:root {
  --bg: #070b0f;
  --bg-soft: #0d151c;
  --card: #111c25;
  --border: rgba(255, 255, 255, 0.08);
  --text: #e5e7eb;
  --dim: #9ca3af;
  --faint: #6b7280;
  --emerald: #10b981;
  --emerald-light: #34d399;
  --gold: #fbbf24;
  --sky: #38bdf8;
  --red: #ef4444;
}

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

html {
  scroll-behavior: smooth;
}

body {
  background:
    radial-gradient(1200px 600px at 80% -10%, rgba(16, 185, 129, 0.08), transparent 60%),
    radial-gradient(900px 500px at 10% 10%, rgba(56, 189, 248, 0.06), transparent 55%),
    var(--bg);
  color: var(--text);
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
  line-height: 1.6;
  min-height: 100vh;
  -webkit-font-smoothing: antialiased;
}

/* ---------- topbar ---------- */
.topbar {
  position: sticky;
  top: 0;
  z-index: 10;
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 14px 24px;
  background: rgba(7, 11, 15, 0.82);
  backdrop-filter: blur(12px);
  border-bottom: 1px solid var(--border);
}

.brand {
  display: flex;
  align-items: center;
  gap: 10px;
}

.brand-icon {
  font-size: 26px;
  color: var(--gold);
}

.brand-name {
  font-size: 20px;
  font-weight: 800;
  letter-spacing: 0.5px;
}

.gold {
  color: var(--gold);
}

.lang-btn {
  background: var(--bg-soft);
  border: 1px solid var(--border);
  color: var(--dim);
  border-radius: 10px;
  padding: 8px 14px;
  font-size: 14px;
  font-weight: 700;
  cursor: pointer;
  transition: all 0.15s;
}

.lang-btn:hover {
  color: var(--text);
  background: rgba(255, 255, 255, 0.08);
}

/* ---------- hero ---------- */
.hero {
  text-align: center;
  padding: 88px 24px 64px;
  max-width: 720px;
  margin: 0 auto;
}

.hero-title {
  font-size: clamp(44px, 9vw, 84px);
  font-weight: 900;
  letter-spacing: -1px;
  line-height: 1.05;
}

.tagline {
  color: var(--dim);
  font-size: clamp(16px, 3.4vw, 20px);
  margin-top: 18px;
  max-width: 520px;
  margin-left: auto;
  margin-right: auto;
}

.downloads {
  display: flex;
  flex-wrap: wrap;
  justify-content: center;
  gap: 14px;
  margin-top: 36px;
}

.btn {
  display: inline-flex;
  align-items: center;
  gap: 12px;
  padding: 14px 24px;
  border-radius: 14px;
  text-decoration: none;
  font-weight: 800;
  color: #fff;
  min-width: 230px;
  justify-content: center;
  border: 1px solid transparent;
  transition: transform 0.15s, box-shadow 0.15s;
}

.btn-icon {
  font-size: 22px;
}

.btn-store {
  display: block;
  font-size: 15px;
}

.btn-soon {
  display: block;
  font-size: 11px;
  opacity: 0.75;
  font-weight: 600;
}

.btn-android {
  background: linear-gradient(135deg, #0f9d58, #1b7f3f);
  box-shadow: 0 8px 24px rgba(15, 157, 88, 0.25);
}

.btn-ios {
  background: linear-gradient(135deg, #0ea5e9, #2563eb);
  box-shadow: 0 8px 24px rgba(14, 165, 233, 0.25);
}

.btn:hover {
  transform: translateY(-2px);
}

.btn[aria-disabled="true"] {
  cursor: not-allowed;
  opacity: 0.92;
}

.soon-note {
  color: var(--faint);
  font-size: 13px;
  margin-top: 16px;
}

/* ---------- sections ---------- */
.section {
  max-width: 920px;
  margin: 0 auto;
  padding: 32px 24px 40px;
}

.section-title {
  text-align: center;
  font-size: 26px;
  font-weight: 800;
  margin-bottom: 28px;
  color: var(--text);
}

.cards {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(240px, 1fr));
  gap: 16px;
}

.card {
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: 16px;
  padding: 28px 22px;
  text-align: center;
  transition: transform 0.15s, border-color 0.15s;
}

.card:hover {
  transform: translateY(-3px);
}

.card-cotuong { border-top: 3px solid #f59e0b; }
.card-chess { border-top: 3px solid var(--sky); }
.card-coup { border-top: 3px solid #c084fc; }

.card-icon {
  font-size: 44px;
  display: block;
  margin-bottom: 12px;
}

.card h3 {
  font-size: 19px;
  font-weight: 800;
  margin-bottom: 6px;
}

.card p {
  color: var(--dim);
  font-size: 14px;
}

/* ---------- features ---------- */
.features {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(240px, 1fr));
  gap: 16px;
}

.feature {
  background: var(--bg-soft);
  border: 1px solid var(--border);
  border-radius: 16px;
  padding: 24px 20px;
  text-align: center;
}

.feature-icon {
  font-size: 30px;
  display: block;
  margin-bottom: 10px;
}

.feature h3 {
  font-size: 16px;
  font-weight: 800;
  margin-bottom: 4px;
}

.feature p {
  color: var(--dim);
  font-size: 13.5px;
}

/* ---------- footer ---------- */
.footer {
  text-align: center;
  padding: 28px 16px 36px;
  color: var(--faint);
  font-size: 13px;
  border-top: 1px solid var(--border);
  margin-top: 24px;
}

@media (max-width: 480px) {
  .hero {
    padding-top: 56px;
  }
  .btn {
    min-width: 100%;
  }
  .topbar {
    padding: 12px 16px;
  }
}