/* =====================================================
   MathTest – exam.css  |  làm bài + kết quả + xem lại
   ===================================================== */

.exam-app{display:flex;flex-direction:column;gap:14px}

/* ---------- Top bar (timer) ---------- */
.exam-bar{position:sticky;top:62px;z-index:55;display:flex;align-items:center;gap:12px;padding:12px 14px;background:var(--surface);border:1px solid var(--border);border-radius:14px;box-shadow:var(--shadow)}
.admin-bar .exam-bar{top:94px}
.exam-exit{flex:none;width:38px;height:38px;border:0;border-radius:10px;background:var(--surface-2);color:var(--text);font-size:18px;cursor:pointer}
.exam-exit:hover{background:var(--red-soft);color:var(--red)}
.exam-bar-title{flex:1;min-width:0;font-weight:700;font-size:14px;white-space:nowrap;overflow:hidden;text-overflow:ellipsis}
.exam-timer{flex:none;display:inline-flex;align-items:center;gap:6px;font-variant-numeric:tabular-nums;font-weight:800;font-size:18px;color:var(--primary);background:var(--primary-soft);padding:7px 12px;border-radius:10px}
.exam-timer::before{content:"⏱";font-size:14px}
.exam-timer.warn{color:var(--orange);background:var(--orange-soft)}
.exam-timer.danger{color:#fff;background:var(--red);animation:examPulse 1s infinite}
@keyframes examPulse{50%{opacity:.65}}

/* ---------- Sub bar ---------- */
.exam-sub{display:flex;align-items:center;justify-content:space-between;gap:10px}
.exam-progress{font-size:13.5px;color:var(--muted);font-weight:600}
.exam-progress b{color:var(--text)}
.exam-submit{padding:9px 16px;font-size:13.5px}

/* ---------- Question card ---------- */
.exam-card{padding:18px}
.q-top{display:flex;align-items:center;gap:8px;flex-wrap:wrap;margin-bottom:10px}
.q-no{font-size:12px;font-weight:800;color:var(--primary);background:var(--primary-soft);padding:4px 10px;border-radius:99px}
.q-topic{font-size:11.5px;font-weight:700;color:var(--violet);background:var(--violet-soft);padding:4px 10px;border-radius:99px}
.q-level{font-size:11.5px;font-weight:700;padding:4px 10px;border-radius:99px;color:#0b6b3a;background:#dcfce7}
.q-level[data-lv="Thông hiểu"]{color:#0b5cab;background:#dbeafe}
.q-level[data-lv="Vận dụng"]{color:#9a5b00;background:#fef3c7}
.q-level[data-lv="Vận dụng cao"]{color:#b21d3a;background:#ffe0e6}
.q-flag{font-size:11.5px;font-weight:700;color:var(--amber-ink);background:var(--amber-soft);padding:4px 10px;border-radius:99px}
.q-text{font-size:16px;font-weight:600;line-height:1.5;color:var(--text);margin-bottom:14px;white-space:pre-line}
.q-opts{display:grid;grid-template-columns:repeat(2,minmax(0,1fr));gap:10px;align-items:stretch}
.q-opt{display:flex;align-items:center;gap:12px;width:100%;text-align:left;padding:13px 14px;border:1.5px solid var(--border);border-radius:13px;background:var(--surface);color:var(--text);font:inherit;font-size:14.5px;cursor:pointer;transition:border-color .15s,background .15s}
.q-opt:hover{border-color:var(--primary)}
.q-opt.is-sel{border-color:var(--primary);background:var(--primary-soft)}
.q-letter{flex:none;width:30px;height:30px;border-radius:50%;display:grid;place-items:center;font-weight:800;font-size:13px;background:var(--surface-2);color:var(--muted)}
.q-opt.is-sel .q-letter{background:var(--primary);color:#fff}
.q-otext{flex:1;min-width:0}

/* ---------- Phần II: Đúng/Sai ---------- */
.tf-note{font-size:13px;color:var(--muted);margin-bottom:10px}
.tf-list{display:flex;flex-direction:column;gap:10px}
.tf-row{display:flex;align-items:center;gap:12px;flex-wrap:wrap;padding:12px 14px;border:1.5px solid var(--border);border-radius:13px;background:var(--surface)}
.tf-s{flex:1;min-width:200px;font-size:14.5px;line-height:1.5}
.tf-pick{display:flex;gap:8px;flex:none}
.tf-btn{padding:8px 16px;border:1.5px solid var(--border);border-radius:10px;background:var(--surface);color:var(--text);font:inherit;font-weight:700;font-size:13.5px;cursor:pointer;transition:.15s}
.tf-btn.tf-true.is-sel{background:#dcfce7;border-color:#16a34a;color:#0b6b3a}
.tf-btn.tf-false.is-sel{background:#ffe0e6;border-color:#dc2626;color:#b21d3a}

/* ---------- Phần III: Trả lời ngắn ---------- */
.sa-wrap{display:flex;flex-direction:column;gap:8px}
.sa-label{font-size:13.5px;font-weight:700;color:var(--muted)}
.sa-input{width:100%;max-width:280px;padding:13px 14px;border:1.5px solid var(--border);border-radius:13px;background:var(--surface);color:var(--text);font:inherit;font-size:18px;font-weight:700;letter-spacing:.02em}
.sa-input:focus{outline:none;border-color:var(--primary);background:var(--primary-soft)}
/* Phần II tự luận (THCS): ô trình bày lời giải */
.sa-work{display:flex;flex-direction:column;gap:8px;margin-bottom:16px}
.sa-work-input{width:100%;padding:12px 14px;border:1.5px solid var(--border);border-radius:13px;background:var(--surface);color:var(--text);font:inherit;font-size:15px;line-height:1.6;resize:vertical;min-height:96px}
.sa-work-input:focus{outline:none;border-color:var(--primary);background:var(--primary-soft)}
.rev-work{margin:8px 0;padding:10px 12px;border-radius:11px;background:var(--surface-2);font-size:14px}
.rev-work-text{margin-top:5px;white-space:pre-wrap;line-height:1.6;color:var(--text)}
.rev-work-empty{color:var(--muted);font-size:13.5px}
.pr-note{display:flex;gap:7px;align-items:flex-start;margin:12px 0;padding:10px 12px;border-radius:11px;background:var(--primary-soft);color:var(--primary);font-size:13px;line-height:1.5;font-weight:600}

/* ---------- Review: Đúng/Sai & Trả lời ngắn ---------- */
.rev-tf-list{display:flex;flex-direction:column;gap:8px;margin-top:8px}
.rev-tf{padding:10px 12px;border-radius:11px;border:1px solid var(--border);background:var(--surface-2)}
.rev-tf.ok{border-color:#16a34a;background:#f0fdf4}
.rev-tf.no{border-color:#dc2626;background:#fef2f2}
.rev-tf-s{font-size:14px;font-weight:600;line-height:1.5}
.rev-tf-r{font-size:12.5px;color:var(--muted);margin-top:4px}
.rev-tf-e{font-size:12.5px;color:var(--muted);margin-top:3px;font-style:italic}
.rev-sa{font-size:14px;margin:8px 0;padding:10px 12px;border-radius:11px;background:var(--surface-2)}
.rev-tag-part{background:var(--amber-soft);color:var(--amber-ink)}

/* ---------- Result: breakdown 3 phần ---------- */
.result-parts{display:grid;grid-template-columns:repeat(3,1fr);gap:10px;margin:16px 0}
.result-parts .rp{display:flex;flex-direction:column;align-items:center;gap:2px;padding:12px 6px;border-radius:13px;background:var(--surface-2)}
.result-parts .rp span{font-size:12px;font-weight:700;color:var(--muted)}
.result-parts .rp b{font-size:16px}
.result-parts .rp small{font-size:11.5px;color:var(--primary);font-weight:700}

/* ---------- Navigator part labels ---------- */
.nav-part{grid-column:1/-1;font-size:11.5px;font-weight:800;color:var(--muted);text-transform:uppercase;letter-spacing:.04em;margin-top:6px}

/* ---------- Actions ---------- */
.exam-actions{display:grid;grid-template-columns:1fr auto 1fr;gap:8px}
.exam-actions .btn{padding:11px 10px;font-size:13.5px}
#markBtn.is-on{background:var(--amber-soft);border-color:var(--amber-ink);color:var(--amber-ink)!important}

/* ---------- Navigator ---------- */
.exam-nav{padding:16px}
.exam-nav-head{display:flex;align-items:center;justify-content:space-between;gap:8px;flex-wrap:wrap;font-size:12.5px;font-weight:800;text-transform:uppercase;letter-spacing:.05em;color:var(--text);margin-bottom:12px}
.exam-legend{display:inline-flex;align-items:center;gap:10px;font-size:11px;font-weight:600;text-transform:none;letter-spacing:0;color:var(--muted)}
.lg{display:inline-block;width:12px;height:12px;border-radius:4px;margin-right:3px;vertical-align:-2px}
.lg-done{background:var(--primary)}
.lg-mark{background:var(--amber-soft);border:1.5px solid var(--amber-ink)}
.exam-nav-grid{display:grid;grid-template-columns:repeat(auto-fill,minmax(40px,1fr));gap:8px}
.nav-cell{aspect-ratio:1;border:1.5px solid var(--border);border-radius:10px;background:var(--surface);color:var(--muted);font:inherit;font-weight:700;font-size:13px;cursor:pointer;transition:all .12s}
.nav-cell:hover{border-color:var(--primary);color:var(--primary)}
.nav-cell.is-done{background:var(--primary);border-color:var(--primary);color:#fff}
.nav-cell.is-mark{border-color:var(--amber-ink);box-shadow:inset 0 0 0 2px var(--amber-soft)}
.nav-cell.is-current{outline:2px solid var(--primary);outline-offset:2px}

/* ---------- Toast ---------- */
.exam-toast{position:fixed;left:50%;bottom:84px;transform:translate(-50%,16px);z-index:120;max-width:90vw;background:var(--text);color:var(--surface);padding:11px 18px;border-radius:12px;font-size:13.5px;font-weight:600;box-shadow:0 10px 30px rgba(0,0,0,.3);opacity:0;transition:opacity .25s,transform .25s}
.exam-toast.show{opacity:1;transform:translate(-50%,0)}

/* ---------- Result ---------- */
.result{padding:22px 20px}
.result-auto{margin:-4px 0 14px;padding:10px 14px;border-radius:12px;background:var(--orange-soft);color:var(--orange);font-weight:700;font-size:13.5px;text-align:center}
.result-score{display:flex;align-items:center;gap:18px;margin-bottom:18px}
.rs-circle{flex:none;width:104px;height:104px;border-radius:50%;display:flex;flex-direction:column;align-items:center;justify-content:center;background:linear-gradient(135deg,var(--primary-2),var(--primary));color:#fff;box-shadow:0 10px 24px rgba(37,99,235,.4)}
.rs-circle b{font-size:34px;font-weight:800;line-height:1}
.rs-circle small{font-size:13px;opacity:.85}
.rs-info{display:flex;flex-direction:column;gap:4px}
.rs-info b{font-size:18px;font-weight:800;color:var(--text)}
.rs-info span{font-size:13.5px;color:var(--muted)}
.result-counts{display:grid;grid-template-columns:repeat(3,1fr);gap:10px;margin-bottom:20px}
.rc{display:flex;flex-direction:column;align-items:center;gap:2px;padding:14px 6px;border-radius:13px;font-size:12.5px;font-weight:600;color:var(--muted)}
.rc b{font-size:24px;font-weight:800}
.rc-green{background:var(--green-soft)}.rc-green b{color:var(--green)}
.rc-red{background:var(--red-soft)}.rc-red b{color:var(--red)}
.rc-gray{background:var(--surface-2)}.rc-gray b{color:var(--text)}
.result-h{margin:0 0 12px;font-size:15px;font-weight:800;color:var(--text)}
.topic-bars{display:flex;flex-direction:column;gap:12px;margin-bottom:22px}
.topic-head{display:flex;justify-content:space-between;font-size:13px;font-weight:600;color:var(--text);margin-bottom:5px}
.topic-bar{height:9px;border-radius:99px;background:var(--surface-2);overflow:hidden}
.topic-bar span{display:block;height:100%;border-radius:99px;background:linear-gradient(90deg,var(--primary-2),var(--primary))}
.result-actions{display:flex;flex-direction:column;gap:10px}

/* ---------- Review ---------- */
.review{display:flex;flex-direction:column;gap:14px}
.review-top{display:flex;align-items:center;gap:12px}
.review-top h3{margin:0;font-size:18px;font-weight:800;color:var(--text)}
.review-lock{padding:12px 15px;border-radius:12px;background:#fff7ed;border:1px solid #fed7aa;color:#9a3412;font-size:13.5px;line-height:1.5}
.review-lock a{color:#c2410c;font-weight:700}
[data-theme="dark"] .review-lock{background:#2a1c0c;border-color:#7c3a12;color:#fdba74}
.rev-q{padding:16px;border-left:4px solid var(--border)}
.rev-q.rev-right{border-left-color:var(--green)}
.rev-q.rev-wrong{border-left-color:var(--red)}
.rev-q.rev-blank{border-left-color:var(--muted)}
.rev-q-top{display:flex;align-items:center;justify-content:space-between;gap:8px;margin-bottom:8px}
.rev-tag{font-size:12px;font-weight:800;padding:4px 10px;border-radius:99px}
.rev-tag-right{background:var(--green-soft);color:var(--green)}
.rev-tag-wrong{background:var(--red-soft);color:var(--red)}
.rev-tag-blank{background:var(--surface-2);color:var(--muted)}
.rev-opts{display:grid;grid-template-columns:repeat(2,minmax(0,1fr));gap:8px;margin-top:10px;align-items:stretch}
.rev-opt{display:flex;align-items:center;gap:10px;padding:10px 12px;border:1.5px solid var(--border);border-radius:11px;font-size:14px}
.rev-opt.is-correct{border-color:var(--green);background:var(--green-soft)}
.rev-opt.is-correct .q-letter{background:var(--green);color:#fff}
.rev-opt.is-wrong{border-color:var(--red);background:var(--red-soft)}
.rev-opt.is-wrong .q-letter{background:var(--red);color:#fff}
.rev-explain{margin-top:12px;padding:11px 14px;border-radius:11px;background:var(--surface-2);font-size:13.5px;color:var(--text);line-height:1.55;white-space:pre-line}
.rev-ai{margin-top:12px;padding:8px 14px;font-size:13px}
.rev-ai-out:not(:empty){margin-top:10px}
.rev-ai-loading{color:var(--muted);font-size:13.5px}
.rev-ai-box{padding:12px 14px;border-radius:11px;background:var(--primary-soft);font-size:13.5px;line-height:1.6;color:var(--text)}
.rev-ai-box.rev-ai-err{background:var(--red-soft);color:var(--red)}

@media (min-width:700px){
  .result-actions{flex-direction:row}
  .result-actions .btn{flex:1}
  .q-text{font-size:17px}
}

/* ---------- Hình vẽ trong câu hỏi (đồ thị / bảng biến thiên) ---------- */
.q-fig{margin:0 0 14px;overflow-x:auto;text-align:center}
.q-fig svg{max-width:340px;width:100%;height:auto;display:inline-block}
/* Hình chứng minh hình học: nét đen trắng rõ ràng dù AI quên đặt màu */
.q-fig svg line,.q-fig svg polygon,.q-fig svg polyline,.q-fig svg path,.q-fig svg circle{stroke:#111}
.q-fig svg polygon,.q-fig svg path{fill:none}
.q-fig svg text{fill:#111}
/* Hình minh hoạ & bảng biến thiên: ĐEN TRẮNG giống đề PDF (currentColor theo nền sáng/tối). */
.fig-bbt{border-collapse:collapse;margin:4px auto;font-size:14px;color:inherit}
.fig-bbt th,.fig-bbt td{border:1px solid currentColor;padding:5px 12px;text-align:center;min-width:30px;white-space:nowrap}
.fig-bbt th{font-weight:700}
.fig-bbt td.b{font-weight:700}
.fig-graph{display:block;max-width:280px;width:100%;height:auto;margin:6px auto;color:inherit;background:transparent;border:0}
.fig-graph .axis{stroke:currentColor;stroke-width:1}
.fig-graph .curve{fill:none;stroke:currentColor;stroke-width:2}
.fig-graph .dot{fill:currentColor}
.fig-graph .lbl{font-size:11px;fill:currentColor}
.fig-graph .bar{fill:none;stroke:currentColor;stroke-width:1.2}
.fig-graph .poly{fill:none;stroke:currentColor;stroke-width:1.6}
.fig-graph .edge{stroke:currentColor;stroke-width:1.8;fill:none}
.fig-graph .edge.dash{stroke:currentColor;stroke-width:1.2;stroke-dasharray:4 3;opacity:.65}

/* ---------- Luyện tập theo chuyên đề ---------- */
.practice-grade{font-size:16px;font-weight:800;margin:18px 0 10px;color:var(--text)}
.practice-grid{display:grid;grid-template-columns:repeat(auto-fill,minmax(220px,1fr));gap:12px}
.practice-topic{display:flex;align-items:center;justify-content:space-between;gap:10px;padding:14px 16px;border:1.5px solid var(--border);border-radius:14px;background:var(--surface);color:var(--text);font:inherit;text-align:left;cursor:pointer;transition:.15s}
.practice-topic:hover{border-color:var(--primary);background:var(--primary-soft);transform:translateY(-1px)}
.pt-name{font-weight:700;font-size:14.5px}
.pt-go{font-size:12.5px;font-weight:700;color:var(--primary);flex:none}
.practice-card{padding:18px}
.practice-loading{padding:30px;text-align:center;color:var(--muted)}
.practice-head{display:flex;align-items:center;justify-content:space-between;gap:8px;flex-wrap:wrap;margin-bottom:12px;padding-bottom:10px;border-bottom:1px solid var(--border)}
.practice-topic-name{font-weight:800;font-size:14px}
.practice-stat{font-size:13px;color:var(--muted)}
.practice-back{padding:6px 10px;font-size:12.5px}
.practice-card .q-opt.is-locked{cursor:default}
.practice-card .q-opt.is-correct{border-color:#16a34a;background:#f0fdf4}
.practice-card .q-opt.is-correct .q-letter{background:#16a34a;color:#fff}
.practice-card .q-opt.is-wrong{border-color:#dc2626;background:#fef2f2}
.practice-card .q-opt.is-wrong .q-letter{background:#dc2626;color:#fff}
.practice-fb{margin-top:12px}
.pfb{font-weight:700;padding:10px 12px;border-radius:11px;font-size:14px}
.pfb-ok{background:#dcfce7;color:#0b6b3a}
.pfb-no{background:#ffe0e6;color:#b21d3a}
.pfb-e{margin-top:8px;font-size:13.5px;color:var(--muted);line-height:1.5}
.practice-actions{margin-top:14px}
.practice-actions .btn{width:100%}

/* Phân số xếp tầng (tử trên / mẫu dưới, có gạch ngang) — dùng cho công thức hiển thị. */
.frac{display:inline-flex;flex-direction:column;vertical-align:middle;text-align:center;line-height:1.05;margin:0 .15em;}
.frac-n{padding:0 .3em;border-bottom:1px solid currentColor;}
.frac-d{padding:0 .3em;}
.frac-n.frac-rad{padding-bottom:.08em;}
.frac-d.frac-rad{padding-top:.2em;}
/* Gạch chéo ẩn giữa tử/mẫu: ẩn khỏi màn hình nhưng còn trong text/trợ năng (đọc ra "a/b"). */
.screen-reader-text{position:absolute;width:1px;height:1px;overflow:hidden;clip:rect(0 0 0 0)}

/* Dấu căn có vạch trên trùm biểu thức. */
.sqrt{white-space:nowrap;}
.sqrt-r{border-top:1px solid currentColor;padding:.02em .2em 0 .04em;}
.sqrt-sym{display:inline-block;}
.sqrt.tall{display:inline-flex;align-items:center;vertical-align:middle;}
.sqrt.tall .sqrt-sym{transform:scaleY(2);transform-origin:center;margin-right:-.02em;}
.sqrt.tall .sqrt-r{align-self:stretch;padding-top:.08em;display:flex;flex-direction:column;justify-content:center;}

.q-pts{color:#b45309;font-weight:600;font-size:.85em;}