/* ── Google Fonts ─────────────────────────────────────────────────────────── */
@import url('https://fonts.googleapis.com/css2?family=Inter:wght@400;500;600;700&display=swap');

/* ── Base typography ──────────────────────────────────────────────────────── */
body {
  font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
}

/* ── Navbar overrides ─────────────────────────────────────────────────────── */
.navbar {
  background: linear-gradient(135deg, #1a1f36 0%, #16213e 60%, #0f3460 100%) !important;
  box-shadow: 0 2px 16px rgba(0, 0, 0, 0.35);
  padding-top: 0.5rem;
  padding-bottom: 0.5rem;
  border-bottom: 1px solid rgba(255, 255, 255, 0.07);
}

/* Brand / site title */
.navbar-brand, .navbar-title {
  font-weight: 700;
  font-size: 1.1rem;
  letter-spacing: 0.02em;
  color: #e8eaf6 !important;
  transition: opacity 0.2s;
}
.navbar-brand:hover {
  opacity: 0.85;
}

/* Nav links */
.navbar-nav .nav-link {
  font-size: 0.875rem;
  font-weight: 500;
  color: rgba(232, 234, 246, 0.82) !important;
  padding: 0.4rem 0.75rem !important;
  border-radius: 6px;
  transition: color 0.2s ease, background 0.2s ease;
  white-space: nowrap;
}
.navbar-nav .nav-link:hover {
  color: #ffffff !important;
  background: rgba(255, 255, 255, 0.1);
}
.navbar-nav .nav-link.active {
  color: #90caf9 !important;
  background: rgba(144, 202, 249, 0.12);
}

/* ── Flag language switcher ───────────────────────────────────────────────── */
/* The two flag li items sit in .navbar-nav.ms-auto (quarto right toolbar) */
.quarto-navbar-tools .nav-item a,
#lang-btn-en,
#lang-btn-vn {
  font-size: 1.25rem;
  line-height: 1;
  padding: 0.25rem 0.45rem !important;
  border-radius: 6px;
  text-decoration: none !important;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  transition: transform 0.15s ease, background 0.2s ease, box-shadow 0.2s ease;
  cursor: pointer;
  border: 2px solid transparent;
}

#lang-btn-en:hover,
#lang-btn-vn:hover {
  transform: scale(1.15);
  background: rgba(255, 255, 255, 0.12);
}

/* Active language flag gets a glowing border */
li.lang-active > a,
li.lang-active > span {
  border: 2px solid rgba(144, 202, 249, 0.7) !important;
  background: rgba(144, 202, 249, 0.15) !important;
  box-shadow: 0 0 8px rgba(144, 202, 249, 0.4);
  transform: scale(1.1);
}

/* ── Navbar search icon ───────────────────────────────────────────────────── */
#quarto-search .quarto-search-button {
  color: rgba(232, 234, 246, 0.8) !important;
}
#quarto-search .quarto-search-button:hover {
  color: #ffffff !important;
}

/* ── Responsive mobile navbar ────────────────────────────────────────────── */
.navbar-toggler {
  border-color: rgba(255, 255, 255, 0.25) !important;
}
.navbar-toggler-icon {
  filter: invert(1);
}

/* ── TOC sidebar subtle styling ──────────────────────────────────────────── */
#TOC .nav-link {
  font-size: 0.85rem;
  color: #475569;
  transition: color 0.15s;
}
#TOC .nav-link:hover,
#TOC .nav-link.active {
  color: #1a237e;
  font-weight: 600;
}
#TOC .nav-link.active {
  border-left: 3px solid #3f51b5;
  padding-left: calc(0.5rem - 3px);
}