:root {
  --bg: #FFFFFF;
  --surface: #F4F4F5;
  --border: #DCDCE0;
  --text: #111111;
  --text-secondary: #3F3F46;
  --text-muted: #6B7280;
  --accent: #111111;
  --accent-contrast: #FFFFFF;
  --success: #065F46;
}

@media (prefers-color-scheme: dark) {
  :root {
    --bg: #111113;
    --surface: #1C1C1F;
    --border: #303034;
    --text: #F2F2F3;
    --text-secondary: #C7C7CC;
    --text-muted: #9A9AA1;
    --accent: #F2F2F3;
    --accent-contrast: #111113;
    --success: #34D399;
  }
}

* {
  box-sizing: border-box;
}

html, body {
  margin: 0;
  padding: 0;
}

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

.wrap {
  max-width: 720px;
  margin: 0 auto;
  padding: 0 20px 96px;
}

header.site {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 28px 0 20px;
  border-bottom: 1px solid var(--border);
  margin-bottom: 40px;
  gap: 16px;
  flex-wrap: wrap;
}

.brand {
  display: flex;
  align-items: center;
  gap: 10px;
  text-decoration: none;
  color: var(--text);
  font-weight: 700;
  font-size: 17px;
}

.brand .mark {
  width: 30px;
  height: 30px;
  border-radius: 8px;
  background: var(--accent);
  color: var(--accent-contrast);
  display: flex;
  align-items: center;
  justify-content: center;
  flex-shrink: 0;
}

.brand .mark svg {
  width: 16px;
  height: 16px;
}

nav.site {
  display: flex;
  align-items: center;
  gap: 18px;
  font-size: 14px;
}

nav.site a {
  color: var(--text-secondary);
  text-decoration: none;
}

nav.site a:hover {
  color: var(--text);
  text-decoration: underline;
}

#lang-toggle {
  appearance: none;
  border: 1px solid var(--border);
  background: var(--surface);
  color: var(--text);
  border-radius: 999px;
  padding: 6px 14px;
  font-size: 13px;
  font-weight: 600;
  cursor: pointer;
  font-family: inherit;
}

#lang-toggle:hover {
  border-color: var(--text-muted);
}

h1 {
  font-size: 28px;
  line-height: 1.25;
  margin: 0 0 6px;
}

h2 {
  font-size: 19px;
  margin: 40px 0 12px;
  padding-top: 8px;
}

h3 {
  font-size: 16px;
  margin: 20px 0 8px;
}

p, li {
  color: var(--text-secondary);
  font-size: 15px;
}

.meta {
  color: var(--text-muted);
  font-size: 13px;
  margin: 0 0 32px;
}

ul, ol {
  padding-left: 22px;
}

li {
  margin-bottom: 6px;
}

.card {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 12px;
  padding: 18px 20px;
  margin: 16px 0;
}

.card p:last-child {
  margin-bottom: 0;
}

a {
  color: inherit;
}

.tag {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  font-size: 12px;
  font-weight: 600;
  color: var(--success);
  background: color-mix(in srgb, var(--success) 12%, transparent);
  border-radius: 999px;
  padding: 4px 10px;
  margin: 0 6px 6px 0;
}

table {
  width: 100%;
  border-collapse: collapse;
  font-size: 14px;
  margin: 12px 0 20px;
}

th, td {
  text-align: left;
  padding: 10px 12px;
  border-bottom: 1px solid var(--border);
  color: var(--text-secondary);
  vertical-align: top;
}

th {
  color: var(--text);
  font-weight: 600;
  white-space: nowrap;
}

footer.site {
  margin-top: 64px;
  padding-top: 24px;
  border-top: 1px solid var(--border);
  color: var(--text-muted);
  font-size: 13px;
}

.lang-block[data-lang="vi"] {
  display: none;
}

html[data-lang="vi"] .lang-block[data-lang="en"] {
  display: none;
}

html[data-lang="vi"] .lang-block[data-lang="vi"] {
  display: block;
}

.home-links {
  display: grid;
  gap: 14px;
  margin-top: 24px;
}

.home-links a.card-link {
  display: block;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 12px;
  padding: 18px 20px;
  text-decoration: none;
  color: var(--text);
  font-weight: 600;
  font-size: 16px;
}

.home-links a.card-link span {
  display: block;
  color: var(--text-muted);
  font-weight: 400;
  font-size: 13px;
  margin-top: 4px;
}

.home-links a.card-link:hover {
  border-color: var(--text-muted);
}