/* ── Reset & Variables ────────────────────────────────────────────────────── */
*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }

:root {
  --bg:       #0d1117;
  --bg2:      #161b22;
  --bg3:      #1c2128;
  --border:   #30363d;
  --text:     #e6edf3;
  --text-dim: #8b949e;
  --accent:   #f78166;
  --accent2:  #58a6ff;
  --green:    #3fb950;
  --amber:    #ffa657;
  --radius:   8px;
}

html { scroll-behavior: smooth; }

body {
  font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Helvetica, Arial, sans-serif;
  background: var(--bg);
  color: var(--text);
  line-height: 1.6;
  font-size: 15px;
}

/* ── Header / Hero ────────────────────────────────────────────────────────── */
header {
  background: linear-gradient(160deg, #0d1117 0%, #161b22 60%, #1a1f2e 100%);
  border-bottom: 1px solid var(--border);
  padding: 80px 24px 64px;
  text-align: center;
  position: relative;
  overflow: hidden;
}

header::before {
  content: '';
  position: absolute; inset: 0;
  background: radial-gradient(ellipse at 50% 0%, rgba(88,166,255,.08) 0%, transparent 70%);
  pointer-events: none;
}

.hero-inner { position: relative; max-width: 760px; margin: 0 auto; }

.badge {
  display: inline-block;
  font-size: 28px; font-weight: 800;
  letter-spacing: 3px; color: var(--text);
  margin-bottom: 20px;
  text-shadow: 0 0 40px rgba(88,166,255,.3);
}
.badge span { color: var(--accent); }

.tagline {
  font-size: 18px; font-weight: 500;
  color: var(--text-dim); margin-bottom: 16px;
  letter-spacing: .5px;
}

.sub {
  font-size: 15px; color: var(--text-dim);
  max-width: 560px; margin: 0 auto 28px;
}

.hero-tags {
  display: flex; flex-wrap: wrap; gap: 8px; justify-content: center;
}
.hero-tags span {
  background: var(--bg3); border: 1px solid var(--border);
  border-radius: 20px; padding: 4px 14px;
  font-size: 12px; color: var(--text-dim);
  font-family: 'SF Mono', 'Fira Code', monospace;
}

/* ── Nav ──────────────────────────────────────────────────────────────────── */
nav {
  position: sticky; top: 0; z-index: 100;
  background: rgba(13,17,23,.92);
  backdrop-filter: blur(12px);
  border-bottom: 1px solid var(--border);
  display: flex; gap: 0; justify-content: center;
  padding: 0 16px;
  overflow-x: auto;
}

nav a {
  display: inline-block;
  padding: 14px 20px;
  color: var(--text-dim);
  text-decoration: none;
  font-size: 14px; font-weight: 500;
  border-bottom: 2px solid transparent;
  transition: color .15s, border-color .15s;
  white-space: nowrap;
}
nav a:hover, nav a.active {
  color: var(--text);
  border-bottom-color: var(--accent2);
}

/* ── Sections ─────────────────────────────────────────────────────────────── */
section {
  max-width: 960px; margin: 0 auto;
  padding: 64px 24px;
  border-bottom: 1px solid var(--border);
}

section:last-of-type { border-bottom: none; }

h2 {
  font-size: 24px; font-weight: 700;
  margin-bottom: 8px; color: var(--text);
}

h3 {
  font-size: 16px; font-weight: 600;
  color: var(--text); margin: 28px 0 12px;
}

.section-intro {
  color: var(--text-dim); margin-bottom: 32px;
  max-width: 680px;
}

/* ── Feature groups ──────────────────────────────────────────────────────── */
h3.feature-group {
  font-size: 13px;
  font-weight: 600;
  letter-spacing: .08em;
  text-transform: uppercase;
  color: var(--accent2);
  margin: 40px 0 4px;
  padding-bottom: 6px;
  border-bottom: 1px solid var(--border);
}

/* ── Cards ────────────────────────────────────────────────────────────────── */
.card-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(260px, 1fr));
  gap: 16px; margin-top: 32px;
}

.card {
  background: var(--bg2);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 20px;
  transition: border-color .15s, transform .15s;
}
.card:hover {
  border-color: var(--accent2);
  transform: translateY(-2px);
}

.card-icon { font-size: 24px; margin-bottom: 10px; }
.card h3 { margin: 0 0 8px; font-size: 15px; }
.card p { font-size: 13px; color: var(--text-dim); line-height: 1.55; }

/* ── Simulation params ────────────────────────────────────────────────────── */
.sim-params {
  display: flex; flex-direction: column; gap: 1px;
  border: 1px solid var(--border); border-radius: var(--radius);
  overflow: hidden; margin-top: 24px;
}
.param {
  display: grid; grid-template-columns: 130px 140px 1fr;
  gap: 12px; align-items: center;
  background: var(--bg2); padding: 12px 16px;
  border-bottom: 1px solid var(--border);
  font-size: 13px;
}
.param:last-child { border-bottom: none; }
.param-name { font-weight: 600; color: var(--text); }
.param-range {
  font-family: 'SF Mono', 'Fira Code', monospace;
  font-size: 12px; color: var(--accent2);
}
.param-desc { color: var(--text-dim); }

/* ── Code blocks ──────────────────────────────────────────────────────────── */
.code-block {
  background: var(--bg3);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 16px 18px;
  font-family: 'SF Mono', 'Fira Code', 'Consolas', monospace;
  font-size: 12.5px; line-height: 1.7;
  color: #a5d6ff;
  white-space: pre;
  overflow-x: auto;
  margin: 12px 0;
}

/* ── Steps ────────────────────────────────────────────────────────────────── */
.steps { display: flex; flex-direction: column; gap: 16px; margin-top: 24px; }

.step {
  display: flex; gap: 20px; align-items: flex-start;
}
.step-num {
  flex-shrink: 0;
  width: 32px; height: 32px; border-radius: 50%;
  background: var(--accent2);
  color: #000; font-weight: 700; font-size: 14px;
  display: flex; align-items: center; justify-content: center;
  margin-top: 2px;
}
.step-body { flex: 1; }
.step-body h3 { margin-top: 4px; }

/* ── Table ────────────────────────────────────────────────────────────────── */
table {
  width: 100%; border-collapse: collapse;
  margin-top: 24px; font-size: 13px;
}
th {
  background: var(--bg3); color: var(--text-dim);
  font-weight: 600; font-size: 11px; text-transform: uppercase;
  letter-spacing: .6px; padding: 10px 14px;
  border: 1px solid var(--border); text-align: left;
}
td {
  padding: 9px 14px;
  border: 1px solid var(--border);
  color: var(--text-dim);
  vertical-align: top;
}
td:first-child {
  font-family: 'SF Mono', 'Fira Code', monospace;
  font-size: 12px; color: var(--green); font-weight: 600;
}
td:nth-child(2) {
  font-family: 'SF Mono', 'Fira Code', monospace;
  font-size: 12px; color: var(--accent2);
}
tr:hover td { background: var(--bg2); }

/* ── FAQ ──────────────────────────────────────────────────────────────────── */
details {
  background: var(--bg2);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  margin-bottom: 8px;
  overflow: hidden;
}
details[open] { border-color: var(--accent2); }

summary {
  padding: 14px 18px;
  cursor: pointer; font-weight: 500;
  list-style: none; display: flex; align-items: center; gap: 10px;
  user-select: none;
}
summary::before {
  content: '›';
  font-size: 18px; color: var(--accent2);
  transition: transform .2s; display: inline-block;
}
details[open] summary::before { transform: rotate(90deg); }

details p {
  padding: 0 18px 16px; color: var(--text-dim); font-size: 14px;
}

/* ── Footer ───────────────────────────────────────────────────────────────── */
footer {
  text-align: center; padding: 40px 24px;
  color: var(--text-dim); font-size: 13px;
  border-top: 1px solid var(--border);
}

/* ── Responsive ───────────────────────────────────────────────────────────── */
@media (max-width: 640px) {
  header { padding: 48px 16px 40px; }
  .badge { font-size: 22px; }
  section { padding: 40px 16px; }
  .param { grid-template-columns: 1fr; gap: 4px; }
  .param-range { color: var(--accent2); }
  table { font-size: 12px; }
  td, th { padding: 7px 10px; }
  .step { flex-direction: column; gap: 8px; }
  nav a { padding: 12px 14px; font-size: 13px; }
}

/* ── Lang switcher ───────────────────────────────────────────────────────── */
.lang-switcher {
  margin-left: auto;
  display: flex;
  gap: 4px;
  align-items: center;
}
.lang-btn {
  background: none;
  border: 1px solid var(--border);
  color: var(--text-dim);
  font-size: 11px;
  font-weight: 600;
  letter-spacing: .05em;
  padding: 2px 7px;
  border-radius: 4px;
  cursor: pointer;
  transition: border-color .15s, color .15s;
}
.lang-btn:hover { border-color: var(--accent2); color: var(--text); }
.lang-btn.active { border-color: var(--accent2); color: var(--accent2); }