*{margin:0;padding:0;box-sizing:border-box}
:root{--primary:#e74c3c;--primary-light:#ff6b6b;--bg:#f5f7fa;--card:#fff;--text:#2c3e50;--text-light:#7f8c8d;--success:#27ae60;--success-light:#2ecc71;--danger:#e74c3c;--border:#e8ecf1;--shadow:0 2px 12px rgba(0,0,0,.08)}
body{font-family:-apple-system,BlinkMacSystemFont,'Segoe UI','PingFang SC','Hiragino Sans GB','Microsoft YaHei',sans-serif;background:var(--bg);color:var(--text);min-height:100vh;line-height:1.6}
.header{background:linear-gradient(135deg,#c0392b,#e74c3c);color:#fff;padding:20px 0;text-align:center;box-shadow:0 2px 20px rgba(231,76,60,.3);position:sticky;top:0;z-index:100}
.header h1{font-size:1.5rem;font-weight:600;letter-spacing:1px}
.header .subtitle{font-size:.85rem;opacity:.85;margin-top:4px}
.container{max-width:1100px;margin:0 auto;padding:24px 20px}

/* Start Page */
.start-page{text-align:center;padding:50px 24px}
.start-page h2{font-size:1.8rem;margin-bottom:10px;color:var(--text)}
.start-page .desc{color:var(--text-light);margin-bottom:36px;font-size:1rem}
.mode-select{display:flex;gap:20px;justify-content:center;margin-bottom:36px;flex-wrap:wrap}
.mode-card{background:var(--card);border:2px solid var(--border);border-radius:16px;padding:28px 40px;cursor:pointer;transition:all .2s;min-width:180px}
.mode-card:hover{border-color:var(--primary);transform:translateY(-2px);box-shadow:0 4px 16px rgba(231,76,60,.15)}
.mode-card.active{border-color:var(--primary);background:rgba(231,76,60,.04);box-shadow:0 4px 16px rgba(231,76,60,.15)}
.mode-card .mode-icon{font-size:2rem;margin-bottom:8px}
.mode-card .mode-name{font-size:1.1rem;font-weight:600;margin-bottom:4px}
.mode-card .mode-desc{font-size:.8rem;color:var(--text-light)}
.section-select{display:flex;gap:10px;justify-content:center;flex-wrap:wrap;margin-bottom:30px}
.section-btn{padding:10px 20px;border-radius:10px;background:var(--card);border:2px solid var(--border);cursor:pointer;font-size:.95rem;font-weight:500;transition:all .2s}
.section-btn:hover{border-color:var(--primary);color:var(--primary)}
.section-btn.active{background:var(--primary);color:#fff;border-color:var(--primary)}
.btn{padding:12px 32px;border-radius:12px;border:none;cursor:pointer;font-size:1rem;font-weight:600;transition:all .2s}
.btn-primary{background:var(--primary);color:#fff;box-shadow:0 2px 8px rgba(231,76,60,.3)}
.btn-primary:hover{background:var(--primary-light)}
.btn-primary:disabled{opacity:.5;cursor:not-allowed}
.btn-outline{background:transparent;border:2px solid var(--border);color:var(--text);padding:10px 24px;border-radius:10px;cursor:pointer;font-size:.95rem;font-weight:500;transition:all .2s}
.btn-outline:hover{border-color:var(--primary);color:var(--primary)}
.btn-outline:disabled{opacity:.4;cursor:not-allowed;border-color:var(--border);color:var(--text-light);background:var(--card)}
.btn-outline:disabled:hover{border-color:var(--border);color:var(--text-light)}

/* Quiz Page */
.nav-tabs{display:flex;gap:10px;margin-bottom:20px;flex-wrap:wrap}
.nav-tab{padding:10px 20px;border-radius:12px;background:var(--card);border:2px solid var(--border);cursor:pointer;font-size:.95rem;font-weight:500;transition:all .2s;user-select:none}
.nav-tab:hover{border-color:var(--primary);color:var(--primary)}
.nav-tab.active{background:var(--primary);color:#fff;border-color:var(--primary);box-shadow:0 2px 8px rgba(231,76,60,.3)}
.nav-tab .badge{display:inline-block;background:rgba(255,255,255,.3);padding:1px 8px;border-radius:10px;font-size:.75rem;margin-left:6px}
.nav-tab.active .badge{background:rgba(255,255,255,.3)}

.progress-bar-wrap{background:var(--border);border-radius:20px;height:10px;margin-bottom:20px;overflow:hidden}
.progress-bar{height:100%;background:linear-gradient(90deg,var(--primary),var(--primary-light));border-radius:20px;transition:width .3s}

.stats-row{display:flex;gap:12px;margin-bottom:20px;flex-wrap:wrap}
.stat-card{flex:1;min-width:80px;background:var(--card);border-radius:12px;padding:14px;text-align:center;box-shadow:var(--shadow)}
.stat-card .num{font-size:1.5rem;font-weight:700;color:var(--primary)}
.stat-card .label{font-size:.8rem;color:var(--text-light);margin-top:4px}

.q-nav-grid{display:flex;flex-wrap:wrap;gap:5px;margin-bottom:16px}
.q-nav-dot{width:30px;height:30px;border-radius:8px;display:flex;align-items:center;justify-content:center;font-size:.72rem;font-weight:600;cursor:pointer;border:1.5px solid var(--border);background:var(--card);transition:all .2s}
.q-nav-dot:hover{border-color:var(--primary)}
.q-nav-dot.current{border-color:var(--primary);background:rgba(231,76,60,.08);color:var(--primary);font-weight:700}
.q-nav-dot.correct-dot{background:rgba(39,174,96,.15);border-color:var(--success);color:var(--success)}
.q-nav-dot.wrong-dot{background:rgba(231,76,60,.15);border-color:var(--danger);color:var(--danger)}
.q-nav-dot.unanswered{background:var(--card);border-color:var(--border);color:var(--text-light)}

.quiz-layout{display:flex;gap:32px;align-items:flex-start}
.quiz-main{flex:1;min-width:0;order:1}
.quiz-sidebar{width:280px;flex-shrink:0;position:sticky;top:20px;order:2}
.sidebar-header{margin-bottom:16px;padding-bottom:16px;border-bottom:2px solid var(--border)}
.sidebar-title{font-size:1rem;font-weight:600;color:var(--text);margin-bottom:8px}
.sidebar-toggle{display:none;width:36px;height:36px;border-radius:8px;background:var(--card);border:2px solid var(--border);cursor:pointer;align-items:center;justify-content:center;font-size:1.2rem;transition:all .2s}
.sidebar-toggle:hover{border-color:var(--primary);color:var(--primary)}
.sidebar-content{max-height:70vh;overflow-y:auto;padding-right:8px}
.sidebar-content::-webkit-scrollbar{width:6px}
.sidebar-content::-webkit-scrollbar-track{background:var(--border);border-radius:3px}
.sidebar-content::-webkit-scrollbar-thumb{background:var(--primary);border-radius:3px}

.mobile-nav-btn{display:none;width:100%;padding:12px;border-radius:10px;background:var(--card);border:2px solid var(--border);margin-bottom:16px;cursor:pointer;font-size:.9rem;font-weight:500;text-align:center;transition:all .2s}
.mobile-nav-btn:hover{border-color:var(--primary);color:var(--primary)}

/* Slide container */
.slide-container{overflow:hidden;position:relative;min-height:300px;max-width:100%}
.slide-wrapper{display:flex;transition:transform .35s cubic-bezier(.4,0,.2,1);max-width:100%}
.slide-page{min-width:100%;flex-shrink:0;overflow:hidden;max-width:100%;box-sizing:border-box}

.question-card{background:var(--card);border-radius:16px;padding:32px;box-shadow:var(--shadow);box-sizing:border-box;overflow-wrap:break-word;word-wrap:break-word;width:600px;max-width:600px;margin-left:auto;margin-right:auto;overflow-y:auto;max-height:70vh}
.question-card .q-header{display:flex;align-items:flex-start;gap:12px;margin-bottom:8px}
.question-card .q-number{display:inline-flex;align-items:center;justify-content:center;background:var(--primary);color:#fff;width:32px;height:32px;border-radius:50%;font-size:.9rem;font-weight:600;flex-shrink:0}
.question-card .q-text{font-size:1.15rem;font-weight:500;word-wrap:break-word;overflow-wrap:break-word;word-break:break-word;white-space:normal;flex:1;min-width:0;line-height:1.8}
.options-list{margin-top:24px;display:flex;flex-direction:column;gap:14px}
.option-item{display:flex;align-items:flex-start;gap:12px;padding:16px 20px;border-radius:12px;border:2px solid var(--border);cursor:pointer;transition:all .2s;user-select:none}
.option-item:hover{border-color:var(--primary);background:rgba(231,76,60,.03)}
.option-item.selected{border-color:var(--primary);background:rgba(231,76,60,.06)}
.option-item .opt-label{width:32px;height:32px;border-radius:50%;background:var(--border);text-align:center;line-height:32px;font-weight:600;font-size:.9rem;flex-shrink:0;transition:all .2s}
.option-item.selected .opt-label{background:var(--primary);color:#fff}
.option-item.correct{border-color:var(--success);background:rgba(39,174,96,.06)}
.option-item.correct .opt-label{background:var(--success);color:#fff}
.option-item.wrong{border-color:var(--danger);background:rgba(231,76,60,.06)}
.option-item.wrong .opt-label{background:var(--danger);color:#fff}
.option-item.dimmed{opacity:.5;pointer-events:none}
.option-item .opt-text{padding-top:4px;font-size:1rem;line-height:1.6}

.answer-area{margin-top:24px;padding:18px 20px;border-radius:12px;background:#f8f9fa;font-size:1rem;display:none}
.answer-area.show{display:block}
.answer-area .ans-label{font-weight:600;margin-bottom:4px}
.answer-area .ans-label.correct-label{color:var(--success)}
.answer-area .ans-label.wrong-label{color:var(--danger)}
.answer-area .ans-content{color:var(--text);white-space:pre-wrap}

.textarea-wrap{margin-top:20px}
.textarea-wrap textarea{width:100%;min-height:140px;border:2px solid var(--border);border-radius:12px;padding:16px;font-size:1rem;font-family:inherit;resize:vertical;transition:border-color .2s;background:#fefefe}
.textarea-wrap textarea:focus{outline:none;border-color:var(--primary)}

.btn-row{display:flex;gap:12px;margin-top:24px;flex-wrap:wrap;justify-content:space-between}
.nav-btns{display:flex;gap:10px}

.result-banner{padding:16px 20px;border-radius:12px;margin-bottom:16px;text-align:center;font-size:1.1rem;font-weight:600}
.result-banner.pass{background:rgba(39,174,96,.1);color:var(--success);border:1.5px solid rgba(39,174,96,.3)}
.result-banner.fail{background:rgba(231,76,60,.1);color:var(--danger);border:1.5px solid rgba(231,76,60,.3)}

.auto-next-hint{margin-top:12px;text-align:center;font-size:.85rem;color:var(--success);animation:fadeIn .3s}
@keyframes fadeIn{from{opacity:0;transform:translateY(6px)}to{opacity:1;transform:translateY(0)}}

.footer{text-align:center;padding:30px 0 20px;color:var(--text-light);font-size:.8rem}
@media(max-width:600px){
.container{padding:12px 10px}
.header{padding:14px 0}
.header h1{font-size:1.2rem}
.header .subtitle{font-size:.75rem}
.start-page{padding:24px 12px}
.start-page h2{font-size:1.3rem}
.mode-select{gap:10px;margin-bottom:20px}
.mode-card{padding:16px 18px;min-width:0;flex:1}
.mode-card .mode-icon{font-size:1.6rem}
.mode-card .mode-name{font-size:.95rem}
.mode-card .mode-desc{font-size:.72rem}
.btn{padding:10px 24px;font-size:.9rem}
.btn-outline{padding:8px 16px;font-size:.85rem}
.nav-tabs{gap:6px;margin-bottom:12px}
.nav-tab{padding:6px 12px;font-size:.8rem;border-radius:8px}
.nav-tab .badge{font-size:.7rem;padding:0 6px}
.stats-row{gap:6px;margin-bottom:12px}
.stat-card{padding:8px 4px;min-width:0;border-radius:10px}
.stat-card .num{font-size:1.05rem}
.stat-card .label{font-size:.65rem}
.q-nav-grid{gap:6px;margin-bottom:12px}
.q-nav-dot{width:32px;height:32px;border-radius:8px;font-size:.78rem}
.question-card{padding:16px;border-radius:12px;box-sizing:border-box;width:auto;max-width:100%}
.question-card .q-number{width:24px;height:24px;font-size:.72rem}
.question-card .q-text{font-size:.95rem;word-wrap:break-word;overflow-wrap:break-word;word-break:break-word;white-space:normal}
.options-list{margin-top:12px;gap:8px}
.option-item{padding:10px 12px;border-radius:8px;gap:8px;-webkit-tap-highlight-color:transparent}
.option-item .opt-label{width:24px;height:24px;line-height:24px;font-size:.78rem}
.option-item .opt-text{font-size:.9rem;padding-top:2px}
.answer-area{padding:10px 12px;font-size:.88rem;margin-top:12px}
.textarea-wrap textarea{min-height:100px;font-size:.88rem;padding:10px}
.slide-container{min-height:200px}
.btn-row{margin-top:16px;gap:8px}
.nav-btns{gap:8px}
.result-banner{padding:12px 16px;font-size:.95rem}
.auto-next-hint{font-size:.78rem;margin-top:8px}
.progress-bar-wrap{margin-bottom:12px;height:6px}
.quiz-layout{flex-direction:column;gap:16px}
.quiz-sidebar{width:100%;position:static;order:2}
.quiz-main{width:100%;order:1}
.sidebar-content{display:none;max-height:60vh;padding-right:0;background:var(--card);border-radius:12px;padding:16px;margin-top:12px}
.sidebar-content.show{display:block}
.sidebar-header{display:none}
.mobile-nav-btn{display:block}
.q-nav-grid{gap:8px}
}