:root { --bg: #0b2a4a; --card: #123c66; --text: #eaf3ff; --soft: #b9d3f0; --accent: #ffd54a; --link: #8fd1ff; }
* { box-sizing: border-box; }
body { margin: 0; background: var(--bg); color: var(--text); font: 16px/1.6 -apple-system, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif; }
main { max-width: 820px; margin: 0 auto; padding: 24px 16px 64px; }
header { display: flex; align-items: center; gap: 14px; margin-bottom: 12px; }
header img { width: 56px; height: 56px; border-radius: 12px; }
h1 { font-size: 26px; margin: 0; }
h2 { color: var(--accent); font-size: 20px; margin: 28px 0 8px; }
h3 { font-size: 17px; margin: 18px 0 6px; }
a { color: var(--link); }
.card { background: var(--card); border-radius: 14px; padding: 18px 20px; margin: 16px 0; }
.lang { display: flex; gap: 8px; margin: 8px 0 18px; }
.lang a { padding: 6px 14px; border-radius: 999px; background: var(--card); text-decoration: none; color: var(--text); }
.soft { color: var(--soft); }
.button { display: inline-block; background: var(--accent); color: #2a2100; font-weight: 700; padding: 12px 20px; border-radius: 10px; text-decoration: none; margin: 8px 0; }
ol, ul { padding-left: 22px; }
li { margin: 4px 0; }
code { background: #0b2a4a; padding: 2px 6px; border-radius: 6px; }
footer { margin-top: 40px; color: var(--soft); font-size: 14px; }
hr { border: 0; border-top: 1px solid #24527f; margin: 36px 0; }
.card > h2:first-child { margin-top: 0; }

/* One language at a time (data-lang set from ?lang= or the browser language); both without JS. */
html[data-lang="vi"] .en, html[data-lang="en"] .vi { display: none !important; }
html[data-lang="vi"] .pick-vi, html[data-lang="en"] .pick-en { background: var(--accent); color: #2a2100; font-weight: 700; }