:root {
  --accent: #0A84FF;
  --bg: #ffffff;
  --bg-elevated: #f5f5f7;
  --text: #1d1d1f;
  --text-muted: #6e6e73;
  --border: #d2d2d7;
  --container: 720px;
  --radius: 12px;
}

@media (prefers-color-scheme: dark) {
  :root {
    --bg: #000000;
    --bg-elevated: #1c1c1e;
    --text: #f5f5f7;
    --text-muted: #98989d;
    --border: #2c2c2e;
  }
}

*,
*::before,
*::after {
  box-sizing: border-box;
}

html {
  -webkit-text-size-adjust: 100%;
}

body {
  margin: 0;
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
  font-size: 17px;
  line-height: 1.6;
  color: var(--text);
  background: var(--bg);
  -webkit-font-smoothing: antialiased;
}

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

a:hover {
  text-decoration: underline;
}

.site-header {
  position: sticky;
  top: 0;
  z-index: 10;
  background: color-mix(in srgb, var(--bg) 92%, transparent);
  backdrop-filter: saturate(180%) blur(20px);
  -webkit-backdrop-filter: saturate(180%) blur(20px);
  border-bottom: 1px solid var(--border);
}

.site-header__inner {
  max-width: var(--container);
  margin: 0 auto;
  padding: 14px 24px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 16px;
}

.brand {
  font-weight: 600;
  font-size: 17px;
  color: var(--text);
  letter-spacing: -0.01em;
}

.brand:hover {
  text-decoration: none;
}

.lang-switch {
  display: inline-flex;
  gap: 4px;
  font-size: 14px;
  color: var(--text-muted);
}

.lang-switch a,
.lang-switch span {
  padding: 4px 8px;
  border-radius: 6px;
}

.lang-switch span {
  color: var(--text);
  background: var(--bg-elevated);
  font-weight: 500;
}

main {
  max-width: var(--container);
  margin: 0 auto;
  padding: 48px 24px 64px;
}

h1 {
  font-size: 40px;
  line-height: 1.15;
  letter-spacing: -0.02em;
  margin: 0 0 16px;
}

h2 {
  font-size: 24px;
  line-height: 1.25;
  letter-spacing: -0.01em;
  margin: 40px 0 12px;
}

h3 {
  font-size: 19px;
  margin: 24px 0 8px;
}

p,
ul,
ol {
  margin: 0 0 16px;
}

ul,
ol {
  padding-left: 24px;
}

li {
  margin-bottom: 6px;
}

.lede {
  font-size: 20px;
  color: var(--text-muted);
  margin-bottom: 32px;
}

.cards {
  display: grid;
  grid-template-columns: 1fr;
  gap: 12px;
  margin: 32px 0;
}

@media (min-width: 600px) {
  .cards {
    grid-template-columns: repeat(3, 1fr);
  }
}

.card {
  display: block;
  padding: 20px;
  background: var(--bg-elevated);
  border-radius: var(--radius);
  color: var(--text);
  border: 1px solid var(--border);
  transition: transform 0.15s ease;
}

.card:hover {
  text-decoration: none;
  transform: translateY(-2px);
}

.card__title {
  font-weight: 600;
  margin-bottom: 4px;
}

.card__desc {
  font-size: 14px;
  color: var(--text-muted);
}

.btn {
  display: inline-block;
  padding: 12px 22px;
  background: var(--accent);
  color: #ffffff;
  border-radius: 980px;
  font-weight: 500;
  font-size: 16px;
}

.btn:hover {
  text-decoration: none;
  filter: brightness(1.08);
}

details {
  border-top: 1px solid var(--border);
  padding: 16px 0;
}

details:last-of-type {
  border-bottom: 1px solid var(--border);
}

summary {
  cursor: pointer;
  font-weight: 500;
  list-style: none;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 12px;
}

summary::-webkit-details-marker {
  display: none;
}

summary::after {
  content: "+";
  font-size: 22px;
  color: var(--text-muted);
  font-weight: 300;
  transition: transform 0.15s ease;
}

details[open] summary::after {
  content: "−";
}

details > *:not(summary) {
  margin-top: 12px;
  color: var(--text-muted);
}

.callout {
  padding: 14px 18px;
  background: var(--bg-elevated);
  border-left: 3px solid var(--accent);
  border-radius: 6px;
  margin: 24px 0;
  font-size: 15px;
}

.muted {
  color: var(--text-muted);
  font-size: 14px;
}

.site-footer {
  border-top: 1px solid var(--border);
  margin-top: 64px;
  padding: 32px 24px;
  text-align: center;
  font-size: 14px;
  color: var(--text-muted);
}

.site-footer__links {
  display: flex;
  flex-wrap: wrap;
  justify-content: center;
  gap: 8px 20px;
  margin-bottom: 12px;
}

.site-footer__links a {
  color: var(--text-muted);
}

.site-footer__links a:hover {
  color: var(--text);
}