/* =============================================
   DESIGN TOKENS & GLOBAL STYLES
   TESOL Vietnam 2026
   ============================================= */

@import url('https://fonts.googleapis.com/css2?family=Inter:wght@300;400;500;600;700&family=Outfit:wght@300;400;500;600;700;800;900&family=Playfair+Display:ital,wght@0,400;0,500;0,600;0,700;1,400;1,500&display=swap');

/* --- CSS Variables --- */
:root {
  /* Colors */
  --color-primary: #1A3C6E;
  --color-primary-dark: #0F2548;
  --color-primary-light: #2A5298;
  --color-accent: #F5A623;
  --color-accent-dark: #D4891A;
  --color-accent-light: #FFB84D;
  --color-white: #FFFFFF;
  --color-black: #0A0A0A;
  --color-gray-50: #F9FAFB;
  --color-gray-100: #F3F4F6;
  --color-gray-200: #E5E7EB;
  --color-gray-300: #D1D5DB;
  --color-gray-400: #9CA3AF;
  --color-gray-500: #6B7280;
  --color-gray-600: #4B5563;
  --color-gray-700: #374151;
  --color-gray-800: #1F2937;
  --color-gray-900: #111827;

  /* Typography */
  --font-body: 'Inter', -apple-system, BlinkMacSystemFont, sans-serif;
  --font-heading: 'Outfit', sans-serif;
  --font-display: 'Playfair Display', Georgia, serif;

  /* Font Sizes */
  --text-xs: 0.75rem;
  --text-sm: 0.875rem;
  --text-base: 1rem;
  --text-lg: 1.125rem;
  --text-xl: 1.25rem;
  --text-2xl: 1.5rem;
  --text-3xl: 1.875rem;
  --text-4xl: 2.25rem;
  --text-5xl: 3rem;
  --text-6xl: 3.75rem;
  --text-7xl: 4.5rem;

  /* Spacing */
  --space-1: 0.25rem;
  --space-2: 0.5rem;
  --space-3: 0.75rem;
  --space-4: 1rem;
  --space-5: 1.25rem;
  --space-6: 1.5rem;
  --space-8: 2rem;
  --space-10: 2.5rem;
  --space-12: 3rem;
  --space-16: 4rem;
  --space-20: 5rem;
  --space-24: 6rem;
  --space-32: 8rem;

  /* Border Radius */
  --radius-sm: 4px;
  --radius-md: 8px;
  --radius-lg: 12px;
  --radius-xl: 16px;
  --radius-2xl: 24px;
  --radius-full: 9999px;

  /* Shadows */
  --shadow-sm: 0 1px 2px rgba(0, 0, 0, 0.05);
  --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.1), 0 2px 4px -1px rgba(0, 0, 0, 0.06);
  --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.1), 0 4px 6px -2px rgba(0, 0, 0, 0.05);
  --shadow-xl: 0 20px 25px -5px rgba(0, 0, 0, 0.1), 0 10px 10px -5px rgba(0, 0, 0, 0.04);
  --shadow-2xl: 0 25px 50px -12px rgba(0, 0, 0, 0.25);
  --shadow-inner: inset 0 2px 4px rgba(0, 0, 0, 0.06);
  --shadow-card: 0 8px 32px rgba(0, 0, 0, 0.08);
  --shadow-card-hover: 0 16px 48px rgba(0, 0, 0, 0.14);

  /* Transitions */
  --transition-fast: 150ms ease;
  --transition-base: 250ms ease;
  --transition-slow: 400ms ease;
  --transition-spring: 300ms cubic-bezier(0.34, 1.56, 0.64, 1);

  /* Layout */
  --container-max: 1280px;
  --container-padding: 1.5rem;
  --header-height: 80px;
}

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

html {
  scroll-behavior: smooth;
  font-size: 16px;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

body {
  font-family: var(--font-body);
  font-size: var(--text-base);
  line-height: 1.6;
  color: var(--color-gray-800);
  background-color: var(--color-white);
  overflow-x: hidden;
}

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

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

ul, ol {
  list-style: none;
}

button {
  cursor: pointer;
  border: none;
  background: none;
  font-family: inherit;
}

input, textarea, select {
  font-family: inherit;
}

/* --- Container --- */
.container {
  max-width: var(--container-max);
  margin: 0 auto;
  padding: 0 var(--container-padding);
}

/* --- Section Spacing --- */
.section {
  padding: var(--space-24) 0;
}

.section--lg {
  padding: var(--space-32) 0;
}

.section--sm {
  padding: var(--space-16) 0;
}

/* --- Section Labels --- */
.section-label {
  display: inline-flex;
  align-items: center;
  gap: var(--space-2);
  font-family: var(--font-heading);
  font-size: var(--text-sm);
  font-weight: 600;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  color: var(--color-accent);
  margin-bottom: var(--space-4);
}

.section-label::before {
  content: '';
  width: 24px;
  height: 2px;
  background: var(--color-accent);
  border-radius: 2px;
}

/* --- Typography --- */
.heading-xl {
  font-family: var(--font-heading);
  font-size: clamp(var(--text-4xl), 5vw, var(--text-7xl));
  font-weight: 800;
  line-height: 1.1;
  letter-spacing: -0.02em;
  color: var(--color-white);
}

.heading-lg {
  font-family: var(--font-heading);
  font-size: clamp(var(--text-3xl), 4vw, var(--text-5xl));
  font-weight: 700;
  line-height: 1.2;
  letter-spacing: -0.02em;
  color: var(--color-gray-900);
}

.heading-md {
  font-family: var(--font-heading);
  font-size: clamp(var(--text-2xl), 3vw, var(--text-4xl));
  font-weight: 700;
  line-height: 1.25;
  letter-spacing: -0.01em;
  color: var(--color-gray-900);
}

.heading-sm {
  font-family: var(--font-heading);
  font-size: clamp(var(--text-xl), 2vw, var(--text-2xl));
  font-weight: 600;
  line-height: 1.35;
  color: var(--color-gray-900);
}

.text-accent {
  color: var(--color-accent);
}

.text-primary {
  color: var(--color-primary);
}

.text-muted {
  color: var(--color-gray-500);
}

/* --- Buttons --- */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: var(--space-2);
  padding: 0.875rem 2rem;
  font-family: var(--font-heading);
  font-size: var(--text-sm);
  font-weight: 600;
  letter-spacing: 0.02em;
  border-radius: var(--radius-full);
  transition: all var(--transition-base);
  cursor: pointer;
  border: 2px solid transparent;
  white-space: nowrap;
}

.btn-primary {
  background: var(--color-accent);
  color: var(--color-white);
  border-color: var(--color-accent);
  box-shadow: 0 4px 15px rgba(245, 166, 35, 0.4);
}

.btn-primary:hover {
  background: var(--color-accent-dark);
  border-color: var(--color-accent-dark);
  transform: translateY(-2px);
  box-shadow: 0 8px 25px rgba(245, 166, 35, 0.5);
}

.btn-outline {
  background: transparent;
  color: var(--color-white);
  border-color: rgba(255, 255, 255, 0.5);
}

.btn-outline:hover {
  background: rgba(255, 255, 255, 0.1);
  border-color: var(--color-white);
  transform: translateY(-2px);
}

.btn-outline-dark {
  background: transparent;
  color: var(--color-primary);
  border-color: var(--color-primary);
}

.btn-outline-dark:hover {
  background: var(--color-primary);
  color: var(--color-white);
  transform: translateY(-2px);
}

.btn-lg {
  padding: 1.125rem 2.5rem;
  font-size: var(--text-base);
}

.btn-sm {
  padding: 0.625rem 1.25rem;
  font-size: var(--text-xs);
}

/* --- Animations --- */
@keyframes fadeInUp {
  from {
    opacity: 0;
    transform: translateY(30px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

@keyframes fadeIn {
  from { opacity: 0; }
  to { opacity: 1; }
}

@keyframes slideInLeft {
  from {
    opacity: 0;
    transform: translateX(-30px);
  }
  to {
    opacity: 1;
    transform: translateX(0);
  }
}

@keyframes pulse {
  0%, 100% { transform: scale(1); }
  50% { transform: scale(1.05); }
}

@keyframes shimmer {
  0% { background-position: -200% center; }
  100% { background-position: 200% center; }
}

/* Scroll-triggered animations */
.fade-in {
  opacity: 0;
  transform: translateY(25px);
  transition: opacity 0.7s ease, transform 0.7s ease;
}

.fade-in.visible {
  opacity: 1;
  transform: translateY(0);
}

.fade-in-left {
  opacity: 0;
  transform: translateX(-25px);
  transition: opacity 0.7s ease, transform 0.7s ease;
}

.fade-in-left.visible {
  opacity: 1;
  transform: translateX(0);
}

.fade-in-right {
  opacity: 0;
  transform: translateX(25px);
  transition: opacity 0.7s ease, transform 0.7s ease;
}

.fade-in-right.visible {
  opacity: 1;
  transform: translateX(0);
}

.delay-1 { transition-delay: 0.1s; }
.delay-2 { transition-delay: 0.2s; }
.delay-3 { transition-delay: 0.3s; }
.delay-4 { transition-delay: 0.4s; }
.delay-5 { transition-delay: 0.5s; }
.delay-6 { transition-delay: 0.6s; }

/* --- Dividers --- */
.divider {
  width: 60px;
  height: 4px;
  background: linear-gradient(90deg, var(--color-accent), var(--color-accent-light));
  border-radius: 2px;
  margin: var(--space-4) 0;
}

.divider--center {
  margin: var(--space-4) auto;
}

/* --- Background Utilities --- */
.bg-primary { background-color: var(--color-primary); }
.bg-dark { background-color: var(--color-gray-900); }
.bg-light { background-color: var(--color-gray-50); }
.bg-accent { background-color: var(--color-accent); }

/* --- Tag / Badge --- */
.tag {
  display: inline-flex;
  align-items: center;
  padding: 0.25rem 0.875rem;
  background: rgba(245, 166, 35, 0.12);
  color: var(--color-accent-dark);
  border: 1px solid rgba(245, 166, 35, 0.3);
  border-radius: var(--radius-full);
  font-size: var(--text-xs);
  font-weight: 600;
  letter-spacing: 0.05em;
  text-transform: uppercase;
}

/* --- Grid Layouts --- */
.grid-2 {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: var(--space-8);
}

.grid-3 {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: var(--space-8);
}

.grid-4 {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: var(--space-6);
}

@media (max-width: 1024px) {
  .grid-4 { grid-template-columns: repeat(2, 1fr); }
  .grid-3 { grid-template-columns: repeat(2, 1fr); }
}

@media (max-width: 768px) {
  .grid-2, .grid-3, .grid-4 { grid-template-columns: 1fr; }

  :root {
    --container-padding: 1.25rem;
  }

  .section { padding: var(--space-16) 0; }
  .section--lg { padding: var(--space-20) 0; }
}

/* --- Scroll Indicator --- */
.scroll-indicator {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: var(--space-2);
  cursor: pointer;
}

.scroll-indicator__mouse {
  width: 24px;
  height: 38px;
  border: 2px solid rgba(255, 255, 255, 0.5);
  border-radius: 12px;
  display: flex;
  align-items: flex-start;
  justify-content: center;
  padding-top: 6px;
}

.scroll-indicator__dot {
  width: 4px;
  height: 8px;
  background: rgba(255, 255, 255, 0.7);
  border-radius: 2px;
  animation: scrollDot 2s infinite;
}

@keyframes scrollDot {
  0% { transform: translateY(0); opacity: 1; }
  75% { transform: translateY(10px); opacity: 0; }
  100% { transform: translateY(0); opacity: 0; }
}

.scroll-indicator__text {
  font-size: var(--text-xs);
  color: rgba(255, 255, 255, 0.5);
  letter-spacing: 0.1em;
  text-transform: uppercase;
}