/* =========================
   VARIABLES
========================= */
:root {
  /* COLORS */
  --primary-color: #4da6ff;       /* xanh dương sáng */
  --primary-light: #80c1ff;       /* xanh da trời nhạt */
  --primary-dark: #006bb3;        /* xanh dương đậm */
  --secondary-color: #1a75ff;     /* xanh nhấn */
  --secondary-light: #66b3ff;     /* xanh nhạt hơn */
  --accent-color: #99ccff;        /* nhấn phụ */

  --bg-dark: #e6f2ff;             /* nền sáng xanh nhạt */
  --bg-overlay-1: rgba(230,242,255,0.65);
  --bg-overlay-2: rgba(220,235,255,0.85);
  --bg-soft: #f0f8ff;

  --card-bg: rgba(255,255,255,0.85);  /* nền card trắng mờ */
  --card-soft: rgba(77,166,255,0.05);
  --card-hover: rgba(77,166,255,0.08);
  --card-border: rgba(77,166,255,0.28);

  --text-color: #0a1f3d;          /* chữ tối trên nền sáng */
  --text-soft: #1a3d66;           /* chữ phụ */
  --text-muted: #4d79b3;

  --white: #ffffff;
  --danger-soft: #ffb4b4;

  /* SHADOWS */
  --shadow: 0 8px 24px rgba(0,0,0,0.18);
  --shadow-hover: 0 14px 30px rgba(0,0,0,0.25);
  --gold-glow: 0 0 18px rgba(77,166,255,0.3);

  /* BORDER RADIUS & TRANSITION */
  --radius-sm: 10px;
  --radius-md: 14px;
  --radius-lg: 18px;
  --transition: all 0.3s ease;

  /* CONTAINER */
  --container-width: 1200px;
}

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

html {
  scroll-behavior: smooth;
}

body {
  font-family: 'Arial', sans-serif;
  font-size:16px;
  line-height:1.65;
  color: var(--text-color);
  background:
    linear-gradient(var(--bg-overlay-1), var(--bg-overlay-2)),
    url("https://images.unsplash.com/photo-1507525428034-b723cf961d3e") no-repeat center center fixed;
  background-size: cover;
}

img {
  max-width:100%;
  display:block;
}

a {
  color: var(--primary-color);
  text-decoration: none;
  transition: var(--transition);
}

a:hover {
  color: var(--primary-light);
}

p {
  margin-bottom:1rem;
}

.container {
  width:min(92%, var(--container-width));
  margin:0 auto;
}

/* =========================
   HEADER
========================= */
.site-header {
  position: sticky;
  top:0;
  z-index:1000;
  width:100%;
  background: rgba(240,248,255,0.95);
  backdrop-filter: blur(8px);
  box-shadow: var(--shadow);
  border-bottom: 1px solid var(--card-border);
}

.header-inner {
  min-height: 82px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap:24px;
}

.logo {
  font-size:30px;
  font-weight:700;
  color: var(--primary-color);
  text-shadow: 0 0 8px rgba(77,166,255,0.3);
}

.logo:hover {
  color: var(--primary-light);
}

.menu-icon {
  display:none;
  background:none;
  border:none;
  color: var(--primary-color);
  font-size:30px;
  cursor:pointer;
}

.menu-icon:hover {
  color: var(--primary-light);
}

.navbar {
  flex:1;
  display:flex;
  justify-content:flex-end;
}

.nav-list {
  list-style:none;
  display:flex;
  align-items:center;
  gap:8px;
}

.nav-list li a {
  display:block;
  padding:11px 15px;
  border-radius: var(--radius-sm);
  color: var(--primary-dark);
  font-size:15px;
  font-weight:700;
  transition: var(--transition);
}

.nav-list li a:hover {
  background: linear-gradient(135deg, var(--primary-light), var(--primary-color));
  color:#ffffff;
  box-shadow: var(--gold-glow);
  transform: translateY(-2px);
}

/* =========================
   MAIN CONTENT
========================= */
.main-content {
  padding:50px 0 80px;
}

.section-card,
.cta {
  padding:28px;
  border-radius: var(--radius-lg);
  background: linear-gradient(180deg, rgba(240,248,255,0.92), rgba(220,235,255,0.9));
  border:1px solid var(--card-border);
  box-shadow: var(--shadow);
  backdrop-filter: blur(8px);
}

.section-title {
  margin-bottom:12px;
  text-align:center;
  font-size:clamp(1.5rem,3vw,2rem);
  color: var(--primary-color);
  text-shadow: 0 0 6px rgba(77,166,255,0.2);
}

.section-subtitle,
.lead-text {
  margin-bottom:20px;
  text-align:center;
  color: var(--text-soft);
}

/* =========================
   GRIDS
========================= */
.reward-grid,
.info-grid,
.feature-grid,
.activity-grid,
.gallery {
  display:grid;
  gap:16px;
}

.reward-grid-5 {
  grid-template-columns: repeat(5, minmax(0,1fr));
}

.info-grid-4 {
  grid-template-columns: repeat(4, minmax(0,1fr));
}

.feature-grid,
.activity-grid {
  grid-template-columns: repeat(auto-fit, minmax(220px,1fr));
}

.reward-item,
.info-item,
.feature-item,
.activity-item {
  height:100%;
  padding:18px;
  border-radius: var(--radius-md);
  background: var(--card-soft);
  border:1px solid rgba(77,166,255,0.1);
  transition: var(--transition);
}

.reward-item:hover,
.info-item:hover,
.feature-item:hover,
.activity-item:hover {
  transform: translateY(-3px);
  box-shadow: var(--gold-glow), var(--shadow-hover);
  background: var(--card-hover);
}

.reward-item h3,
.info-item .label,
.sub-title {
  color: var(--primary-light);
}

/* =========================
   BUTTONS
========================= */
.btn {
  display:inline-flex;
  align-items:center;
  justify-content:center;
  min-height:48px;
  padding:0.85rem 1.5rem;
  border-radius:999px;
  font-weight:700;
  text-decoration:none;
  box-shadow: var(--shadow);
  transition: var(--transition);
}

.btn-primary {
  background: linear-gradient(135deg, var(--primary-light), var(--primary-color));
  color:#ffffff;
}

.btn-primary:hover {
  color:#e6f2ff;
  filter: brightness(1.08);
  box-shadow: 0 6px 20px rgba(77,166,255,0.4);
  transform: translateY(-2px);
}

.btn-secondary {
  background: linear-gradient(135deg, #3399ff, #1a75ff);
  color: #ffffff;
}

.btn-secondary:hover {
  background: linear-gradient(135deg, var(--primary-color), #3399ff);
  color:#e6f2ff;
  transform: translateY(-2px) scale(1.02);
}

/* =========================
   GALLERY
========================= */
.gallery img {
  width:100%;
  height:240px;
  object-fit:cover;
  border-radius: var(--radius-md);
  border:1px solid rgba(77,166,255,0.18);
  box-shadow: var(--shadow);
  transition: var(--transition);
}

.gallery img:hover {
  transform: scale(1.03);
}

/* =========================
   TABLES
========================= */
.download-table {
  width:100%;
  border-collapse:collapse;
  background: rgba(255,255,255,0.85);
  border:1px solid rgba(77,166,255,0.2);
  border-radius:12px;
  overflow:hidden;
}

.download-table th,
.download-table td {
  padding:14px 16px;
  text-align:left;
  border-bottom:1px solid rgba(0,0,0,0.05);
  color: var(--text-soft);
}

.download-table th {
  background: rgba(77,166,255,0.14);
  color: var(--primary-dark);
  font-weight:700;
}

.download-table tr:hover td {
  background: rgba(77,166,255,0.05);
}

/* =========================
   FOOTER
========================= */
.site-footer {
  margin-top:40px;
  background: rgba(230,242,255,0.95);
  border-top:1px solid rgba(77,166,255,0.14);
}

.footer-bar {
  height:4px;
  background: linear-gradient(to right, #1a75ff, #4da6ff, #80c1ff, #1a75ff);
}

.footer-content {
  padding:30px 0;
  text-align:center;
  color: var(--text-soft);
  font-size:15px;
}

/* =========================
   RESPONSIVE
========================= */
@media (max-width:1200px) {
  .reward-grid-5 { grid-template-columns: repeat(3,1fr); }
}

@media (max-width:1100px) {
  .gallery { grid-template-columns: repeat(2,1fr); }
  .content-grid { grid-template-columns:1fr; }
}

@media (max-width:992px) {
  .intro-wrap { grid-template-columns:1fr; }
  .reward-grid-5 { grid-template-columns: repeat(2,1fr); }
  .info-grid-4 { grid-template-columns: repeat(2,1fr); }

  .header-inner { flex-wrap: wrap; padding:14px 0; }
  .menu-icon { display:block; }
  .navbar { display:none; width:100%; flex:0 0 100%; }
  .navbar.active { display:block; }
  .nav-list { flex-direction: column; align-items:stretch; gap:0; margin-top:10px; }
  .nav-list li a { width:100%; padding:14px 16px; border-radius:0; border-top:1px solid rgba(0,0,0,0.05); }
}

@media (max-width:768px) {
  .main-content { padding:35px 0 60px; }
  .section-card, .cta { padding:20px; }
  .reward-grid-5, .info-grid-4, .feature-grid, .activity-grid, .gallery { grid-template-columns:1fr; }
  .hero-actions, .cta-actions { flex-direction:column; }
  .btn { width:100%; }
}

@media (max-width:576px) {
  body { font-size:14px; }
  .logo { font-size:22px; }
  .section-title { font-size:1.35rem; }
  .gallery img { height:220px; }
  .footer-content { font-size:14px; }
}

/* =========================
   ACTIVITY TABLE
========================= */
.activity-title {
    text-align: center;
    color: #1a75ff;
    font-size: 2rem;
    margin-bottom: 20px;
}

.activity-section {
    overflow-x: auto;
}

.activity-table {
    width: 100%;
    border-collapse: collapse;
    background-color: #e6f2ff;
    box-shadow: 0 4px 8px rgba(0,0,0,0.05);
    border-radius: 8px;
    overflow: hidden;
}

.activity-table th,
.activity-table td {
    padding: 12px 15px;
    text-align: center;
    font-size: 0.95rem;
    border-bottom: 1px solid #d0e6ff;
}

.activity-table th {
    background-color: #4da6ff;
    color: #ffffff;
    font-weight: bold;
    text-transform: uppercase;
}

.activity-table tbody tr:nth-child(even) {
    background-color: #cce6ff;
}

.activity-table tbody tr:hover {
    background-color: #99ccff;
}

.activity-table td {
    color: #0a1f3d;
}

@media (max-width: 768px) {
    .activity-table th,
    .activity-table td {
        padding: 10px;
        font-size: 0.85rem;
    }
}