.ot3{--paper:#f4eedd;--paper-deep:#eae1c8;--ink:#211e19;--ink-soft:#4a453d;--seal:#b5322a;--seal-deep:#8e241d;--bamboo:#4b5a3c;--bamboo-bright:#3a9a4a;--gold:#b08a4e;--rule:#c9bfa0}.ot3 *{box-sizing:border-box}.ot3{scroll-behavior:smooth;overflow-anchor:none;margin:0;background:var(--paper);background-image:radial-gradient(ellipse at 20% 10%,rgba(181,50,42,.05),transparent 40%),radial-gradient(ellipse at 80% 90%,rgba(75,90,60,.06),transparent 45%);color:var(--ink);font-family:Noto Sans,Noto Sans SC,sans-serif;line-height:1.6}.ot3: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}.ot3 .wrap{max-width:960px;margin:0 auto;padding:0 24px 120px}.ot3 header.hero{position:relative;padding:56px 24px 48px;text-align:center;border-bottom:1px solid var(--rule);overflow:hidden}.ot3 .date-tag{font-size:.75rem;letter-spacing:.18em;color:var(--ink-soft);margin-bottom:28px}.ot3 .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(181,50,42,.15);position:relative}.ot3 .seal-box:after{content:"";position:absolute;inset:6px;border:1px solid var(--seal);border-radius:3px;opacity:.5}.ot3 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}.ot3 h1.cn .red{color:var(--seal)}.ot3 .pinyin-line{font-size:1rem;color:var(--seal);font-style:italic;margin-bottom:6px}.ot3 .subtitle{font-size:1rem;color:var(--ink-soft)}.ot3 .subtitle strong{color:var(--bamboo);font-weight:700}.ot3 .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}.ot3 .tts-note{max-width:640px;margin:18px auto 0;font-size:.82rem;color:var(--ink-soft);text-align:center;font-style:italic}.ot3 .tts-note b{color:var(--seal);font-style:normal}.ot3 .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)}.ot3 .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}.ot3 .vp-status{font-weight:700}.ot3 .vp-status.ok{color:var(--bamboo)}.ot3 .vp-status.warn{color:var(--seal)}.ot3 .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}.ot3 .back-link:hover{color:var(--seal);background:var(--paper-deep)}.ot3 .lesson-nav{display:flex;justify-content:center;align-items:center;gap:14px;flex-wrap:wrap;padding:32px 24px 0}.ot3 .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}.ot3 .prev-link:hover{color:var(--seal-deep);border-color:var(--seal);background:var(--paper-deep)}.ot3 .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}.ot3 .next-link:hover{color:var(--paper);background:var(--seal)}.ot3 footer.pagefoot-note{text-align:center;padding:18px 24px 0;color:var(--ink-soft);font-size:.8rem;letter-spacing:.04em}.ot3 .toc{border:1px solid var(--rule);border-radius:6px;background:var(--paper-deep);padding:18px 22px;margin:28px 0 26px}.ot3 section{position:relative;padding:56px 0 8px;scroll-margin-top:20px}.ot3 section+section{border-top:1px solid var(--rule)}.ot3 .sec-head{display:flex;align-items:baseline;gap:16px;margin-bottom:30px}.ot3 .sec-num{font-size:2.4rem;font-weight:900;color:var(--seal);line-height:1}.ot3 .sec-num,.ot3 .sec-title-cn{font-family:"Noto Serif SC",serif}.ot3 .sec-title-cn{font-size:1.6rem;font-weight:600;color:var(--ink)}.ot3 .sec-title-py{font-size:.8rem;color:var(--seal);font-style:italic;margin:1px 0 2px}.ot3 .sec-title-vn{font-size:.95rem;color:var(--ink-soft);font-style:italic}.ot3 .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(33,30,25,.08),0 1px 0 rgba(33,30,25,.04);transform:rotate(var(--tilt,0deg));transition:transform .15s ease,box-shadow .15s ease}.ot3 .pin-card:hover{transform:rotate(0deg) translateY(-2px);box-shadow:0 8px 18px rgba(33,30,25,.12)}.ot3 .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)}.ot3 .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}.ot3 .pin-card .py{font-size:.8rem;color:var(--ink-soft);display:block;margin-top:4px}.ot3 .pin-card .vn{font-size:.82rem;color:var(--bamboo);font-weight:600;margin-top:3px;display:block}.ot3 .fc-wrap{max-width:480px;margin:0 auto}.ot3 .fc-card{border:1px solid var(--rule);border-radius:14px;background:var(--paper-deep);padding:22px 18px;text-align:center;margin-bottom:14px}.ot3 .fc-input-row{display:flex;gap:10px;margin-bottom:10px}.ot3 .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)}.ot3 .fc-input-row input:focus{outline:2px solid var(--seal);outline-offset:1px}.ot3 .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}.ot3 .fc-input-row button:hover{opacity:.85}.ot3 .fc-feedback{text-align:center;font-size:.9rem;font-weight:700;min-height:1.4em;margin-bottom:8px}.ot3 .fc-feedback.correct{color:var(--bamboo-bright)}.ot3 .fc-feedback.wrong{color:var(--seal)}.ot3 .fc-feedback .hz{font-family:"Noto Serif SC",serif}.ot3 .fc-stats{display:flex;justify-content:space-between;align-items:center;font-size:.8rem;color:var(--ink-soft)}.ot3 .fc-link{background:none;border:none;padding:0;font-size:.8rem;color:var(--bamboo);font-weight:700;cursor:pointer}.ot3 .fc-link:hover{color:var(--seal)}.ot3 .fc-deck{display:flex;gap:8px;justify-content:center;flex-wrap:wrap;margin-bottom:12px}.ot3 .fc-chip{border:1px solid var(--rule);background:transparent;color:var(--ink-soft);border-radius:16px;padding:5px 14px;font-size:.8rem;font-weight:700;cursor:pointer}.ot3 .fc-chip.active{background:var(--seal);border-color:var(--seal);color:#fff}.ot3 .fc-progress{height:6px;background:var(--rule);border-radius:3px;overflow:hidden}.ot3 .fc-bar{height:100%;width:0;background:var(--bamboo-bright);transition:width .25s}.ot3 .fc-count{text-align:right;font-size:.75rem;color:var(--ink-soft);margin:4px 2px 10px}.ot3 .fc-tag{font-size:.75rem;min-height:1em;margin-bottom:2px}.ot3 .fc-hintline,.ot3 .fc-tag{font-style:italic;color:var(--seal)}.ot3 .fc-hintline{font-size:.95rem;min-height:1.3em;margin-top:6px}.ot3 .fc-actions{display:flex;gap:14px;justify-content:center;flex-wrap:wrap;margin-bottom:8px}.ot3 .fc-rd{font-weight:400;font-style:italic;color:var(--ink-soft);font-size:.85rem;margin-left:4px}.ot3 .fc-done{text-align:center;border:1px dashed var(--bamboo);border-radius:10px;padding:12px;margin-top:12px;font-size:.9rem}.ot3 .fc-done[hidden]{display:none}.ot3 .fc-done-title{font-family:"Noto Serif SC",serif;font-weight:700;color:var(--bamboo);font-size:1.1rem;margin-bottom:4px}.ot3 .sentence-stack{display:flex;flex-direction:column;gap:8px;margin:0 auto}.ot3 .sentence-card{background:var(--paper-deep);border:1px solid var(--rule);border-radius:10px;padding:12px 16px;text-align:center}.ot3 .sentence-card.speaker-a{border-left:4px solid var(--seal);border-radius:0 10px 10px 10px}.ot3 .sentence-card.speaker-b{border-left:4px solid var(--bamboo);border-radius:0 10px 10px 10px}.ot3 .sentence-hz{font-family:"Noto Serif SC",serif;font-size:1.35rem;font-weight:700;color:var(--ink)}.ot3 .sentence-hz .hl{color:var(--seal)}.ot3 .sentence-py{font-size:.82rem;color:var(--seal);font-style:italic;margin-top:2px}.ot3 .sentence-vn{font-size:.88rem;color:var(--ink-soft);margin-top:2px}.ot3 .sub-head{margin-top:36px;margin-bottom:16px}.ot3 .sub-head .t{font-family:"Noto Serif SC",serif;font-size:1.1rem;font-weight:700;color:var(--ink)}.ot3 .sub-head .d{font-size:.82rem;color:var(--ink-soft);margin-left:10px}.ot3 .hz-story{border-left:3px solid var(--bamboo);background:rgba(75,90,60,.06);border-radius:0 6px 6px 0;padding:12px 16px;margin-bottom:14px}.ot3 .hz-parts{display:flex;flex-wrap:wrap;align-items:center;gap:8px;margin-bottom:8px}.ot3 .hz-parts .part{font-family:"Noto Serif SC",serif;font-weight:700;color:var(--bamboo);background:var(--paper-deep);border:1px solid var(--rule);border-radius:4px;padding:4px 10px;font-size:1rem}.ot3 .hz-parts .part i{font-family:inherit;font-style:italic;font-weight:400;color:var(--ink-soft);font-size:.78rem;margin-left:4px}.ot3 .hz-parts .plus{color:var(--seal);font-weight:900}.ot3 .hz-story p{margin:0;font-size:.9rem;color:var(--ink-soft);line-height:1.65}.ot3 .fc-input-row input{min-width:0;width:100%;box-sizing:border-box}.ot3 .char-steps{background:#fff;border:1px solid var(--rule);border-radius:4px;padding:24px 26px;margin-bottom:20px;box-shadow:0 2px 6px rgba(33,30,25,.08),0 1px 0 rgba(33,30,25,.04)}.ot3 .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)}.ot3 .char-steps-title .big{font-family:"Noto Serif SC",serif;font-size:3rem;font-weight:700;line-height:1.1;color:var(--seal)}.ot3 .char-steps-title .meta{font-size:1rem;color:var(--ink-soft)}.ot3 .hw-box{display:flex;flex-direction:column;align-items:center;gap:10px}.ot3 .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 .5px),linear-gradient(90deg,var(--rule) .5px,transparent .5px);background-size:75px 75px,75px 75px,25px 25px,25px 25px;border:2px solid var(--seal);border-radius:4px}.ot3 .hw-controls-row{display:flex;gap:8px}.ot3 .hw-replay{font-size:.92rem;padding:7px 16px;border:1px solid var(--rule);border-radius:6px;background:var(--paper);color:var(--ink);cursor:pointer;font-family:Noto Sans,sans-serif}.ot3 .hw-replay:hover{background:var(--paper-deep)}.ot3 .quiz-btn{border-color:var(--seal);color:var(--seal)}.ot3 .hw-quiz-status{font-size:.92rem;color:var(--bamboo);min-height:1.2em}.ot3 .speakable{cursor:pointer;position:relative}.ot3 .speakable:after{content:"🔊";font-size:.65rem;position:absolute;top:-6px;right:-14px;background:var(--paper);border:1px solid var(--rule);border-radius:50%;width:18px;height:18px;display:flex;align-items:center;justify-content:center;opacity:0;transition:opacity .15s,transform .15s;pointer-events:none;z-index:2}.ot3 .speakable:focus-visible:after,.ot3 .speakable:hover:after{opacity:1;transform:scale(1.18)}.ot3 .speakable.speaking:after{opacity:1;background:var(--seal);border-color:var(--seal)}.ot3 .reveal{opacity:0;transform:translateY(18px);transition:opacity .5s ease,transform .5s ease}.ot3 .mode-picker{display:flex;gap:6px;justify-content:center;margin:10px auto 0;flex-wrap:wrap}.ot3 .mode-btn{font-size:.85rem;padding:6px 14px;border:1px solid var(--rule);border-radius:999px;background:var(--paper);color:var(--ink);cursor:pointer;font-family:Noto Sans,sans-serif}.ot3 .mode-btn.active{background:var(--seal);border-color:var(--seal);color:#fff;font-weight:700}.ot3[data-mode=hanzi] .meta,.ot3[data-mode=hanzi] .pinyin-line,.ot3[data-mode=hanzi] .subtitle-vn,.ot3[data-mode=hanzi] [class*=py],.ot3[data-mode=hanzi] [class*=vn],.ot3[data-mode=pinyin] .meta,.ot3[data-mode=pinyin] .subtitle-vn,.ot3[data-mode=pinyin] [class*=vn]{display:none!important}.ot3 .ex-speak-btn{background:none;border:none;cursor:pointer;font-size:.9rem;opacity:.5;padding:0 2px;vertical-align:baseline;transition:opacity .15s}.ot3 .ex-speak-btn:hover{opacity:1}.ot3 .vt-wrap{overflow-x:auto;margin-bottom:8px}.ot3 .vt-num{text-align:center;width:2.6em;color:var(--ink-soft)}.ot3 .vt-hz{font-family:"Noto Serif SC",serif;font-size:1.25rem;white-space:nowrap}.ot3 .vt-py{color:var(--seal);white-space:nowrap}.ot3 .vt-pos{color:var(--ink-soft);font-style:italic;white-space:nowrap}.ot3 .vt-ex{font-family:"Noto Serif SC",serif}.ot3 .scope-bar{gap:8px;margin:6px 0 14px;align-items:center;font-size:.8rem;color:var(--ink-soft)}.ot3 .scope-bar,.ot3 .tabbar{display:flex;justify-content:center;flex-wrap:wrap}.ot3 .tabbar{gap:6px;margin-bottom:22px}.ot3 .tab-btn{border:1px solid var(--rule);background:#fff;color:var(--ink-soft);border-radius:10px 10px 0 0;padding:9px 16px;font-size:.9rem;font-weight:700;cursor:pointer}.ot3 .tab-btn.active{background:var(--seal);border-color:var(--seal);color:#fff}.ot3 .tab-panel[hidden]{display:none}.ot3 .fc-wrap{max-width:560px}.ot3 .q-prompt{font-family:"Noto Serif SC",serif;font-size:1.8rem;font-weight:700;color:var(--ink);line-height:1.4}.ot3 .q-prompt.small{font-size:1.25rem;font-family:Noto Sans,"Noto Serif SC",sans-serif}.ot3 .opt-grid{display:grid;grid-template-columns:1fr 1fr;gap:10px;margin-bottom:10px}@media (max-width:520px){.ot3 .opt-grid{grid-template-columns:1fr}}.ot3 .opt-btn{padding:12px 10px;border:1px solid var(--rule);background:#fff;border-radius:10px;font-family:"Noto Serif SC",Noto Sans,sans-serif;font-size:1.05rem;cursor:pointer;text-align:center;color:var(--ink)}.ot3 .opt-btn:hover:not(:disabled){border-color:var(--seal)}.ot3 .opt-btn.ok{background:rgba(58,154,74,.15);border-color:var(--bamboo-bright);font-weight:700}.ot3 .opt-btn.bad{background:rgba(181,50,42,.12);border-color:var(--seal)}.ot3 .opt-btn:disabled{cursor:default}.ot3 .rd-tools{display:flex;gap:14px;justify-content:center;flex-wrap:wrap;margin:10px 0 14px;font-size:.85rem;color:var(--ink-soft)}.ot3 .rd-tools label{cursor:pointer}.ot3 .rd-line{background:#fff;border:1px solid var(--rule);border-left:4px solid var(--bamboo);border-radius:0 8px 8px 0;padding:10px 14px;margin-bottom:10px}.ot3 .rd-hz{font-family:"Noto Serif SC",serif;font-size:1.2rem;cursor:pointer}.ot3 .rd-py{font-size:.82rem;color:var(--seal);font-style:italic}.ot3 .rd-vn{font-size:.85rem;color:var(--ink-soft)}.ot3 .rd-off .rd-py-x,.ot3 .rd-off-vn .rd-vn-x{display:none}.ot3 .wr-chips{display:flex;gap:8px;justify-content:center;flex-wrap:wrap;margin-bottom:14px}.ot3 .wr-chip{font-family:"Noto Serif SC",serif;font-size:1.4rem;width:48px;height:48px;border:1px solid var(--rule);background:#fff;border-radius:8px;cursor:pointer}.ot3 .wr-chip.active{background:var(--seal);color:#fff;border-color:var(--seal)}.ot3 .wr-card{text-align:center}.ot3 .wr-info{margin-bottom:8px;font-size:.95rem}.ot3 .wr-info .big{font-family:"Noto Serif SC",serif;font-size:2.2rem;font-weight:700;color:var(--seal)}.ot3 .wr-empty{text-align:center;color:var(--ink-soft);font-style:italic}.ot3{position:relative}.ot3-top{display:flex;justify-content:space-between;align-items:center;padding:14px 14px 0;position:absolute;top:0;left:0;right:0;z-index:3}