:root {
  --bg: #0b0f1a;
  --bg-alt: #121829;
  --bg-card: #16203a;
  --border: #24304f;
  --text: #e7ecf5;
  --text-dim: #9aa7c2;
  --accent: #4f9cff;
  --accent-2: #7df0c5;
  --warn: #ffb547;
  --mono: ui-monospace, SFMono-Regular, Menlo, Monaco, Consolas, "Liberation Mono", "Courier New", monospace;
  --sans: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
}

* { box-sizing: border-box; }
html, body { margin: 0; padding: 0; }
body {
  font-family: var(--sans);
  background: var(--bg);
  color: var(--text);
  line-height: 1.65;
  font-size: 16.5px;
  -webkit-font-smoothing: antialiased;
}

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

.container {
  max-width: 960px;
  margin: 0 auto;
  padding: 0 24px;
}

header.site {
  background: linear-gradient(180deg, #0b0f1a 0%, #0d1326 100%);
  border-bottom: 1px solid var(--border);
  padding: 18px 0;
  position: sticky;
  top: 0;
  z-index: 100;
  backdrop-filter: blur(8px);
  background-color: rgba(11, 15, 26, 0.85);
}

header.site .nav {
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: 24px;
  flex-wrap: wrap;
}

.brand {
  display: flex;
  align-items: center;
  gap: 10px;
  font-weight: 700;
  font-size: 17px;
  color: var(--text);
}
.brand .dot {
  width: 11px; height: 11px; border-radius: 50%;
  background: linear-gradient(135deg, var(--accent), var(--accent-2));
  box-shadow: 0 0 12px rgba(79, 156, 255, 0.7);
}

nav.primary a {
  color: var(--text-dim);
  margin-left: 18px;
  font-size: 14.5px;
  font-weight: 500;
}
nav.primary a:hover { color: var(--text); text-decoration: none; }

.hero {
  padding: 72px 0 48px;
  background:
    radial-gradient(ellipse at 30% 0%, rgba(79, 156, 255, 0.18), transparent 60%),
    radial-gradient(ellipse at 80% 20%, rgba(125, 240, 197, 0.12), transparent 60%);
}
.hero h1 {
  font-size: 42px;
  line-height: 1.15;
  margin: 0 0 16px;
  letter-spacing: -0.02em;
}
.hero .subtitle {
  font-size: 19px;
  color: var(--text-dim);
  max-width: 720px;
  margin: 0 0 28px;
}
.hero .tagline {
  display: inline-block;
  padding: 6px 12px;
  border: 1px solid var(--border);
  border-radius: 999px;
  font-size: 13px;
  color: var(--accent-2);
  background: rgba(125, 240, 197, 0.08);
  margin-bottom: 20px;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.08em;
}

section { padding: 42px 0; }
section.alt { background: var(--bg-alt); border-top: 1px solid var(--border); border-bottom: 1px solid var(--border); }

h2 {
  font-size: 28px;
  margin: 0 0 20px;
  letter-spacing: -0.01em;
}
h3 {
  font-size: 21px;
  margin: 28px 0 12px;
  color: var(--text);
}
h4 {
  font-size: 17px;
  margin: 22px 0 10px;
  color: var(--accent-2);
  text-transform: uppercase;
  letter-spacing: 0.05em;
}

p { margin: 0 0 14px; color: var(--text); }
ul, ol { margin: 0 0 16px; padding-left: 22px; }
li { margin-bottom: 6px; }

.modules {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(270px, 1fr));
  gap: 18px;
  margin-top: 24px;
}
.module-card {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: 12px;
  padding: 22px;
  transition: border-color 0.2s, transform 0.2s;
  display: block;
  color: var(--text);
}
.module-card:hover {
  border-color: var(--accent);
  transform: translateY(-2px);
  text-decoration: none;
}
.module-card .num {
  font-size: 12px;
  color: var(--accent-2);
  font-weight: 700;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  margin-bottom: 8px;
}
.module-card h3 {
  margin: 0 0 8px;
  font-size: 18px;
  color: var(--text);
}
.module-card p {
  color: var(--text-dim);
  font-size: 14px;
  margin: 0;
}

.objectives {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
  gap: 14px;
  margin-top: 20px;
}
.obj {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: 10px;
  padding: 18px;
  font-size: 14.5px;
  color: var(--text-dim);
}
.obj strong { color: var(--text); display: block; margin-bottom: 4px; font-size: 15px; }

/* module page */
.breadcrumb {
  font-size: 13px;
  color: var(--text-dim);
  margin: 28px 0 6px;
}
.breadcrumb a { color: var(--text-dim); }
.module-header {
  padding: 22px 0 32px;
  border-bottom: 1px solid var(--border);
  margin-bottom: 34px;
}
.module-header .num {
  font-size: 13px;
  color: var(--accent-2);
  font-weight: 700;
  letter-spacing: 0.1em;
  text-transform: uppercase;
}
.module-header h1 {
  font-size: 36px;
  margin: 6px 0 12px;
  letter-spacing: -0.02em;
}
.module-header .lead {
  font-size: 17px;
  color: var(--text-dim);
  max-width: 760px;
}

.toc {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: 10px;
  padding: 18px 22px;
  margin: 0 0 34px;
  font-size: 14.5px;
}
.toc strong { display: block; margin-bottom: 8px; color: var(--accent-2); font-size: 12px; letter-spacing: 0.08em; text-transform: uppercase; }
.toc ol { margin: 0; padding-left: 20px; }
.toc li { color: var(--text-dim); }
.toc a { color: var(--text); }

.callout {
  border-left: 3px solid var(--accent);
  background: rgba(79, 156, 255, 0.06);
  padding: 14px 18px;
  margin: 18px 0;
  border-radius: 4px;
  font-size: 15px;
}
.callout.warn {
  border-left-color: var(--warn);
  background: rgba(255, 181, 71, 0.06);
}
.callout.tip {
  border-left-color: var(--accent-2);
  background: rgba(125, 240, 197, 0.06);
}
.callout strong { color: var(--text); }

pre, code {
  font-family: var(--mono);
  font-size: 13.5px;
}
pre {
  background: #0a0f1f;
  border: 1px solid var(--border);
  border-radius: 8px;
  padding: 16px 18px;
  overflow-x: auto;
  line-height: 1.55;
  margin: 16px 0;
}
code { color: var(--accent-2); }
pre code { color: #cfd8ec; background: none; }
p code, li code { background: rgba(125, 240, 197, 0.09); padding: 2px 6px; border-radius: 4px; }

table {
  width: 100%;
  border-collapse: collapse;
  margin: 16px 0;
  font-size: 14.5px;
}
th, td {
  padding: 10px 12px;
  border-bottom: 1px solid var(--border);
  text-align: left;
  vertical-align: top;
}
th { color: var(--accent-2); font-weight: 600; font-size: 13px; text-transform: uppercase; letter-spacing: 0.05em; }
tbody tr:hover { background: rgba(79, 156, 255, 0.04); }

.resources {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: 10px;
  padding: 20px 24px;
  margin: 28px 0;
}
.resources h4 { margin-top: 0; }
.resources ul { padding-left: 20px; }
.resources li { color: var(--text-dim); font-size: 14.5px; }
.resources li a { color: var(--accent); }

.module-nav {
  display: flex;
  justify-content: space-between;
  gap: 16px;
  margin: 48px 0 24px;
  padding-top: 24px;
  border-top: 1px solid var(--border);
}
.module-nav a {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: 10px;
  padding: 14px 18px;
  flex: 1;
  max-width: 48%;
  color: var(--text);
  transition: border-color 0.2s;
}
.module-nav a:hover { border-color: var(--accent); text-decoration: none; }
.module-nav a .label { font-size: 12px; color: var(--text-dim); display: block; }
.module-nav a.next { text-align: right; }
.module-nav a.prev::before { content: "← "; }
.module-nav a.next::after { content: " →"; }

footer.site {
  border-top: 1px solid var(--border);
  padding: 40px 0;
  margin-top: 60px;
  color: var(--text-dim);
  font-size: 14px;
  text-align: center;
}

@media (max-width: 640px) {
  .hero h1 { font-size: 32px; }
  .module-header h1 { font-size: 28px; }
  nav.primary a { margin-left: 12px; font-size: 13px; }
  .module-nav { flex-direction: column; }
  .module-nav a { max-width: 100%; }
}