*{box-sizing:border-box}:root{--orange:#ea580c;--amber:#f59e0b;--orange-dark:#c2410c;--orange-soft:#fff7ed;--ink:#172033;--muted:#667085;--line:#e5eaf0;--bg:#f8fafc}body{margin:0;background:linear-gradient(145deg,#f8fafc 0%,#fffaf3 55%,#f4f7fb 100%);color:var(--ink);font-family:Inter,"Segoe UI",Arial,sans-serif;font-size:16px;line-height:1.6}.site-nav{height:72px;background:#fff;border-bottom:1px solid var(--line);display:flex;align-items:center;justify-content:space-between;padding:0 max(24px,calc((100vw - 1200px)/2));position:sticky;top:0;z-index:20}.site-nav a{text-decoration:none;color:#526076;font-size:14px;font-weight:700;margin-left:22px}.site-nav .brand{display:flex;align-items:center;gap:9px;font-size:20px;color:#1d2940;margin:0;font-weight:850;letter-spacing:-.02em}.brand-mark{width:36px;height:36px;display:grid;place-items:center;border:1px solid #fed7aa;border-radius:11px;background:linear-gradient(135deg,#fff7ed,#ffedd5);font-size:21px}.site-nav .active{color:var(--orange-dark)}.site-nav .teacher{padding:9px 14px;border:1px solid #d8e0ea;border-radius:10px}.learning-layout{max-width:1200px;margin:0 auto;display:grid;grid-template-columns:255px 1fr;gap:28px;padding:34px 24px 72px}.learning-sidebar{background:#fff;border:1px solid var(--line);border-radius:18px;padding:14px;align-self:start;position:sticky;top:96px;box-shadow:0 8px 30px #1720330a}.side-title{padding:8px 10px 13px;font-size:11px;font-weight:850;letter-spacing:.12em;color:#98a2b3}.learning-sidebar details{border-top:1px solid #f0f2f5}.learning-sidebar>details:first-of-type{border-top:0}.learning-sidebar summary{list-style:none;cursor:pointer;padding:12px 9px;display:flex;align-items:center;gap:9px;font-size:14px;font-weight:800;color:#25334a}.learning-sidebar summary::-webkit-details-marker{display:none}.learning-sidebar summary b{margin-left:auto;color:#98a2b3}.side-icon{width:27px;height:27px;border-radius:8px;background:var(--orange-soft);color:var(--orange-dark);display:grid;place-items:center;font-size:12px}.side-icon.muted{background:#f2f4f7;color:#98a2b3}.nested{margin-left:11px!important;border-top:0!important;border-left:1px solid #edf0f4;padding-left:10px}.nested summary{font-size:13px;padding:9px 7px}.side-levels{display:grid;gap:3px;padding:0 0 9px 5px}.side-levels a{margin:0!important;padding:7px 10px;border-radius:8px;color:#475467;font-size:12.5px!important;font-weight:650!important}.side-levels a:hover{background:var(--orange-soft);color:var(--orange-dark)}.side-levels a.soon{color:#b0b7c3;background:#fafbfc}.side-levels a.soon:hover{color:#98a2b3;background:#f5f6f7}.soon-label{margin-left:auto;font-size:9px;color:#aab1bc;background:#f3f4f6;padding:2px 6px;border-radius:999px}.learning-main{min-height:630px}.learning-welcome{padding:54px 58px;background:#fff;border:1px solid var(--line);border-radius:24px;min-height:520px;position:relative;overflow:hidden}.learning-welcome:after{content:"A";position:absolute;right:-20px;bottom:-120px;font-size:420px;line-height:1;font-weight:900;color:#fff7ed;z-index:0}.learning-welcome>*{position:relative;z-index:1}.learning-welcome>span{font-size:12px;font-weight:850;letter-spacing:.12em;color:var(--orange-dark)}.learning-welcome h1{font-size:42px;line-height:1.15;letter-spacing:-.035em;margin:12px 0}.learning-welcome p{max-width:650px;color:var(--muted);font-size:16px}.welcome-cards{display:grid;grid-template-columns:repeat(3,1fr);gap:12px;margin-top:44px}.welcome-cards div{padding:20px;border:1px solid var(--line);border-radius:16px;background:#fff}.welcome-cards b{display:block;color:var(--orange);font-size:12px}.welcome-cards strong,.welcome-cards span{display:block}.welcome-cards strong{margin:5px 0}.welcome-cards span{font-size:12px;color:var(--muted)}.blank-learning{max-width:1050px;margin:auto;padding:36px 24px}.blank-learning>a{color:var(--orange-dark);text-decoration:none;font-weight:700;font-size:13px}.blank-learning>div{height:520px;display:grid;place-content:center;text-align:center;color:#98a2b3}.blank-learning span{font-size:11px;font-weight:850;letter-spacing:.12em}.blank-learning h1{color:#667085;margin:8px 0}.blank-learning p{margin:0}footer{text-align:center;padding:30px;color:#8993a4;font-size:12px;border-top:1px solid var(--line)}
/* Existing program grid pages */.learn-shell{max-width:1180px;margin:auto;padding:54px 24px 80px}.program-hero{text-align:center;max-width:800px;margin:0 auto 42px}.program-hero>span,.section-title>span{font-size:12px;letter-spacing:.12em;font-weight:800;color:var(--orange-dark)}.program-hero h1{font-size:42px;line-height:1.15;letter-spacing:-.04em;margin:12px 0 16px}.program-hero p,.section-title p{color:var(--muted)}.unit-grid{display:grid;grid-template-columns:repeat(3,1fr);gap:16px}.unit-grid article{background:#fff;border:1px solid var(--line);border-radius:18px;padding:22px}.unit-grid small{color:var(--orange-dark);font-weight:800}.unit-grid h3{font-size:22px;margin:5px 0 16px}.unit-grid article div{display:grid;grid-template-columns:1fr 1fr;gap:7px}.unit-grid a{text-decoration:none;color:#475467;background:#f7f9fc;border-radius:9px;padding:9px;font-size:12px;font-weight:650}.unit-grid a:hover{background:var(--orange-soft);color:var(--orange-dark)}
@media(max-width:800px){.site-nav div a:not(.active):not(.teacher){display:none}.learning-layout{grid-template-columns:1fr;padding:18px 14px}.learning-sidebar{position:static}.learning-welcome{padding:34px 24px}.learning-welcome h1{font-size:34px}.welcome-cards{grid-template-columns:1fr}.unit-grid{grid-template-columns:1fr}}
test

/* V6.5.5 persistent learning navigator */
.learning-layout{max-width:1380px;grid-template-columns:285px minmax(0,1fr);gap:22px}
.learning-sidebar{border-radius:16px;padding:10px;max-height:calc(100vh - 104px);overflow:auto;box-shadow:0 10px 30px rgba(15,23,42,.06)}
.tree-home{display:flex!important;align-items:center;gap:9px;margin:0!important;padding:9px 8px 12px!important;text-decoration:none;color:var(--ink)!important;font-size:13px!important}
.tree-home .side-icon,.learning-sidebar>details>summary .side-icon{background:linear-gradient(135deg,#fff7ed,#ffedd5);color:#c2410c}
.learning-sidebar summary:hover,.tree-stage:hover,.tree-unit>a:hover,.tree-parts a:hover{background:#fff7ed}
.chev{font-size:11px}.tree-list{display:grid;gap:2px;padding:2px 0 8px}
.tree-stage{display:flex!important;align-items:center;justify-content:space-between;gap:8px;margin:0!important;padding:7px 9px!important;border-radius:8px;text-decoration:none;color:#475569!important;font-size:12.5px!important;font-weight:700!important}
.tree-stage small{font-size:8px;color:#a3abb8;font-weight:650}.tree-stage.disabled{color:#aab1bc!important;background:#fafbfc}
.tree-stage.current{color:#fff!important;background:linear-gradient(135deg,#ea580c,#f59e0b);box-shadow:0 5px 13px rgba(234,88,12,.18)}
.tree-stage.current b{color:#fff}.tree-units{margin:4px 0 7px 13px;padding-left:9px;border-left:1px solid #fed7aa;display:grid;gap:2px}
.tree-unit>a{display:flex!important;margin:0!important;padding:6px 9px!important;border-radius:7px;text-decoration:none;color:#5a6576!important;font-size:12px!important;font-weight:700!important}
.tree-unit.selected>a{color:#c2410c!important;background:#fff7ed;font-weight:850!important}
.tree-parts{display:grid;gap:1px;margin:2px 0 5px 10px;padding-left:9px;border-left:1px solid #f3e2cf}
.tree-parts a{margin:0!important;padding:5px 8px!important;border-radius:6px;text-decoration:none;color:#7b8493!important;font-size:11.5px!important;font-weight:650!important}
.tree-parts a.active{color:#c2410c!important;background:linear-gradient(90deg,#fff7ed,#fff);font-weight:850!important}
.content-panel{min-width:0}.program-hero{text-align:left;max-width:none;margin:0 0 22px;padding:28px 30px;background:linear-gradient(135deg,#fff 0%,#fff7ed 72%,#ffedd5 100%);border:1px solid #fed7aa;border-radius:20px;box-shadow:0 8px 24px rgba(234,88,12,.06)}
.program-hero h1{background:linear-gradient(90deg,#172033 0 55%,#ea580c);-webkit-background-clip:text;background-clip:text;color:transparent}
.unit-grid{grid-template-columns:repeat(3,minmax(0,1fr));gap:13px}.unit-grid article{border-radius:15px;padding:18px;box-shadow:0 5px 16px rgba(15,23,42,.035);transition:.16s}.unit-grid article:hover{transform:translateY(-2px);border-color:#fdba74;box-shadow:0 10px 24px rgba(234,88,12,.08)}
.unit-grid small{color:#c2410c}.unit-grid a:hover{background:linear-gradient(135deg,#fff7ed,#ffedd5);color:#c2410c}
.brand-mark img{width:25px;height:25px;display:block}
@media(max-width:900px){.learning-layout{grid-template-columns:1fr}.learning-sidebar{position:static;max-height:none}.unit-grid{grid-template-columns:1fr 1fr}}
@media(max-width:620px){.unit-grid{grid-template-columns:1fr}}

/* V6.5.6 book landing */
.book-hero{display:grid;grid-template-columns:170px minmax(0,1fr);gap:28px;align-items:center;padding:28px!important}.book-cover-wrap{min-height:215px}.book-cover,.book-cover-placeholder{width:150px;height:210px;border-radius:10px;box-shadow:0 12px 28px rgba(15,23,42,.15)}.book-cover{object-fit:cover;display:block}.book-cover-placeholder{display:flex;flex-direction:column;align-items:center;justify-content:center;background:linear-gradient(145deg,#ea580c,#f59e0b);color:#fff;border:1px solid #fdba74;text-align:center}.book-cover-placeholder span{font-size:34px}.book-cover-placeholder small{font-size:10px;letter-spacing:.16em;margin-top:9px}.book-cover-placeholder b{font-size:23px;margin:3px 0}.book-cover-placeholder em{font-size:10px;font-style:normal;opacity:.78}.book-intro{min-width:0}.book-intro h1{margin-top:9px}.book-intro>p{max-width:760px;line-height:1.75}.book-highlights{display:flex;flex-wrap:wrap;gap:7px;margin-top:15px}.book-highlights span{font-size:11px;font-weight:800;color:#9a3412;background:#fff7ed;border:1px solid #fed7aa;border-radius:999px;padding:7px 10px}.cover-hint{font-size:11px!important;color:#98a2b3!important;margin:13px 0 0!important}.unit-grid article small{letter-spacing:.04em}.unit-grid article h3{margin-top:7px}
@media(max-width:700px){.book-hero{grid-template-columns:1fr}.book-cover-wrap{min-height:0}.book-cover,.book-cover-placeholder{width:120px;height:168px}}

/* V6.5.7 Stage pages are introduction articles only */
.book-landing{display:grid;gap:20px}
.book-landing-hero{display:grid;grid-template-columns:190px minmax(0,1fr);gap:34px;align-items:center;padding:34px;background:linear-gradient(135deg,#fff 0%,#fff8ee 72%,#ffedd5 100%);border:1px solid #fed7aa;border-radius:22px;box-shadow:0 10px 30px rgba(234,88,12,.065)}
.book-landing .book-cover-wrap{min-height:238px;display:grid;place-items:center}
.book-landing .book-cover,.book-landing .book-cover-placeholder{width:166px;height:232px}
.book-heading .eyebrow,.section-kicker{display:block;color:#c2410c;font-size:11px;font-weight:900;letter-spacing:.13em}
.book-heading h1{font-size:40px;line-height:1.12;letter-spacing:-.035em;margin:10px 0 12px;color:#172033}
.book-meta{display:flex;flex-wrap:wrap;gap:7px;margin-bottom:17px}.book-meta span{padding:6px 9px;border:1px solid #fed7aa;border-radius:999px;background:#fffaf5;color:#9a3412;font-size:11px;font-weight:800}
.book-overview{max-width:800px;margin:0;color:#536074;font-size:15.5px;line-height:1.85}
.intro-section{padding:28px 30px;background:#fff;border:1px solid #e5eaf0;border-radius:18px;box-shadow:0 5px 18px rgba(15,23,42,.035)}
.intro-section h2{font-size:25px;letter-spacing:-.02em;margin:5px 0 20px}
.feature-grid{display:grid;grid-template-columns:repeat(3,minmax(0,1fr));gap:12px}
.feature-grid article{position:relative;padding:19px 18px 18px;border:1px solid #f1e5d8;border-radius:14px;background:linear-gradient(145deg,#fffdf9,#fff)}
.feature-grid article>span{display:inline-grid;place-items:center;width:28px;height:28px;border-radius:9px;background:linear-gradient(135deg,#ea580c,#f59e0b);color:#fff;font-size:10px;font-weight:900;box-shadow:0 4px 10px rgba(234,88,12,.15)}
.feature-grid h3{font-size:16px;line-height:1.35;margin:12px 0 8px;color:#202c42}.feature-grid p{font-size:13px;line-height:1.7;color:#667085;margin:0}
.components-section{background:linear-gradient(135deg,#fff,#fffaf5)}.component-list{display:grid;grid-template-columns:repeat(3,1fr);gap:10px}
.component-list div{display:flex;align-items:center;gap:11px;padding:13px 14px;background:#fff;border:1px solid #f0e2d3;border-radius:12px}.component-list span{display:grid;place-items:center;width:34px;height:34px;border-radius:9px;background:#fff7ed;color:#c2410c;font-size:10px;font-weight:900}.component-list b{font-size:12.5px;color:#344054}
.sidebar-tip{display:flex;align-items:center;gap:14px;padding:14px 18px;border-left:4px solid #f59e0b;background:#fff7ed;border-radius:10px;color:#7c4a20}.sidebar-tip b{white-space:nowrap;font-size:12px}.sidebar-tip span{font-size:12px;line-height:1.55}
@media(max-width:900px){.feature-grid,.component-list{grid-template-columns:1fr}.book-landing-hero{grid-template-columns:1fr}.book-landing .book-cover-wrap{justify-content:start}.sidebar-tip{align-items:flex-start;flex-direction:column;gap:4px}}

/* V6.5.9 book cover sizing */
.book-landing .book-cover-wrap{min-height:330px}.book-landing .book-cover{width:225px;height:auto;max-height:330px;object-fit:contain;filter:drop-shadow(0 12px 16px rgba(15,23,42,.16))}
.book-landing .book-cover-placeholder{width:210px;height:294px}.book-cover-placeholder em{display:none!important}
@media(max-width:900px){.book-landing .book-cover{width:205px;max-height:300px}}

/* V6.6.0 — Stage editorial flow: cover first, article below */
.book-landing-hero{display:block!important;padding:34px 38px!important}
.book-landing .book-cover-wrap{min-height:0!important;display:flex!important;justify-content:flex-start!important;align-items:flex-start!important;margin:0 0 28px!important}
.book-landing .book-cover{width:230px!important;height:auto!important;max-height:340px!important;object-fit:contain!important;filter:drop-shadow(0 13px 18px rgba(15,23,42,.17))}
.book-landing .book-cover-placeholder{width:230px!important;height:320px!important}
.book-heading{max-width:900px}
.book-heading h1{margin-top:8px!important}
.book-overview{max-width:900px!important}
.site-footer{text-align:center;padding:24px 20px 30px;color:#7b8798;font-size:12px;border-top:1px solid var(--line);background:rgba(255,255,255,.72)}
.floating-support{position:fixed;right:18px;bottom:18px;z-index:900;display:inline-flex;align-items:center;gap:8px;background:linear-gradient(145deg,rgba(255,255,255,.98),rgba(248,250,252,.96));border:1px solid #dbe7f3;border-radius:14px;padding:8px 11px;box-shadow:0 12px 30px rgba(15,23,42,.12),0 2px 8px rgba(217,119,6,.08);text-decoration:none;color:#172033;backdrop-filter:blur(10px);transition:.18s}
.floating-support .zalo-mini{width:26px;height:26px;border-radius:8px;display:grid;place-items:center;background:linear-gradient(145deg,#1688f8,#0068ff);color:#fff;font-size:9px;font-weight:800;letter-spacing:-.03em;box-shadow:0 4px 10px rgba(0,104,255,.22)}
.floating-support b{font-size:11px;color:#475569;font-weight:650}.floating-support:hover{transform:translateY(-2px);box-shadow:0 16px 34px rgba(15,23,42,.16)}
@media(max-width:760px){.book-landing-hero{padding:25px!important}.book-landing .book-cover{width:190px!important}.floating-support{right:10px;bottom:18px;padding:7px 9px}.floating-support b{display:none}.floating-support .zalo-mini{width:28px;height:28px}}

/* V6.6.1 — final Stage intro composition */
.book-landing-hero{display:block!important;padding:34px 40px 38px!important}
.book-landing .book-cover-wrap{display:flex!important;justify-content:center!important;align-items:flex-start!important;margin:0 auto 30px!important;min-height:0!important}
.book-landing .book-cover{display:block;width:265px!important;max-width:44vw!important;height:auto!important;max-height:none!important;object-fit:contain!important;filter:drop-shadow(0 12px 18px rgba(15,23,42,.16))}
.book-heading{max-width:820px!important;margin:0 auto!important}
.book-heading .eyebrow{margin-bottom:8px}
.book-heading h1{font-size:36px!important;line-height:1.14!important;margin:0 0 12px!important}
.book-meta{margin-bottom:16px!important}
.book-overview{max-width:820px!important;font-size:15px!important;line-height:1.8!important}
.book-cover-placeholder{display:none!important}
@media(max-width:760px){.book-landing-hero{padding:24px!important}.book-landing .book-cover{width:220px!important;max-width:72vw!important}.book-heading h1{font-size:30px!important}}