@import url('https://fonts.googleapis.com/css2?family=Noto+Sans+SC:wght@300;400;500;700&display=swap');

:root {
  --color-primary: #000000;
  --color-secondary: #333333;
  --color-accent: #1e3a8a;
  --color-background: #ffffff;
  --color-surface: #f8f9fa;
  --color-text: #212529;
  --color-text-muted: #6c757d;
  
  --font-family-sans: 'Noto Sans SC', -apple-system, BlinkMacSystemFont, sans-serif;
  --font-weight-light: 300;
  --font-weight-normal: 400;
  --font-weight-medium: 500;
  --font-weight-bold: 700;
  
  --spacing-xs: 0.25rem;
  --spacing-sm: 0.5rem;
  --spacing-md: 1rem;
  --spacing-lg: 1.5rem;
  --spacing-xl: 3rem;
  
  --border-radius-sm: 0.25rem;
  --border-radius-md: 0.5rem;
  --border-radius-lg: 0.75rem;
  
  --shadow-sm: 0 1px 3px rgba(0, 0, 0, 0.1);
  --shadow-md: 0 4px 6px rgba(0, 0, 0, 0.1);
  --shadow-lg: 0 10px 15px rgba(0, 0, 0, 0.1);
}

* {
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
}

body {
  font-family: var(--font-family-sans);
  font-weight: var(--font-weight-normal);
  color: var(--color-text);
  background-color: var(--color-background);
  line-height: 1.6;
  margin: 0;
  padding: 0;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

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

a {
  color: var(--color-accent);
  text-decoration: none;
  transition: color 0.2s ease;
}

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

h1, h2, h3, h4, h5, h6 {
  font-weight: var(--font-weight-bold);
  line-height: 1.2;
  margin-top: 0;
  margin-bottom: var(--spacing-md);
}

p {
  margin-top: 0;
  margin-bottom: var(--spacing-md);
}

.container {
  width: 100%;
  max-width: 1200px;
  margin: 0 auto;
  padding: 0 var(--spacing-md);
}

@media (min-width: 768px) {
  .container {
    padding: 0 var(--spacing-lg);
  }
}

.text-center {
  text-align: center;
}

.flex {
  display: flex;
}

.items-center {
  align-items: center;
}

.justify-between {
  justify-content: space-between;
}

.space-x-6 > * + * {
  margin-left: var(--spacing-lg);
}

.grid {
  display: grid;
}

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

.gap-8 {
  gap: var(--spacing-xl);
}

@media (min-width: 768px) {
  .md\:grid-cols-3 {
    grid-template-columns: repeat(3, minmax(0, 1fr));
  }
}

.rounded-lg {
  border-radius: var(--border-radius-lg);
}

.shadow-sm {
  box-shadow: var(--shadow-sm);
}

.shadow-md {
  box-shadow: var(--shadow-md);
}

.shadow-lg {
  box-shadow: var(--shadow-lg);
}

.bg-white {
  background-color: var(--color-background);
}

.bg-gray-100 {
  background-color: var(--color-surface);
}

.bg-gray-900 {
  background-color: var(--color-primary);
}

.bg-blue-600 {
  background-color: var(--color-accent);
}

.text-white {
  color: #ffffff;
}

.text-gray-900 {
  color: var(--color-primary);
}

.text-gray-700 {
  color: var(--color-secondary);
}

.text-xl {
  font-size: 1.25rem;
}

.text-2xl {
  font-size: 1.5rem;
}

.text-3xl {
  font-size: 1.875rem;
}

.text-4xl {
  font-size: 2.25rem;
}

.text-5xl {
  font-size: 3rem;
}

.font-bold {
  font-weight: var(--font-weight-bold);
}

.font-medium {
  font-weight: var(--font-weight-medium);
}

.py-4 {
  padding-top: var(--spacing-md);
  padding-bottom: var(--spacing-md);
}

.py-8 {
  padding-top: var(--spacing-xl);
  padding-bottom: var(--spacing-xl);
}

.py-16 {
  padding-top: calc(var(--spacing-xl) * 2);
  padding-bottom: calc(var(--spacing-xl) * 2);
}

.px-4 {
  padding-left: var(--spacing-md);
  padding-right: var(--spacing-md);
}

.px-6 {
  padding-left: calc(var(--spacing-md) * 1.5);
  padding-right: calc(var(--spacing-md) * 1.5);
}

.px-8 {
  padding-left: var(--spacing-xl);
  padding-right: var(--spacing-xl);
}

.mb-2 {
  margin-bottom: var(--spacing-sm);
}

.mb-4 {
  margin-bottom: var(--spacing-md);
}

.mb-6 {
  margin-bottom: calc(var(--spacing-md) * 1.5);
}

.mb-8 {
  margin-bottom: var(--spacing-xl);
}

.mb-12 {
  margin-bottom: calc(var(--spacing-xl) * 1.5);
}

.mt-0 {
  margin-top: 0;
}

.h-screen {
  height: 100vh;
}

.h-64 {
  height: 16rem;
}

.h-96 {
  height: 24rem;
}

.relative {
  position: relative;
}

.hover\:text-blue-600:hover {
  color: var(--color-accent);
}

.hover\:bg-blue-700:hover {
  background-color: #1e40af;
}

.transition {
  transition-property: color, background-color, border-color, text-decoration-color, fill, stroke, opacity, box-shadow, transform, filter, backdrop-filter;
  transition-timing-function: cubic-bezier(0.4, 0, 0.2, 1);
  transition-duration: 150ms;
}

.duration-200 {
  transition-duration: 200ms;
}

footer {
  margin-top: auto;
}

nav a {
  position: relative;
}

nav a::after {
  content: '';
  position: absolute;
  bottom: -2px;
  left: 0;
  width: 0;
  height: 1px;
  background-color: var(--color-accent);
  transition: width 0.2s ease;
}

nav a:hover::after {
  width: 100%;
}

.card {
  background-color: var(--color-surface);
  border-radius: var(--border-radius-lg);
  padding: var(--spacing-xl);
  transition: transform 0.2s ease, box-shadow 0.2s ease;
}

.card:hover {
  transform: translateY(-4px);
  box-shadow: var(--shadow-lg);
}

.hero {
  background: linear-gradient(135deg, var(--color-primary) 0%, var(--color-secondary) 100%);
  color: white;
  position: relative;
  overflow: hidden;
}

.hero::before {
  content: '';
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  background: url('https://hpi-hub.tos-cn-beijing.volces.com/static/batch_17/1757536741276-3475.jpg') center/cover;
  opacity: 0.2;
  z-index: 0;
}

.hero-content {
  position: relative;
  z-index: 1;
}

.btn {
  display: inline-block;
  padding: var(--spacing-sm) var(--spacing-lg);
  border-radius: var(--border-radius-md);
  font-weight: var(--font-weight-medium);
  text-align: center;
  transition: all 0.2s ease;
}

.btn-primary {
  background-color: var(--color-accent);
  color: white;
}

.btn-primary:hover {
  background-color: #1e40af;
  transform: translateY(-2px);
  box-shadow: var(--shadow-md);
}

.fade-in {
  animation: fadeIn 0.6s ease-in;
}

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