/* ==========================================================================
   TOANTEN — Modern Minimalist & Elegant Styling
   ========================================================================== */

:root {
  --bg-primary: #0a0e17;
  --bg-secondary: #111827;
  --bg-card: rgba(17, 24, 39, 0.7);
  --border-subtle: rgba(255, 255, 255, 0.08);
  --border-hover: rgba(56, 189, 248, 0.35);
  
  --accent-cyan: #38bdf8;
  --accent-blue: #6366f1;
  --accent-purple: #a855f7;
  --accent-amber: #f59e0b;
  --accent-emerald: #10b981;
  
  --text-primary: #f8fafc;
  --text-secondary: #94a3b8;
  --text-muted: #64748b;
  
  --nav-height: 74px;
  --font-sans: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
  --font-brand: 'Montserrat', var(--font-sans);
  
  --radius-lg: 20px;
  --radius-md: 14px;
  --radius-full: 9999px;
  
  --transition-smooth: all 0.35s cubic-bezier(0.4, 0, 0.2, 1);
}

/* Reset cơ bản */
*, *::before, *::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

html {
  scroll-behavior: smooth;
}

body {
  font-family: var(--font-sans);
  background-color: var(--bg-primary);
  color: var(--text-primary);
  line-height: 1.6;
  min-height: 100vh;
  display: flex;
  flex-direction: column;
  background-image: 
    radial-gradient(circle at 15% 15%, rgba(99, 102, 241, 0.12) 0%, transparent 40%),
    radial-gradient(circle at 85% 85%, rgba(56, 189, 248, 0.1) 0%, transparent 45%);
  background-attachment: fixed;
  overflow-x: hidden;
}

/* ==========================================================================
   Sticky Header / Navbar (Tối giản & Sang trọng)
   ========================================================================== */
.navbar {
  position: sticky;
  top: 0;
  left: 0;
  width: 100%;
  height: var(--nav-height);
  background: rgba(10, 14, 23, 0.82);
  backdrop-filter: blur(16px);
  -webkit-backdrop-filter: blur(16px);
  border-bottom: 1px solid var(--border-subtle);
  z-index: 1000;
  transition: var(--transition-smooth);
}

.nav-container {
  max-width: 1200px;
  height: 100%;
  margin: 0 auto;
  padding: 0 24px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 20px;
}

/* Logo & Thương hiệu bên trái */
.nav-brand {
  display: flex;
  align-items: center;
  gap: 14px;
  text-decoration: none;
  color: inherit;
  transition: transform 0.25s ease;
}

.nav-brand:hover {
  transform: translateY(-1px);
}

.logo-wrapper {
  position: relative;
  width: 44px;
  height: 44px;
  border-radius: var(--radius-full);
  padding: 2px;
  background: linear-gradient(135deg, var(--accent-cyan), var(--accent-blue));
  box-shadow: 0 0 16px rgba(56, 189, 248, 0.35);
}

.logo-img {
  width: 100%;
  height: 100%;
  border-radius: var(--radius-full);
  object-fit: cover;
  background: var(--bg-secondary);
  display: block;
}

.logo-status-dot {
  position: absolute;
  bottom: 0;
  right: 0;
  width: 11px;
  height: 11px;
  background: var(--accent-emerald);
  border: 2px solid var(--bg-primary);
  border-radius: var(--radius-full);
  box-shadow: 0 0 8px var(--accent-emerald);
}

.brand-text-group {
  display: flex;
  flex-direction: column;
}

.brand-name {
  font-family: var(--font-brand);
  font-weight: 900;
  font-size: 1.25rem;
  letter-spacing: 1.5px;
  background: linear-gradient(135deg, #ffffff 40%, var(--accent-cyan) 100%);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  text-shadow: 0 2px 10px rgba(56, 189, 248, 0.25);
}

.brand-tagline {
  font-size: 0.65rem;
  font-weight: 700;
  letter-spacing: 2px;
  color: var(--text-muted);
}

/* 5 Mục chọn "1", "2", "3", "4", "5" */
.nav-tabs {
  display: flex;
  align-items: center;
  gap: 10px;
  background: rgba(17, 24, 39, 0.7);
  padding: 6px 8px;
  border-radius: var(--radius-full);
  border: 1px solid var(--border-subtle);
  box-shadow: inset 0 2px 6px rgba(0, 0, 0, 0.4);
}

.nav-tab {
  position: relative;
  width: 42px;
  height: 42px;
  border-radius: var(--radius-full);
  border: 1px solid transparent;
  background: transparent;
  color: var(--text-secondary);
  font-family: var(--font-brand);
  font-size: 1.05rem;
  font-weight: 800;
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  outline: none;
  transition: var(--transition-smooth);
}

.nav-tab:hover {
  color: #ffffff;
  background: rgba(255, 255, 255, 0.06);
  transform: translateY(-2px);
}

/* Hiệu ứng Sáng Đèn (Active Glow) khi nút được chọn */
.nav-tab.active {
  color: #040812;
  background: linear-gradient(135deg, #38bdf8 0%, #818cf8 100%);
  border-color: rgba(255, 255, 255, 0.4);
  box-shadow: 
    0 0 20px rgba(56, 189, 248, 0.7),
    0 0 40px rgba(99, 102, 241, 0.35);
  transform: scale(1.08);
}

.nav-tab.active .tab-number {
  position: relative;
  z-index: 2;
  font-weight: 900;
}

/* ==========================================================================
   Main Content & 5 Section Panels
   ========================================================================== */
.main-content {
  flex: 1;
  max-width: 1200px;
  width: 100%;
  margin: 0 auto;
  padding: 48px 24px;
  display: flex;
  flex-direction: column;
  justify-content: center;
}

/* Khung nội dung (Panel) */
.content-panel {
  display: none;
  opacity: 0;
  transform: translateY(16px) scale(0.99);
  transition: opacity 0.4s ease, transform 0.4s ease;
  outline: none;
}

.content-panel.active {
  display: block;
  opacity: 1;
  transform: translateY(0) scale(1);
  animation: fadeInPanel 0.45s cubic-bezier(0.16, 1, 0.3, 1) forwards;
}

@keyframes fadeInPanel {
  from {
    opacity: 0;
    transform: translateY(20px) scale(0.98);
  }
  to {
    opacity: 1;
    transform: translateY(0) scale(1);
  }
}

.panel-inner {
  background: var(--bg-card);
  backdrop-filter: blur(20px);
  -webkit-backdrop-filter: blur(20px);
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-lg);
  padding: 56px 48px;
  box-shadow: 
    0 20px 40px -15px rgba(0, 0, 0, 0.5),
    0 0 50px -10px rgba(56, 189, 248, 0.08);
  position: relative;
  overflow: hidden;
}

.panel-inner::before {
  content: '';
  position: absolute;
  top: 0;
  left: 20%;
  right: 20%;
  height: 2px;
  background: linear-gradient(90deg, transparent, var(--accent-cyan), transparent);
}

/* Typography & Badges */
.badge {
  display: inline-block;
  font-size: 0.75rem;
  font-weight: 800;
  letter-spacing: 2px;
  padding: 6px 14px;
  border-radius: var(--radius-full);
  background: rgba(56, 189, 248, 0.15);
  border: 1px solid rgba(56, 189, 248, 0.3);
  color: var(--accent-cyan);
  margin-bottom: 20px;
}

.badge-cyan { background: rgba(56, 189, 248, 0.15); border-color: rgba(56, 189, 248, 0.4); color: var(--accent-cyan); }
.badge-purple { background: rgba(168, 85, 247, 0.15); border-color: rgba(168, 85, 247, 0.4); color: var(--accent-purple); }
.badge-amber { background: rgba(245, 158, 11, 0.15); border-color: rgba(245, 158, 11, 0.4); color: var(--accent-amber); }
.badge-emerald { background: rgba(16, 185, 129, 0.15); border-color: rgba(16, 185, 129, 0.4); color: var(--accent-emerald); }

.panel-title {
  font-family: var(--font-brand);
  font-size: 2.5rem;
  font-weight: 900;
  line-height: 1.25;
  margin-bottom: 16px;
  color: #ffffff;
}

.gradient-text {
  background: linear-gradient(135deg, var(--accent-cyan) 0%, #a855f7 100%);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
}

.panel-desc {
  font-size: 1.125rem;
  color: var(--text-secondary);
  max-width: 720px;
  margin-bottom: 40px;
  line-height: 1.7;
}

/* Cards & Placeholders */
.card-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
  gap: 24px;
}

.feature-card {
  background: rgba(255, 255, 255, 0.03);
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-md);
  padding: 30px;
  transition: var(--transition-smooth);
}

.feature-card:hover {
  transform: translateY(-4px);
  background: rgba(255, 255, 255, 0.05);
  border-color: var(--border-hover);
  box-shadow: 0 12px 30px -10px rgba(56, 189, 248, 0.2);
}

.card-icon {
  font-size: 2rem;
  margin-bottom: 16px;
}

.feature-card h3 {
  font-size: 1.2rem;
  font-weight: 700;
  margin-bottom: 8px;
  color: #ffffff;
}

.feature-card p {
  font-size: 0.95rem;
  color: var(--text-secondary);
}

.placeholder-box {
  background: rgba(255, 255, 255, 0.02);
  border: 2px dashed rgba(255, 255, 255, 0.1);
  border-radius: var(--radius-md);
  padding: 60px 24px;
  text-align: center;
}

.ph-circle {
  width: 64px;
  height: 64px;
  margin: 0 auto 20px;
  border-radius: var(--radius-full);
  background: rgba(56, 189, 248, 0.12);
  border: 2px solid var(--accent-cyan);
}

.ph-purple { background: rgba(168, 85, 247, 0.12); border-color: var(--accent-purple); }
.ph-amber { background: rgba(245, 158, 11, 0.12); border-color: var(--accent-amber); }

.placeholder-box h3 {
  font-size: 1.25rem;
  font-weight: 700;
  color: #ffffff;
  margin-bottom: 8px;
}

.placeholder-box p {
  color: var(--text-muted);
  font-size: 0.95rem;
}

/* Contact box Section 5 */
.contact-box {
  background: rgba(255, 255, 255, 0.03);
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-md);
  padding: 32px;
  display: flex;
  flex-direction: column;
  gap: 16px;
  max-width: 480px;
}

.contact-item {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding-bottom: 12px;
  border-bottom: 1px solid rgba(255, 255, 255, 0.05);
}

.contact-label {
  font-weight: 600;
  color: var(--text-muted);
}

.contact-value {
  color: var(--accent-cyan);
  text-decoration: none;
  font-weight: 600;
}

.contact-value:hover {
  text-decoration: underline;
}

.status-online {
  color: var(--accent-emerald);
}

/* ==========================================================================
   Footer
   ========================================================================== */
.footer {
  text-align: center;
  padding: 24px;
  font-size: 0.85rem;
  color: var(--text-muted);
  border-top: 1px solid var(--border-subtle);
}

/* ==========================================================================
   Responsive (Mobile & Tablet)
   ========================================================================== */
@media (max-width: 768px) {
  .nav-container {
    padding: 0 16px;
  }

  .brand-tagline {
    display: none;
  }

  .nav-tabs {
    gap: 6px;
    padding: 4px 6px;
  }

  .nav-tab {
    width: 36px;
    height: 36px;
    font-size: 0.95rem;
  }

  .panel-inner {
    padding: 36px 24px;
  }

  .panel-title {
    font-size: 1.85rem;
  }
}