/* Cẩm nang ĐGNL — shared styles for the section index + article pages.
   Orange accent (the Luyện thi ĐGNL product colour), same type system as the
   marketing home page (DM Sans + DM Serif Display). */

*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }

:root {
  --ink: #1a1a1a;
  --ink-muted: #5a5a5a;
  --ink-faint: #999;
  --surface: #faf9f7;
  --surface-alt: #f2f0ec;
  --border: rgba(0, 0, 0, 0.09);
  --orange: #eb6200;
  --orange-dark: #c8540a;
  --orange-light: #fff3ea;
  --purple: #5b4fcf;
  --gold: #c9952a;
  --green: #1a7a4a;
  --amber: #b45309;
  --content-width: 720px;
}

html { scroll-behavior: smooth; }

body {
  font-family: 'DM Sans', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
  background: var(--surface);
  color: var(--ink);
  line-height: 1.75;
  padding-top: 58px;
  -webkit-font-smoothing: antialiased;
}

/* ── nav ── */
.site-nav {
  position: fixed; top: 0; left: 0; right: 0; z-index: 100;
  display: flex; align-items: center; justify-content: space-between;
  padding: 0 2rem; height: 58px;
  background: rgba(250, 249, 247, 0.92);
  backdrop-filter: blur(12px);
  border-bottom: 1px solid var(--border);
}
.nav-logo {
  font-family: 'DM Serif Display', serif;
  font-size: 1.3rem; color: var(--ink); text-decoration: none; letter-spacing: 0.3px;
}
.nav-links { display: flex; gap: 0.3rem; align-items: center; }
.nav-link {
  font-size: 0.85rem; font-weight: 500; padding: 6px 14px;
  border-radius: 999px; text-decoration: none; color: var(--ink-muted);
  transition: all 0.16s; white-space: nowrap;
}
.nav-link:hover { color: var(--ink); background: var(--surface-alt); }
.nav-link.active { color: var(--orange); }
.nav-link.cta { background: var(--orange); color: #fff; }
.nav-link.cta:hover { background: var(--orange-dark); }

.nav-toggle {
  display: none; background: none; border: none; cursor: pointer;
  width: 40px; height: 40px; padding: 9px;
}
.nav-toggle span {
  display: block; height: 2px; background: var(--ink); border-radius: 2px;
  transition: transform 0.2s, opacity 0.2s;
}
.nav-toggle span + span { margin-top: 5px; }
.nav-toggle[aria-expanded="true"] span:nth-child(1) { transform: translateY(7px) rotate(45deg); }
.nav-toggle[aria-expanded="true"] span:nth-child(2) { opacity: 0; }
.nav-toggle[aria-expanded="true"] span:nth-child(3) { transform: translateY(-7px) rotate(-45deg); }

@media (max-width: 760px) {
  .site-nav { padding: 0 1rem; }
  .nav-toggle { display: block; }
  .nav-links {
    position: absolute; top: 58px; left: 0; right: 0;
    flex-direction: column; align-items: stretch; gap: 0;
    background: var(--surface); border-bottom: 1px solid var(--border);
    padding: 0.5rem 1rem 0.9rem;
    box-shadow: 0 12px 24px rgba(0, 0, 0, 0.06);
    display: none;
  }
  .nav-links.open { display: flex; }
  .nav-link { padding: 11px 6px; font-size: 0.95rem; border-radius: 8px; }
  .nav-link.hide-sm { display: block; }
  .nav-link.cta { text-align: center; margin-top: 0.4rem; }
}

/* ── hero ── */
.hero {
  background: linear-gradient(135deg, #f5822e, #eb6200);
  color: #fff;
  padding: 3.25rem 1.5rem 2.75rem;
  text-align: center;
}
.hero .eyebrow {
  display: inline-block;
  background: rgba(255, 255, 255, 0.18);
  border-radius: 999px;
  padding: 4px 14px;
  font-size: 0.75rem; font-weight: 600;
  letter-spacing: 0.1em; text-transform: uppercase;
  margin-bottom: 1rem;
}
.hero h1 {
  font-family: 'DM Serif Display', serif;
  font-size: clamp(1.7rem, 4.2vw, 2.6rem);
  line-height: 1.18; font-weight: 400;
  max-width: 720px; margin: 0 auto 0.8rem;
}
.hero p {
  font-size: 1.02rem; opacity: 0.92;
  max-width: 560px; margin: 0 auto;
}

/* ── section index ── */
.wrap { max-width: 940px; margin: 0 auto; padding: 3rem 1.5rem 5rem; }

.group-title {
  font-family: 'DM Serif Display', serif;
  font-size: 1.5rem; margin: 2.75rem 0 1.25rem;
}
.group-title:first-child { margin-top: 0; }

.card-grid { display: grid; grid-template-columns: 1fr 1fr; gap: 1.1rem; }
@media (max-width: 640px) { .card-grid { grid-template-columns: 1fr; } }

.card {
  display: flex; flex-direction: column; gap: 0.6rem;
  padding: 1.5rem 1.4rem;
  background: #fff;
  border: 1px solid var(--border);
  border-radius: 16px;
  text-decoration: none; color: inherit;
  transition: transform 0.18s, box-shadow 0.18s;
}
.card:hover { transform: translateY(-3px); box-shadow: 0 14px 34px rgba(0, 0, 0, 0.07); }
.card .kicker {
  font-size: 0.72rem; font-weight: 700; letter-spacing: 0.08em;
  text-transform: uppercase; color: var(--orange);
}
.card h3 {
  font-family: 'DM Serif Display', serif;
  font-size: 1.22rem; line-height: 1.25; font-weight: 400; color: var(--ink);
}
.card p { font-size: 0.9rem; color: var(--ink-muted); line-height: 1.6; }
.card .more {
  margin-top: auto; padding-top: 0.4rem;
  font-size: 0.85rem; font-weight: 600; color: var(--orange);
}

/* ── article ── */
article { max-width: var(--content-width); margin: 0 auto; padding: 2.5rem 1.5rem 4rem; }

.breadcrumb { font-size: 0.8rem; color: var(--ink-faint); margin-bottom: 1.75rem; }
.breadcrumb a { color: var(--orange); text-decoration: none; }
.breadcrumb a:hover { text-decoration: underline; }

.article-meta { font-size: 0.8rem; color: var(--ink-faint); margin-bottom: 2rem; }

article h1 {
  font-family: 'DM Serif Display', serif;
  font-size: clamp(1.7rem, 4vw, 2.3rem);
  line-height: 1.2; font-weight: 400;
  margin-bottom: 1.5rem;
}
article h2 {
  font-family: 'DM Serif Display', serif;
  font-size: 1.45rem; font-weight: 400;
  margin: 2.5rem 0 0.75rem;
}
article h3 { font-size: 1.12rem; font-weight: 700; margin: 1.75rem 0 0.5rem; }
article p { margin-bottom: 1.1rem; color: var(--ink-muted); }
article ul, article ol { margin: 0.4rem 0 1.2rem 1.4rem; color: var(--ink-muted); }
article li { margin-bottom: 0.5rem; }
article strong { color: var(--ink); }
article a { color: var(--orange-dark); }

article .lead { font-size: 1.1rem; color: var(--ink); }

.table-wrap { overflow-x: auto; margin: 1.25rem 0; }
article table { border-collapse: collapse; width: 100%; font-size: 0.9rem; min-width: 460px; }
article th, article td {
  border: 1px solid var(--border); padding: 0.55rem 0.8rem; text-align: left;
  vertical-align: top;
}
article th { background: var(--surface-alt); font-weight: 700; color: var(--ink); }

.callout {
  border-radius: 12px; padding: 1.1rem 1.35rem; margin: 1.75rem 0;
  font-size: 0.95rem;
}
.callout > strong:first-child { display: block; margin-bottom: 0.35rem; font-size: 0.9rem; }
.callout p:last-child { margin-bottom: 0; }
.callout-orange { background: var(--orange-light); border-left: 4px solid var(--orange); }
.callout-orange strong { color: var(--orange-dark); }
.callout-green { background: #edfdf4; border-left: 4px solid var(--green); }
.callout-green strong { color: var(--green); }
.callout-amber { background: #fffbeb; border-left: 4px solid var(--amber); }
.callout-amber strong { color: var(--amber); }
.callout-plain { background: var(--surface-alt); border-left: 4px solid var(--ink-faint); font-size: 0.85rem; color: var(--ink-muted); }

.cta-box {
  background: var(--ink); color: #fff;
  border-radius: 16px; padding: 1.75rem;
  margin: 2.5rem 0 1rem; text-align: center;
}
.cta-box h3 { font-family: 'DM Serif Display', serif; font-weight: 400; font-size: 1.3rem; color: #fff; margin-bottom: 0.5rem; }
.cta-box p { color: rgba(255, 255, 255, 0.7); font-size: 0.92rem; margin-bottom: 1.1rem; }
.cta-btn {
  display: inline-block;
  background: var(--orange); color: #fff;
  padding: 12px 26px; border-radius: 999px;
  font-weight: 600; text-decoration: none; font-size: 0.95rem;
  transition: background 0.16s;
}
.cta-btn:hover { background: var(--orange-dark); }

.related { margin-top: 3rem; padding-top: 1.75rem; border-top: 1px solid var(--border); }
.related h2 { font-size: 1.1rem; font-weight: 700; font-family: 'DM Sans', sans-serif; margin: 0 0 0.75rem; }
.related ul { list-style: none; margin: 0; }
.related li { margin-bottom: 0.5rem; }
.related a { color: var(--orange-dark); text-decoration: none; font-weight: 500; }
.related a:hover { text-decoration: underline; }

/* ── footer ── */
footer {
  background: var(--ink); color: rgba(255, 255, 255, 0.5);
  padding: 2.5rem 2rem;
  display: flex; align-items: center; justify-content: space-between;
  flex-wrap: wrap; gap: 1rem;
}
.footer-logo { font-family: 'DM Serif Display', serif; font-size: 1.15rem; color: #fff; text-decoration: none; }
.footer-links { display: flex; gap: 1.25rem; flex-wrap: wrap; }
footer a { font-size: 0.84rem; color: rgba(255, 255, 255, 0.5); text-decoration: none; }
footer a:hover { color: #fff; }
.footer-copy { width: 100%; text-align: center; font-size: 0.78rem; margin-top: 0.75rem; }