }
.lg10-dang-card.active{ box-shadow:var(--lg10-shadow-lg); }
.lg10-dang-ribbon{
  flex:none; width:110px; display:flex; align-items:center; justify-content:center; color:#fff;
  font-size:25px; font-weight:900; letter-spacing:.5px;
  clip-path:polygon(0 0, calc(100% - 20px) 0, 100% 50%, calc(100% - 20px) 100%, 0 100%);
}
.lg10-dang-card-info{ flex:1; min-width:0; display:flex; flex-direction:column; justify-content:center; gap:4px; padding:14px 18px; }
.lg10-dang-card-name{ font-size:14.5px; font-weight:800; color:var(--lg10-ink); line-height:1.35; }
.lg10-dang-card-meta{ font-size:12px; color:var(--lg10-ink-soft); }
.lg10-dang-card .lg10-dang-status,
.lg10-chuong-card .lg10-dang-status{ flex:none; align-self:center; margin-right:16px; }
.lg10-dang-card-icon{
  flex:none; width:50px; height:50px; border-radius:50%; display:flex; align-items:center; justify-content:center;
  font-size:19px; align-self:center; margin-right:18px;
}
.lg10-theme-1 .lg10-dang-ribbon{ background:linear-gradient(120deg,#e0303f,#ae1f2b); }
.lg10-theme-1 .lg10-dang-status{ background:#fdeaec; color:#c2202e; border:1px solid #f7c9ce; }
.lg10-theme-1 .lg10-dang-card-icon, .lg10-theme-1 .lg10-stat-icon{ background:#fdeaec; color:#c2202e; }
.lg10-theme-2 .lg10-dang-ribbon{ background:linear-gradient(120deg,#3b74e0,#1c3f96); }
.lg10-theme-2 .lg10-dang-status{ background:#e8f0ff; color:#2952c4; border:1px solid #c7d8fb; }
.lg10-theme-2 .lg10-dang-card-icon, .lg10-theme-2 .lg10-stat-icon{ background:#e8f0ff; color:#2952c4; }
.lg10-theme-3 .lg10-dang-ribbon{ background:linear-gradient(120deg,#3aab68,#227a48); }
.lg10-theme-3 .lg10-dang-status{ background:#e8f8ee; color:#1f7a45; border:1px solid #c3ecd2; }
.lg10-theme-3 .lg10-dang-card-icon, .lg10-theme-3 .lg10-stat-icon{ background:#e8f8ee; color:#1f7a45; }
.lg10-theme-4 .lg10-dang-ribbon{ background:linear-gradient(120deg,#9161e6,#6a3fc0); }
.lg10-theme-4 .lg10-dang-status{ background:#f1ecfd; color:#6a3fc0; border:1px solid #ddccf9; }
.lg10-theme-4 .lg10-dang-card-icon, .lg10-theme-4 .lg10-stat-icon{ background:#f1ecfd; color:#6a3fc0; }
.lg10-theme-5 .lg10-dang-ribbon{ background:linear-gradient(120deg,#f5941f,#d9720a); }
.lg10-theme-5 .lg10-dang-status{ background:#fff3e5; color:#c76a0a; border:1px solid #fcdba9; }
.lg10-theme-5 .lg10-dang-card-icon, .lg10-theme-5 .lg10-stat-icon{ background:#fff3e5; color:#c76a0a; }

.lg10-dang-head{ display:flex; align-items:center; gap:10px; flex-wrap:wrap; margin:0 0 6px; }
.lg10-dang-head h2{ font-size:18px; font-weight:800; margin:0; }
.lg10-dang-badge{ font-size:11px; font-weight:700; color:#fff; background:var(--lg10-orange); padding:3px 10px; border-radius:999px; }
.lg10-dang-note{ font-size:13px; color:var(--lg10-ink-soft); margin:0 0 18px; }

/* Trang thai tien do: Chua luyen (xam) / Dang luyen (cam) / Da hoan thanh (xanh la) */
.lg10-dang-status{ font-size:11px; font-weight:700; padding:3px 10px; border-radius:999px; }
.lg10-dang-status-chua{ background:var(--lg10-bg); color:var(--lg10-ink-soft); border:1px solid var(--lg10-line); }
.lg10-dang-status-dang{ background:#fff3ea; color:var(--lg10-orange); border:1px solid #ffd9bd; }
.lg10-dang-status-xong{ background:#eef9f1 !important; color:#1f7a45 !important; border:1px solid #cdeed9 !important; }
.lg10-dang-status-xong::before{ content:"✓ "; }

.lg10-login-note{
  display:flex; align-items:center; gap:8px; background:#fff8f2; border:1px dashed var(--lg10-orange);
  border-radius:12px; padding:10px 14px; font-size:12.5px; color:var(--lg10-ink-soft); margin-bottom:16px;
}
.lg10-login-note a{ color:var(--lg10-orange); font-weight:700; }

.lg10-toolbar{ display:flex; align-items:center; justify-content:space-between; flex-wrap:wrap; gap:12px; margin-bottom:18px; }
.lg10-score{
  display:inline-flex; align-items:center; gap:8px; font-size:14px; font-weight:800; color:#fff;
  background:linear-gradient(120deg,var(--lg10-red),var(--lg10-red-dark)); padding:9px 18px; border-radius:999px;
  box-shadow:0 10px 20px -8px var(--lg10-red); font-variant-numeric:tabular-nums;
}
.lg10-sound-toggle{
  display:inline-flex; align-items:center; gap:8px; font-size:12.5px; font-weight:700; color:var(--lg10-ink);
  background:#fff; border:1.5px solid var(--lg10-line); padding:8px 14px; border-radius:999px; cursor:pointer;
}
.lg10-sound-toggle:hover{ border-color:var(--lg10-orange); color:var(--lg10-orange); }

.lg10-quiz{
  background:var(--lg10-card); border:1px solid var(--lg10-line); border-radius:var(--lg10-radius);
  box-shadow:var(--lg10-shadow); padding:20px 22px; margin-bottom:16px;
}
.lg10-quiz.answered.right{ border-color:#bfe6cc; }
.lg10-quiz.answered.wrong{ border-color:#f3c6c9; }
.lg10-quiz-head{ display:flex; align-items:flex-start; gap:12px; margin-bottom:16px; }
.lg10-quiz-badge{
  flex:none; display:inline-flex; align-items:center; margin:2px 0 0; font-size:12.5px; font-weight:800; color:#fff;
  background:linear-gradient(120deg,var(--lg10-blue),var(--lg10-blue-dark)); padding:7px 22px 7px 14px;
  clip-path:polygon(0 0, calc(100% - 10px) 0, 100% 50%, calc(100% - 10px) 100%, 0 100%);
}
.lg10-quiz-question{ flex:1; min-width:0; font-size:15px; line-height:1.75; margin:0; }
.lg10-quiz-opts{ display:grid; grid-template-columns:1fr 1fr; gap:10px; margin-bottom:12px; }
.lg10-opt{
  position:relative; display:flex; align-items:center; gap:10px; text-align:left; background:#fff;
  border:1.5px solid var(--lg10-line); border-radius:12px; padding:11px 44px 11px 14px; cursor:pointer;
  font-size:14.5px; color:var(--lg10-ink); transition:border-color .15s ease, background .15s ease, transform .1s ease;
}
.lg10-opt:hover:not(:disabled){ border-color:var(--lg10-red); background:#fbf4f4; transform:translateY(-1px); }
.lg10-opt-key{ flex:none; width:24px; height:24px; border-radius:7px; background:var(--lg10-bg); color:var(--lg10-ink-soft); display:flex; align-items:center; justify-content:center; font-weight:800; font-size:12px; }
.lg10-opt-text{ flex:1; line-height:1.5; }
.lg10-opt.correct{ border-color:var(--lg10-green); background:#eef9f1; }
.lg10-opt.correct .lg10-opt-key{ background:var(--lg10-green); color:#fff; }
.lg10-opt.wrong{ border-color:var(--lg10-red); background:#fdecec; }
.lg10-opt.wrong .lg10-opt-key{ background:var(--lg10-red); color:#fff; }
.lg10-opt:disabled{ cursor:not-allowed; }
.lg10-opt:disabled:not(.correct):not(.wrong){ opacity:.55; }
.lg10-opt.correct::after, .lg10-opt.wrong::after{
  content:''; position:absolute; right:12px; top:50%; transform:translateY(-50%);
  width:22px; height:22px; border-radius:50%; color:#fff; display:flex; align-items:center; justify-content:center;
  font-size:12px; font-weight:900; line-height:1;
}
.lg10-opt.correct::after{ content:'✓'; background:var(--lg10-green); }
.lg10-opt.wrong::after{ content:'✕'; background:var(--lg10-red); }

.lg10-feedback{ display:flex; align-items:center; gap:6px; font-size:13.5px; font-weight:700; min-height:20px; margin-bottom:4px; }
.lg10-feedback.ok{ color:#1f7a45; } .lg10-feedback.no{ color:var(--lg10-red); }

.lg10-toggle-btn{
  border:1.5px solid #c7d8fb; background:#fff; color:var(--lg10-blue); cursor:pointer; font-size:12.5px;
  font-weight:700; padding:8px 14px; border-radius:9px; display:none; align-items:center; gap:8px; margin-top:6px;
}
.lg10-toggle-btn:hover{ border-color:var(--lg10-blue); background:#f2f6ff; }
.lg10-quiz.answered .lg10-toggle-btn{ display:inline-flex; }
.lg10-chev{ display:inline-block; transition:transform .15s ease; }
.lg10-quiz.open .lg10-chev{ transform:rotate(180deg); }
.lg10-solution{
  display:none; margin-top:14px; padding:16px 18px; background:var(--lg10-bg); border-left:5px solid var(--lg10-green);
  border-radius:10px; font-size:14px; line-height:1.8;
}
.lg10-quiz.open .lg10-solution{ display:block; }
.lg10-solution-label{ display:block; color:var(--lg10-green); font-weight:800; margin-bottom:6px; }

@media (max-width:700px){
  .lg10-hub-head h1{ font-size:22px; }
  .lg10-quiz-opts{ grid-template-columns:1fr; }
  .lg10-quiz{ padding:16px; }
  .lg10-method-box{ padding:16px; }
  .lg10-formula-body{ flex-direction:column; gap:8px; }
  .lg10-formula-label{ border-right:none; padding-right:0; border-bottom:1px dashed #f0d3d6; padding-bottom:6px; flex:none; }
  .lg10-dang-ribbon{ width:64px; font-size:19px; }
  .lg10-dang-card-info{ padding:12px 10px; }
  .lg10-dang-card .lg10-dang-status{ display:none; }
  .lg10-dang-card-icon{ width:40px; height:40px; font-size:16px; margin-right:10px; }
  .lg10-quiz-head{ gap:8px; }
  .lg10-hub-hero{ flex-direction:column; align-items:flex-start; }
  .lg10-chuong-stats{ grid-template-columns:1fr 1fr; }
  .lg10-chuong-top{ flex-wrap:wrap; }
}

/* FIX: class .right toan cuc trong home.css (text-align:right) bi trung voi class .right cua lg10-quiz (dap an dung) */
.lg10-quiz.right, .lg10-quiz.wrong{ text-align:left; }

/* Nut "Lam lai dang nay" trong toolbar cua moi Dang */
.lg10-reset-btn{
  display:inline-flex; align-items:center; gap:8px; font-size:12.5px; font-weight:700; color:#c0392b;
  background:#fff; border:1.5px solid #f0c6c2; padding:8px 14px; border-radius:999px; cursor:pointer;
}
.lg10-reset-btn:hover{ background:#fdecea; border-color:#c0392b; }

/* ============================================================================
   LUYEN DE (lamde.php) - lam tron 1 de, chi biet dung/sai sau khi Nop bai.
   Tai su dung toi da class .lg10-opt/.lg10-quiz/.lg10-feedback/.lg10-solution
   sales cua "Chon chuong" (xemchuong.php) de dong bo giao dien - phan duoi day
   chi la CSS RIENG cho trang thai "dang chon, chua nop" (.selected, KHONG to
   mau dung/sai) va cac khoi UI moi (toolbar nop bai, banner ket qua).
   ============================================================================ */
.lg10-de-note{
  display:flex; align-items:flex-start; gap:10px; background:#eef4ff; border:1px solid #c7d8fb;
  color:var(--lg10-ink); border-radius:12px; padding:14px 16px; font-size:13.5px; line-height:1.7; margin-bottom:18px;
}
.lg10-de-note i{ color:var(--lg10-blue); margin-top:2px; }

/* Trang thai "da chon nhung chua nop bai": chi highlight nhe, KHONG the hien
   dung/sai (khac han .correct/.wrong chi duoc gan sau khi bam Nop bai). */
.lg10-opt-de.selected{
  border-color:var(--lg10-blue); background:#eef4ff;
}
.lg10-opt-de.selected .lg10-opt-key{ background:var(--lg10-blue); color:#fff; }

.lg10-de-img{
  display:block; max-width:100%; height:auto; margin:12px 0; border-radius:10px; border:1px solid var(--lg10-line);
}

/* Thanh cong cu Nop bai - hien o dau va cuoi danh sach cau hoi */
.lg10-de-toolbar{
  position:sticky; top:8px; z-index:20; display:flex; align-items:center; justify-content:space-between; gap:12px;
  background:#fff; border:1.5px solid var(--lg10-line); border-radius:14px; padding:12px 18px;
  box-shadow:var(--lg10-shadow); margin-bottom:18px;
}
.lg10-de-toolbar-bottom{ position:static; margin-top:4px; }
.lg10-de-progress{ font-size:13.5px; color:var(--lg10-ink-soft); }
.lg10-de-progress b{ color:var(--lg10-ink); font-size:15px; }
.lg10-de-submit-btn{
  flex:none; display:inline-flex; align-items:center; gap:8px; font-size:14px; font-weight:800; color:#fff;
  background:linear-gradient(120deg,var(--lg10-green),#1f9d52); border:none; padding:11px 22px; border-radius:999px;
  cursor:pointer; box-shadow:0 6px 16px -6px rgba(31,157,82,.55);
}
.lg10-de-submit-btn:hover{ filter:brightness(1.05); transform:translateY(-1px); }

/* Dong ho dem nguoc 90 phut lam bai, dat trong toolbar (tren + duoi) */
.lg10-de-timer{
  display:flex; align-items:center; gap:7px; font-size:14px; font-weight:800; color:var(--lg10-ink);
  background:#f3f6fb; border:1px solid var(--lg10-line); border-radius:999px; padding:8px 14px; white-space:nowrap;
  font-variant-numeric:tabular-nums;
}
.lg10-de-timer.lg10-de-timer-warn{ color:#a15c00; background:#fff3d6; border-color:#f0d999; }
.lg10-de-timer.lg10-de-timer-out{ color:#c0392b; background:#fdecea; border-color:#f0c6c2; animation:lg10DeTimerPulse 1.2s ease-in-out infinite; }
@keyframes lg10DeTimerPulse{ 0%,100%{ opacity:1; } 50%{ opacity:.55; } }

/* Toast noi bao het gio lam bai - hien co dinh o dau man hinh, tu dong bien mat
   sau 15s hoac bam nut dong. */
.lg10-de-timeout-toast{
  position:fixed; top:14px; left:50%; transform:translateX(-50%); z-index:999;
  display:flex; align-items:center; gap:10px; background:#fdecea; border:1.5px solid #f0c6c2; color:#c0392b;
  border-radius:14px; padding:12px 18px; font-size:13.5px; font-weight:700; box-shadow:0 10px 30px -10px rgba(192,57,43,.45);
  max-width:92vw;
}
.lg10-de-timeout-toast i{ font-size:16px; }
.lg10-de-timeout-toast button{
  flex:none; background:none; border:none; color:#c0392b; font-size:16px; font-weight:900; cursor:pointer; line-height:1; padding:0 0 0 6px;
}

/* Banner ket qua sau khi nop bai */
.lg10-de-result{
  display:flex; align-items:center; gap:18px; background:linear-gradient(120deg,#fff8ec,#fff); border:1.5px solid #f0d999;
  border-radius:16px; padding:18px 22px; margin-bottom:18px;
}
.lg10-de-result-score{ flex:none; display:flex; align-items:baseline; }
.lg10-de-result-num{ font-size:40px; font-weight:900; color:var(--lg10-orange); line-height:1; }
.lg10-de-result-den{ font-size:18px; font-weight:700; color:var(--lg10-ink-soft); }
.lg10-de-result-info{ flex:1; min-width:0; }
.lg10-de-result-title{ font-size:16px; font-weight:800; color:var(--lg10-ink); margin-bottom:2px; }
.lg10-de-result-sub{ font-size:13.5px; color:var(--lg10-ink-soft); }

@media (max-width:700px){
  .lg10-de-toolbar{ position:static; flex-wrap:wrap; justify-content:center; }
  .lg10-de-progress, .lg10-de-timer{ flex:1 1 auto; text-align:center; justify-content:center; }
  .lg10-de-result{ flex-wrap:wrap; }
  .lg10-de-timeout-toast{ top:8px; padding:10px 14px; font-size:12.5px; }
}