/* ============================================================
   css/landing.css — Trang chủ & trang giới thiệu (SEO)
   ============================================================ */

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

:root {
  --blue: #4f83ff;
  --blue-dark: #3356c8;
  --ink: #1b2340;
  --muted: #5b6b8c;
  --good: #10b981;
  --danger: #ef4444;
  --warn: #f59e0b;
  --card: #ffffff;
  --shadow: 0 6px 24px rgba(20, 40, 90, 0.10);
  --radius: 18px;
}

html { scroll-behavior: smooth; }

body {
  font-family: 'Be Vietnam Pro', system-ui, -apple-system, sans-serif;
  color: var(--ink);
  background: linear-gradient(180deg, #cfe6ff 0%, #eaf6ff 100%);
  line-height: 1.7;
  min-height: 100vh;
}

.wrap { max-width: 820px; margin: 0 auto; padding: 0 20px 60px; }

/* Header / hero */
.hero {
  text-align: center;
  padding: 46px 0 30px;
}
.hero__logo { font-size: 78px; animation: float 2.6s ease-in-out infinite; }
@keyframes float { 0%, 100% { transform: translateY(0); } 50% { transform: translateY(-10px); } }
h1 {
  font-family: 'Baloo 2', sans-serif;
  font-weight: 800;
  font-size: clamp(30px, 7vw, 46px);
  color: var(--blue-dark);
  margin-top: 8px;
  line-height: 1.15;
}
.hero__tagline { font-size: clamp(16px, 4vw, 20px); color: var(--blue); font-weight: 700; margin-top: 6px; }
.hero__note {
  display: inline-block;
  margin-top: 14px;
  background: #fff;
  border-radius: 999px;
  padding: 8px 18px;
  font-size: 14px;
  box-shadow: var(--shadow);
  color: var(--muted);
}

.cta-row { display: flex; flex-wrap: wrap; gap: 12px; justify-content: center; margin-top: 22px; }
.cta {
  display: inline-block;
  text-decoration: none;
  font-family: 'Baloo 2', sans-serif;
  font-weight: 800;
  font-size: 19px;
  padding: 15px 30px;
  border-radius: 14px;
  min-height: 54px;
  color: #fff;
  background: linear-gradient(180deg, #34d399, #10b981);
  box-shadow: 0 8px 24px rgba(16, 185, 129, 0.4);
}
.cta--ghost { background: #fff; color: var(--blue-dark); box-shadow: var(--shadow); }
.cta:active { transform: scale(0.98); }

/* Sections */
section { margin-top: 34px; }
h2 {
  font-family: 'Baloo 2', sans-serif;
  font-weight: 800;
  font-size: clamp(22px, 5vw, 28px);
  color: var(--blue-dark);
  margin-bottom: 12px;
}
h3 { font-family: 'Baloo 2', sans-serif; font-weight: 700; font-size: 18px; margin-bottom: 4px; }

.card {
  background: var(--card);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
  padding: 20px;
}
.card + .card { margin-top: 12px; }

p { margin-bottom: 10px; }
ul { margin: 8px 0 8px 22px; }
li { margin-bottom: 6px; }

/* 3 nguyên tắc */
.principles { display: grid; gap: 12px; grid-template-columns: repeat(auto-fit, minmax(200px, 1fr)); }
.principle {
  background: #fff;
  border-radius: var(--radius);
  box-shadow: var(--shadow);
  padding: 18px;
  border-top: 5px solid var(--blue);
}
.principle:nth-child(1) { border-top-color: #60a5fa; }
.principle:nth-child(2) { border-top-color: #34d399; }
.principle:nth-child(3) { border-top-color: #f87171; }
.principle .icon { font-size: 30px; }
.principle p { color: var(--muted); font-size: 14px; margin-bottom: 0; }

/* Bước chơi */
.steps { display: flex; flex-direction: column; gap: 10px; }
.step { display: flex; gap: 12px; align-items: flex-start; }
.step__num {
  flex: 0 0 34px;
  width: 34px; height: 34px;
  border-radius: 50%;
  background: var(--blue);
  color: #fff;
  display: flex; align-items: center; justify-content: center;
  font-family: 'Baloo 2', sans-serif; font-weight: 800;
}

/* FAQ */
details.faq {
  background: #fff;
  border-radius: 14px;
  box-shadow: var(--shadow);
  padding: 14px 18px;
  margin-bottom: 10px;
}
details.faq summary {
  font-weight: 700;
  cursor: pointer;
  font-size: 16px;
  list-style: none;
}
details.faq summary::-webkit-details-marker { display: none; }
details.faq summary::before { content: '➕ '; color: var(--blue); }
details.faq[open] summary::before { content: '➖ '; }
details.faq p { margin-top: 8px; color: #334155; font-size: 15px; }

/* Author */
.author {
  display: flex; align-items: center; gap: 14px;
  background: #fff; border-radius: var(--radius); box-shadow: var(--shadow); padding: 16px;
}
.author__avatar { font-size: 42px; }
.author__name { font-weight: 800; color: var(--blue-dark); }
.author__meta { font-size: 14px; color: var(--muted); }

/* Footer */
footer {
  margin-top: 40px;
  text-align: center;
  color: var(--muted);
  font-size: 13px;
  padding-top: 20px;
  border-top: 1px solid rgba(20,40,90,0.08);
}
footer a { color: var(--blue-dark); font-weight: 700; text-decoration: none; }
.footer-nav { display: flex; gap: 16px; justify-content: center; flex-wrap: wrap; margin-bottom: 10px; }

.badge {
  display: inline-block;
  background: #fff;
  border-radius: 999px;
  padding: 4px 12px;
  font-size: 13px;
  font-weight: 700;
  color: var(--blue-dark);
  box-shadow: var(--shadow);
  margin: 0 4px 6px 0;
}