@import url('https://fonts.googleapis.com/css2?family=Inter:wght@300;400;500;600;700;800&family=Fira+Code:wght@400;500&display=swap');

:root {
  --primary: #6366f1;
  --primary-dark: #4f46e5;
  --secondary: #a855f7;
  --accent: #ec4899;
  --code-bg: #0f172a;
  --text: #1e293b;
  --text-muted: #64748b;
  --border: rgba(99,102,241,0.15);
  --glass: rgba(255,255,255,0.75);
  --glass-border: rgba(255,255,255,0.5);
  --radius: 16px;
}

body {
  font-family: 'Inter', system-ui, sans-serif;
  color: var(--text);
  background: #f1f5f9;
  line-height: 1.8;
  letter-spacing: -0.01em;
}

/* Hero */
.sd-hero {
  background: linear-gradient(135deg, #4f46e5 0%, #7c3aed 50%, #db2777 100%);
  background-size: 200% 200%;
  animation: hero-shift 8s ease infinite alternate;
  padding: 5rem 1.5rem 7rem;
  text-align: center;
  position: relative;
  overflow: hidden;
}
.sd-hero::before {
  content: '';
  position: absolute;
  inset: 0;
  background: url("data:image/svg+xml,%3Csvg width='60' height='60' viewBox='0 0 60 60' xmlns='http://www.w3.org/2000/svg'%3E%3Cg fill='none' fill-rule='evenodd'%3E%3Cg fill='%23ffffff' fill-opacity='0.03'%3E%3Cpath d='M36 34v-4h-2v4h-4v2h4v4h2v-4h4v-2h-4zm0-30V0h-2v4h-4v2h4v4h2V6h4V4h-4zM6 34v-4H4v4H0v2h4v4h2v-4h4v-2H6zM6 4V0H4v4H0v2h4v4h2V6h4V4H6z'/%3E%3C/g%3E%3C/g%3E%3C/svg%3E");
}
@keyframes hero-shift {
  0% { background-position: 0% 50%; }
  100% { background-position: 100% 50%; }
}
.sd-hero h1 {
  font-size: clamp(2rem, 5vw, 3.5rem);
  font-weight: 800;
  color: #fff;
  letter-spacing: -0.03em;
  margin-bottom: 1rem;
  text-shadow: 0 2px 20px rgba(0,0,0,0.2);
  animation: fade-up 0.7s ease both;
}
.sd-hero .lead {
  color: rgba(255,255,255,0.85);
  font-size: 1.15rem;
  font-weight: 300;
  max-width: 680px;
  margin: 0 auto 2rem;
  animation: fade-up 0.7s 0.1s ease both;
}
.sd-hero-badges {
  display: flex;
  gap: 0.5rem;
  justify-content: center;
  flex-wrap: wrap;
  animation: fade-up 0.7s 0.2s ease both;
}
.sd-badge {
  background: rgba(255,255,255,0.15);
  backdrop-filter: blur(10px);
  border: 1px solid rgba(255,255,255,0.25);
  color: #fff;
  padding: 0.35rem 1rem;
  border-radius: 100px;
  font-size: 0.8rem;
  font-weight: 500;
  letter-spacing: 0.02em;
}
@keyframes fade-up {
  from { opacity: 0; transform: translateY(20px); }
  to   { opacity: 1; transform: translateY(0); }
}

/* Layout */
.sd-layout {
  max-width: 1200px;
  margin: -3rem auto 0;
  padding: 0 1.5rem 4rem;
  display: grid;
  grid-template-columns: 240px 1fr;
  gap: 2rem;
  align-items: start;
}

/* TOC */
.sd-toc {
  background: var(--glass);
  backdrop-filter: blur(20px);
  -webkit-backdrop-filter: blur(20px);
  border: 1px solid var(--glass-border);
  border-radius: var(--radius);
  padding: 1.5rem;
  position: sticky;
  top: 1.5rem;
  box-shadow: 0 4px 24px rgba(0,0,0,0.06);
}
.sd-toc h5 {
  font-size: 0.7rem;
  font-weight: 700;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  color: var(--text-muted);
  margin-bottom: 1rem;
}
.sd-toc ol {
  list-style: none;
  padding: 0;
  margin: 0;
  counter-reset: toc-counter;
}
.sd-toc li {
  counter-increment: toc-counter;
  margin-bottom: 0.1rem;
}
.sd-toc a {
  display: flex;
  align-items: center;
  gap: 0.6rem;
  color: var(--text-muted);
  text-decoration: none;
  font-size: 0.82rem;
  padding: 0.4rem 0.6rem;
  border-radius: 8px;
  transition: all 0.2s;
}
.sd-toc a::before {
  content: counter(toc-counter);
  background: var(--border);
  color: var(--primary);
  font-weight: 700;
  font-size: 0.7rem;
  width: 20px;
  height: 20px;
  border-radius: 6px;
  display: flex;
  align-items: center;
  justify-content: center;
  flex-shrink: 0;
}
.sd-toc a:hover { background: rgba(99,102,241,0.08); color: var(--primary); }
.sd-toc a.active { background: rgba(99,102,241,0.1); color: var(--primary); font-weight: 600; }

/* Main content card */
.sd-content {
  background: var(--glass);
  backdrop-filter: blur(20px);
  -webkit-backdrop-filter: blur(20px);
  border: 1px solid var(--glass-border);
  border-radius: var(--radius);
  padding: 3rem 3.5rem;
  box-shadow: 0 4px 40px rgba(0,0,0,0.06);
  font-size: 1.05rem;
}

/* Typography */
.sd-content h2 {
  font-size: 1.6rem;
  font-weight: 700;
  color: #0f172a;
  margin-top: 3rem;
  margin-bottom: 1rem;
  padding-top: 1.5rem;
  border-top: 1px solid var(--border);
  letter-spacing: -0.02em;
}
.sd-content h2:first-of-type { margin-top: 0; padding-top: 0; border-top: none; }
.sd-content h3 {
  font-size: 1.2rem;
  font-weight: 600;
  color: var(--primary-dark);
  margin-top: 2rem;
  margin-bottom: 0.75rem;
}
.sd-content h4 {
  font-size: 1rem;
  font-weight: 600;
  color: #334155;
  margin-top: 1.5rem;
  margin-bottom: 0.5rem;
}
.sd-content p { margin-bottom: 1.1rem; }

/* Inline code */
.sd-content code {
  font-family: 'Fira Code', monospace;
  font-size: 0.88em;
  background: rgba(99,102,241,0.08);
  color: var(--primary-dark);
  padding: 0.15em 0.45em;
  border-radius: 6px;
  border: 1px solid rgba(99,102,241,0.12);
}

/* Pre / Code blocks */
.sd-content pre {
  background: var(--code-bg);
  border-radius: 14px;
  padding: 0 0 1.25rem;
  margin: 1.5rem 0;
  overflow: hidden;
  box-shadow: 0 8px 30px rgba(0,0,0,0.2);
  border: 1px solid rgba(255,255,255,0.05);
}
.sd-content pre::before {
  content: '● ● ●';
  display: block;
  background: rgba(255,255,255,0.05);
  padding: 0.6rem 1rem;
  margin-bottom: 1rem;
  font-size: 0.7rem;
  color: rgba(255,255,255,0.3);
  letter-spacing: 0.4em;
  border-bottom: 1px solid rgba(255,255,255,0.05);
}
.sd-content pre code {
  background: none;
  border: none;
  color: #a5b4fc;
  font-size: 0.9rem;
  padding: 0 1.5rem;
  line-height: 1.7;
  display: block;
}

/* Tables */
.sd-content .table-responsive { border-radius: 14px; overflow: hidden; margin: 1.5rem 0; box-shadow: 0 4px 20px rgba(0,0,0,0.06); }
.sd-content table { width: 100%; border-collapse: collapse; margin: 0; font-size: 0.95rem; }
.sd-content thead { background: linear-gradient(135deg, var(--primary), var(--secondary)); color: #fff; }
.sd-content th { padding: 0.9rem 1.25rem; font-weight: 600; font-size: 0.85rem; letter-spacing: 0.03em; text-transform: uppercase; }
.sd-content td { padding: 0.85rem 1.25rem; border-bottom: 1px solid rgba(0,0,0,0.05); background: #fff; }
.sd-content tr:last-child td { border-bottom: none; }
.sd-content tbody tr:hover td { background: rgba(99,102,241,0.04); }
.sd-content .tableCaption { text-align: center; font-size: 0.82rem; color: var(--text-muted); margin-top: -1rem; margin-bottom: 1.5rem; font-style: italic; }

/* Figures */
.sd-content figure { margin: 2rem 0; text-align: center; }
.sd-content figure img {
  max-width: 100%;
  border-radius: 12px;
  box-shadow: 0 8px 30px rgba(0,0,0,0.1);
  transition: transform 0.3s, box-shadow 0.3s;
  border: 1px solid rgba(0,0,0,0.06);
}
.sd-content figure img:hover { transform: translateY(-4px); box-shadow: 0 16px 40px rgba(0,0,0,0.15); }
.sd-content figcaption { font-size: 0.82rem; color: var(--text-muted); margin-top: 0.6rem; font-style: italic; }

/* Lists */
.sd-content ul, .sd-content ol { padding-left: 1.5rem; margin-bottom: 1rem; }
.sd-content li { margin-bottom: 0.4rem; }
.sd-content li > p { margin-bottom: 0.4rem; }

/* Callout / Interview Q&A */
.sd-qa {
  background: linear-gradient(135deg, rgba(99,102,241,0.06), rgba(168,85,247,0.06));
  border-left: 3px solid var(--primary);
  border-radius: 0 12px 12px 0;
  padding: 1.25rem 1.5rem;
  margin: 1.25rem 0;
}
.sd-qa strong { color: var(--primary-dark); }

/* Back to top */
#btn-back-to-top {
  position: fixed;
  bottom: 2rem;
  right: 2rem;
  width: 48px;
  height: 48px;
  border-radius: 50%;
  background: linear-gradient(135deg, var(--primary), var(--secondary));
  color: #fff;
  border: none;
  cursor: pointer;
  display: none;
  align-items: center;
  justify-content: center;
  box-shadow: 0 4px 20px rgba(99,102,241,0.4);
  transition: transform 0.2s, box-shadow 0.2s;
  z-index: 999;
}
#btn-back-to-top:hover { transform: translateY(-3px); box-shadow: 0 8px 30px rgba(99,102,241,0.5); }

/* Responsive */
@media (max-width: 900px) {
  .sd-layout { grid-template-columns: 1fr; margin-top: -2rem; }
  .sd-toc { position: static; }
  .sd-content { padding: 2rem 1.5rem; }
  .sd-hero { padding: 4rem 1.5rem 5rem; }
}