/* Design system + base styles */
:root {
  --bg-primary: #f8fafc;
  --bg-secondary: #f1f5f9;
  --bg-card: #ffffff;
  --bg-card-hover: #ffffff;
  --text-primary: #0f172a;
  --text-secondary: #475569;
  --accent-1: #4f46e5; /* Indigo */
  --accent-2: #ec4899; /* Pink */
  --accent-3: #06b6d4; /* Cyan */
  --gradient-primary: linear-gradient(135deg, #4f46e5, #ec4899);
  --gradient-hot: linear-gradient(135deg, #f59e0b, #ec4899);
  --glow-purple: 0 10px 25px rgba(79, 70, 229, 0.25);
  --glow-cyan: 0 10px 25px rgba(236, 72, 153, 0.25);
  --border-radius: 12px;
  --transition: all 0.3s ease;
  --container-width: 1200px;
}

@import url('https://fonts.googleapis.com/css2?family=Inter:wght@400;500;600&family=Space+Grotesk:wght@600;700&display=swap');

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

html {
  scroll-behavior: smooth;
  font-size: 16px;
}

body {
  font-family: 'Inter', sans-serif;
  background-color: var(--bg-primary);
  color: var(--text-primary);
  overflow-x: hidden;
  scroll-behavior: smooth;
}

/* Hiệu ứng chuyển trang mượt mà */
body.page-transition {
    animation: fadeIn 0.5s ease-in-out;
}
@keyframes fadeIn {
    from { opacity: 0; transform: translateY(10px); }
    to { opacity: 1; transform: translateY(0); }
}

h1, h2, h3, h4, h5, h6 {
  font-family: 'Space Grotesk', sans-serif;
  font-weight: 700;
  line-height: 1.2;
  margin-bottom: 1rem;
}

p {
  margin-bottom: 1rem;
  color: var(--text-secondary);
}

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

ul {
  list-style: none;
}

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

/* Layout */
.container {
  max-width: var(--container-width);
  margin: 0 auto;
  padding: 0 2rem;
}

.section {
  padding: 5rem 0;
  min-height: 60vh;
}

/* Typography */
.section-header {
  text-align: center;
  margin-bottom: 4rem;
}

.section-title {
  font-size: 2.5rem;
  background: var(--gradient-primary);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  display: inline-block;
  margin-bottom: 0.5rem;
}

.section-subtitle {
  font-size: 1.1rem;
  color: var(--text-secondary);
  font-weight: 500;
}

/* Buttons */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  padding: 0.8rem 2rem;
  font-family: 'Space Grotesk', sans-serif;
  font-weight: 600;
  border-radius: var(--border-radius);
  cursor: pointer;
  transition: var(--transition);
  border: none;
  outline: none;
}

.btn-primary {
  background: var(--gradient-primary);
  color: #fff;
  box-shadow: var(--glow-purple);
}

.btn-primary:hover {
  box-shadow: var(--glow-cyan);
  transform: translateY(-3px);
}

.btn-secondary {
  background: transparent;
  color: var(--text-primary);
  border: 2px solid var(--accent-1);
}

.btn-secondary:hover {
  background: rgba(124, 58, 237, 0.1);
  box-shadow: var(--glow-purple);
  transform: translateY(-3px);
}

/* Scrollbar & Selection */
::-webkit-scrollbar {
  width: 10px;
}
::-webkit-scrollbar-track {
  background: var(--bg-primary);
}
::-webkit-scrollbar-thumb {
  background: var(--bg-card-hover);
  border-radius: 5px;
}
::-webkit-scrollbar-thumb:hover {
  background: var(--accent-1);
}

::selection {
  background: var(--accent-1);
  color: #fff;
}