*{box-sizing:border-box}
body{margin:0;font-family:Arial,Helvetica,sans-serif;background:var(--page-bg,#f3f6fb);color:var(--text,#111)}
a{color:var(--primary,#0f5fa8);text-decoration:none}
.topbar{display:flex;justify-content:space-between;align-items:center;gap:18px;padding:12px 24px;background:var(--header-bg,#0f172a);color:#fff;box-shadow:0 8px 24px rgba(15,23,42,.14)}
.brand{display:flex;align-items:center;gap:14px;min-width:0}.brand-logo{width:var(--brand-logo-width,74px);height:var(--brand-logo-height,58px);object-fit:contain;border-radius:10px;background:var(--logo-bg,#fff);padding:4px;max-width:100%;flex:0 0 auto}.brand-text{min-width:0}.brand-text h1{margin:0;font-size:22px;line-height:1.2}.brand-text p{margin:4px 0 0;color:#e2e8f0;font-weight:bold}.topbar nav{display:flex;gap:16px;flex-wrap:wrap}.topbar nav a{color:#fff;font-weight:bold}.container{max-width:1280px;margin:22px auto;padding:0 16px}.footer{text-align:center;color:#64748b;padding:24px}.hero,.card{background:var(--card-bg,#fff);border:1px solid #e5e7eb;border-radius:12px;padding:20px;margin-bottom:18px;box-shadow:0 8px 28px rgba(15,23,42,.06)}.hero h2{font-size:32px;margin:0 0 8px}.form-grid{display:grid;grid-template-columns:repeat(2,minmax(220px,1fr));gap:16px}.form-grid label,.edit-form label{display:flex;flex-direction:column;font-weight:bold;gap:6px}input,select,textarea{border:1px solid #cbd5e1;border-radius:8px;padding:10px;font-size:16px;background:#fff;color:#111}input[type=color]{height:44px;padding:4px}.btn{display:inline-block;border:1px solid #cbd5e1;background:#fff;border-radius:8px;padding:10px 14px;font-weight:bold;cursor:pointer;color:#111}.btn.primary{background:var(--primary,#0f5fa8);color:#fff;border-color:var(--primary,#0f5fa8)}.btn.danger{background:#dc2626;color:#fff;border-color:#dc2626}.btn.small{padding:6px 10px;font-size:13px}.btn:disabled{opacity:.4;cursor:not-allowed}.form-actions{grid-column:1/-1}.chapter-list{display:flex;flex-wrap:wrap;gap:10px}.chapter-list span{background:#eef6ff;border:1px solid #bfdbfe;border-radius:999px;padding:8px 12px}.install-box,.login-box{max-width:560px;margin:50px auto;background:#fff;border-radius:12px;padding:26px;box-shadow:0 10px 30px rgba(15,23,42,.12)}.alert{padding:12px;border-radius:8px;margin:10px 0}.alert.ok{background:#dcfce7;color:#166534}.alert.error{background:#fee2e2;color:#991b1b}.exam-shell{display:grid;grid-template-columns:270px 1fr;gap:16px}.exam-sidebar{background:var(--card-bg,#fff);border-radius:12px;border:1px solid #e5e7eb;padding:14px;position:sticky;top:12px;height:calc(100vh - 24px);overflow:auto}.student-box{border-bottom:1px solid #e5e7eb;margin-bottom:12px}.question-nav{display:flex;flex-direction:column;gap:4px}.question-nav a{padding:8px 10px;border-radius:8px;color:#111;background:#f8fafc}.question-nav a.active{background:var(--primary,#0f5fa8);color:#fff}.exam-main{min-width:0}.exam-title{display:flex;justify-content:space-between;align-items:center}.exam-title h2{font-size:32px;color:var(--primary,#1d4ed8);margin:0 0 12px}.exam-title #timer{font-size:22px;font-weight:bold;color:#dc2626}.practice-free-label{font-size:18px;font-weight:bold;color:var(--primary,#0f5fa8);background:#eef6ff;border:1px solid #bfdbfe;border-radius:999px;padding:8px 12px}.video-wrap{background:#000;border-radius:12px;overflow:hidden;border:1px solid #111}.video-wrap video{width:100%;height:52vh;display:block;background:#000;object-fit:contain}.video-note{color:#fff;background:#111;padding:8px 12px}.question-form{background:var(--card-bg,#fff);border:1px solid #e5e7eb;border-radius:12px;margin-top:12px;padding:14px}.subquestions-grid{display:grid;grid-template-columns:1fr 1fr;gap:12px}.subquestions-grid.one-question-mode{grid-template-columns:1fr}.exam-mode-note{margin:0 0 12px;color:#475569}.subq{border:1px solid #dbe3ef;border-radius:10px;padding:12px}.subq legend{font-weight:bold;color:var(--primary,#0f5fa8)}.subq h3{margin:4px 0 10px}.option{display:flex;gap:8px;align-items:flex-start;padding:6px 0}.option input{margin-top:3px}.exam-actions{display:flex;gap:10px;justify-content:flex-end;border-top:1px solid #e5e7eb;padding-top:12px;margin-top:12px}.score{font-size:28px;color:#dc2626;font-weight:bold}.result-detail{padding:10px;border-bottom:1px solid #e5e7eb}.ok-text{color:#166534}.bad-text{color:#991b1b}.dashboard-grid{display:grid;grid-template-columns:repeat(3,1fr);gap:16px}.stat h2{font-size:42px;margin:0;color:var(--primary,#0f5fa8)}.table{width:100%;border-collapse:collapse;background:#fff}.table th,.table td{border-bottom:1px solid #e5e7eb;padding:10px;text-align:left}.inline-form{display:flex;gap:10px;align-items:end;margin-bottom:14px}.edit-form{display:flex;flex-direction:column;gap:12px}.admin-q{border:1px solid #dbe3ef;border-radius:12px;padding:14px}.answer-grid{display:grid;grid-template-columns:1fr 1fr;gap:12px}.check{flex-direction:row!important;align-items:center}
.mode-grid{display:grid;grid-template-columns:1.15fr .85fr;gap:18px;align-items:start}.mode-card h2{margin-top:0}.form-grid.single{grid-template-columns:1fr}.practice-card{border-top:5px solid var(--primary,#0f5fa8)}.mock-card{border-color:#fecaca;background:#fffafa}.mock-config{background:#fff7ed;border:1px solid #fed7aa;border-radius:10px;padding:14px}.mock-config h3{margin-top:0}.mock-chapters{display:flex;flex-wrap:wrap;gap:8px;margin-top:8px}.mock-chapters span{background:#fff;border:1px solid #fdba74;border-radius:999px;padding:6px 10px}.hint{color:#475569;line-height:1.45}.form-grid small{font-weight:normal;color:#64748b}.student-note{background:#eff6ff;border:1px solid #bfdbfe;color:#1e3a8a;border-radius:10px;padding:12px;line-height:1.45}.mock-hidden-note{background:#fff7ed;border-color:#fed7aa;color:#9a3412}.student-note b{color:#0f172a}.practice-type-fixed{border:1px solid #bfdbfe;background:#eff6ff;color:#1e3a8a;border-radius:10px;padding:12px;font-weight:bold}.logo-preview-wrap{display:flex;align-items:center}.logo-preview{max-width:100%;max-height:420px;border:1px solid #e5e7eb;border-radius:12px;background:#fff;padding:8px}
@media(max-width:1000px){.mode-grid{grid-template-columns:1fr}}
@media(max-width:900px){.exam-main{order:1}.exam-sidebar{order:2}.question-form{margin-top:8px}.video-wrap video{height:34vh}.form-grid,.subquestions-grid,.dashboard-grid,.answer-grid{grid-template-columns:1fr}.exam-shell{grid-template-columns:1fr}.exam-sidebar{position:static;height:auto}.topbar{flex-direction:column;align-items:flex-start}.topbar nav{gap:12px}.video-wrap video{height:36vh}.brand-logo{max-width:45vw}.brand-text h1{font-size:19px}.exam-actions{flex-wrap:wrap;justify-content:flex-start}}

.page-crumb{margin-bottom:12px}.page-crumb a{display:inline-flex;align-items:center;gap:6px;background:var(--card-bg,#fff);border:1px solid #dbe3ef;border-radius:999px;padding:9px 14px;font-weight:bold;color:var(--primary,#0f5fa8);box-shadow:0 6px 18px rgba(15,23,42,.05)}
.practice-switch-box{padding-bottom:12px}.practice-switch-box label{display:block;margin-bottom:8px}.chapter-switch-form{display:flex;flex-direction:column;gap:8px;margin:8px 0 14px}.chapter-switch-form select{width:100%}.chapter-switch-form .btn{align-self:flex-start}

.practice-review-form .practice-option{border:1px solid transparent;border-radius:8px;padding:8px 10px;margin:4px 0;transition:.15s ease}.practice-review-form .practice-option.selected-correct{background:#dcfce7;border-color:#22c55e;color:#166534}.practice-review-form .practice-option.selected-wrong{background:#fee2e2;border-color:#ef4444;color:#991b1b}.practice-review-form .practice-option.correct-answer{background:#ecfdf5;border-color:#16a34a;color:#166534}.answer-feedback{display:none;margin-top:10px;border-radius:10px;padding:10px 12px;line-height:1.45}.answer-feedback.ok{display:block;background:#dcfce7;border:1px solid #22c55e;color:#166534}.answer-feedback.bad{display:block;background:#fff7ed;border:1px solid #fb923c;color:#9a3412}.result-explanation{margin-top:6px;background:#fff7ed;border-left:4px solid #fb923c;border-radius:6px;padding:8px 10px;color:#9a3412}

/* Mobile: ưu tiên hiển thị tình huống/video và câu hỏi trước, danh sách câu hỏi xuống dưới. */