:root {
  --primary: #6366F1; --primary-light: #818CF8; --primary-dark: #4338CA;
  --accent: #F59E0B; --accent-light: #FCD34D;
  --bg: #F1F5F9; --card-bg: #FFFFFF; --text: #0F172A; --text-secondary: #64748B;
  --border: #E2E8F0; --success: #10B981; --danger: #EF4444; --warning: #F59E0B;
  --focus-ring: rgba(99,102,241,0.32);
  --surface-soft: rgba(255,255,255,0.78);
  --sidebar-w: 280px; --radius: 14px;
  --shadow: 0 4px 24px rgba(0,0,0,0.07); --shadow-sm: 0 1px 6px rgba(0,0,0,0.05);
  --shadow-lg: 0 8px 32px rgba(0,0,0,0.1);
}
* { margin:0; padding:0; box-sizing:border-box; }
body { font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", sans-serif; background:
  radial-gradient(1200px 500px at 95% -10%, #dbeafe 0%, rgba(219,234,254,0) 55%),
  radial-gradient(900px 420px at -15% 115%, #fae8ff 0%, rgba(250,232,255,0) 50%),
  var(--bg); color: var(--text); line-height: 1.6; overflow: hidden; height: 100vh; -webkit-font-smoothing: antialiased; }
::selection { background: rgba(99,102,241,0.22); color: var(--text); }

button, input, select, textarea { font: inherit; }
button, [role="button"], .nav-tab, .quiz-choice, .quiz-option, .cat-nav-card, .cat-concept-item, .concept-mini, .search-result-item { -webkit-tap-highlight-color: transparent; }

:where(button, input, select, textarea, [tabindex="0"]):focus-visible {
  outline: none;
  box-shadow: 0 0 0 3px var(--focus-ring);
}

/* ===== SIDEBAR ===== */
.sidebar { position: fixed; left: 0; top: 0; bottom: 0; width: var(--sidebar-w); background: linear-gradient(180deg, #1E1B4B 0%, #312E81 40%, #4338CA 100%); color: white; display: flex; flex-direction: column; z-index: 100; transition: transform 0.35s cubic-bezier(0.4,0,0.2,1); }
.sidebar-header { padding: 22px 20px 14px; border-bottom: 1px solid rgba(255,255,255,0.08); }
.sidebar-header h2 { font-size: 17px; font-weight: 800; margin-bottom: 3px; background: linear-gradient(135deg, #FCD34D, #F59E0B); -webkit-background-clip: text; -webkit-text-fill-color: transparent; letter-spacing: -0.3px; }
.sidebar-header p { font-size: 11px; color: rgba(255,255,255,0.45); }
.nav-tabs { display: flex; padding: 10px 14px 0; gap: 4px; }
.nav-tab { flex: 1; padding: 8px 0; text-align: center; font-size: 12px; font-weight: 600; background: rgba(255,255,255,0.06); border: none; border-radius: 8px 8px 0 0; color: rgba(255,255,255,0.5); cursor: pointer; transition: all 0.2s; }
.nav-tab.active { background: rgba(255,255,255,0.15); color: white; }
.nav-tab:hover { color: rgba(255,255,255,0.85); }
.sidebar-search { padding: 10px 14px; }
.sidebar-search input { width: 100%; padding: 8px 12px; background: rgba(255,255,255,0.08); border: 1px solid rgba(255,255,255,0.12); border-radius: 8px; color: white; font-size: 13px; outline: none; transition: all 0.2s; }
.sidebar-search input::placeholder { color: rgba(255,255,255,0.35); }
.sidebar-search input:focus { border-color: var(--accent); background: rgba(255,255,255,0.12); box-shadow: 0 0 0 3px rgba(245,158,11,0.15); }
.sidebar-list { flex: 1; overflow-y: auto; padding: 2px 10px 14px; }
.sidebar-list::-webkit-scrollbar { width: 3px; }
.sidebar-list::-webkit-scrollbar-thumb { background: rgba(255,255,255,0.15); border-radius: 3px; }

/* Category */
.cat-group { margin-bottom: 6px; }
.cat-header { display: flex; align-items: center; gap: 6px; padding: 7px 10px; border-radius: 8px; cursor: pointer; font-size: 11px; font-weight: 700; color: rgba(255,255,255,0.6); transition: all 0.15s; letter-spacing: 0.3px; text-transform: uppercase; }
.cat-header:hover { background: rgba(255,255,255,0.06); color: rgba(255,255,255,0.9); }
.cat-header .arrow { transition: transform 0.25s; font-size: 10px; }
.cat-header.collapsed .arrow { transform: rotate(-90deg); }
.cat-header .arrow svg { color: rgba(255,255,255,0.4); }
.cat-items { overflow: hidden; transition: max-height 0.35s ease; }
.cat-items.collapsed { max-height: 0 !important; }
.concept-item { display: flex; align-items: center; gap: 8px; padding: 6px 10px 6px 18px; border-radius: 7px; cursor: pointer; transition: all 0.15s; font-size: 12px; color: rgba(255,255,255,0.6); }
.concept-item:hover { background: rgba(255,255,255,0.08); color: white; }
.concept-item.active { background: rgba(245,158,11,0.15); color: var(--accent); font-weight: 600; }
.concept-item.bookmarked .title { color: rgba(255,255,255,0.95); }
.concept-item .num { width: 22px; height: 22px; display: flex; align-items: center; justify-content: center; background: rgba(255,255,255,0.06); border-radius: 6px; font-size: 10px; font-weight: 700; flex-shrink: 0; }
.concept-item.active .num { background: var(--accent); color: #1E1B4B; }
.concept-item .title { white-space: nowrap; overflow: hidden; text-overflow: ellipsis; flex: 1; }
.concept-item .bookmark-icon { font-size: 11px; opacity: 0.3; cursor: pointer; transition: opacity 0.15s; }
.concept-item .bookmark-icon:hover { opacity: 1; }
.concept-item.bookmarked .bookmark-icon { opacity: 0.7; }

/* ===== MAIN ===== */
.main { margin-left: var(--sidebar-w); height: 100vh; display: flex; flex-direction: column; overflow: hidden; }
.topbar { padding: 16px 28px; background: var(--surface-soft); border-bottom: 1px solid rgba(226,232,240,0.9); backdrop-filter: blur(10px); display: flex; align-items: center; gap: 12px; flex-shrink: 0; position: sticky; top: 0; z-index: 70; }
.topbar h1 { font-size: 18px; font-weight: 800; background: linear-gradient(135deg, var(--primary), var(--primary-light)); -webkit-background-clip: text; -webkit-text-fill-color: transparent; }
.topbar .badge { padding: 4px 10px; background: linear-gradient(135deg, var(--primary), var(--primary-light)); color: white; border-radius: 20px; font-size: 10px; font-weight: 700; letter-spacing: 0.3px; }
.breadcrumb { margin-left: auto; font-size: 12px; color: var(--text-secondary); cursor: pointer; transition: color 0.2s; }
.breadcrumb:hover { color: var(--primary); }
.topbar-progress { position: absolute; left: 0; right: 0; bottom: -1px; height: 2px; background: rgba(148,163,184,0.18); overflow: hidden; }
.topbar-progress-bar { display: block; width: 100%; height: 100%; background: linear-gradient(90deg, var(--accent), var(--primary)); transform-origin: left center; transform: scaleX(0); transition: transform 0.14s linear; }

.content-area { flex: 1; overflow-y: auto; padding: 20px 28px 40px; scroll-behavior: smooth; }
.content-area::-webkit-scrollbar { width: 5px; }
.content-area::-webkit-scrollbar-thumb { background: #CBD5E1; border-radius: 5px; }

/* ===== CONCEPT CARD ===== */
.concept-card { background: var(--card-bg); border-radius: var(--radius); box-shadow: var(--shadow-sm); border: 1px solid rgba(226,232,240,0.7); overflow: hidden; max-width: 840px; margin: 0 auto 20px; animation: cardIn 0.35s ease; }
@keyframes cardIn { from { opacity:0; transform:translateY(16px); } to { opacity:1; transform:translateY(0); } }
.concept-card-header { padding: 22px 28px; background: linear-gradient(135deg, var(--primary) 0%, var(--primary-light) 100%); color: white; position: relative; overflow: hidden; }
.concept-card-header::before { content:''; position:absolute; right:-20px; top:-20px; width:120px; height:120px; background:rgba(255,255,255,0.08); border-radius:50%; }
.concept-card-header .concept-num { display: inline-block; padding: 3px 10px; background: rgba(255,255,255,0.18); border-radius: 16px; font-size: 10px; font-weight: 700; margin-bottom: 8px; letter-spacing: 0.5px; }
.concept-card-header h2 { font-size: 22px; font-weight: 800; margin-bottom: 2px; }
.concept-card-header .subtitle { font-size: 13px; opacity: 0.85; }
.concept-card-body { padding: 24px 28px; }
.scenario-box { background: linear-gradient(135deg, #FEF3C7, #FDE68A); border-left: 4px solid var(--accent); padding: 14px 18px; border-radius: 0 10px 10px 0; margin-bottom: 20px; font-size: 14px; }
.scenario-box .label { font-weight: 700; color: #92400E; margin-bottom: 4px; font-size: 11px; letter-spacing: 0.5px; text-transform: uppercase; }
.content-text { font-size: 15px; line-height: 1.85; color: var(--text); margin-bottom: 20px; }
.content-text p { margin-bottom: 10px; }
.content-text strong { color: var(--primary-dark); font-weight: 700; }
.steps-box { background: linear-gradient(135deg, #F0FDF4, #DCFCE7); border-radius: 12px; padding: 18px 22px; margin-bottom: 20px; }
.steps-box h4 { color: #166534; margin-bottom: 12px; font-size: 13px; font-weight: 700; letter-spacing: 0.3px; }
.step-item { display: flex; gap: 10px; margin-bottom: 8px; font-size: 13px; }
.step-item .step-num { width: 22px; height: 22px; background: var(--success); color: white; border-radius: 50%; display: flex; align-items: center; justify-content: center; font-size: 11px; font-weight: 700; flex-shrink: 0; margin-top: 1px; }
.tip-box { background: linear-gradient(135deg, #EEF2FF, #E0E7FF); border-radius: 12px; padding: 18px 22px; margin-bottom: 20px; border-left: 4px solid var(--primary); }
.tip-box h4 { color: var(--primary-dark); margin-bottom: 6px; font-size: 13px; font-weight: 700; }
.tip-box p { font-size: 14px; color: #3730A3; line-height: 1.7; }
.image-box { text-align: center; margin: 20px 0 0; }
.image-box img { max-width: 100%; border-radius: 10px; box-shadow: var(--shadow); border: 1px solid var(--border); }
.image-box .caption { font-size: 12px; color: var(--text-secondary); margin-top: 8px; }
.nav-buttons { display: flex; justify-content: space-between; max-width: 840px; margin: 0 auto; padding: 0 0 32px; gap: 10px; }
.nav-btn { padding: 9px 18px; background: white; border: 1.5px solid var(--border); border-radius: 10px; font-size: 13px; color: var(--primary); cursor: pointer; font-weight: 600; transition: all 0.2s; }
.nav-btn:hover { background: var(--primary); color: white; border-color: var(--primary); box-shadow: 0 6px 16px rgba(99,102,241,0.26); transform: translateY(-1px); }
.nav-btn:disabled { opacity: 0.3; cursor: not-allowed; }
.nav-btn:disabled:hover { background: white; color: var(--text-secondary); border-color: var(--border); box-shadow: none; }

/* ===== OVERVIEW ===== */
.overview-page { max-width: 840px; margin: 0 auto; }
.overview-page .welcome { text-align: center; padding: 32px 0 24px; }
.overview-page .welcome h2 { font-size: 26px; font-weight: 800; margin-bottom: 6px; background: linear-gradient(135deg, var(--primary), var(--accent)); -webkit-background-clip: text; -webkit-text-fill-color: transparent; letter-spacing: -0.5px; }
.overview-page .welcome p { color: var(--text-secondary); font-size: 14px; }
.stats-row { display: grid; grid-template-columns: repeat(4, 1fr); gap: 12px; margin: 20px 0; }
.stat-card { background: white; border-radius: 12px; padding: 18px; text-align: center; box-shadow: var(--shadow-sm); border: 1px solid rgba(226,232,240,0.7); transition: transform 0.2s, box-shadow 0.2s; }
.stat-card:hover { transform: translateY(-2px); }
.stat-card .stat-num { font-size: 28px; font-weight: 800; }
.stat-card:nth-child(1) .stat-num { color: var(--primary); }
.stat-card:nth-child(2) .stat-num { color: var(--success); }
.stat-card:nth-child(3) .stat-num { color: var(--warning); }
.stat-card:nth-child(4) .stat-num { color: var(--accent); }
.stat-card .stat-label { font-size: 11px; color: var(--text-secondary); margin-top: 2px; font-weight: 600; }
.cat-nav-card { background: white; border-radius: 12px; box-shadow: var(--shadow-sm); padding: 16px 20px; margin-bottom: 10px; cursor: pointer; transition: all 0.25s; display: flex; align-items: center; gap: 14px; border: 1.5px solid transparent; }
.cat-nav-card:hover { box-shadow: var(--shadow); transform: translateX(4px); border-color: var(--primary); }
.cat-nav-card .cat-icon { width: 42px; height: 42px; border-radius: 12px; display: flex; align-items: center; justify-content: center; flex-shrink: 0; }
.cat-nav-card .cat-icon svg { width: 22px; height: 22px; }
.cat-nav-card .cat-info h3 { font-size: 15px; font-weight: 700; color: var(--text); }
.cat-nav-card .cat-info p { font-size: 12px; color: var(--text-secondary); margin-top: 1px; }
.cat-nav-card .cat-range { margin-left: auto; font-size: 12px; color: var(--primary); font-weight: 700; background: #EEF2FF; padding: 4px 10px; border-radius: 16px; white-space: nowrap; }

/* Category sub-page */
.cat-sub-page { max-width: 840px; margin: 0 auto; }
.cat-sub-header { background: white; border-radius: var(--radius); box-shadow: var(--shadow-sm); padding: 24px; margin-bottom: 18px; border-left: 5px solid var(--primary); }
.cat-sub-header h2 { font-size: 20px; font-weight: 800; color: var(--primary); margin-bottom: 4px; }
.cat-sub-header p { font-size: 13px; color: var(--text-secondary); }
.cat-concept-list { display: flex; flex-direction: column; gap: 8px; }
.cat-concept-item { background: white; border-radius: 10px; box-shadow: var(--shadow-sm); padding: 14px 18px; cursor: pointer; transition: all 0.2s; display: flex; align-items: center; gap: 12px; border: 1.5px solid transparent; }
.cat-concept-item:hover { box-shadow: var(--shadow); transform: translateX(4px); border-color: var(--primary); }
.cat-concept-item .cci-num { width: 32px; height: 32px; background: linear-gradient(135deg, var(--primary), var(--primary-light)); color: white; border-radius: 9px; display: flex; align-items: center; justify-content: center; font-size: 12px; font-weight: 800; flex-shrink: 0; }
.cat-concept-item .cci-title { font-size: 14px; font-weight: 600; }
.cat-concept-item .cci-preview { font-size: 12px; color: var(--text-secondary); margin-top: 2px; white-space: nowrap; overflow: hidden; text-overflow: ellipsis; }
.cat-concept-item .cci-arrow { margin-left: auto; color: var(--text-secondary); font-size: 14px; transition: transform 0.2s; }
.cat-concept-item:hover .cci-arrow { color: var(--primary); }
.cat-concept-item:hover .cci-arrow svg { transform: translateX(3px); }

/* Concepts grid */
.concepts-grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(175px, 1fr)); gap: 10px; margin: 20px 0 32px; }
.concept-mini { background: white; border-radius: 10px; padding: 14px; cursor: pointer; box-shadow: var(--shadow-sm); transition: all 0.2s; border: 1.5px solid transparent; }
.concept-mini:hover { border-color: var(--primary); transform: translateY(-3px); box-shadow: var(--shadow); }
.concept-mini .mini-num { display: inline-block; width: 26px; height: 26px; background: linear-gradient(135deg, var(--primary), var(--primary-light)); color: white; border-radius: 7px; text-align: center; line-height: 26px; font-size: 11px; font-weight: 800; margin-bottom: 6px; }
.concept-mini .mini-title { font-size: 13px; font-weight: 600; color: var(--text); }

/* ===== QUIZ ===== */
.quiz-page { max-width: 740px; margin: 0 auto; }
.quiz-setup { background: white; border-radius: var(--radius); box-shadow: var(--shadow-sm); border: 1px solid rgba(226,232,240,0.7); padding: 32px; text-align: center; }
.quiz-setup h3 { font-size: 22px; font-weight: 800; margin-bottom: 6px; background: linear-gradient(135deg, var(--primary), var(--primary-light)); -webkit-background-clip: text; -webkit-text-fill-color: transparent; }
.quiz-setup p { color: var(--text-secondary); margin-bottom: 22px; font-size: 14px; }
.quiz-options { display: grid; grid-template-columns: repeat(3, 1fr); gap: 10px; margin-bottom: 22px; }
.quiz-option { padding: 16px; background: var(--bg); border: 2px solid var(--border); border-radius: 12px; cursor: pointer; transition: all 0.2s; text-align: center; }
.quiz-option:hover { border-color: var(--primary); }
.quiz-option.selected { border-color: var(--primary); background: #EEF2FF; box-shadow: 0 0 0 3px rgba(99,102,241,0.1); }
.quiz-option .opt-num { font-size: 24px; font-weight: 800; color: var(--primary); }
.quiz-option .opt-label { color: var(--text-secondary); font-size: 12px; margin-top: 2px; }
.quiz-cat-select { display: flex; gap: 16px; flex-wrap: wrap; justify-content: center; margin-bottom: 20px; }
.quiz-cat-select label { font-size: 13px; color: var(--text-secondary); font-weight: 600; }
.quiz-cat-select select { padding: 6px 12px; border: 2px solid var(--border); border-radius: 8px; font-size: 13px; outline: none; transition: border-color 0.2s; }
.quiz-cat-select select:focus { border-color: var(--primary); }
.start-quiz-btn { padding: 12px 36px; background: linear-gradient(135deg, var(--primary), var(--primary-light)); color: white; border: none; border-radius: 12px; font-size: 15px; font-weight: 700; cursor: pointer; transition: all 0.25s; letter-spacing: 0.3px; }
.start-quiz-btn:hover { transform: translateY(-2px); box-shadow: 0 6px 20px rgba(99,102,241,0.35); }
.quiz-active { display: none; }
.quiz-progress { background: white; border-radius: 12px; box-shadow: var(--shadow-sm); border: 1px solid rgba(226,232,240,0.7); padding: 12px 20px; margin-bottom: 16px; display: flex; align-items: center; gap: 12px; }
.quiz-progress .progress-bar { flex: 1; height: 6px; background: #E2E8F0; border-radius: 3px; overflow: hidden; }
.quiz-progress .progress-fill { height: 100%; background: linear-gradient(90deg, var(--primary), var(--accent)); border-radius: 3px; transition: width 0.4s ease; }
.quiz-progress .progress-text { font-size: 12px; color: var(--text-secondary); font-weight: 700; white-space: nowrap; }
.quiz-question-card { background: white; border-radius: var(--radius); box-shadow: var(--shadow-sm); border: 1px solid rgba(226,232,240,0.7); padding: 24px; margin-bottom: 16px; animation: cardIn 0.3s ease; }
.quiz-question-card .q-tag { display: inline-block; padding: 4px 12px; background: #EEF2FF; color: var(--primary); border-radius: 20px; font-size: 11px; font-weight: 700; margin-bottom: 12px; }
.quiz-question-card .q-text { font-size: 16px; font-weight: 700; margin-bottom: 20px; line-height: 1.6; color: var(--text); }
.quiz-choices { display: flex; flex-direction: column; gap: 8px; }
.quiz-choice { padding: 12px 16px; background: var(--bg); border: 2px solid var(--border); border-radius: 10px; cursor: pointer; font-size: 14px; transition: all 0.2s; display: flex; align-items: center; gap: 10px; }
.quiz-choice:hover { border-color: var(--primary); background: #EEF2FF; transform: translateX(2px); }
.quiz-choice .choice-letter { width: 26px; height: 26px; background: white; border: 2px solid var(--border); border-radius: 50%; display: flex; align-items: center; justify-content: center; font-weight: 800; font-size: 12px; flex-shrink: 0; transition: all 0.2s; }
.quiz-choice.correct { border-color: var(--success); background: #F0FDF4; }
.quiz-choice.correct .choice-letter { background: var(--success); color: white; border-color: var(--success); }
.quiz-choice.wrong { border-color: var(--danger); background: #FEF2F2; }
.quiz-choice.wrong .choice-letter { background: var(--danger); color: white; border-color: var(--danger); }
.quiz-choice.disabled { pointer-events: none; opacity: 0.5; }
.quiz-choice.disabled.correct { opacity: 1; }
.quiz-explanation { margin-top: 16px; padding: 14px 18px; background: #F0FDF4; border-radius: 10px; border-left: 4px solid var(--success); font-size: 13px; line-height: 1.7; display: none; }
.quiz-explanation.show { display: block; animation: cardIn 0.3s ease; }
.quiz-explanation .exp-label { font-weight: 700; color: #166534; margin-bottom: 3px; }
.quiz-next { margin-top: 14px; text-align: right; display: none; }
.quiz-next.show { display: block; animation: cardIn 0.2s ease; }
.quiz-next button { padding: 9px 22px; background: linear-gradient(135deg, var(--primary), var(--primary-light)); color: white; border: none; border-radius: 10px; font-size: 13px; font-weight: 700; cursor: pointer; transition: all 0.2s; }
.quiz-next button:hover { box-shadow: 0 4px 12px rgba(99,102,241,0.3); }
.quiz-result { display: none; background: white; border-radius: var(--radius); box-shadow: var(--shadow-sm); padding: 36px; text-align: center; animation: cardIn 0.4s ease; }
.quiz-result.show { display: block; }
.quiz-result .score-circle { width: 110px; height: 110px; border-radius: 50%; margin: 0 auto 18px; display: flex; align-items: center; justify-content: center; font-size: 34px; font-weight: 800; }
.quiz-result .score-circle.high { background: linear-gradient(135deg, #D1FAE5, #A7F3D0); color: #065F46; }
.quiz-result .score-circle.mid { background: linear-gradient(135deg, #FEF3C7, #FDE68A); color: #92400E; }
.quiz-result .score-circle.low { background: linear-gradient(135deg, #FEE2E2, #FECACA); color: #991B1B; }
.quiz-result h3 { font-size: 22px; font-weight: 800; margin-bottom: 6px; }
.quiz-result p { color: var(--text-secondary); margin-bottom: 22px; font-size: 14px; }
.quiz-result .result-stats { display: flex; justify-content: center; gap: 28px; margin-bottom: 24px; }
.quiz-result .result-stat { text-align: center; }
.quiz-result .result-stat .rs-num { font-size: 24px; font-weight: 800; }
.quiz-result .result-stat .rs-label { font-size: 11px; color: var(--text-secondary); font-weight: 600; }
.quiz-result button { padding: 10px 26px; background: var(--primary); color: white; border: none; border-radius: 10px; font-size: 14px; font-weight: 700; cursor: pointer; transition: all 0.2s; }
.quiz-result button:hover { box-shadow: 0 4px 12px rgba(99,102,241,0.3); }

/* Open answer */
.open-answer-card { background: white; border-radius: var(--radius); box-shadow: var(--shadow-sm); border: 1px solid rgba(226,232,240,0.7); padding: 24px; margin-bottom: 16px; animation: cardIn 0.3s ease; }
.open-answer-card textarea { width: 100%; min-height: 90px; padding: 12px; border: 2px solid var(--border); border-radius: 10px; font-size: 14px; font-family: inherit; resize: vertical; outline: none; margin-top: 12px; transition: border-color 0.2s; line-height: 1.6; }
.open-answer-card textarea:focus { border-color: var(--primary); box-shadow: 0 0 0 3px rgba(99,102,241,0.1); }
.open-answer-card .submit-answer { margin-top: 12px; padding: 8px 20px; background: var(--primary); color: white; border: none; border-radius: 8px; font-size: 13px; font-weight: 700; cursor: pointer; transition: all 0.2s; }
.open-answer-card .submit-answer:hover { box-shadow: 0 4px 12px rgba(99,102,241,0.3); }
.open-answer-card .model-answer { margin-top: 16px; padding: 14px 18px; background: #F0FDF4; border-radius: 10px; border-left: 4px solid var(--success); font-size: 13px; line-height: 1.7; display: none; }
.open-answer-card .model-answer.show { display: block; animation: cardIn 0.3s ease; }
.open-answer-card .model-answer .ma-label { font-weight: 700; color: #166534; margin-bottom: 4px; }

/* Search */
.search-results { max-width: 840px; margin: 0 auto; }
.search-result-item { background: white; border-radius: 10px; box-shadow: var(--shadow-sm); border: 1px solid rgba(226,232,240,0.7); padding: 16px 20px; margin-bottom: 8px; cursor: pointer; transition: all 0.2s; border-left: 4px solid var(--primary); }
.search-result-item:hover { box-shadow: var(--shadow); transform: translateX(4px); }
.search-result-item .sr-title { font-size: 15px; font-weight: 700; color: var(--primary); }
.search-result-item .sr-cat { font-size: 11px; color: var(--text-secondary); margin-left: 8px; background: var(--bg); padding: 2px 8px; border-radius: 10px; }
.search-result-item .sr-preview { font-size: 12px; color: var(--text-secondary); margin-top: 4px; line-height: 1.5; }
.search-result-item .sr-preview mark { background: #FEF08A; padding: 0 2px; border-radius: 2px; }
.no-results { text-align: center; padding: 48px 0; color: var(--text-secondary); }
.no-results svg { width:48px; height:48px; stroke-width:1.5; }

/* Bookmarks */
.bookmarks-page { max-width: 840px; margin: 0 auto; }
.bookmarks-page .empty { text-align: center; padding: 48px 0; color: var(--text-secondary); }

/* Mobile overlay */
.sidebar-overlay { display: none; position: fixed; inset: 0; background: rgba(0,0,0,0.4); z-index: 90; }
.sidebar-overlay.show { display: block; }
.mobile-toggle { display: none; position: fixed; bottom: 16px; right: 16px; width: 44px; height: 44px; background: linear-gradient(135deg, var(--primary), var(--primary-light)); color: white; border: none; border-radius: 50%; font-size: 18px; cursor: pointer; box-shadow: 0 4px 16px rgba(99,102,241,0.35); z-index: 200; align-items: center; justify-content: center; padding: 0; }
.mobile-toggle svg { width: 20px; height: 20px; }

/* ===== MOBILE ===== */
@media (max-width: 768px) {
  :root { --sidebar-w: 260px; }
  .sidebar { transform: translateX(-100%); box-shadow: none; transition: transform 0.35s cubic-bezier(0.4,0,0.2,1); }
  .sidebar.open { transform: translateX(0); box-shadow: 4px 0 24px rgba(0,0,0,0.3); }
  .main { margin-left: 0; }
  .mobile-toggle { display: flex; align-items: center; justify-content: center; }
  .topbar { padding: 10px 14px; flex-wrap: wrap; gap: 4px; top: 0; z-index: 50; }
  .topbar h1 { font-size: 15px; }
  .topbar .badge { font-size: 9px; padding: 2px 6px; }
  .breadcrumb { display: none; }
  .topbar-progress { height: 1.5px; }
  .content-area { padding: 10px; }
  .concept-card { border-radius: 10px; margin-bottom: 12px; }
  .concept-card-header { padding: 16px 18px; }
  .concept-card-header::before { display: none; }
  .concept-card-header h2 { font-size: 18px; }
  .concept-card-body { padding: 16px 18px; }
  .scenario-box { padding: 12px 14px; font-size: 13px; margin-bottom: 16px; }
  .content-text { font-size: 14px; line-height: 1.8; }
  .steps-box, .tip-box { padding: 14px 16px; margin-bottom: 16px; }
  .nav-buttons { padding: 0 0 24px; gap: 6px; }
  .nav-btn { flex: 1; padding: 10px 10px; font-size: 12px; text-align: center; }
  .overview-page .welcome { padding: 20px 0 12px; }
  .overview-page .welcome h2 { font-size: 18px; }
  .stats-row { grid-template-columns: repeat(2, 1fr); gap: 6px; }
  .stat-card { padding: 12px 6px; }
  .stat-card .stat-num { font-size: 22px; }
  .cat-nav-card { padding: 12px 14px; gap: 10px; }
  .cat-nav-card .cat-icon { width: 36px; height: 36px; font-size: 18px; border-radius: 10px; }
  .cat-nav-card .cat-icon svg { width: 18px; height: 18px; }
  .cat-nav-card .cat-info h3 { font-size: 14px; }
  .cat-nav-card .cat-range { font-size: 10px; padding: 3px 8px; }
  .concepts-grid { grid-template-columns: repeat(2, 1fr); gap: 6px; margin: 14px 0 24px; }
  .concept-mini { padding: 10px; }
  .concept-mini .mini-title { font-size: 12px; }
  .quiz-setup { padding: 20px 16px; }
  .quiz-option { padding: 12px 8px; }
  .quiz-question-card { padding: 16px; }
  .quiz-question-card .q-text { font-size: 15px; }
  .quiz-choice { padding: 10px 12px; font-size: 13px; }
  .open-answer-card { padding: 16px; }
  .quiz-result { padding: 24px 14px; }
  .quiz-result .score-circle { width: 90px; height: 90px; font-size: 28px; }
  .cat-concept-item { padding: 12px 14px; }
  .cat-concept-item .cci-num { width: 28px; height: 28px; font-size: 11px; border-radius: 8px; }
  body { padding-bottom: env(safe-area-inset-bottom); }
  .mobile-toggle { bottom: calc(16px + env(safe-area-inset-bottom)); right: calc(16px + env(safe-area-inset-right)); }
}
@media (max-width: 380px) {
  .quiz-options { grid-template-columns: 1fr; }
}

@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after { animation: none !important; transition: none !important; scroll-behavior: auto !important; }
}