.b3{--paper:#f1f6f1;--paper-deep:#dfeadf;--ink:#16302b;--ink-soft:#44605a;--seal:#d0527a;--seal-deep:#9b2f57;--bamboo:#2c7a68;--bamboo-bright:#3a9a4a;--gold:#cfa94f;--rule:#c3dccf}.b3 *{box-sizing:border-box}.b3{scroll-behavior:smooth;margin:0;background:var(--paper);background-image:radial-gradient(ellipse at 20% 10%,rgba(208,82,122,.05),transparent 40%),radial-gradient(ellipse at 80% 90%,rgba(44,122,104,.06),transparent 45%);color:var(--ink);font-family:Noto Sans,Noto Sans SC,sans-serif;line-height:1.6}.b3:before{content:"";position:fixed;inset:0;pointer-events:none;opacity:.5;background-image:url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='120' height='120'%3E%3Cfilter id='n'%3E%3CfeTurbulence type='fractalNoise' baseFrequency='0.9' numOctaves='2' stitchTiles='stitch'/%3E%3C/filter%3E%3Crect width='100%25' height='100%25' filter='url(%23n)' opacity='0.04'/%3E%3C/svg%3E");z-index:1}.b3 .wrap{max-width:960px;margin:0 auto;padding:0 24px 120px}.b3 header.hero{padding:56px 24px 48px;text-align:center;border-bottom:1px solid var(--rule);overflow:hidden}.b3 .date-tag{font-size:.75rem;letter-spacing:.18em;color:var(--ink-soft);margin-bottom:28px}.b3 .seal-box{width:88px;height:88px;margin:0 auto 22px;border:3px solid var(--seal);border-radius:6px;display:flex;align-items:center;justify-content:center;color:var(--seal);font-family:"Noto Serif SC",serif;font-weight:900;font-size:1.5rem;transform:rotate(-3deg);box-shadow:0 0 0 1px rgba(208,82,122,.15);position:relative}.b3 .seal-box:after{content:"";position:absolute;inset:6px;border:1px solid var(--seal);border-radius:3px;opacity:.5}.b3 h1.cn{font-family:"Noto Serif SC",serif;font-weight:900;font-size:clamp(1.8rem,6vw,3rem);color:var(--ink);margin:0 0 6px;letter-spacing:.02em}.b3 .pinyin-line,.b3 h1.cn .red{color:var(--seal)}.b3 .pinyin-line{font-size:1rem;font-style:italic;margin-bottom:6px}.b3 .subtitle{font-size:1rem;color:var(--ink-soft)}.b3 .subtitle strong{color:var(--bamboo);font-weight:700}.b3 .brush-rule{width:140px;height:3px;margin:26px auto 0;background:linear-gradient(90deg,transparent,var(--seal) 20%,var(--seal) 80%,transparent);border-radius:2px;opacity:.8}.b3 .tts-note{max-width:640px;margin:18px auto 0;font-size:.82rem;color:var(--ink-soft);text-align:center;font-style:italic}.b3 .tts-note b{color:var(--seal);font-style:normal}.b3 .voice-picker{display:flex;align-items:center;justify-content:center;gap:8px;flex-wrap:wrap;margin-top:14px;font-size:.82rem;color:var(--ink-soft)}.b3 .voice-picker select{font-family:Noto Sans,sans-serif;font-size:.82rem;padding:5px 10px;border:1px solid var(--rule);border-radius:4px;background:var(--paper-deep);color:var(--ink);max-width:260px}.b3 .vp-status{font-weight:700}.b3 .vp-status.ok{color:var(--bamboo)}.b3 .vp-status.warn{color:var(--seal)}.b3 .back-link{display:inline-block;margin:14px 0 0 14px;font-size:.85rem;color:var(--ink-soft);text-decoration:none;border:1px solid var(--seal);border-radius:6px;padding:4px 10px}.b3 .back-link:hover{color:var(--seal);background:var(--paper-deep)}.b3 .lesson-nav{display:flex;justify-content:center;align-items:center;gap:14px;flex-wrap:wrap;padding:32px 24px 0}.b3 .prev-link{display:inline-block;font-size:.9rem;color:var(--ink-soft);text-decoration:none;border:1px solid var(--rule);border-radius:6px;padding:8px 16px;font-weight:700}.b3 .prev-link:hover{color:var(--seal-deep);border-color:var(--seal);background:var(--paper-deep)}.b3 .next-link{display:inline-block;font-size:.9rem;color:var(--seal-deep);text-decoration:none;border:1px solid var(--seal);border-radius:6px;padding:8px 16px;font-weight:700}.b3 .next-link:hover{color:var(--paper);background:var(--seal)}.b3 footer.pagefoot-note{text-align:center;padding:18px 24px 0;color:var(--ink-soft);font-size:.8rem;letter-spacing:.04em}.b3 .toc{border:1px solid var(--rule);border-radius:6px;background:var(--paper-deep);padding:18px 22px;margin:28px 0 26px}.b3 .toc-title{font-weight:700;color:var(--seal);font-size:.85rem;margin-bottom:12px}.b3 .toc-list{list-style:none;margin:0;padding:0;display:grid;gap:8px}.b3 .toc-list a{display:flex;align-items:baseline;gap:10px;text-decoration:none;color:var(--ink);padding:2px 0}.b3 .toc-list a:hover .toc-cn,.b3 .toc-list a:hover .toc-vn,.b3 .toc-num{color:var(--seal)}.b3 .toc-num{font-weight:700;min-width:1.8em;flex-shrink:0}.b3 .toc-cn{font-family:"Noto Serif SC",serif;font-weight:600;flex-shrink:0}.b3 .toc-vn{color:var(--ink-soft);font-size:.88rem}.b3 section{position:relative;padding:56px 0 8px;scroll-margin-top:20px}.b3 section+section{border-top:1px solid var(--rule)}.b3 .sec-head{display:flex;align-items:baseline;gap:16px;margin-bottom:30px}.b3 .sec-num{font-size:2.4rem;font-weight:900;color:var(--seal);line-height:1}.b3 .sec-num,.b3 .sec-title-cn{font-family:"Noto Serif SC",serif}.b3 .sec-title-cn{font-size:1.6rem;font-weight:600;color:var(--ink)}.b3 .sec-title-py{font-size:.8rem;color:var(--seal);font-style:italic;margin:1px 0 2px}.b3 .sec-title-vn{font-size:.95rem;color:var(--ink-soft);font-style:italic}.b3 .pin-grid{display:grid;grid-template-columns:repeat(auto-fit,minmax(150px,1fr));gap:14px;margin-bottom:28px}.b3 .pin-card{position:relative;background:#fff;border:1px solid var(--rule);border-radius:4px;padding:20px 12px 14px;text-align:center;box-shadow:0 2px 6px rgba(22,48,43,.08),0 1px 0 rgba(22,48,43,.04);transform:rotate(var(--tilt,0deg));transition:transform .15s ease,box-shadow .15s ease}.b3 .pin-card:hover{transform:rotate(0deg) translateY(-2px);box-shadow:0 8px 18px rgba(22,48,43,.12)}.b3 .pin-card:before{content:"";position:absolute;top:6px;left:50%;transform:translateX(-50%);width:11px;height:11px;border-radius:50%;background:var(--pin-color,var(--seal));box-shadow:0 1px 2px rgba(0,0,0,.35)}.b3 .pin-card .emoji{font-size:1.2rem;line-height:1;display:block;margin-top:8px}.b3 .pin-card .hz{font-family:"Noto Serif SC",serif;font-size:1.55rem;font-weight:700;color:var(--ink);display:inline-block;margin-top:2px}.b3 .pin-card .py{font-size:.8rem;color:var(--ink-soft);display:block;margin-top:4px}.b3 .pin-card .vn{font-size:.82rem;color:var(--bamboo);font-weight:600;margin-top:3px;display:block}.b3 .fc-wrap{max-width:480px;margin:0 auto}.b3 .fc-card{border:1px solid var(--rule);border-radius:14px;background:var(--paper-deep);padding:22px 18px;text-align:center;margin-bottom:14px}.b3 .fc-card .vn-hint{font-size:1.5rem;font-weight:700;color:var(--ink)}.b3 .fc-card .tap-hint{font-size:.75rem;color:var(--ink-soft);margin-top:8px}.b3 .fc-input-row{display:flex;gap:10px;margin-bottom:10px}.b3 .fc-input-row input{flex:1;padding:10px 12px;font-family:"Noto Serif SC",serif;font-size:1.15rem;border:1px solid var(--rule);border-radius:10px;background:var(--paper);color:var(--ink)}.b3 .fc-input-row input:focus{outline:2px solid var(--seal);outline-offset:1px}.b3 .fc-input-row button{padding:10px 18px;border:none;border-radius:10px;background:var(--seal);color:#fff;font-size:.95rem;font-weight:700;cursor:pointer}.b3 .fc-input-row button:hover{opacity:.85}.b3 .fc-feedback{text-align:center;font-size:.9rem;font-weight:700;min-height:1.4em;margin-bottom:8px}.b3 .fc-feedback.correct{color:var(--bamboo-bright)}.b3 .fc-feedback.wrong{color:var(--seal)}.b3 .fc-feedback .hz{font-family:"Noto Serif SC",serif}.b3 .fc-stats{display:flex;justify-content:space-between;align-items:center;font-size:.8rem;color:var(--ink-soft)}.b3 .fc-link{background:none;border:none;padding:0;font-size:.8rem;color:var(--bamboo);font-weight:700;cursor:pointer}.b3 .fc-link:hover{color:var(--seal)}.b3 .dialogue-group{margin-bottom:32px;text-align:center}.b3 .dialogue-label{display:inline-block;font-size:.75rem;letter-spacing:.12em;text-transform:uppercase;color:var(--ink-soft);font-weight:700;margin-bottom:10px;border-left:3px solid var(--seal);padding-left:10px}.b3 .sentence-stack{display:flex;flex-direction:column;gap:8px;margin:0 auto}.b3 .sentence-card{background:var(--paper-deep);border:1px solid var(--rule);border-radius:10px;padding:12px 16px;text-align:center}.b3 .sentence-card.speaker-a{border-left:4px solid var(--seal);border-radius:0 10px 10px 10px}.b3 .sentence-card.speaker-b{border-left:4px solid var(--bamboo);border-radius:0 10px 10px 10px}.b3 .sentence-tag{font-size:.72rem;color:var(--ink-soft);font-weight:700;letter-spacing:.06em;text-transform:uppercase;margin-bottom:4px}.b3 .sentence-hz{font-family:"Noto Serif SC",serif;font-size:1.35rem;font-weight:700;color:var(--ink)}.b3 .sentence-hz .hl{color:var(--seal)}.b3 .sentence-hz .hl2{color:var(--bamboo-bright)}.b3 .sentence-py{font-size:.82rem;color:var(--seal);font-style:italic;margin-top:2px}.b3 .sentence-vn{font-size:.88rem;color:var(--ink-soft);margin-top:2px}.b3 .sentence-arrow{text-align:center;color:var(--ink-soft);font-size:1.1rem;line-height:1}.b3 .sub-head{margin-top:36px;margin-bottom:16px}.b3 .sub-head .t{font-family:"Noto Serif SC",serif;font-size:1.1rem;font-weight:700;color:var(--ink)}.b3 .sub-head .d{font-size:.82rem;color:var(--ink-soft);margin-left:10px}.b3 .vtc-wrap{max-width:640px;margin:0 auto}.b3 .vtc-levels{display:flex;justify-content:center;gap:8px;flex-wrap:wrap;margin-bottom:18px}.b3 .vtc-level-btn{font-family:Noto Sans,sans-serif;font-size:.85rem;font-weight:700;padding:6px 16px;border-radius:20px;border:1px solid var(--rule);background:var(--paper-deep);color:var(--ink-soft);cursor:pointer;transition:background .15s,color .15s,border-color .15s}.b3 .vtc-level-btn:hover{border-color:var(--seal)}.b3 .vtc-level-btn.active{background:var(--seal);border-color:var(--seal);color:#fff}.b3 .vtc-bar{display:flex;align-items:center;justify-content:space-between;font-size:1rem;font-weight:700;color:var(--ink-soft);margin-bottom:16px}.b3 .vtc-hearts{letter-spacing:2px}.b3 .vtc-check{color:var(--bamboo-bright)}.b3 .vtc-check b{font-size:1.15rem}.b3 .vtc-photo-area{position:relative;height:200px;margin-bottom:24px}.b3 .vtc-string{position:absolute;top:14px;left:4px;right:4px;height:2px;background:repeating-linear-gradient(90deg,var(--seal) 0 8px,transparent 8px 14px);opacity:.6}.b3 .vtc-pin{position:absolute;top:5px;left:50%;transform:translateX(-50%) rotate(-8deg);width:13px;height:20px;background:var(--blue,var(--bamboo));border-radius:3px;box-shadow:0 2px 3px rgba(0,0,0,.3);z-index:2}.b3 .vtc-photo{position:absolute;top:24px;left:50%;width:210px;height:160px;transform:translateX(-50%) translateX(-160%) rotate(-8deg);opacity:0;perspective:900px}.b3 .vtc-photo.vtc-slide-in{animation:vtcSlideIn .55s cubic-bezier(.2,.8,.3,1) forwards}@keyframes vtcSlideIn{0%{transform:translateX(-50%) translateX(-160%) rotate(-8deg);opacity:0}60%{transform:translateX(-50%) translateX(6%) rotate(2deg);opacity:1}to{transform:translateX(-50%) rotate(-2deg);opacity:1}}.b3 .vtc-photo-inner{position:relative;width:100%;height:100%;transform-style:preserve-3d;transition:transform .6s ease;border-radius:6px;box-shadow:0 6px 16px rgba(22,48,43,.2)}.b3 .vtc-photo-inner.flipped{transform:rotateY(180deg)}.b3 .vtc-photo-face{position:absolute;inset:0;backface-visibility:hidden;display:flex;flex-direction:column;align-items:center;justify-content:center;gap:8px;padding:10px;border-radius:6px;border:6px solid #fff}.b3 .vtc-face-img{background:var(--paper-deep)}.b3 .vtc-face-img .vtc-emoji{font-size:2.6rem;line-height:1}.b3 .vtc-face-img .vtc-vn{font-size:.95rem;font-weight:700;color:var(--ink);text-align:center}.b3 .vtc-face-py{transform:rotateY(180deg);background:var(--seal)}.b3 .vtc-face-py .vtc-py{font-size:1.25rem;font-style:italic;color:#fff;font-weight:700;text-align:center}.b3 .vtc-tiles{display:grid;grid-template-columns:repeat(auto-fit,minmax(110px,1fr));gap:10px}.b3 .vtc-tile{font-family:"Noto Serif SC",serif;font-size:1.05rem;font-weight:700;padding:14px 8px;border:none;border-radius:4px;cursor:pointer;color:var(--ink);box-shadow:0 3px 6px rgba(22,48,43,.15);transition:transform .12s ease}.b3 .vtc-tile:hover:not(:disabled){transform:translateY(-2px)}.b3 .vtc-tile:disabled{cursor:default;opacity:.55}.b3 .vtc-tile.tile-y{background:#f0d879}.b3 .vtc-tile.tile-p{background:#eda7bb}.b3 .vtc-tile.tile-b{background:#9dc4e6}.b3 .vtc-tile.tile-g{background:#a3d9b5}.b3 .vtc-tile.correct{outline:3px solid var(--bamboo-bright);opacity:1}.b3 .vtc-tile.wrong{animation:vtcShake .4s ease}@keyframes vtcShake{0%,to{transform:translateX(0)}25%{transform:translateX(-6px)}75%{transform:translateX(6px)}}.b3 .vtc-result{text-align:center}.b3 .vtc-result-title{font-size:1.4rem;font-weight:900;color:var(--seal);margin-bottom:6px}.b3 .vtc-result-score{font-size:1rem;color:var(--ink-soft);margin-bottom:16px}.b3 .vtc-retry{padding:10px 22px;border-radius:20px;border:1px solid var(--bamboo);background:transparent;color:var(--bamboo);font-weight:700;cursor:pointer}.b3 .vtc-retry:hover{background:var(--bamboo);color:#fff}.b3 .pattern-box{background:var(--paper-deep);border:2px solid var(--rule);border-radius:14px;padding:18px 20px;margin-bottom:18px;text-align:center}.b3 .pattern-label{font-size:.75rem;font-weight:700;letter-spacing:.1em;color:var(--ink-soft);text-transform:uppercase;margin-bottom:10px}.b3 .pattern-row{display:flex;align-items:center;justify-content:center;gap:8px;flex-wrap:wrap}.b3 .pattern-chip{color:#fff;border-radius:8px;padding:6px 12px;font-family:"Noto Serif SC",serif;font-size:1.1rem;font-weight:700}.b3 .pattern-chip.c1{background:var(--seal)}.b3 .pattern-chip.c2{background:var(--bamboo)}.b3 .pattern-chip.c3{background:var(--gold)}.b3 .pattern-plus{font-size:1.3rem;color:var(--ink-soft)}.b3 .pattern-desc{font-size:.88rem;color:var(--ink-soft);margin-top:12px;line-height:1.7;text-align:left}.b3 .pattern-desc .term{font-family:"Noto Serif SC",serif;font-weight:700;color:var(--ink)}.b3 .pattern-ex{margin-top:12px}.b3 .pattern-ex .sentence-hz{font-size:1.15rem}.b3 .pattern-ex .py{font-size:.78rem;color:var(--seal);font-style:italic}.b3 .pattern-ex .vn{font-size:.8rem;color:var(--ink-soft)}.b3 .confuse-card{background:#fff;border:1px solid var(--rule);border-radius:4px;padding:22px 26px;margin-bottom:18px;box-shadow:0 2px 6px rgba(22,48,43,.08),0 1px 0 rgba(22,48,43,.04)}.b3 .confuse-card:last-child{margin-bottom:0}.b3 .confuse-label{font-size:.8rem;font-weight:700;letter-spacing:.1em;text-transform:uppercase;color:var(--seal);margin-bottom:10px}.b3 .confuse-title{font-family:"Noto Serif SC",serif;font-size:1.6rem;font-weight:700;color:var(--ink);margin-bottom:12px;padding-bottom:12px;border-bottom:1px dashed var(--rule)}.b3 .confuse-title .term{color:var(--seal)}.b3 .confuse-body{font-size:1.08rem;color:var(--ink);line-height:1.85}.b3 .confuse-body .term{font-family:"Noto Serif SC",serif;font-size:1.15em;font-weight:700;color:var(--seal-deep)}.b3 .formula-banner{display:flex;align-items:center;justify-content:center;gap:14px;flex-wrap:wrap;text-align:center;max-width:640px;margin:0 auto 22px;background:linear-gradient(135deg,var(--seal) 0,var(--seal-deep) 100%);border-radius:14px;padding:18px 22px;box-shadow:0 6px 16px rgba(208,82,122,.22)}.b3 .formula-term{font-family:"Noto Serif SC",serif;font-size:1.35rem;font-weight:900;color:#fff;white-space:nowrap}.b3 .formula-term .plus{font-size:1rem;font-weight:400;opacity:.75;margin:0 2px}.b3 .formula-divider{width:1px;align-self:stretch;background:rgba(255,255,255,.3)}.b3 .formula-py{font-style:italic;font-size:.92rem;color:rgba(255,255,255,.85);white-space:nowrap}.b3 .formula-vn{font-size:.92rem;color:#fff;font-weight:600}.b3 .formula-vn .note{font-style:italic;font-weight:400;color:rgba(255,255,255,.8)}.b3 .char-steps{background:#fff;border:1px solid var(--rule);border-radius:4px;padding:24px 26px;margin-bottom:20px;box-shadow:0 2px 6px rgba(22,48,43,.08),0 1px 0 rgba(22,48,43,.04)}.b3 .char-steps-title{display:flex;flex-direction:column;align-items:center;gap:6px;text-align:center;margin-bottom:14px;padding-bottom:14px;border-bottom:1px dashed var(--rule)}.b3 .char-steps-title .big{font-family:"Noto Serif SC",serif;font-size:3rem;font-weight:700;line-height:1.1;color:var(--seal)}.b3 .char-steps-title .meta{font-size:1rem;color:var(--ink-soft)}.b3 .char-story{font-size:1.08rem;color:var(--ink);line-height:1.85;margin-bottom:18px}.b3 .char-story .term{font-family:"Noto Serif SC",serif;font-size:1.15em;font-weight:700;color:var(--seal-deep)}.b3 .hw-box{display:flex;flex-direction:column;align-items:center;gap:10px}.b3 .hw-target{width:150px;height:150px;background-color:var(--paper-deep);background-image:linear-gradient(var(--rule) 1px,transparent 1px),linear-gradient(90deg,var(--rule) 1px,transparent 1px),linear-gradient(var(--rule) .5px,transparent 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.speakable:hover:after{opacity:1;transform:scale(1.18)}.b3 .speakable.speaking:after{opacity:1;background:var(--seal);border-color:var(--seal)}.b3 .reveal{opacity:0;transform:translateY(18px);transition:opacity .5s ease,transform .5s ease}.b3 .reveal.visible{opacity:1;transform:none}.b3 .mode-picker{display:flex;gap:6px;justify-content:center;margin:10px auto 0;flex-wrap:wrap}.b3 .mode-btn{font-size:.85rem;padding:6px 14px;border:1px solid var(--rule);border-radius:999px;background:var(--paper);cursor:pointer;font-family:Noto Sans,sans-serif}.b3 .mode-btn.active{background:var(--seal);border-color:var(--seal);font-weight:700}.b3 .mode-picker-float{position:fixed;top:50%;right:14px;transform:translateY(-50%);z-index:50;display:flex;flex-direction:column;gap:8px;padding:10px 8px;background:var(--paper);border:1px solid var(--rule);border-radius:14px;box-shadow:0 4px 14px rgba(22,48,43,.12)}.b3 .mode-picker-float .mode-btn{writing-mode:vertical-rl;text-orientation:mixed;padding:12px 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