:root{
  --bg:#07111f;
  --panel:#0d1b2a;
  --panel-2:#10253d;
  --text:#eaf4ff;
  --muted:#9eb6cf;
  --accent:#4fc3f7;
  --accent-2:#8fdcff;
  --gold:#f4c542;
  --border:rgba(143,220,255,0.18);
  --white:#ffffff;
  --shadow:0 12px 36px rgba(0,0,0,0.28);
  --glow:0 0 0 1px rgba(79,195,247,0.08), 0 20px 50px rgba(0,0,0,0.22);
  --radius:18px;
  --max:1200px;
}

*{box-sizing:border-box}
html{scroll-behavior:smooth}
body{
  margin:0;
  font-family: "Outfit", Arial, sans-serif;
  background:
    radial-gradient(circle at top left, rgba(79,195,247,0.08), transparent 28%),
    linear-gradient(180deg, #06101d 0%, #081423 100%);
  color:var(--text);
  line-height:1.7;
}

a{color:var(--accent); text-decoration:none}
a:hover{text-decoration:underline}

img{max-width:100%; height:auto; display:block}

.authority-banner{
  background:linear-gradient(90deg,#0b2740,#133b60);
  color:#dff4ff;
  text-align:center;
  padding:0.65rem 1rem;
  font-size:0.95rem;
  border-bottom:1px solid rgba(255,255,255,0.08);
}

.vb-upgrade-banner{
  background:linear-gradient(90deg,#fff2b8,#ffd95b);
  color:#332500;
  text-align:center;
  padding:0.85rem 1rem;
  font-size:0.98rem;
  font-weight:600;
}
.vb-upgrade-banner a{
  color:#0b57d0;
  font-weight:800;
}

nav{
  position:sticky;
  top:0;
  z-index:1000;
  background:rgba(7,17,31,0.92);
  backdrop-filter:blur(10px);
  border-bottom:1px solid rgba(255,255,255,0.08);
}

.nav-inner{
  max-width:var(--max);
  margin:0 auto;
  display:flex;
  align-items:center;
  justify-content:space-between;
  gap:1rem;
  padding:0.9rem 1rem;
}

.nav-brand{
  color:#fff;
  font-weight:800;
  font-size:1.25rem;
  letter-spacing:0.4px;
}

.nav-links{
  display:flex;
  gap:1rem;
  align-items:center;
  flex-wrap:wrap;
}

.nav-links a{
  color:#dcecff;
  font-size:0.96rem;
}

.nav-cta{
  display:inline-flex;
  align-items:center;
  gap:0.5rem;
  padding:0.7rem 1rem;
  border-radius:999px;
  background:linear-gradient(135deg,#1f8fff,#0a66c2);
  color:#fff;
  font-weight:700;
  box-shadow:var(--shadow);
}
.nav-cta:hover{text-decoration:none; opacity:.92}

.sidebar-toggle{
  display:none;
  border:1px solid var(--border);
  background:rgba(255,255,255,0.04);
  color:#fff;
  padding:0.55rem 0.8rem;
  border-radius:12px;
  cursor:pointer;
  font-size:1rem;
}

.page-layout{
  max-width:var(--max);
  margin:0 auto;
  display:grid;
  grid-template-columns:300px minmax(0,1fr);
  gap:1.5rem;
  padding:1.5rem 1rem 2rem;
}

.sidebar{
  position:sticky;
  top:90px;
  align-self:start;
  max-height:calc(100vh - 110px);
  overflow:auto;
  background:linear-gradient(180deg, rgba(16,37,61,0.98), rgba(9,21,36,0.98));
  border:1px solid var(--border);
  border-radius:20px;
  padding:1.2rem;
  box-shadow:var(--glow);
}

.sidebar h5{
  margin:1rem 0 0.7rem;
  color:#fff;
  font-size:0.95rem;
  text-transform:uppercase;
  letter-spacing:0.08em;
}

.sidebar a{
  display:block;
  color:#d3e6fa;
  padding:0.58rem 0.75rem;
  border-radius:10px;
  margin-bottom:0.2rem;
  line-height:1.35;
}

.sidebar a:hover,
.sidebar a.active{
  background:rgba(79,195,247,0.12);
  color:#fff;
  text-decoration:none;
}

.sidebar-close{
  display:none;
}

.sidebar-overlay{
  display:none;
}

.main-content{
  min-width:0;
}

.hero{
  display:grid;
  grid-template-columns:minmax(0,1.4fr) minmax(280px,0.8fr);
  gap:1.4rem;
  align-items:stretch;
}

.hero > div{
  background:linear-gradient(180deg, rgba(18,36,58,0.96), rgba(11,24,39,0.96));
  border:1px solid var(--border);
  border-radius:24px;
  padding:1.7rem;
  box-shadow:var(--glow);
}

.hero-badge{
  display:inline-block;
  background:rgba(79,195,247,0.12);
  color:var(--accent-2);
  padding:0.45rem 0.8rem;
  border-radius:999px;
  font-size:0.86rem;
  font-weight:700;
  margin-bottom:1rem;
}

.hero h1{
  margin:0 0 0.8rem;
  font-size:clamp(2rem,4vw,3.2rem);
  line-height:1.1;
  color:#fff;
}

.hero h1 span{
  color:var(--accent);
}

.hero-sub{
  font-size:1.06rem;
  color:var(--muted);
  max-width:760px;
}

.hero-buttons{
  display:flex;
  gap:0.9rem;
  flex-wrap:wrap;
  margin-top:1.2rem;
}

.btn{
  display:inline-flex;
  align-items:center;
  justify-content:center;
  gap:0.45rem;
  padding:0.9rem 1.2rem;
  border-radius:14px;
  font-weight:700;
  text-decoration:none;
  transition:0.2s ease;
}

.btn:hover{
  text-decoration:none;
  transform:translateY(-1px);
}

.btn-primary{
  background:linear-gradient(135deg,#1e90ff,#0078d4);
  color:#fff;
}

.btn-outline{
  border:1px solid var(--border);
  color:#fff;
  background:rgba(255,255,255,0.03);
}

.version-card h3{
  margin-top:0;
  color:#fff;
}

.version-item{
  display:flex;
  justify-content:space-between;
  gap:1rem;
  padding:0.7rem 0;
  border-bottom:1px solid rgba(255,255,255,0.08);
}

.version-item:last-child{
  border-bottom:none;
}

.version-item .label{
  color:var(--muted);
}

.version-item .value{
  color:#fff;
  font-weight:600;
  text-align:right;
}

.stats-row{
  display:grid;
  grid-template-columns:repeat(4,1fr);
  gap:1rem;
  margin:1.5rem 0;
}

.stat{
  background:rgba(255,255,255,0.03);
  border:1px solid var(--border);
  border-radius:18px;
  padding:1rem;
  text-align:center;
  box-shadow:var(--glow);
}

.stat-num{
  display:block;
  font-size:1.35rem;
  font-weight:800;
  color:var(--accent);
}

.stat-label{
  display:block;
  color:var(--muted);
  font-size:0.92rem;
  margin-top:0.25rem;
}

section{
  margin:2rem 0;
}

.section-label{
  color:var(--accent-2);
  text-transform:uppercase;
  letter-spacing:0.1em;
  font-size:0.8rem;
  font-weight:700;
  margin-bottom:0.4rem;
}

section h2{
  margin:0 0 0.7rem;
  font-size:clamp(1.5rem,2vw,2.1rem);
  color:#fff;
}

.section-intro{
  color:var(--muted);
  max-width:850px;
}

.content-card,
.course-path,
.lesson-summary-box,
.lesson-note-box,
.exercise-box,
.figure-box,
.compare-box,
.book-feature-box,
.cta-banner{
  background:rgba(255,255,255,0.03);
  border:1px solid var(--border);
  border-radius:20px;
  padding:1.4rem;
  box-shadow:var(--glow);
}

.lesson-note-box{
  background:rgba(244,197,66,0.08);
  border-left:4px solid var(--gold);
}

.split-grid{
  display:grid;
  grid-template-columns:repeat(2,minmax(0,1fr));
  gap:1.2rem;
}

.quick-points,
.mini-points{
  padding-left:1.2rem;
  color:var(--muted);
}

.quick-points li,
.mini-points li{
  margin-bottom:0.55rem;
}

.figure-box{
  text-align:center;
}

.figure-box p{
  color:var(--muted);
  margin-bottom:0;
}

.books-grid,
.resources-grid,
.topic-grid,
.course-steps{
  display:grid;
  grid-template-columns:repeat(auto-fit,minmax(240px,1fr));
  gap:1rem;
}

.book-card,
.resource-card,
.topic-card,
.course-step{
  background:rgba(255,255,255,0.03);
  border:1px solid var(--border);
  border-radius:18px;
  overflow:hidden;
  box-shadow:var(--glow);
}

.book-card img{
  width:100%;
  aspect-ratio:3/4;
  object-fit:cover;
}

.book-info{
  padding:1rem;
}

.book-info h4,
.resource-card h4,
.topic-card h4,
.course-step h4{
  margin:0 0 0.5rem;
  color:#fff;
}

.book-info p,
.resource-card p,
.topic-card p,
.course-step p{
  color:var(--muted);
  margin:0.35rem 0;
}

.resource-card,
.topic-card,
.course-step{
  padding:1rem;
}

.book-links a{
  font-weight:700;
}

.divider{
  border:none;
  border-top:1px solid rgba(255,255,255,0.08);
  margin:2rem 0;
}

footer{
  max-width:var(--max);
  margin:2rem auto 0;
  padding:0 1rem 2rem;
  color:var(--muted);
}

.footer-links,
.footer-version-links,
.footer-other-links{
  display:flex;
  flex-wrap:wrap;
  gap:1rem;
  margin:0.5rem 0 1rem;
}

.copyright{
  margin-top:1rem;
  font-size:0.92rem;
}

.floating-vbnet-cta{
  position:fixed;
  right:18px;
  bottom:18px;
  z-index:998;
  background:linear-gradient(135deg,#00a2ff,#0a66c2);
  color:#fff;
  font-weight:700;
  padding:0.85rem 1rem;
  border-radius:999px;
  box-shadow:var(--shadow);
}
.floating-vbnet-cta:hover{text-decoration:none}

.mini-book{
  margin-top:1rem;
  padding:0.9rem;
  border:1px solid var(--border);
  border-radius:16px;
  background:rgba(255,255,255,0.03);
}
.mini-book h6{
  color:#fff;
  font-size:0.92rem;
  margin:0 0 0.7rem;
}

@media (max-width: 1024px){
  .page-layout{
    grid-template-columns:1fr;
  }
  .sidebar{
    position:fixed;
    top:0;
    left:0;
    width:min(320px,86vw);
    max-height:100vh;
    height:100vh;
    border-radius:0 18px 18px 0;
    transform:translateX(-100%);
    transition:transform 0.25s ease;
    z-index:1002;
  }
  .sidebar.open{
    transform:translateX(0);
  }
  .sidebar-close{
    display:inline-flex;
    align-items:center;
    justify-content:center;
    width:36px;
    height:36px;
    border-radius:10px;
    border:1px solid var(--border);
    background:rgba(255,255,255,0.04);
    color:#fff;
    cursor:pointer;
    margin-bottom:0.8rem;
  }
  .sidebar-overlay{
    position:fixed;
    inset:0;
    background:rgba(0,0,0,0.55);
    z-index:1001;
  }
  .sidebar-overlay.active{
    display:block;
  }
  .sidebar-toggle{
    display:inline-flex;
  }
  .hero{
    grid-template-columns:1fr;
  }
  .stats-row{
    grid-template-columns:repeat(2,1fr);
  }
  .split-grid{
    grid-template-columns:1fr;
  }
  .nav-links,
  .nav-cta{
    display:none;
  }
}

@media (max-width: 640px){
  .stats-row{
    grid-template-columns:1fr;
  }
  .hero > div,
  .content-card,
  .course-path,
  .lesson-summary-box,
  .lesson-note-box,
  .exercise-box,
  .figure-box,
  .compare-box,
  .book-feature-box,
  .cta-banner{
    padding:1.1rem;
  }
  .floating-vbnet-cta{
    right:12px;
    bottom:12px;
    padding:0.75rem 0.95rem;
    font-size:0.92rem;
  }
}