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p{font-size:16px;font-weight:750;margin:9px 0}.book-cover{background:radial-gradient(circle at 90% 15%,#b8eee0,transparent 35%),linear-gradient(140deg,#effaf3,#fff8e6);border-radius:17px;min-height:430px;display:flex;flex-direction:column;align-items:center;justify-content:center;text-align:center;padding:38px 30px}.book-cover .cover-icon{width:116px;height:116px;display:grid;place-items:center;border-radius:35px;background:#fff;box-shadow:0 15px 29px #11725d16;font-size:67px;transform:rotate(-6deg)}.book-cover h2{font-size:clamp(35px,5vw,59px);max-width:600px;color:#117967;margin:26px 0 13px}.book-cover p{font-size:19px;max-width:440px}.book-cover small{font-size:12px;letter-spacing:2px;color:#4b8e7d;font-weight:900;margin-top:30px}.book-controls{display:flex;justify-content:space-between;align-items:center;gap:12px}.book-controls>span{font-size:12px;color:#7a948a;font-weight:800}.steps-container{padding-top:48px}.steps-row{display:grid;grid-template-columns:repeat(3,1fr);gap:20px;margin-bottom:44px}.step-tile{background:white;border:1px solid var(--border);border-radius:20px;padding:30px 28px}.step-index{font-size:11px;letter-spacing:1.2px;font-weight:900;color:#128872}.step-visual{display:block;font-size:45px;margin:18px 0 12px}.step-tile h2{font-size:25px;letter-spacing:-.5px;margin:0 0 9px}.step-tile p{margin:0;color:#667e78;line-height:1.8;font-size:14px}.practice-panel{border-radius:24px;background:#fff;border:1px solid var(--border);padding:39px}.check-work{display:grid;grid-template-columns:.8fr 1.2fr;gap:30px}.example-quote{background:linear-gradient(150deg,#e3f6ed,#dff1ff);border-radius:18px;padding:28px;align-self:start}.example-quote p{font-weight:750;font-size:21px;line-height:1.5;margin:15px 0}.example-quote small{font-size:13px;color:#42716b}.worksheet{display:flex;flex-direction:column;gap:9px}.worksheet label{font-weight:750;font-size:13px;margin-top:5px}.worksheet textarea{border:1px solid #d6e5e0;border-radius:12px;width:100%;padding:13px 15px;resize:vertical;min-height:75px;color:#234944;background:#fbfefd}.worksheet textarea::placeholder{color:#95a7a0}.inline-actions{margin-top:9px}.answer-box{background:#ecf8ee;border:1px solid #bdebd2;border-radius:13px;padding:18px;margin:10px 0}.answer-box p{margin:8px 0 6px}.answer-box small{font-size:12px;color:#627a70}.tip-strip{background:#eaf7f1;display:flex;gap:20px;align-items:center;margin-top:28px;padding:21px 24px;border-radius:17px;color:#40635d}.tip-strip span{font-size:32px}.tip-strip 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strong{display:block;font-size:16px;margin-bottom:5px}.feedback-box p{margin:0;line-height:1.75;font-size:14px}.exercise-bottom{margin-top:24px;display:flex;gap:12px;align-items:center;justify-content:space-between;flex-wrap:wrap}.exercise-bottom .btn-primary{margin-left:auto}.result-screen{text-align:center;padding:35px 10px}.result-emoji{font-size:70px}.result-screen h2{font-size:32px;margin:10px 0}.result-screen .result-score{font-size:48px;color:#098776;font-weight:900;line-height:1.3}.result-screen p{max-width:510px;color:#637e74;margin:12px auto 0}.privacy-note{margin:26px auto 0;max-width:850px;display:flex;gap:14px;align-items:start;color:#5d7770;font-size:13px;padding:14px 4px}.privacy-note span{font-size:22px}.privacy-note p{margin:0}.page-hero h1 .emoji{display:inline-block;vertical-align:middle}.site-footer{margin-top:30px}
@media(max-width:1050px){.feature-grid{grid-template-columns:repeat(2,1fr)}.hero-grid{gap:15px}.floating-note{font-size:12px}.note-b{left:-5px}.note-a{right:0}.book-layout{grid-template-columns:225px minmax(0,1fr)}.book-paper{padding:34px 38px}}
@media(max-width:760px){.container{width:min(100% - 30px,1180px)}.header-inner{min-height:69px}.brand-mark{width:39px;height:39px}.brand-title{font-size:14px}.brand-title small{font-size:8px;letter-spacing:1.3px}.menu-toggle{display:block}.site-nav{display:none;position:absolute;top:69px;left:0;right:0;background:white;box-shadow:0 10px 25px #0a4c3c12;padding:12px 15px 17px;border-top:1px solid #e8f0e9;flex-direction:column;align-items:stretch}.site-nav.open{display:flex}.nav-link{font-size:15px;padding:13px}.hero-grid{grid-template-columns:1fr;min-height:0;padding:52px 0 43px}.hero-content h1{letter-spacing:-1.3px;font-size:clamp(34px,8vw,48px)}.hero-content>p{font-size:15px}.hero-visual{min-height:345px}.browser-mock{width:min(390px,87%)}.mock-question{font-size:21px}.note-a{top:4px}.note-b{bottom:6px;left:0}.section-pad{padding:58px 0}.section-heading h2{font-size:29px}.journey-panel{grid-template-columns:1fr;padding:33px 30px}.journey-art{height:170px}.big-check{width:130px;height:130px;font-size:86px}.orbit-one{right:30%}.mini-steps{grid-template-columns:1fr}.book-layout{grid-template-columns:1fr}.book-sidebar{position:static;padding:15px}.book-index{display:flex;flex-direction:row;overflow-x:auto;padding:2px 0 5px;gap:6px;scrollbar-width:thin}.book-index-btn{flex:0 0 163px;min-height:60px}.steps-row{grid-template-columns:1fr;gap:13px}.step-tile{padding:23px}.step-visual{margin:9px 0;font-size:38px}.check-work{grid-template-columns:1fr}.practice-panel{padding:24px}.exercise-shell{padding:25px}.page-hero{padding:47px 0}.footer-inner{flex-direction:column}.footer-links{gap:11px}.site-footer{margin-top:20px}}
@media(max-width:520px){.feature-grid{grid-template-columns:1fr}.feature-card{min-height:0;padding:23px}.hero-actions{align-items:stretch}.hero-actions>.btn{width:100%}.hero-notes{gap:8px 12px}.browser-mock{padding:0 15px 18px}.mock-question{font-size:18px}.mock-reply{font-size:13px}.mock-verdict{padding:11px}.floating-note{padding:9px 11px;font-size:10px}.section-heading h2{font-size:27px}.journey-panel{padding:29px 22px}.book-paper{min-height:440px;padding:27px 22px}.book-paper h2{font-size:28px}.book-paper p,.book-paper li{font-size:14px}.book-controls .btn{padding:11px;min-height:45px;font-size:12px}.book-controls>span{font-size:10px}.mode-tabs{display:grid;grid-template-columns:1fr 1fr;width:100%}.mode-tab{padding:10px 6px;font-size:12px}.exercise-shell{padding:19px 17px}.choice-btn{font-size:14px;padding:13px}.exercise-bottom .btn{font-size:12px;padding:10px}.page-hero h1{font-size:33px}.page-hero p{font-size:14px}}
@media(prefers-reduced-motion:reduce){*,*:before,*:after{scroll-behavior:auto!important;transition:none!important}}
/* Giữ sách số gọn trong màn hình điện thoại; mục lục cuộn ngang độc lập. */
.book-layout,.book-sidebar,.book-main{min-width:0;max-width:100%}
.book-index{max-width:100%}
@media(max-width:760px){.book-layout{grid-template-columns:minmax(0,1fr)}.book-index{width:100%;overflow-x:auto}}
/* Thư viện học liệu, các trang đọc và chatbot */
.site-nav{gap:6px}.nav-link{white-space:nowrap}
.article-home{padding:24px 0 58px}.article-home-more{text-align:center;margin:28px 0 0}.articles-grid{display:grid;grid-template-columns:repeat(3,minmax(0,1fr));gap:20px}.article-card{border-radius:20px;display:block;background:#fff;border:1px solid #e0ece7;overflow:hidden;box-shadow:0 9px 25px #163d3312;color:#1b4540;text-decoration:none;transition:transform .18s,box-shadow .18s}.article-card:hover{transform:translateY(-3px);box-shadow:0 15px 28px #163d3324}.article-photo{display:block;object-fit:cover;width:100%;height:186px;background:#eff8f3}.article-card-body{padding:20px 21px 22px}.article-category{display:inline-block;font-size:11px;font-weight:850;letter-spacing:.4px;color:#0d816c;background:#e5f6ef;border-radius:30px;padding:5px 12px;margin-bottom:9px}.article-card h3{font-size:19px;line-height:1.4;margin:0 0 10px}.article-card p{font-size:13px;color:#53736b;line-height:1.7;min-height:66px;margin:0}.article-more{display:inline-block;color:#0d806e;font-weight:850;margin-top:17px;font-size:13px}.article-filters{display:flex;gap:11px;align-items:center;flex-wrap:wrap;margin-bottom:26px}.article-filters label{font-weight:800;font-size:13px}.article-filters select,.article-filters input{border:1px solid #cddfd7;border-radius:12px;padding:13px;background:#fff;min-height:48px;font-size:14px;color:#2e544b}.article-filters input{min-width:min(330px,100%)}.empty-message{text-align:center;color:#6a8178;padding:25px}.article-detail{max-width:870px;margin:0 auto}.article-detail #article-reader{padding:25px 0}.article-detail #article-reader>.article-photo{height:clamp(260px,40vw,420px);border-radius:20px;margin-bottom:26px}.article-detail h2{font-size:clamp(26px,4vw,40px);line-height:1.35;margin:12px 0 15px}.article-lead{font-weight:750;color:#4d6d61;font-size:17px}.article-detail #article-reader>p{line-height:1.85;color:#3f5b53;font-size:16px;margin:0 0 19px}.article-related{margin:45px 0 0;border-top:1px solid #d5e9dd;padding:25px 0}.article-related .articles-grid{grid-template-columns:repeat(2,minmax(0,1fr))}.pdf-download{font-size:12px;text-decoration:none;white-space:nowrap;color:#0b7669;font-weight:850;background:#e7f6ef;border-radius:8px;padding:8px 12px}.book-toolbar{flex-wrap:wrap;gap:8px}.footer-inner{align-items:start}.footer-inner>div:first-child{max-width:590px}.footer-links{flex-wrap:wrap;max-width:430px}.footer-admin{border:1px solid #cae8da;border-radius:10px;padding:10px 13px;background:#e9f9f1;color:#136951!important;min-height:44px;display:inline-flex;align-items:center}.footer-bottom{display:flex;gap:10px;justify-content:space-between;flex-wrap:wrap}.sr-only{position:absolute;overflow:hidden;clip:rect(0,0,0,0);white-space:nowrap;width:1px;height:1px;padding:0;border:0}.chat-widget{position:fixed;right:16px;bottom:16px;z-index:110}.chat-launch{border:4px solid #fff;border-radius:50%;width:76px;height:76px;overflow:hidden;padding:0;box-shadow:0 7px 25px #145b4c4d;background:#f6fff9;cursor:pointer;display:block;margin-left:auto}.chat-launch img{width:100%;height:100%;object-fit:cover;object-position:center 19%}.chat-bubble{position:absolute;right:83px;bottom:15px;max-width:235px;filter:drop-shadow(0 4px 10px #1a504428)}.chat-bubble button{color:#23564c;background:#fff;border:1px solid #bcdfd0;border-radius:16px 16px 2px 16px;min-height:46px;padding:11px 13px;font-weight:750;font-size:12px;text-align:left}.chat-panel{position:absolute;right:0;bottom:92px;width:min(370px,calc(100vw - 22px));height:min(560px,calc(100vh - 120px));display:flex;flex-direction:column;background:#fff;border:1px solid #c8e4d4;border-radius:22px;overflow:hidden;box-shadow:0 15px 60px #0a51464a}.chat-panel[hidden],.chat-bubble[hidden]{display:none!important}.chat-head{display:flex;align-items:center;gap:11px;background:linear-gradient(130deg,#0e836e,#126b76);color:white;padding:12px 15px}.chat-head img{width:44px;height:44px;object-fit:cover;object-position:center 24%;border:2px solid #fff;border-radius:50%}.chat-head div{flex:1;min-width:0}.chat-head strong{display:block;font-size:15px}.chat-head small{font-size:11px;color:#e9fff5}.chat-head button{border:0;color:white;background:#ffffff24;font-size:26px;border-radius:8px;width:44px;height:44px}.chat-messages{flex:1;overflow:auto;padding:15px;display:flex;flex-direction:column;gap:11px}.chat-message{padding:12px 14px;border-radius:16px;max-width:91%;font-size:13px;line-height:1.65;color:#31564b}.chat-message p{margin:0}.chat-message.student{align-self:flex-end;background:#dcf5e9;border-bottom-right-radius:4px}.chat-message.teacher{align-self:flex-start;background:#f2f7f5;border-bottom-left-radius:4px}.chat-message a{font-weight:850;color:#097766;display:inline-block;margin-top:8px}.chat-chips{display:flex;gap:6px;overflow-x:auto;padding:8px 12px;border-top:1px solid #edf1ee}.chat-chips button{flex:0 0 auto;border:1px solid #a2d9c4;color:#166d5a;background:#e7f6ee;padding:7px 10px;border-radius:30px;font-size:11px;min-height:38px}.chat-panel form{display:flex;padding:10px;gap:7px;border-top:1px solid #e3eee9}.chat-panel form input{flex:1;min-width:0;padding:11px;border:1px solid #d2e5dd;border-radius:12px;font-size:13px}.chat-panel form button{background:#0e8e76;color:white;border:0;border-radius:10px;padding:9px 13px;min-height:44px;font-weight:800}.chat-footnote{font-size:10px;text-align:center;margin:0 9px 10px;color:#708981}
@media(max-width:980px){.articles-grid{grid-template-columns:repeat(2,minmax(0,1fr))}}@media(max-width:720px){.articles-grid{grid-template-columns:1fr}.article-card{display:grid;grid-template-columns:130px 1fr}.article-card .article-photo{height:100%;min-height:185px}.article-card-body{padding:15px}.article-card h3{font-size:16px}.article-card p{font-size:12px;min-height:0}.article-related .articles-grid{grid-template-columns:1fr}.article-filters{display:grid;grid-template-columns:1fr}.article-filters select,.article-filters input{width:100%}.chat-launch{width:62px;height:62px}.chat-bubble{right:70px;bottom:10px;max-width:190px}.chat-panel{bottom:76px;height:min(550px,calc(100vh - 101px))}.chat-widget{bottom:10px;right:10px}.footer-bottom{padding-bottom:86px}}@media(max-width:400px){.article-card{grid-template-columns:100px 1fr}.article-card h3{font-size:14px}.article-card .article-photo{min-height:160px}.chat-bubble{max-width:165px}.chat-bubble button{font-size:11px}}
@media(min-width:761px) and (max-width:1100px){.menu-toggle{display:block}.site-nav{display:none;position:absolute;top:82px;left:0;right:0;background:#fff;box-shadow:0 10px 25px #0a4c3c12;padding:12px 18px 18px;border-top:1px solid #e7efe9;flex-direction:column;align-items:stretch}.site-nav.open{display:flex}.nav-link{padding:14px 18px}}