/* xetaiduoi1tan — giao diện trắng, tối giản */

:root {
  --bg: #ffffff;
  --paper: #f8fafc;
  --text: #111827;
  --muted: #4b5563;
  --line: #e5e7eb;
  --accent: #1d4ed8;
  --accent-hover: #1e40af;
  --radius: 10px;
  --max: 40rem;
  --max-wide: 48rem;
}

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

html {
  scroll-behavior: smooth;
}

body {
  margin: 0;
  font-family: "Be Vietnam Pro", system-ui, -apple-system, sans-serif;
  font-size: 1.05rem;
  line-height: 1.65;
  color: var(--text);
  background: var(--bg);
  -webkit-font-smoothing: antialiased;
}

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

a:hover {
  color: var(--accent-hover);
  text-decoration: underline;
  text-underline-offset: 3px;
}

.inner {
  width: min(100% - 2rem, var(--max-wide));
  margin-inline: auto;
}

.inner--narrow {
  width: min(100% - 2rem, var(--max));
}

/* Header */
.site-header {
  border-bottom: 1px solid var(--line);
  background: var(--bg);
}

.site-header__row {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 0.75rem 1.25rem;
  padding: 1rem 0;
}

.brand {
  font-weight: 700;
  font-size: 1.05rem;
  color: var(--text);
  text-decoration: none;
}

.brand:hover {
  color: var(--accent);
  text-decoration: none;
}

.brand span {
  color: var(--muted);
  font-weight: 600;
}

.nav {
  display: flex;
  flex-wrap: wrap;
  gap: 0.5rem 1.25rem;
  flex: 1;
  justify-content: flex-start;
}

@media (min-width: 640px) {
  .nav {
    justify-content: center;
  }
}

.nav a {
  color: var(--muted);
  font-size: 0.95rem;
  font-weight: 500;
  text-decoration: none;
}

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

.nav a[aria-current="page"] {
  color: var(--text);
  font-weight: 600;
}

/* Buttons */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  padding: 0.55rem 1rem;
  font-family: inherit;
  font-size: 0.95rem;
  font-weight: 600;
  border-radius: 999px;
  border: 1px solid transparent;
  cursor: pointer;
  text-decoration: none;
}

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

.btn--solid {
  background: var(--accent);
  border-color: var(--accent);
  color: #fff;
}

.btn--solid:hover {
  background: var(--accent-hover);
  border-color: var(--accent-hover);
  color: #fff;
}

.btn--line {
  background: #fff;
  border-color: var(--line);
  color: var(--text);
}

.btn--line:hover {
  border-color: #cbd5e1;
  color: var(--text);
}

.btn--sm {
  padding: 0.4rem 0.85rem;
  font-size: 0.875rem;
}

.header-cta {
  margin-left: auto;
}

@media (min-width: 640px) {
  .header-cta {
    margin-left: 0;
  }
}

/* Main blocks */
.hero {
  padding: 2.5rem 0 2rem;
}

.hero h1 {
  margin: 0 0 1rem;
  font-size: clamp(1.65rem, 4vw, 2.1rem);
  font-weight: 700;
  line-height: 1.2;
  letter-spacing: -0.02em;
}

.lead {
  margin: 0 0 1.5rem;
  color: var(--muted);
  font-size: 1.05rem;
}

.actions {
  display: flex;
  flex-wrap: wrap;
  gap: 0.65rem;
  margin: 0 0 2rem;
}

.section {
  padding: 2rem 0;
  border-top: 1px solid var(--line);
}

.section h2 {
  margin: 0 0 0.75rem;
  font-size: 1.2rem;
  font-weight: 700;
}

.section p {
  margin: 0 0 0.75rem;
  color: var(--muted);
}

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

.box {
  padding: 1.25rem 1.35rem;
  border-radius: var(--radius);
  background: var(--paper);
  border: 1px solid var(--line);
}

.notice {
  margin-top: 1rem;
  padding: 1rem 1.1rem;
  border-radius: var(--radius);
  border: 1px solid #fde68a;
  background: #fffbeb;
  color: #78350f;
  font-size: 0.95rem;
}

.notice strong {
  color: #451a03;
}

/* Footer */
.site-footer {
  margin-top: 2rem;
  padding: 1.75rem 0 2.5rem;
  border-top: 1px solid var(--line);
  font-size: 0.9rem;
  color: var(--muted);
}

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

.site-footer a:hover {
  color: var(--accent);
}

.footer-row {
  display: flex;
  flex-direction: column;
  gap: 1rem;
}

@media (min-width: 560px) {
  .footer-row {
    flex-direction: row;
    justify-content: space-between;
    align-items: flex-start;
  }
}

.footer-nav {
  display: flex;
  flex-wrap: wrap;
  gap: 0.75rem 1.25rem;
}

/* Breadcrumb */
.breadcrumb {
  font-size: 0.875rem;
  color: var(--muted);
  padding: 1.25rem 0 0;
}

.breadcrumb a {
  color: var(--muted);
}

.breadcrumb a:hover {
  color: var(--accent);
}

.breadcrumb-current {
  color: var(--text);
}

/* Article */
.page-main {
  padding-bottom: 2.5rem;
}

.article-head {
  padding: 0.5rem 0 1.25rem;
  border-bottom: 1px solid var(--line);
  margin-bottom: 1.5rem;
}

.article-head h1 {
  margin: 0 0 0.5rem;
  font-size: clamp(1.35rem, 3.2vw, 1.75rem);
  line-height: 1.25;
  font-weight: 700;
}

.meta {
  margin: 0;
  font-size: 0.9rem;
  color: var(--muted);
}

.prose {
  max-width: var(--max);
}

.prose > * + * {
  margin-top: 1rem;
}

.prose h2 {
  margin: 2rem 0 0.5rem;
  font-size: 1.1rem;
  font-weight: 700;
}

.prose h2:first-of-type {
  margin-top: 1.25rem;
}

.prose p,
.prose li {
  color: var(--muted);
}

.prose ul {
  padding-left: 1.2rem;
}

.prose li + li {
  margin-top: 0.35rem;
}

.lede {
  font-size: 1.05rem;
  color: var(--text);
}

.faq {
  margin-top: 2rem;
  padding: 1.25rem;
  border-radius: var(--radius);
  border: 1px solid var(--line);
  background: var(--paper);
}

.faq h2 {
  margin: 0 0 1rem;
  font-size: 1.05rem;
}

.faq dl {
  margin: 0;
}

.faq dt {
  font-weight: 600;
  color: var(--text);
  margin-top: 0.9rem;
  font-size: 0.95rem;
}

.faq dt:first-child {
  margin-top: 0;
}

.faq dd {
  margin: 0.35rem 0 0;
  color: var(--muted);
  font-size: 0.95rem;
}

.source {
  margin-top: 2rem;
  padding-top: 1.25rem;
  border-top: 1px solid var(--line);
  font-size: 0.95rem;
  color: var(--muted);
}

/* Listing / contact */
.page-title {
  margin: 0 0 0.5rem;
  font-size: 1.5rem;
  font-weight: 700;
}

.sub {
  margin: 0 0 1.5rem;
  color: var(--muted);
  max-width: var(--max);
}

.card-list {
  list-style: none;
  margin: 0 0 1.5rem;
  padding: 0;
}

.card-list li {
  padding: 1.25rem;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  margin-bottom: 0.75rem;
  background: var(--bg);
}

.card-list h2 {
  margin: 0 0 0.35rem;
  font-size: 1.05rem;
  font-weight: 600;
}

.card-list p {
  margin: 0;
  font-size: 0.95rem;
  color: var(--muted);
}

.grid-2 {
  display: grid;
  gap: 1rem;
}

@media (min-width: 640px) {
  .grid-2 {
    grid-template-columns: 1fr 1fr;
  }
}

.panel {
  padding: 1.25rem;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  background: var(--paper);
}

.panel h2 {
  margin: 0 0 0.75rem;
  font-size: 1rem;
  font-weight: 600;
}

.panel p {
  margin: 0 0 1rem;
  font-size: 0.95rem;
  color: var(--muted);
}

.contact-list {
  margin: 0;
  padding: 0;
  list-style: none;
}

.contact-list li + li {
  margin-top: 0.5rem;
}