:root{
  --vtk-radius: 16px;
  --vtk-radius-sm: 12px;
  --vtk-shadow: 0 10px 24px rgba(15,23,42,.06);
  --vtk-border: 1px solid rgba(15,23,42,.10);
  --vtk-soft: rgba(15,23,42,.04);
  --vtk-soft2: rgba(15,23,42,.06);
  --vtk-text: #0f172a;
  --vtk-muted: rgba(15,23,42,.72);
  --vtk-muted2: rgba(15,23,42,.58);
  --vtk-red: #e10600;
  --vtk-blue: #14afe8;
  --vtk-bg: #f8fafc;
}

.vtk-wrap{
  background: var(--vtk-bg);
}

.vtk-card{
  background:#fff;
  border: var(--vtk-border);
  border-radius: var(--vtk-radius);
  box-shadow: var(--vtk-shadow);
}
.vtk-card--flat{
  box-shadow: 0 8px 18px rgba(15,23,42,.05);
}

/* HERO */
.vtk-hero{ padding: 4px 0 14px; }
.vtk-heroGrid{
  display:grid;
  grid-template-columns: 1.1fr .9fr;
  gap: 14px;
  align-items: stretch;
}
@media (max-width: 980px){
  .vtk-heroGrid{ grid-template-columns: 1fr; }
}

.vtk-heroMain{
  padding: 18px 18px 16px;
  position: relative;
  overflow: hidden;
}
.vtk-heroMain:before{
  content:"";
  position:absolute; inset:0;
  background:
    radial-gradient(700px 320px at 18% 18%, rgba(225,6,0,.12), rgba(0,0,0,0) 60%),
    radial-gradient(700px 320px at 90% 20%, rgba(20,175,232,.12), rgba(0,0,0,0) 60%);
  pointer-events:none;
}
.vtk-heroMain > *{ position:relative; }
.vtk-kicker{
  display:inline-flex;
  gap:8px;
  align-items:center;
  font-size: 12px;
  font-weight: 900;
  letter-spacing: .2px;
  padding: 6px 10px;
  border-radius: 999px;
  background: rgba(0,0,0,.045);
  border: var(--vtk-border);
}
.vtk-title{
  margin: 10px 0 8px;
  font-size: 30px;
  line-height: 1.12;
  letter-spacing: -.3px;
  color: var(--vtk-text);
}
@media (max-width: 520px){ .vtk-title{ font-size: 24px; } }
.vtk-desc{
  margin: 0 0 14px;
  color: var(--vtk-muted);
  font-size: 14px;
  line-height: 1.55;
  max-width: 62ch;
}
.vtk-ctas{ display:flex; gap:10px; flex-wrap:wrap; }

.vtk-btn{
  display:inline-flex;
  align-items:center;
  justify-content:center;
  gap:8px;
  border-radius: 999px;
  padding: 11px 14px;
  border: 1px solid rgba(0,0,0,.12);
  background:#fff;
  color:#111;
  text-decoration:none;
  font-weight: 900;
  font-size: 13px;
}
.vtk-btn:hover{ filter: brightness(.98); }
.vtk-btn--primary{
  background: var(--vtk-red);
  border-color: rgba(225,6,0,.25);
  color:#fff;
}
.vtk-btn--ghost{
  background: rgba(0,0,0,.04);
  border-color: rgba(0,0,0,.08);
}
.vtk-pills{ display:flex; gap:8px; flex-wrap:wrap; margin-top: 14px; }
.vtk-pill{
  background: rgba(0,0,0,.045);
  border: var(--vtk-border);
  border-radius: 999px;
  padding: 7px 10px;
  font-size: 12px;
  font-weight: 800;
  color: rgba(0,0,0,.76);
}

/* HERO SIDE (two stacked tiles) */
.vtk-heroSide{
  display:grid;
  grid-template-rows: auto 1fr;
  gap: 14px;
}
.vtk-heroMedia{
  border-radius: var(--vtk-radius);
  overflow:hidden;
  position:relative;
  min-height: 220px;
  border: var(--vtk-border);
  box-shadow: var(--vtk-shadow);
  background: #f7f7f7;
}
.vtk-heroMedia img{
  width:100%;
  height:100%;
  object-fit: cover;
  display:block;
}
.vtk-heroMedia:after{
  content:"";
  position:absolute; inset:0;
  background: linear-gradient(0deg, rgba(0,0,0,.20), rgba(0,0,0,0) 60%);
  pointer-events:none;
}

.vtk-quick{
  padding: 16px;
}
.vtk-quickTitle{
  font-weight: 950;
  font-size: 14px;
  margin: 0 0 10px;
}
.vtk-check{
  display:grid;
  gap: 8px;
  margin: 0;
  padding: 0;
  list-style: none;
}
.vtk-check li{
  display:flex;
  gap:10px;
  align-items:flex-start;
  padding: 10px 12px;
  border-radius: var(--vtk-radius-sm);
  background: rgba(0,0,0,.035);
  border: var(--vtk-border);
  font-size: 13px;
  color: rgba(0,0,0,.78);
}
.vtk-check li b{ color:#111; }
.vtk-check .dot{
  width: 10px; height: 10px; border-radius: 999px;
  background: rgba(225,6,0,.35);
  flex: 0 0 auto;
  margin-top: 4px;
}
.vtk-quickCtas{ display:grid; gap:10px; margin-top: 12px; }

/* TOPICS */
.vtk-topics{ padding: 6px 0 16px; }
.vtk-topicGrid{
  display:grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 12px;
}
@media (max-width: 980px){ .vtk-topicGrid{ grid-template-columns: repeat(2, 1fr); } }
@media (max-width: 520px){ .vtk-topicGrid{ grid-template-columns: 1fr; } }

.vtk-topic{
  text-decoration:none;
  color: inherit;
  padding: 14px;
  border-radius: var(--vtk-radius);
  border: var(--vtk-border);
  background: #fff;
  box-shadow: 0 8px 18px rgba(15,23,42,.05);
  display:flex;
  gap: 12px;
  align-items:flex-start;
}
.vtk-topic:hover{ transform: translateY(-1px); }
.vtk-ico{
  width: 40px; height: 40px;
  border-radius: 14px;
  display:flex; align-items:center; justify-content:center;
  background: rgba(225,6,0,.10);
  border: 1px solid rgba(225,6,0,.18);
  font-size: 18px;
  flex: 0 0 auto;
}
.vtk-topic:nth-child(2) .vtk-ico{ background: rgba(20,175,232,.10); border-color: rgba(20,175,232,.18); }
.vtk-topic:nth-child(3) .vtk-ico{ background: rgba(0,0,0,.06); border-color: rgba(0,0,0,.10); }
.vtk-topic:nth-child(4) .vtk-ico{ background: var(--vtk-soft); border-color: rgba(0,0,0,.10); }

.vtk-topicT{ font-weight: 950; margin: 0 0 4px; font-size: 13px; }
.vtk-topicD{ margin:0; color: var(--vtk-muted2); font-size: 12.5px; line-height: 1.45; }

/* LAYOUT */
.vtk-section{ padding: 10px 0 18px; }
.vtk-layout{
  display:grid;
  grid-template-columns: 1fr 360px;
  gap: 14px;
  align-items:start;
}
@media (max-width: 1040px){ .vtk-layout{ grid-template-columns: 1fr; } }

.vtk-main .vtk-card{ padding: 16px; }
.vtk-side{ position: sticky; top: 14px; }
@media (max-width: 1040px){ .vtk-side{ position: static; } }
.vtk-side .vtk-card{ padding: 16px; }

.vtk-sideTitle{ font-weight: 950; font-size: 14px; margin: 0 0 10px; }
.vtk-sideDesc{ margin:0 0 10px; font-size: 12.5px; color: var(--vtk-muted2); }
.vtk-sideBtns{ display:grid; gap:10px; }

/* Content prose */
.vtk-prose :where(h2){ margin: 18px 0 10px; font-size: 18px; }
.vtk-prose :where(h3){ margin: 14px 0 8px; font-size: 15px; }
.vtk-prose :where(p, li){ color: rgba(0,0,0,.78); line-height: 1.7; }
.vtk-prose :where(hr){ border:0; border-top: 1px dashed rgba(0,0,0,.16); margin: 16px 0; }
.vtk-prose :where(a){ color: var(--vtk-red); text-decoration: none; font-weight: 800; }
.vtk-prose :where(a:hover){ text-decoration: underline; }

/* POSTS */
.vtk-headRow{
  display:flex; justify-content:space-between; align-items:flex-end;
  gap: 12px; flex-wrap:wrap;
  margin-bottom: 12px;
}
.vtk-h2{ margin:0; font-size: 18px; font-weight: 950; letter-spacing: -.2px; }
.vtk-sub{ margin:4px 0 0; color: var(--vtk-muted2); font-size: 12.5px; }

.vtk-feature{
  display:grid;
  grid-template-columns: 1fr 1.15fr;
  gap: 12px;
  overflow:hidden;
}
@media (max-width: 820px){ .vtk-feature{ grid-template-columns: 1fr; } }

.vtk-featureMedia{
  position:relative;
  min-height: 220px;
  border-radius: var(--vtk-radius);
  overflow:hidden;
  background:#f4f4f4;
  border: var(--vtk-border);
}
.vtk-featureMedia img{ width:100%; height:100%; object-fit:cover; display:block; }
.vtk-featureBody{ padding: 14px; }
.vtk-featureK{ font-size: 12px; font-weight: 950; color: rgba(0,0,0,.62); }
.vtk-featureT{ margin: 8px 0 8px; font-size: 18px; line-height: 1.25; }
.vtk-featureT a{ color:#111; text-decoration:none; }
.vtk-featureE{ margin: 0 0 10px; color: var(--vtk-muted); line-height: 1.55; }
.vtk-featureCTA{ display:flex; gap:10px; flex-wrap:wrap; }

.vtk-postGrid{
  display:grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 12px;
}
@media (max-width: 980px){ .vtk-postGrid{ grid-template-columns: repeat(2, 1fr); } }
@media (max-width: 520px){ .vtk-postGrid{ grid-template-columns: 1fr; } }

.vtk-post{
  overflow:hidden;
  display:flex;
  flex-direction:column;
}
.vtk-postThumb{
  width:100%;
  aspect-ratio: 16 / 9;
  background:#f4f4f4;
  overflow:hidden;
  border-radius: var(--vtk-radius);
  border: var(--vtk-border);
}
.vtk-postThumb img{ width:100%; height:100%; object-fit:cover; display:block; }
.vtk-postBody{ padding: 12px 4px 2px; }
.vtk-postT{ margin:0 0 6px; font-size: 14px; line-height: 1.35; font-weight: 950; }
.vtk-postT a{ text-decoration:none; color:#111; }
.vtk-postE{
  margin:0;
  color: var(--vtk-muted);
  font-size: 12.5px;
  line-height: 1.55;
  display:-webkit-box;
  -webkit-line-clamp: 3;
  -webkit-box-orient: vertical;
  overflow:hidden;
}

/* RELATED (sidebar) */
.vtk-relatedList{ display:grid; gap: 10px; }
.vtk-relatedItem{
  display:grid;
  grid-template-columns: 56px 1fr;
  gap: 10px;
  align-items:center;
  text-decoration:none;
  color: inherit;
  padding: 10px;
  border-radius: var(--vtk-radius-sm);
  background: rgba(0,0,0,.035);
  border: var(--vtk-border);
}
.vtk-relatedItem:hover{ background: rgba(0,0,0,.05); }
.vtk-relatedThumb{
  width: 56px; height: 56px;
  border-radius: 14px;
  overflow:hidden;
  background:#eee;
  border: 1px solid rgba(0,0,0,.08);
}
.vtk-relatedThumb img{ width:100%; height:100%; object-fit:cover; display:block; }
.vtk-relatedT{
  margin:0;
  font-weight: 900;
  font-size: 12.5px;
  line-height: 1.35;
  color:#111;
}
.vtk-relatedE{
  margin: 3px 0 0;
  font-size: 12px;
  color: var(--vtk-muted2);
  line-height: 1.4;
  display:-webkit-box;
  -webkit-line-clamp: 2;
  -webkit-box-orient: vertical;
  overflow:hidden;
}

/* HUB */
.vtk-hubGrid{
  display:grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 12px;
}
@media (max-width: 980px){ .vtk-hubGrid{ grid-template-columns: repeat(2, 1fr); } }
@media (max-width: 520px){ .vtk-hubGrid{ grid-template-columns: 1fr; } }
.vtk-hubCard{ padding: 16px; }
.vtk-hubTop{ display:flex; gap: 12px; align-items:flex-start; margin-bottom: 10px; }
.vtk-hubTop .vtk-ico{ width: 44px; height:44px; border-radius: 16px; font-size: 18px; }
.vtk-hubT{ font-weight: 950; margin: 0 0 4px; font-size: 14px; }
.vtk-hubD{ margin:0; color: var(--vtk-muted2); font-size: 12.5px; line-height: 1.45; }
.vtk-miniList{ display:grid; gap: 8px; margin-top: 10px; }
.vtk-mini{
  display:flex; gap:10px; align-items:center;
  text-decoration:none; color: inherit;
  padding: 9px 10px;
  border-radius: var(--vtk-radius-sm);
  background: rgba(0,0,0,.035);
  border: var(--vtk-border);
}
.vtk-mini:hover{ background: rgba(0,0,0,.05); }
.vtk-mini .t{
  font-weight: 900;
  font-size: 12.5px;
  line-height: 1.35;
  display:-webkit-box;
  -webkit-line-clamp: 2;
  -webkit-box-orient: vertical;
  overflow:hidden;
}
.vtk-mini .chev{ margin-left:auto; opacity:.55; font-weight:900; }


/* ===== Knowledge: compact grids (desktop) ===== */
@media (min-width: 1200px){
  .vtk-postGrid{ grid-template-columns: repeat(4, 1fr); gap: 12px; }
}
.vtk-post{ padding: 12px; }
.vtk-post__thumb{ border-radius: 14px; overflow:hidden; aspect-ratio: 16 / 10; }
.vtk-post__body{ padding: 10px 4px 4px; }
.vtk-post__t{ font-size: 14px; line-height: 1.35; margin: 0 0 6px; }
.vtk-post__e{ font-size: 12px; line-height: 1.45; opacity: .78; margin: 0; display: -webkit-box; -webkit-line-clamp: 3; -webkit-box-orient: vertical; overflow:hidden; }

/* Quick topic cards for /kien-thuc */
.vtk-quickGrid{
  display:grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 12px;
}
@media (max-width: 980px){
  .vtk-quickGrid{ grid-template-columns: 1fr; }
}
.vtk-quickCard{
  display:flex;
  gap: 12px;
  align-items:flex-start;
  padding: 14px;
  border: 1px solid rgba(0,0,0,.08);
  border-radius: 16px;
  background: #fff;
  box-shadow: 0 10px 24px rgba(0,0,0,.05);
  text-decoration:none;
  color: inherit;
}
.vtk-quickCard:hover{ transform: translateY(-2px); box-shadow: 0 14px 30px rgba(0,0,0,.08); }
.vtk-quickIco{ width: 36px; height: 36px; display:flex; align-items:center; justify-content:center; border-radius: 12px; background: rgba(225,6,0,.08); font-size: 18px; }
.vtk-quickT{ font-weight: 900; }
.vtk-quickD{ font-size: 12px; opacity: .78; margin-top: 2px; }