:root{--bg-grad-a: #dce7fb;--bg-grad-b: #f2f6fe;--primary: #4f6af5;--primary-fill: #4359e6;--primary-ink: #4359e6;--primary-fixed: #4359e6;--on-primary: #ffffff;--primary-soft: #eef2fe;--primary-soft-hover: #e1e8fc;--ink: #10193b;--ink-soft: #606c8a;--card: #ffffff;--line: #e4eaf6;--line-strong: #c9d6f6;--well: #f3f7fd;--sticky-bg: rgba(242, 246, 254, .82);--gold: #f5b942;--green: #3e9b4f;--green-ink: #297038;--green-tint: rgba(62, 155, 79, .12);--danger: #e25c5c;--danger-ink: #c23a3a;--danger-tint: rgba(226, 92, 92, .12);--pastel-green-bg: #e8f6e4;--pastel-green-ink: #297038;--pastel-pink-bg: #fde9f3;--pastel-pink-ink: #b93573;--pastel-orange-bg: #fdf0e0;--pastel-orange-ink: #8f5a10;--pastel-teal-bg: #e3f5f2;--pastel-teal-ink: #1b6f62;--pastel-lavender-bg: #ecebfc;--pastel-lavender-ink: #5648c8;--pastel-peach-bg: #fbe9dc;--pastel-peach-ink: #a34e22;--hero-grad: radial-gradient(380px 300px at 88% 118%, rgba(139, 152, 255, .55), transparent 70%), linear-gradient(135deg, #414fd8 0%, #5566ee 100%);--hero-shadow: 0 18px 44px rgba(65, 79, 216, .35);--btn-glow: 0 8px 20px rgba(79, 106, 245, .35);--shadow: 0 10px 30px rgba(63, 89, 180, .1);--shadow-lift: 0 16px 40px rgba(63, 89, 180, .16);--radius-lg: 24px;--radius: 16px;--header-h: 60px;color-scheme:light dark}@media (prefers-color-scheme: dark){:root{--bg-grad-a: #0d1230;--bg-grad-b: #141b3d;--primary: #6f88ff;--primary-fill: #6f88ff;--primary-ink: #a9baff;--primary-fixed: #4359e6;--on-primary: #10193b;--primary-soft: #232b55;--primary-soft-hover: #2a3263;--ink: #edf0fa;--ink-soft: #a6b0cc;--card: #1a2142;--line: #2a3358;--line-strong: #3a4470;--well: #151b3c;--sticky-bg: rgba(13, 18, 48, .8);--green: #58b96b;--green-ink: #8fd6a0;--green-tint: rgba(143, 214, 160, .14);--danger: #e25c5c;--danger-ink: #f2a19d;--danger-tint: rgba(226, 92, 92, .18);--pastel-green-bg: #1e3326;--pastel-green-ink: #93d6a0;--pastel-pink-bg: #3b2334;--pastel-pink-ink: #f2a7ce;--pastel-orange-bg: #3b2d1c;--pastel-orange-ink: #f0bc80;--pastel-teal-bg: #1a3430;--pastel-teal-ink: #8cd9cc;--pastel-lavender-bg: #272450;--pastel-lavender-ink: #b7b0ff;--pastel-peach-bg: #3c2921;--pastel-peach-ink: #f1b092;--hero-grad: radial-gradient(380px 300px at 88% 118%, rgba(123, 140, 255, .4), transparent 70%), linear-gradient(135deg, #3a48c9 0%, #4d5ee6 100%);--hero-shadow: 0 18px 44px rgba(0, 0, 0, .45);--btn-glow: 0 8px 20px rgba(111, 136, 255, .32);--shadow: 0 10px 30px rgba(0, 0, 0, .35);--shadow-lift: 0 16px 40px rgba(0, 0, 0, .45)}}*{box-sizing:border-box}html{-webkit-text-size-adjust:100%;min-height:100%}@media (prefers-reduced-motion: no-preference){html{scroll-behavior:smooth}}body{margin:0;min-height:100vh;font-family:-apple-system,BlinkMacSystemFont,Segoe UI,Roboto,Helvetica Neue,Arial,sans-serif;background:linear-gradient(135deg,var(--bg-grad-a),var(--bg-grad-b)) no-repeat fixed;background-color:var(--bg-grad-b);color:var(--ink);line-height:1.55;-webkit-font-smoothing:antialiased}.app{max-width:960px;margin:0 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50%;background-size:15px 15px;color:var(--ink);font-size:.92rem}.header-search::placeholder{color:var(--ink-soft)}.header-ring{display:flex;align-items:center;gap:7px;margin-left:auto;text-decoration:none;color:var(--ink-soft);border-radius:999px}.header-ring-text{font-weight:700;font-size:.8rem;font-variant-numeric:tabular-nums;white-space:nowrap}.app-nav-top{display:flex;gap:2px;margin-left:auto;padding:3px;border:1px solid var(--line);border-radius:999px;background:var(--card)}.header-search+.app-nav-top{margin-left:0}.app-tab{display:flex;align-items:center;justify-content:center;gap:7px;min-height:40px;padding:6px 16px;border-radius:999px;color:var(--ink-soft);font-weight:700;font-size:.9rem;text-decoration:none;white-space:nowrap}.app-tab:hover{color:var(--ink)}.app-tab.active{background:var(--primary-fill);color:var(--on-primary);box-shadow:var(--btn-glow)}.app-tab-icon{font-size:1rem;line-height:1}.app-nav-bottom{display:none;position:fixed;left:50%;transform:translate(-50%);bottom:calc(10px + env(safe-area-inset-bottom,0px));z-index:40;width:min(420px,calc(100% - 24px));padding:6px;gap:4px;justify-content:space-between;background:var(--card);border:1px solid var(--line);border-radius:26px;box-shadow:var(--shadow-lift)}.app-nav-bottom .app-tab{flex:1;flex-direction:column;gap:3px;min-height:54px;padding:7px 6px;border-radius:20px;font-size:.72rem}.app-nav-bottom .app-tab-icon{font-size:1.2rem}@media (max-width: 720px){.app-nav-top,.header-search{display:none}.header-ring{margin-left:auto}.app-nav-bottom{display:flex}.app{padding-bottom:118px}.lang-bar{top:var(--header-h)}}@media (prefers-reduced-motion: no-preference){.continue-row,.word-group-head,.progress-unit{transition:background-color .15s ease,transform .15s ease}}h1,h2,h3{line-height:1.25;margin:0;font-weight:700;letter-spacing:-.02em}p{margin:.4em 0}a{color:var(--primary-ink)}code{font-family:ui-monospace,SFMono-Regular,Menlo,Consolas,monospace;font-size:.9em;background:var(--primary-soft);color:var(--ink);padding:1px 6px;border-radius:6px}:focus-visible{outline:2px solid var(--primary);outline-offset:2px;border-radius:8px}.hero :focus-visible{outline-color:#fff}.sr-only{position:absolute;width:1px;height:1px;padding:0;margin:-1px;overflow:hidden;clip:rect(0 0 0 0);white-space:nowrap;border:0}.btn{display:inline-flex;align-items:center;justify-content:center;gap:8px;min-height:44px;padding:10px 20px;border-radius:999px;border:1px solid var(--line);background:var(--card);color:var(--ink);font-size:1rem;font-weight:600;text-decoration:none;cursor:pointer}.btn.primary{background:var(--primary-fill);border-color:transparent;color:var(--on-primary);font-weight:700;box-shadow:var(--btn-glow)}.btn:disabled{opacity:.45;cursor:not-allowed;box-shadow:none}.card{background:var(--card);border:1px solid var(--line);border-radius:var(--radius-lg);box-shadow:var(--shadow)}.chip{display:inline-flex;align-items:center;gap:4px;padding:3px 10px;border-radius:999px;border:1px solid var(--line);background:var(--card);font-size:.76rem;font-weight:600;color:var(--ink-soft);white-space:nowrap}.chip.lvl-beginner{background:var(--pastel-green-bg);border-color:transparent;color:var(--pastel-green-ink)}.chip.lvl-intermediate{background:var(--pastel-orange-bg);border-color:transparent;color:var(--pastel-orange-ink)}.chip.lvl-advanced{background:var(--pastel-pink-bg);border-color:transparent;color:var(--pastel-pink-ink)}.progress-ring{flex-shrink:0}.ring-track{stroke:var(--line)}.ring-fill{stroke:var(--gold)}.ring-primary .ring-fill{stroke:var(--primary)}.ring-text{fill:var(--ink);font-weight:700}.hero{position:relative;isolation:isolate;overflow:hidden;margin-top:20px;padding:30px 26px;border-radius:28px;background:var(--hero-grad);color:#fff;box-shadow:var(--hero-shadow)}.hero>*{position:relative;z-index:1}.hero-swirl{position:absolute;z-index:0;top:-30px;right:-70px;width:66%;max-width:540px;height:auto;mix-blend-mode:multiply;opacity:.8;transform:rotate(9deg);-webkit-mask-image:radial-gradient(72% 72% at 58% 42%,#000 38%,transparent 76%);mask-image:radial-gradient(72% 72% at 58% 42%,#000 38%,transparent 76%);pointer-events:none}.hero:before{content:"";position:absolute;z-index:0;border-radius:50%;background:radial-gradient(closest-side,#ffffff2e,#fff0);filter:blur(28px);transform:rotate(-18deg);pointer-events:none;width:300px;height:300px;top:-100px;right:-80px}.hero-mascot{position:absolute;z-index:2;right:-12px;bottom:-16px;width:74px;height:74px;border-radius:50%;object-fit:cover;object-position:top center;border:3px solid rgba(255,255,255,.9);background:#fff;box-shadow:0 10px 24px #10193b59;transform:rotate(6deg)}.hero h1{font-size:clamp(1.75rem,5vw,2.125rem);font-weight:800;letter-spacing:-.02em}.flag{font-size:1.5rem;vertical-align:-2px}.tagline{color:#fff;font-size:1.02rem;font-weight:500;margin:6px 0 0}.overall-progress{display:inline-block;margin-top:14px;padding:5px 14px;border-radius:999px;background:#0d123047;border:1px solid rgba(255,255,255,.25);color:#fff;font-size:.85rem;font-weight:700}.hero-cta{display:inline-flex;align-items:center;min-height:44px;margin:16px 0 2px;padding:10px 22px;border-radius:999px;background:#fff;color:var(--primary-fixed);font-size:1rem;font-weight:700;text-decoration:none;box-shadow:0 8px 20px #10193b40}@media (prefers-reduced-motion: no-preference){.hero-cta{transition:transform .15s ease}.hero-cta:hover{transform:translateY(-1px)}}.hero-badge{position:absolute;z-index:1;top:20px;right:20px;display:flex;align-items:center;justify-content:center;width:42px;height:42px;border-radius:14px;background:#fff3;border:1px solid rgba(255,255,255,.3);font-size:1.25rem}.continue-row{display:flex;align-items:center;gap:14px;margin-top:16px;padding:13px 16px;background:var(--card);border:1px solid var(--line);border-radius:var(--radius);box-shadow:var(--shadow);color:var(--ink);text-decoration:none}@media (prefers-reduced-motion: no-preference){.continue-row:hover{transform:translateY(-2px);border-color:var(--line-strong);box-shadow:var(--shadow-lift)}}.continue-icon{display:flex;align-items:center;justify-content:center;width:40px;height:40px;border-radius:50%;background:var(--primary-soft);color:var(--primary-ink);font-size:.95rem;flex-shrink:0}.continue-main{display:flex;flex-direction:column;gap:1px;flex:1;min-width:0}.continue-title{font-weight:700}.continue-sub{color:var(--ink-soft);font-size:.85rem}.continue-arrow{color:var(--primary-ink);font-weight:700;flex-shrink:0}.search-box{margin:20px 0 24px}.search-box input{width:100%;min-height:48px;padding:12px 20px 12px 46px;border-radius:999px;border:1px solid var(--line);background-color:var(--card);background-image:url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 24 24' fill='none' stroke='%23606c8a' stroke-width='2' stroke-linecap='round'%3E%3Ccircle cx='11' cy='11' r='7'/%3E%3Cpath d='m20 20-3.5-3.5'/%3E%3C/svg%3E");background-repeat:no-repeat;background-position:16px 50%;background-size:18px 18px;color:var(--ink);font-size:1rem;box-shadow:var(--shadow)}.search-box input::placeholder{color:var(--ink-soft)}.phase{margin-bottom:28px}.phase h2{font-size:.95rem;text-transform:uppercase;letter-spacing:.08em;color:var(--ink-soft);margin-bottom:14px;display:flex;align-items:center;flex-wrap:wrap;gap:8px}.phase-count{display:inline-block;padding:2px 10px;border-radius:999px;background:var(--primary-soft);color:var(--primary-ink);font-size:.72rem;font-weight:700;letter-spacing:0;text-transform:none}.unit-grid{display:grid;grid-template-columns:1fr;gap:16px}@media (min-width: 680px){.unit-grid{grid-template-columns:1fr 1fr}}.unit-card{position:relative;display:flex;align-items:center;gap:14px;min-height:84px;padding:16px;background:var(--card);border:1px solid var(--line);border-radius:var(--radius);box-shadow:var(--shadow);color:var(--ink);text-decoration:none}a.unit-card{cursor:pointer}@media (prefers-reduced-motion: no-preference){a.unit-card{transition:transform .15s ease,box-shadow .15s ease,border-color .15s ease}a.unit-card:hover{transform:translateY(-2px);border-color:var(--line-strong);box-shadow:var(--shadow-lift)}}.unit-card.coming{opacity:.55;box-shadow:none;border-style:dashed}.unit-order{display:flex;align-items:center;justify-content:center;width:46px;height:46px;border-radius:14px;font-size:1.35rem;font-weight:300;color:var(--ink);min-width:46px;text-align:center;font-variant-numeric:tabular-nums;flex-shrink:0}.tint-green{background:var(--pastel-green-bg)}.tint-pink{background:var(--pastel-pink-bg)}.tint-orange{background:var(--pastel-orange-bg)}.tint-teal{background:var(--pastel-teal-bg)}.tint-lavender{background:var(--pastel-lavender-bg)}.unit-main{display:flex;flex-direction:column;gap:1px;min-width:0;flex:1}.unit-vi{font-weight:700;font-size:1.05rem}.unit-en{color:var(--ink-soft);font-size:.88rem}.unit-meta{display:flex;flex-wrap:wrap;align-items:center;gap:6px;margin-top:5px}.docs-count{font-size:.76rem;font-weight:600;color:var(--ink-soft)}.chip.chip-mastery{background:var(--green-tint);border-color:transparent;color:var(--green-ink)}.soon-tag{font-size:.72rem;font-weight:700;text-transform:uppercase;letter-spacing:.05em;color:var(--ink-soft);border:1px dashed var(--line-strong);border-radius:999px;padding:3px 9px;white-space:nowrap}.empty-search{text-align:center;color:var(--ink-soft);padding:32px 0}.site-footer{margin-top:48px;padding-top:20px;border-top:1px solid var(--line);display:flex;flex-direction:column;gap:4px;align-items:center;text-align:center;font-size:.88rem}.footer-note{color:var(--ink-soft)}.langtext,.lt-vi,.lt-primary{display:block}.lt-en,.lt-alt{display:block;font-size:.85em;color:var(--ink-soft);margin-top:2px}.lt-one{cursor:pointer;border-radius:8px}.lt-one .lt-alt{display:none;background:var(--primary-soft);color:var(--ink);padding:3px 8px;margin-top:4px;border-radius:8px}@media (hover: hover){.lt-one:hover .lt-alt{display:block}}.lt-one.is-revealed .lt-alt{display:block}.lt-note{display:block;font-style:italic;font-size:.82em;color:var(--ink-soft);margin-top:4px}.back-link{display:inline-flex;align-items:center;min-height:44px;text-decoration:none;font-weight:600;color:var(--ink)}.lesson-header{padding:24px}.lesson-order{font-size:.78rem;font-weight:700;text-transform:uppercase;letter-spacing:.08em;color:var(--primary-ink)}.lesson-title{margin-top:4px;font-size:1.45rem}.lesson-title .vi{display:block;font-weight:800}.lesson-title .en{display:block;color:var(--ink-soft);font-size:.72em;font-weight:500}.lesson-summary{margin-top:8px;color:var(--ink-soft);font-size:.95rem}.lesson-summary span{display:block}.lesson-meta{display:flex;flex-wrap:wrap;align-items:center;gap:8px;margin-top:12px}.trim-note{display:flex;align-items:baseline;gap:2px;flex-wrap:wrap;margin:12px 0 0;padding:8px 12px;background:var(--primary-soft);border-left:4px solid var(--primary);border-radius:10px;font-size:.85rem}.doc-chip{display:inline-flex;align-items:center;gap:4px;min-height:36px;padding:5px 12px;border-radius:999px;border:1px solid transparent;background:var(--primary-soft);color:var(--primary-ink);font-size:.78rem;font-weight:600;text-decoration:none;max-width:100%}a.doc-chip:hover{background:var(--primary-soft-hover)}.doc-chip.is-disabled{background:transparent;border-style:dashed;border-color:var(--line);color:var(--ink-soft);cursor:not-allowed;opacity:.75}.tabs{display:flex;gap:4px;margin:18px 0;padding:4px;background:var(--card);border:1px solid var(--line);border-radius:999px;box-shadow:var(--shadow)}.tab{flex:1;display:flex;align-items:center;justify-content:center;min-height:44px;text-decoration:none;color:var(--ink-soft);font-weight:700;border-radius:999px}.tab.active{background:var(--primary-fill);color:var(--on-primary);box-shadow:var(--btn-glow)}.lang-bar{position:sticky;top:var(--header-h);z-index:20;display:flex;align-items:center;justify-content:flex-end;gap:12px;padding:8px 20px;margin:0 -20px 16px;background:var(--sticky-bg);backdrop-filter:blur(10px);-webkit-backdrop-filter:blur(10px);border-bottom:1px solid var(--line)}@media (min-width: 680px){.lang-bar{margin:0 -28px 16px;padding:8px 28px}}.lang-bar-label{font-size:.78rem;font-weight:700;text-transform:uppercase;letter-spacing:.06em;color:var(--ink-soft)}.seg{display:inline-flex;gap:2px;padding:3px;border:1px solid var(--line);border-radius:999px;background:var(--card)}.seg-btn{border:0;background:transparent;padding:6px 16px;min-height:44px;min-width:60px;border-radius:999px;font-weight:700;font-size:.85rem;color:var(--ink-soft);cursor:pointer}.seg-btn[aria-pressed=true]{background:var(--primary-fill);color:var(--on-primary)}.section{padding:20px 22px;margin-bottom:20px;scroll-margin-top:calc(var(--header-h) + 8px)}.section-head{display:flex;align-items:center;gap:12px}.section-icon{display:flex;align-items:center;justify-content:center;width:44px;height:44px;border-radius:14px;font-size:1.25rem;flex-shrink:0}.section[data-kind=dialogue] .section-icon{background:var(--pastel-lavender-bg)}.section[data-kind=vocab] .section-icon{background:var(--pastel-green-bg)}.section[data-kind=grammar] .section-icon{background:var(--pastel-pink-bg)}.section[data-kind=pronunciation] .section-icon{background:var(--pastel-teal-bg)}.section[data-kind=phrases] .section-icon{background:var(--pastel-orange-bg)}.section[data-kind=culture] .section-icon{background:var(--pastel-peach-bg)}.section-title{font-size:1.15rem;margin:0}.section-intro{color:var(--ink-soft);font-size:.92rem;margin:10px 0 12px}.dialogue{margin-top:6px}.dl-line{display:flex;gap:12px;padding:12px 0}.dl-line+.dl-line{border-top:1px solid var(--line)}.dl-badge{width:40px;height:40px;border-radius:50%;display:flex;align-items:center;justify-content:center;font-weight:800;font-size:.8rem;flex-shrink:0;margin-top:2px}.sp-0 .dl-badge{background:var(--pastel-lavender-bg);color:var(--pastel-lavender-ink)}.sp-1 .dl-badge{background:var(--pastel-teal-bg);color:var(--pastel-teal-ink)}.dl-body{min-width:0;flex:1}.dl-speaker{display:block;font-size:.75rem;font-weight:700;text-transform:uppercase;letter-spacing:.05em;color:var(--ink-soft);margin-bottom:2px}.dl-text .lt-vi,.dl-text .lt-primary{font-size:1.02rem}.item-grid{display:grid;grid-template-columns:1fr;gap:12px;margin-top:12px}@media (min-width: 620px){.item-grid{grid-template-columns:repeat(2,1fr)}}@media (min-width: 880px){.item-grid{grid-template-columns:repeat(3,1fr)}}.item-card{background:var(--well);border:1px solid var(--line);border-radius:var(--radius);padding:12px 14px}.item-card.flat{background:transparent;border:0;padding:0}.item-term-row{display:flex;align-items:flex-start;justify-content:space-between;gap:8px}.item-term{min-width:0}.item-term .lt-vi,.item-term .lt-primary{font-weight:700;font-size:1.05rem}.item-literal{font-family:ui-monospace,SFMono-Regular,Menlo,Consolas,monospace;font-size:.78rem;color:var(--ink-soft);margin-top:4px}.item-note{background:var(--primary-soft);border-left:3px solid var(--primary);border-radius:10px;padding:6px 10px;font-size:.85rem;margin-top:8px}.item-examples{margin-top:10px}.item-example{margin:0 0 6px;padding-left:10px;border-left:2px solid var(--line-strong);font-size:.9em}.item-example:last-child{margin-bottom:0}.say-btn{border:1px solid 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