/* Apple-inspired Design System */
:root {
  /* Colors */
  --color-black: #000000;
  --color-white: #ffffff;
  --color-gray-100: #fbfbfd;
  --color-gray-200: #f5f5f7;
  --color-gray-300: #e8e8ed;
  --color-gray-400: #d2d2d7;
  --color-gray-500: #86868b;
  --color-gray-600: #515154;
  --color-gray-700: #1d1d1f;
  
  /* Semantic colors */
  --color-primary: #0071e3;
  --color-primary-hover: #0077ed;
  --color-text-primary: #1d1d1f;
  --color-text-secondary: #86868b;
  --color-text-inverted: #f5f5f7;
  --color-background: #ffffff;
  --color-background-elevated: #fbfbfd;
  --color-border: rgba(0, 0, 0, 0.08);
  
  /* Typography */
  --font-body: -apple-system, BlinkMacSystemFont, "SF Pro Text", "SF Pro Icons", "Helvetica Neue", Helvetica, Arial, sans-serif;
  --font-display: "SF Pro Display", -apple-system, BlinkMacSystemFont, "Helvetica Neue", Helvetica, Arial, sans-serif;
  
  /* Spacing */
  --spacing-xs: 4px;
  --spacing-sm: 8px;
  --spacing-md: 16px;
  --spacing-lg: 24px;
  --spacing-xl: 32px;
  --spacing-2xl: 48px;
  --spacing-3xl: 64px;
  --spacing-4xl: 96px;
  
  /* Transitions */
  --transition-fast: 0.25s cubic-bezier(0.4, 0, 0.6, 1);
  --transition-medium: 0.35s cubic-bezier(0.4, 0, 0.6, 1);
  --transition-slow: 0.5s cubic-bezier(0.4, 0, 0.6, 1);
}

/* Dark theme */
[data-theme="dark"] {
  --color-text-primary: #f5f5f7;
  --color-text-secondary: #a1a1a6;
  --color-text-inverted: #1d1d1f;
  --color-background: #000000;
  --color-background-elevated: #1d1d1f;
  --color-border: rgba(255, 255, 255, 0.08);
}

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

html {
  font-size: 17px;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

body {
  font-family: var(--font-body);
  font-weight: 400;
  line-height: 1.47059;
  letter-spacing: -0.022em;
  color: var(--color-text-primary);
  background-color: var(--color-background);
  transition: background-color var(--transition-medium), color var(--transition-medium);
}

/* Typography */
h1, h2, h3, h4, h5, h6 {
  font-family: var(--font-display);
  font-weight: 600;
  letter-spacing: -0.015em;
  line-height: 1.08349;
}

h1 {
  font-size: 3.5rem;
  font-weight: 700;
  letter-spacing: -0.028em;
  line-height: 1.07143;
}

h2 {
  font-size: 2.5rem;
  line-height: 1.1;
}

h3 {
  font-size: 1.75rem;
  line-height: 1.14286;
}

p {
  font-size: 1.125rem;
  line-height: 1.55556;
  letter-spacing: -0.016em;
  color: var(--color-text-secondary);
}

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

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

/* Navigation */
.nav-global {
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  height: 44px;
  background-color: rgba(251, 251, 253, 0.95);
  backdrop-filter: saturate(180%) blur(20px);
  -webkit-backdrop-filter: saturate(180%) blur(20px);
  z-index: 9999;
  transition: background-color var(--transition-medium);
  border-bottom: 1px solid var(--color-border);
}

[data-theme="dark"] .nav-global {
  background-color: rgba(29, 29, 31, 0.95);
  border-bottom: 1px solid rgba(255, 255, 255, 0.08);
}

.nav-container {
  max-width: 980px;
  margin: 0 auto;
  padding: 0 22px;
  height: 100%;
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.nav-brand {
  font-size: 1.25rem;
  font-weight: 600;
  color: var(--color-text-primary);
  text-decoration: none;
  transition: opacity var(--transition-fast);
}

.nav-brand:hover {
  opacity: 0.8;
  color: var(--color-text-primary);
}

.nav-menu {
  display: flex;
  list-style: none;
  gap: var(--spacing-xl);
  align-items: center;
}

.nav-link {
  font-size: 0.75rem;
  color: var(--color-text-primary);
  text-decoration: none;
  transition: opacity var(--transition-fast);
  font-weight: 400;
}

.nav-link:hover {
  opacity: 0.65;
  color: var(--color-text-primary);
}

/* Main content */
main {
  padding-top: 44px;
  min-height: 100vh;
}

/* Hero section */
.hero {
  padding: var(--spacing-4xl) 0;
  text-align: center;
}

.hero-content {
  max-width: 980px;
  margin: 0 auto;
  padding: 0 22px;
}

.hero-title {
  margin-bottom: var(--spacing-lg);
  background: linear-gradient(180deg, #1d1d1f 0%, #86868b 100%);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

[data-theme="dark"] .hero-title {
  background: linear-gradient(180deg, #f5f5f7 0%, #86868b 100%);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.hero-description {
  font-size: 1.5rem;
  line-height: 1.33337;
  font-weight: 400;
  margin-bottom: var(--spacing-2xl);
  max-width: 720px;
  margin-left: auto;
  margin-right: auto;
}

/* Buttons */
.button {
  display: inline-block;
  background: var(--color-primary);
  color: var(--color-white);
  padding: 12px 22px;
  border-radius: 980px;
  font-size: 1rem;
  font-weight: 400;
  text-align: center;
  cursor: pointer;
  border: none;
  transition: all var(--transition-fast);
  text-decoration: none;
}

.button:hover {
  background: var(--color-primary-hover);
  color: var(--color-white);
  transform: scale(1.015);
}

.button-secondary {
  background: transparent;
  color: var(--color-primary);
  border: 1px solid var(--color-primary);
}

.button-secondary:hover {
  background: var(--color-primary);
  color: var(--color-white);
}

/* Cards */
.card {
  background: var(--color-background-elevated);
  border-radius: 18px;
  padding: var(--spacing-xl);
  transition: all var(--transition-medium);
  border: 1px solid var(--color-border);
}

.card:hover {
  transform: translateY(-4px);
  box-shadow: 0 12px 24px rgba(0, 0, 0, 0.08);
}

[data-theme="dark"] .card:hover {
  box-shadow: 0 12px 24px rgba(0, 0, 0, 0.3);
}

.card-title {
  font-size: 1.5rem;
  margin-bottom: var(--spacing-md);
  color: var(--color-text-primary);
}

.card-description {
  font-size: 1rem;
  line-height: 1.52947;
  color: var(--color-text-secondary);
  margin-bottom: var(--spacing-lg);
}

/* Grid layouts */
.grid {
  display: grid;
  gap: var(--spacing-lg);
}

.grid-cols-1 {
  grid-template-columns: 1fr;
}

.grid-cols-2 {
  grid-template-columns: repeat(2, 1fr);
}

.grid-cols-3 {
  grid-template-columns: repeat(3, 1fr);
}

/* Container */
.container {
  max-width: 980px;
  margin: 0 auto;
  padding: 0 22px;
}

.container-wide {
  max-width: 1200px;
  margin: 0 auto;
  padding: 0 22px;
}

/* Section spacing */
.section {
  padding: var(--spacing-4xl) 0;
}

.section-header {
  text-align: center;
  margin-bottom: var(--spacing-3xl);
}

.section-title {
  margin-bottom: var(--spacing-lg);
}

.section-description {
  font-size: 1.25rem;
  max-width: 720px;
  margin: 0 auto;
}

/* Theme toggle */
.theme-toggle {
  position: relative;
}

.theme-toggle-button {
  background: transparent;
  border: none;
  color: var(--color-text-primary);
  font-size: 1.2rem;
  cursor: pointer;
  padding: 8px;
  border-radius: 8px;
  transition: all var(--transition-fast);
  width: 32px;
  height: 32px;
  display: flex;
  align-items: center;
  justify-content: center;
}

.theme-toggle-button:hover {
  background: var(--color-gray-200);
}

[data-theme="dark"] .theme-toggle-button:hover {
  background: var(--color-gray-700);
}

.theme-menu {
  position: absolute;
  top: 100%;
  right: 0;
  margin-top: 8px;
  background: var(--color-background-elevated);
  border: 1px solid var(--color-border);
  border-radius: 12px;
  padding: 8px;
  min-width: 160px;
  box-shadow: 0 8px 24px rgba(0, 0, 0, 0.12);
  opacity: 0;
  visibility: hidden;
  transform: translateY(-10px);
  transition: all var(--transition-fast);
}

[data-theme="dark"] .theme-menu {
  box-shadow: 0 8px 24px rgba(0, 0, 0, 0.4);
}

.theme-menu.active {
  opacity: 1;
  visibility: visible;
  transform: translateY(0);
}

.theme-option {
  display: flex;
  align-items: center;
  gap: 12px;
  padding: 10px 12px;
  border-radius: 8px;
  cursor: pointer;
  transition: all var(--transition-fast);
  font-size: 0.875rem;
  white-space: nowrap;
}

.theme-option:hover {
  background: var(--color-gray-200);
}

[data-theme="dark"] .theme-option:hover {
  background: var(--color-gray-700);
}

.theme-option.active {
  background: var(--color-primary);
  color: var(--color-white);
}

.theme-icon {
  font-size: 1rem;
  width: 16px;
  text-align: center;
}

/* News grid */
.news-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(320px, 1fr));
  gap: var(--spacing-xl);
  margin-bottom: var(--spacing-3xl);
}

.news-card {
  cursor: pointer;
}

.news-date {
  font-size: 0.875rem;
  color: var(--color-text-secondary);
  margin-top: var(--spacing-sm);
}

/* Video grid */
.video-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(300px, 1fr));
  gap: var(--spacing-xl);
}

.video-card {
  cursor: pointer;
  overflow: hidden;
}

.video-thumbnail {
  position: relative;
  width: 100%;
  aspect-ratio: 16 / 9;
  overflow: hidden;
  border-radius: 12px;
  margin-bottom: var(--spacing-md);
}

.video-thumbnail img {
  width: 100%;
  height: 100%;
  object-fit: cover;
  transition: transform var(--transition-medium);
}

.video-card:hover .video-thumbnail img {
  transform: scale(1.05);
}

.video-duration {
  position: absolute;
  bottom: 8px;
  right: 8px;
  background: rgba(0, 0, 0, 0.8);
  color: white;
  padding: 4px 8px;
  border-radius: 4px;
  font-size: 0.75rem;
  font-weight: 500;
}

/* About page styles */
.about-section {
  margin-bottom: var(--spacing-3xl);
}

.about-section h2 {
  font-size: 2rem;
  margin-bottom: var(--spacing-lg);
  color: var(--color-text-primary);
}

.about-section p {
  font-size: 1.125rem;
  line-height: 1.75;
  color: var(--color-text-secondary);
  margin-bottom: var(--spacing-lg);
}

.about-section ul {
  list-style: none;
  padding-left: 0;
}

.about-section ul li {
  position: relative;
  padding-left: var(--spacing-xl);
  margin-bottom: var(--spacing-md);
  font-size: 1.125rem;
  line-height: 1.75;
  color: var(--color-text-secondary);
}

.about-section ul li:before {
  content: "•";
  position: absolute;
  left: 0;
  color: var(--color-primary);
  font-weight: bold;
  font-size: 1.5rem;
  line-height: 1.2;
}

.acknowledgment-group {
  margin-bottom: var(--spacing-2xl);
  padding: var(--spacing-xl);
  background: var(--color-background-elevated);
  border-radius: 18px;
  border: 1px solid var(--color-border);
}

.acknowledgment-group h3 {
  font-size: 1.25rem;
  margin-bottom: var(--spacing-md);
  color: var(--color-text-primary);
  font-weight: 600;
}

.acknowledgment-group p {
  font-size: 1rem;
  color: var(--color-text-secondary);
  line-height: 1.75;
  margin: 0;
}

/* Contact section style */
.about-section a {
  color: var(--color-primary);
  text-decoration: none;
  font-weight: 500;
}

.about-section a:hover {
  text-decoration: underline;
}

/* Footer */
footer {
  background: var(--color-background-elevated);
  border-top: 1px solid var(--color-border);
  padding: var(--spacing-2xl) 0;
  margin-top: var(--spacing-4xl);
}

.footer-content {
  max-width: 980px;
  margin: 0 auto;
  padding: 0 22px;
  text-align: center;
}

.footer-text {
  font-size: 0.75rem;
  color: var(--color-text-secondary);
}

/* Responsive */
@media (max-width: 1024px) {
  .container {
    padding: 0 20px;
  }
  
  .container-wide {
    padding: 0 20px;
  }
  
  .nav-container {
    padding: 0 20px;
  }
}

@media (max-width: 768px) {
  html {
    font-size: 16px;
  }
  
  h1 {
    font-size: 2.5rem;
  }
  
  h2 {
    font-size: 2rem;
  }
  
  .hero-description {
    font-size: 1.25rem;
  }
  
  .nav-menu {
    gap: var(--spacing-md);
  }
  
  .nav-link {
    font-size: 0.7rem;
  }
  
  .container {
    padding: 0 16px;
  }
  
  .container-wide {
    padding: 0 16px;
  }
  
  .nav-container {
    padding: 0 16px;
  }
  
  .grid-cols-2,
  .grid-cols-3 {
    grid-template-columns: 1fr;
  }
  
  .section {
    padding: var(--spacing-2xl) 0;
  }
  
  .news-grid {
    grid-template-columns: 1fr;
    gap: var(--spacing-lg);
  }
  
  .video-grid {
    grid-template-columns: 1fr;
    gap: var(--spacing-lg);
  }
  
  .card {
    padding: var(--spacing-lg);
  }
  
  .card-title {
    font-size: 1.25rem;
  }
  
  .theme-menu {
    right: -8px;
    min-width: 140px;
  }
  
  .about-section {
    margin-bottom: var(--spacing-2xl);
  }
  
  .acknowledgment-group {
    padding: var(--spacing-lg);
    margin-bottom: var(--spacing-lg);
  }
}

@media (max-width: 480px) {
  .nav-menu {
    gap: var(--spacing-sm);
  }
  
  .nav-link {
    display: none;
  }
  
  .nav-link:first-child {
    display: block;
  }
  
  h1 {
    font-size: 2rem;
  }
  
  .hero-description {
    font-size: 1.125rem;
  }
  
  .section {
    padding: var(--spacing-xl) 0;
  }
  
  .container,
  .container-wide {
    padding: 0 12px;
  }
  
  .nav-container {
    padding: 0 12px;
  }
}