:root {
  color-scheme: dark;
  --bg: #0c1115;
  --bg-soft: #10171c;
  --panel: #141c22;
  --line: #29343e;
  --text: #f1f5f4;
  --muted: #a6b5bd;
  --accent: #a7f3c7;
  --accent-dim: #1a3026;
  --max: 720px;
  --site-max: 1080px;
}

* { box-sizing: border-box; }
html, body {
  margin: 0;
  min-height: 100%;
  background:
    radial-gradient(1200px 500px at 10% -10%, #1a3026 0%, transparent 55%),
    linear-gradient(180deg, #0e151a 0%, var(--bg) 40%, #0a0f12 100%);
  color: var(--text);
}
body {
  font: 17px/1.65 "Segoe UI", system-ui, -apple-system, sans-serif;
}
a { color: var(--accent); }
a:hover { text-decoration-thickness: 2px; }
a:focus-visible, button:focus-visible {
  outline: 2px solid var(--accent);
  outline-offset: 3px;
}

.skip-link {
  position: absolute;
  left: 12px;
  top: -48px;
  background: var(--accent);
  color: #062016;
  padding: 8px 12px;
  border-radius: 8px;
  z-index: 20;
  text-decoration: none;
  font-weight: 600;
}
.skip-link:focus { top: 12px; }

.wrap {
  width: min(var(--site-max), calc(100% - 32px));
  margin: 0 auto;
}
.site-header {
  position: sticky;
  top: 0;
  z-index: 10;
  background: rgba(12, 17, 21, 0.94);
  border-bottom: 1px solid var(--line);
  backdrop-filter: blur(10px);
}
.header-row {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 16px;
  min-height: 72px;
}
.brand {
  display: flex;
  align-items: center;
  gap: 12px;
  color: inherit;
  text-decoration: none;
  min-width: 0;
}
.mark {
  flex: 0 0 42px;
  height: 42px;
  border: 1px solid #557c6b;
  border-radius: 50%;
  position: relative;
  background: repeating-radial-gradient(circle, transparent 0 8px, #264b3e 9px 10px);
}
.mark::after {
  content: "";
  position: absolute;
  width: 7px;
  height: 7px;
  border-radius: 50%;
  background: var(--accent);
  top: 9px;
  right: 8px;
}
.brand-name { display: block; font-weight: 750; letter-spacing: -0.4px; }
.brand-sub { display: block; color: var(--muted); font-size: 12px; }
.lang-switch { display: flex; gap: 6px; flex-wrap: wrap; }
.lang-btn {
  min-height: 36px;
  min-width: 44px;
  padding: 4px 10px;
  border: 1px solid var(--line);
  border-radius: 10px;
  background: transparent;
  color: var(--muted);
  text-decoration: none;
  display: inline-flex;
  align-items: center;
  justify-content: center;
}
.lang-btn[aria-current="page"] {
  color: var(--text);
  border-color: var(--accent);
  background: var(--accent-dim);
}

.learn-main {
  width: min(var(--max), calc(100% - 32px));
  margin: 28px auto 64px;
}
.learn-kicker {
  color: var(--muted);
  font-size: 13px;
  letter-spacing: 0.04em;
  text-transform: uppercase;
  margin: 0 0 8px;
}
.learn-main h1 {
  font-size: clamp(1.6rem, 3vw, 2.1rem);
  line-height: 1.2;
  letter-spacing: -0.03em;
  margin: 0 0 12px;
}
.lede {
  color: var(--muted);
  font-size: 1.05rem;
  margin: 0 0 28px;
}
.article-body p { margin: 0 0 1em; }
.article-body h2 {
  font-size: 1.15rem;
  margin: 1.6em 0 0.55em;
}
.article-body ul {
  margin: 0 0 1.2em;
  padding-left: 1.2em;
}
.article-body li { margin: 0.35em 0; }
.meta-line {
  color: var(--muted);
  font-size: 13px;
  margin: 0 0 20px;
}
.cta-row {
  margin-top: 36px;
  padding-top: 20px;
  border-top: 1px solid var(--line);
  display: flex;
  flex-wrap: wrap;
  gap: 12px;
}
.cta {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  min-height: 44px;
  padding: 0 16px;
  border-radius: 12px;
  text-decoration: none;
  font-weight: 650;
}
.cta-primary {
  background: var(--accent);
  color: #062016;
}
.cta-secondary {
  border: 1px solid var(--line);
  color: var(--text);
}
.topic-list {
  list-style: none;
  margin: 0;
  padding: 0;
  display: grid;
  gap: 12px;
}
.topic-list a {
  display: block;
  padding: 16px 18px;
  border: 1px solid var(--line);
  border-radius: 14px;
  background: rgba(20, 28, 34, 0.72);
  text-decoration: none;
  color: inherit;
  transition: border-color 160ms ease, background 160ms ease;
}
.topic-list a:hover {
  border-color: #3d5548;
  background: var(--panel);
}
.topic-list strong { display: block; color: var(--accent); margin-bottom: 4px; }
.topic-list span { color: var(--muted); font-size: 0.95rem; }
.footnote {
  margin-top: 28px;
  color: var(--muted);
  font-size: 13px;
}
.site-footer {
  border-top: 1px solid var(--line);
  padding: 24px 0 40px;
  color: var(--muted);
  font-size: 13px;
}
.nav-learn {
  display: flex;
  flex-wrap: wrap;
  gap: 12px 18px;
  margin: 0 0 24px;
  padding: 0;
  list-style: none;
  font-size: 14px;
}
.nav-learn a { text-decoration: none; }
.nav-learn a[aria-current="page"] { color: var(--text); font-weight: 650; }

@media (max-width: 420px) {
  .wrap, .learn-main { width: min(100% - 24px, var(--site-max)); }
  .header-row { min-height: 64px; }
}

@media (max-width: 640px) {
  .header-row { flex-wrap: wrap; padding: 10px 0; gap: 8px; }
  .lang-switch { width: 100%; }
  .lang-btn { padding: 4px 8px; font-size: 13px; }
}