/* V4: independent critical layout so server-rendered learning resources never become unstyled. */
.dv-body{margin:0;background:#f7f9ff;color:#202b50;font-family:'Be Vietnam Pro',Inter,system-ui,-apple-system,Segoe UI,Arial,sans-serif;font-size:14px;-webkit-font-smoothing:antialiased}
.dv-body *{box-sizing:border-box}.dv-body a{color:inherit;text-decoration:none}.dv-body button,.dv-body input{font:inherit}.dv-wrap{width:min(1160px,calc(100% - 40px));margin:auto}
.dv-header{background:#fff;border-bottom:1px solid #e8ecf8;position:relative;z-index:3}.dv-nav{height:83px;display:flex;align-items:center;justify-content:space-between;gap:20px}.dv-brand{display:flex;gap:12px;align-items:center;min-width:220px}.dv-brand-symbol{display:grid;place-items:center;background:linear-gradient(135deg,#6270f3,#394bd2);color:#fff;font-size:27px;width:49px;height:49px;border-radius:14px;box-shadow:0 9px 20px #5262da3b}.dv-brand strong{display:block;font-size:16px;letter-spacing:-.8px;font-weight:900}.dv-brand em{font-style:normal;color:#5b60ed}.dv-brand small{font-size:10px;color:#8995af;letter-spacing:1px;display:block;margin-top:2px}.dv-nav nav{display:flex;gap:26px;color:#65718a;font-size:12px;font-weight:800}.dv-nav nav a:hover{color:#5063e9}.dv-navlink{background:#eef0ff;color:#5563e5!important;font-size:12px;font-weight:800;border-radius:13px;padding:13px 17px;white-space:nowrap}
.dv-main{padding:25px 0 86px;min-height:75vh}.dv-breadcrumb{display:flex;align-items:center;gap:9px;flex-wrap:wrap;font-size:12px;color:#8390ab;margin-bottom:26px;line-height:1.7}.dv-breadcrumb span[aria-current]{color:#53617e;max-width:650px;white-space:nowrap;overflow:hidden;text-overflow:ellipsis}.dv-breadcrumb a:hover{color:#5462e2}
.dv-hero{position:relative;display:grid;grid-template-columns:minmax(0,1.18fr) minmax(330px,.82fr);gap:44px;align-items:center;border:1px solid #e5eafa;border-radius:30px;padding:47px 49px;background:radial-gradient(circle at 87% 13%,#e7e6ff 0,#f6f7ff 35%,white 77%);box-shadow:0 18px 54px #46588c0b;overflow:hidden}.dv-hero:before{content:'';position:absolute;inset:auto -100px -250px auto;width:600px;height:600px;border:1px dashed #91a1ed55;border-radius:50%;pointer-events:none}.dv-hero-text{position:relative;z-index:1;min-width:0;animation:dv-rise .65s both}.dv-tags{display:flex;gap:8px;flex-wrap:wrap;margin-bottom:26px}.dv-tags a,.dv-tags span{display:inline-block;color:#596bdc;background:#eceeff;border:1px solid #e0e4ff;padding:8px 11px;border-radius:50px;font-size:11px;font-weight:800}.dv-eyebrow{font-size:11px;font-weight:900;letter-spacing:2px;color:#6877e9;margin:0 0 10px}.dv-hero h1{font-size:clamp(27px,3vw,43px);line-height:1.4;letter-spacing:-1.45px;margin:0 0 16px;font-weight:900;overflow-wrap:anywhere}.dv-intro{line-height:1.85;color:#66728e;font-size:14px;max-width:650px}.dv-meta{display:flex;gap:10px;flex-wrap:wrap;margin:24px 0 25px;color:#68779a;font-size:11px;font-weight:800}.dv-meta span{padding:9px 12px;background:#fff;border:1px solid #e9edfd;border-radius:11px}.dv-primary{display:inline-flex;gap:14px;align-items:center;background:#5664ec;color:#fff!important;padding:14px 23px;border-radius:13px;font-size:12px;font-weight:900;box-shadow:0 10px 24px #576bf33c;transition:transform .25s,box-shadow .25s}.dv-primary:hover{transform:translateY(-3px);box-shadow:0 14px 28px #576bf350}
.dv-cover{position:relative;min-height:255px;border-radius:22px;overflow:hidden;background:linear-gradient(125deg,var(--dv-accent,#5b60df),#b09df2);box-shadow:0 26px 35px #48569d31;transform:rotate(2deg);animation:dv-cover-in .8s both}.dv-cover img{width:100%;height:100%;min-height:270px;object-fit:cover;display:block}.dv-cover-foot{position:absolute;bottom:15px;left:16px;right:16px;color:#fff;display:flex;justify-content:space-between;font-size:9px;font-weight:900;letter-spacing:1.2px;opacity:.8;pointer-events:none}
.dv-overview{display:grid;grid-template-columns:minmax(0,1.4fr) minmax(270px,.6fr);gap:22px;margin-top:28px;align-items:stretch}.dv-about,.dv-quick,.dv-section{background:#fff;border:1px solid #e9edf9;border-radius:24px;padding:32px 35px;box-shadow:0 12px 44px #334d8a08}.dv-about h2,.dv-quick h2,.dv-section h2{margin:0 0 12px;font-size:23px;letter-spacing:-.8px}.dv-about>p:not(.dv-eyebrow){line-height:2;color:#66728e;white-space:pre-line;overflow-wrap:anywhere}.dv-statrow{border-top:1px solid #eff0fa;margin-top:24px;padding-top:20px;display:flex;flex-wrap:wrap;gap:12px;font-size:11px;color:#7d88a2}.dv-statrow strong{color:#35446b}.dv-quick h2{display:flex;justify-content:space-between;font-size:19px}.dv-quick h2 span{color:#7c81df}.dv-quick>p{font-size:12px;color:#8894b0;line-height:1.75}.dv-actions{display:grid;gap:10px;margin-top:20px}.dv-action{display:flex;align-items:center;gap:12px;background:#5766eb;color:white!important;border-radius:14px;padding:15px;font-size:12px;font-weight:900;transition:transform .25s,box-shadow .25s;min-height:54px}.dv-action>:last-child{margin-left:auto}.dv-action:hover{transform:translateY(-2px);box-shadow:0 10px 18px #5261e83a}.dv-action.is-video{background:#7053c8}.dv-action.is-answer{background:#20967e}.dv-action-ic{display:grid;place-items:center;width:29px;height:29px;background:#ffffff28;border-radius:9px;font-size:19px}.dv-subnav{display:block;padding:11px 0;color:#5766d8!important;font-weight:850;font-size:12px}.dv-noactions{display:block;color:#7d8aa5;font-size:12px;line-height:1.7}
.dv-section{margin-top:26px;animation:dv-rise .7s both;scroll-margin-top:40px}.dv-section-title{display:flex;align-items:center;justify-content:space-between;gap:20px;margin-bottom:25px}.dv-section-title h2{margin:0}.dv-section-title p{font-size:12px;color:#8390a9;margin:8px 0 0}.dv-pill{white-space:nowrap;background:#eef0ff;border:1px solid #e3e7ff;color:#6571da;border-radius:30px;padding:10px 13px;font-size:11px;font-weight:900}.dv-sheet-grid{display:grid;grid-template-columns:repeat(2,minmax(0,1fr));gap:13px}.dv-sheet{border:1px solid #e9ecf7;background:linear-gradient(130deg,#fff,#fafbff);padding:18px;border-radius:17px;transition:transform .25s,box-shadow .25s}.dv-sheet:hover{transform:translateY(-4px);box-shadow:0 14px 22px #5264af14}.dv-sheet-head{display:flex;align-items:start;gap:12px}.dv-sheet-number{width:36px;height:36px;flex:0 0 36px;border-radius:11px;background:#edf0ff;color:#5364dd;display:grid;place-items:center;font-size:13px;font-weight:900}.dv-sheet h3{font-size:13px;line-height:1.65;margin:5px 0 16px;overflow-wrap:anywhere}.dv-sheet-actions{display:flex;gap:8px;flex-wrap:wrap}.dv-chip,.dv-tag{display:inline-flex;gap:7px;border:1px solid #e4e8ff;border-radius:9px;background:#eff1ff;padding:9px 11px;font-size:11px;font-weight:850;color:#5365d8!important}.dv-chip:hover{background:#e3e8ff}.dv-tag{background:#f6f6ff;color:#7c79ba!important}
.dv-explorer{border:1px solid #e8ecf7;background:#fafbff;border-radius:18px;overflow:hidden}.dv-explorer-toolbar{display:flex;gap:12px;align-items:center;padding:15px;background:#fff;border-bottom:1px solid #e9edfa}.dv-search{display:flex;align-items:center;gap:12px;background:#f7f9fe;border:1px solid #e6eaf7;border-radius:11px;padding:0 15px;flex:1;min-width:0}.dv-search span{font-size:27px;color:#8d9ab8}.dv-search input{background:none;border:0;outline:0;color:#27355c;width:100%;height:46px;font-size:12px}.dv-outline{border:1px solid #dfe4fc;background:#fff;border-radius:11px;padding:14px;color:#5968db;white-space:nowrap;font-size:11px;font-weight:850;cursor:pointer}.dv-outline:hover{background:#eff1ff}.ft-tree{padding:12px 15px 18px}.ft-children{padding:0;margin:0;list-style:none}.ft-children .ft-children{padding-left:21px;margin:5px 0 6px 19px;border-left:1px dashed #ccd7ed}.ft-tree li{list-style:none;margin:4px 0}.ft-folder>summary{display:flex;align-items:center;gap:10px;cursor:pointer;padding:11px;border-radius:11px;font-size:12px;font-weight:850;color:#344466;transition:background .2s;list-style:none;user-select:none}.ft-folder>summary::-webkit-details-marker{display:none}.ft-folder>summary:hover{background:#edf1ff}.ft-chevron{display:inline-block;transition:transform .25s;color:#7e89a5;font-size:19px}.ft-folder[open]>summary .ft-chevron{transform:rotate(180deg)}.ft-folder-ic{background:#fff0d9;color:#dc9d3e;border-radius:9px;font-size:17px;width:32px;height:31px;display:grid;place-items:center}.ft-folder-name{overflow-wrap:anywhere;flex:1}.ft-count{font-size:10px;color:#8d9bb3;background:#eef2f9;padding:6px 8px;border-radius:10px;white-space:nowrap}.ft-file{display:flex;align-items:center;gap:11px;min-height:43px;padding:6px 10px;border-radius:10px;transition:background .2s}.ft-file:hover{background:#f0f3fc}.ft-file-icon{width:30px;height:30px;display:grid;place-items:center;background:#eef0ff;border-radius:9px;color:#5b64d1;flex-shrink:0}.ft-file-name{flex:1;min-width:0;color:#4b5a74;font-size:12px;line-height:1.6;overflow-wrap:anywhere}.ft-file-action{font-size:11px;font-weight:900;color:#5365db!important;border-radius:9px;border:1px solid #dfe6ff;padding:9px 12px;white-space:nowrap;background:#fff}.ft-file-action:hover{background:#e9edff}.ft-file[hidden],.ft-folder[hidden]{display:none!important}
.dv-related-grid{display:grid;grid-template-columns:repeat(2,minmax(0,1fr));gap:12px}.dv-related{display:flex;align-items:center;gap:13px;padding:17px;border:1px solid #e6eafa;border-radius:15px;transition:transform .25s,box-shadow .25s}.dv-related:hover{transform:translateY(-3px);box-shadow:0 10px 20px #5264af14}.dv-related-icon{width:37px;height:37px;display:grid;place-items:center;background:#eff1ff;color:#5d69dd;border-radius:12px;font-size:22px;flex-shrink:0}.dv-related strong{display:block;color:#27365b;font-size:12px;line-height:1.5}.dv-related small{display:block;font-size:10px;color:#8290aa;margin-top:5px}.dv-related>span:last-child{margin-left:auto;color:#586bdc}.dv-footer{background:#fff;border-top:1px solid #e9edfa;padding:25px 0;color:#8993ab;font-size:12px}.dv-footer .dv-wrap{display:flex;justify-content:space-between;gap:15px;flex-wrap:wrap}.dv-footer a{color:#5a64dd;font-weight:800}
@keyframes dv-rise{from{opacity:0;transform:translateY(22px)}to{opacity:1;transform:none}}@keyframes dv-cover-in{from{opacity:0;transform:rotate(5deg) translateY(25px)}to{opacity:1;transform:rotate(2deg)}}
@media(max-width:900px){.dv-hero{grid-template-columns:1fr 360px;gap:20px;padding:34px}.dv-overview{grid-template-columns:1fr}.dv-nav nav{gap:12px}.dv-brand{min-width:180px}}
@media(max-width:720px){.dv-nav{height:74px}.dv-nav nav{display:none}.dv-navlink{padding:11px;font-size:10px}.dv-hero{grid-template-columns:1fr;padding:24px;gap:20px;border-radius:20px}.dv-hero h1{font-size:27px}.dv-cover{max-width:490px;min-height:185px;transform:rotate(0)}.dv-cover img{min-height:185px}.dv-about,.dv-quick,.dv-section{padding:22px}.dv-sheet-grid,.dv-related-grid{grid-template-columns:1fr}.dv-section-title{flex-wrap:wrap;gap:9px}.dv-explorer-toolbar{flex-wrap:wrap}.dv-outline{width:100%}.ft-children .ft-children{padding-left:9px;margin-left:10px}.dv-footer .dv-wrap{flex-direction:column}.dv-breadcrumb{font-size:10px}.dv-wrap{width:min(100% - 28px,1160px)}}
@media(prefers-reduced-motion:reduce){.dv-body *, .dv-body *::before,.dv-body *::after{animation:none!important;transition:none!important;scroll-behavior:auto!important}}
/* Keep generated title and logo fully visible rather than cropping the poster. */
.dv-cover{min-height:0;aspect-ratio:16/9}.dv-cover img{width:100%;height:100%;min-height:0;aspect-ratio:16/9;object-fit:contain}
@media(max-width:720px){.dv-section{animation:none!important}.dv-cover{min-height:0}.dv-cover img{min-height:0}}

/* V5: new visual hierarchy for learning resources / folders */
.dv-body{background:linear-gradient(180deg,#f7f9ff 0%,#fbfcff 100%)}
.dv-hero{box-shadow:0 22px 70px #5063bd12}
.dv-hero:after{content:"✦";position:absolute;right:22px;top:12px;color:#7d83e1;font-size:31px;opacity:.24}
.dv-cover{max-width:100%;box-shadow:0 28px 55px #38488d35}
.dv-cover img{display:block;aspect-ratio:16/9;object-fit:cover}
.dv-section{position:relative}
.dv-section-title h2{line-height:1.4}
.dv-action:focus-visible,.dv-chip:focus-visible,.ft-file-link:focus-visible,.ft-folder>summary:focus-visible{outline:3px solid #6472e9;outline-offset:3px}
.dv-sheet{border:1px solid #e7eafb;background:#fff;box-shadow:0 7px 17px #6674bb08}
.dv-sheet-head h3{flex:1;min-width:0}
.dv-chip{border-radius:11px;min-height:40px;align-items:center;transition:background .22s, transform .22s}
.dv-chip:hover{transform:translateY(-2px)}
.ft-tree{padding:14px 20px 20px}
.ft-folder>summary{border:1px solid transparent;gap:11px;min-height:52px}
.ft-folder[open]>summary{background:#eff2ff;border-color:#e5eaff}
.ft-folder[open]>summary .ft-folder-ic{background:#fceac8;color:#c48b2c}
.ft-file{display:block;padding:0}
.ft-file-link{display:flex;gap:12px;align-items:center;text-decoration:none;min-height:51px;padding:9px 11px;border-radius:12px;color:inherit}
.ft-file-link:hover{background:#eaf0ff}
.ft-file-action{flex-shrink:0;font-size:11px;font-weight:900;color:#5464d9;background:#fff;border:1px solid #dfe6ff;border-radius:9px;padding:8px 12px}
.ft-file-link:hover .ft-file-action{background:#e2e8ff}
.ft-children .ft-children{border-left:2px solid #dae1f6;margin-left:17px}
@media(max-width:720px){.dv-hero{padding:22px}.dv-hero h1{overflow-wrap:anywhere}.dv-cover{box-shadow:0 17px 35px #38488d21}.dv-section{padding:22px}.dv-section-title{align-items:start}.dv-sheet-grid{grid-template-columns:minmax(0,1fr)}.dv-explorer{width:100%;min-width:0}.ft-tree{padding:10px 8px}.ft-children .ft-children{margin-left:8px;padding-left:6px}.ft-folder>summary{font-size:11px;padding:9px 5px}.ft-file-name{font-size:11px}.ft-file-link{gap:7px;padding:9px 4px}.ft-file-action{font-size:10px;padding:7px 8px}.ft-count{white-space:normal;flex-shrink:0;max-width:70px;text-align:center}}