/* ================================
   CSS Custom Properties (Variables)
   ================================ */
:root {
  /* Colors - Dark Theme (Default) */
  --color-bg-primary: #000000;
  --color-bg-secondary: #060641;
  --color-bg-gradient-start: #01022df3;
  --color-bg-gradient-end: #000000;
  --color-surface: #060641;
  --color-text-primary: #ffffff;
  --color-text-secondary: #e0e0e0;
  --color-accent: #ffffff;
  --color-overlay-dark: #060641c6;
  --color-overlay-darker: #000000b1;
  
  /* Spacing */
  --spacing-xs: 4px;
  --spacing-sm: 8px;
  --spacing-md: 16px;
  --spacing-lg: 24px;
  --spacing-xl: 32px;
  --spacing-2xl: 40px;
  
  /* Typography */
  --font-family-base: 'Ubuntu', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen, sans-serif;
  --font-size-base: 1rem;
  --font-size-sm: 0.9rem;
  --font-size-lg: 1.1rem;
  --font-weight-regular: 400;
  --font-weight-medium: 500;
  --font-weight-bold: 700;
  --line-height-base: 1.7;
  
  /* Border Radius */
  --radius-sm: 6px;
  --radius-md: 12px;
  --radius-lg: 16px;
  --radius-full: 999px;
  
  /* Transitions */
  --transition-fast: 0.2s ease;
  --transition-base: 0.3s ease;
  --transition-slow: 0.4s ease;
  
  /* Shadows */
  --shadow-sm: 0 2px 4px rgba(0, 0, 0, 0.1);
  --shadow-md: 0 4px 8px rgba(0, 0, 0, 0.15);
  --shadow-lg: 0 8px 16px rgba(0, 0, 0, 0.2);
  
  /* Z-index */
  --z-index-skip-link: 9999;
  --z-index-header: 100;
  --z-index-overlay: 50;
}

/* Light Theme */
html[data-theme="light"] {
  --color-bg-primary: #f5f7fa;
  --color-bg-secondary: #ffffff;
  --color-bg-gradient-start: #e8eef5;
  --color-bg-gradient-end: #f5f7fa;
  --color-surface: #ffffff;
  --color-text-primary: #111111;
  --color-text-secondary: #4a5568;
  --color-accent: #2563eb;
  --color-overlay-dark: rgba(255, 255, 255, 0.85);
  --color-overlay-darker: rgba(245, 247, 250, 0.7);
}

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

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

html,
body {
  width: 100%;
  height: 100%;
}

body {
  font-family: var(--font-family-base);
  font-size: var(--font-size-base);
  line-height: var(--line-height-base);
  background: linear-gradient(
    to right, 
    var(--color-bg-gradient-start), 
    var(--color-bg-gradient-end)
  );
  color: var(--color-text-primary);
  display: flex;
  align-items: center;
  justify-content: center;
  min-height: 100vh;
}

/* ================================
   Accessibility - Skip Link
   ================================ */
.skip-link {
  position: absolute;
  top: -100px;
  left: var(--spacing-md);
  z-index: var(--z-index-skip-link);
  padding: var(--spacing-sm) var(--spacing-md);
  background: var(--color-accent);
  color: var(--color-bg-primary);
  text-decoration: none;
  border-radius: var(--radius-sm);
  font-weight: var(--font-weight-bold);
}

.skip-link:focus {
  top: var(--spacing-md);
  outline: 3px solid var(--color-accent);
  outline-offset: 2px;
}

/* ================================
   Page Layout
   ================================ */
.page {
  width: 100%;
  height: 100%;
  display: flex;
  align-items: center;
  justify-content: center;
  padding: var(--spacing-md);
}

/* ================================
   Hero Section - BEM Block
   ================================ */
.hero {
  width: 100%;
  max-width: 1400px;
  min-height: 640px;
  background-image:
    linear-gradient(to right, var(--color-overlay-dark) 30%, var(--color-overlay-darker)),
    url("image/download.webp");
  background-position: center;
  background-size: cover;
  background-repeat: no-repeat;
  border-radius: var(--radius-md);
  transition: 
    background-image var(--transition-slow),
    transform var(--transition-base),
    box-shadow var(--transition-base);
  box-shadow: var(--shadow-lg);
  overflow: hidden;
}

.hero:hover,
.hero:focus-within {
  background-image:
    linear-gradient(to right, var(--color-overlay-dark) 30%, transparent),
    url("image/download.webp");
  transform: scale(1.005);
  box-shadow: 0 12px 24px rgba(0, 0, 0, 0.25);
}

/* ================================
   Hero Header - BEM Element
   ================================ */
.hero__header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: var(--spacing-lg);
  gap: var(--spacing-md);
  flex-wrap: wrap;
  position: relative;
  z-index: var(--z-index-header);
}

/* Hero Logo */
.hero__logo {
  font-size: clamp(1.5rem, 4vw, 2rem);
  font-weight: var(--font-weight-bold);
  letter-spacing: 3px;
  text-transform: uppercase;
  color: var(--color-text-primary);
  text-decoration: none;
  transition: opacity var(--transition-fast);
}

.hero__logo:hover,
.hero__logo:focus-visible {
  opacity: 0.8;
  outline: 2px solid var(--color-accent);
  outline-offset: 4px;
  border-radius: var(--radius-sm);
}

/* Hero Navigation */
.hero__nav {
  flex: 1;
  display: flex;
  justify-content: center;
}

.hero__menu {
  list-style: none;
  display: flex;
  gap: var(--spacing-lg);
  padding: 0;
  margin: 0;
  flex-wrap: wrap;
  justify-content: center;
}

.hero__menu-item {
  display: inline-block;
}

.hero__menu-link {
  color: var(--color-text-primary);
  text-decoration: none;
  border-bottom: 2px solid transparent;
  padding-bottom: var(--spacing-xs);
  transition: 
    border-color var(--transition-fast), 
    opacity var(--transition-fast),
    color var(--transition-fast);
  font-weight: var(--font-weight-medium);
  display: inline-block;
}

.hero__menu-link:hover,
.hero__menu-link:focus-visible {
  border-bottom-color: var(--color-accent);
  opacity: 0.85;
  outline: none;
  color: var(--color-accent);
}

.hero__menu-link[aria-current="page"] {
  border-bottom-color: var(--color-accent);
  font-weight: var(--font-weight-bold);
}

/* Theme Toggle Button */
.hero__theme-toggle {
  position: relative;
  background: transparent;
  border: 2px solid var(--color-accent);
  color: var(--color-text-primary);
  border-radius: var(--radius-full);
  padding: 10px 20px;
  cursor: pointer;
  font-size: var(--font-size-sm);
  font-family: var(--font-family-base);
  transition: all var(--transition-fast);
  display: flex;
  align-items: center;
  gap: var(--spacing-sm);
  font-weight: var(--font-weight-medium);
  overflow: hidden;
  min-height: 44px;
  backdrop-filter: blur(8px);
  background: rgba(255, 255, 255, 0.05);
}

html[data-theme="light"] .hero__theme-toggle {
  background: rgba(0, 0, 0, 0.03);
}

.hero__theme-toggle::before {
  content: '';
  position: absolute;
  inset: 0;
  border-radius: inherit;
  padding: 2px;
  background: linear-gradient(135deg, var(--color-accent), transparent);
  -webkit-mask: 
    linear-gradient(#fff 0 0) content-box, 
    linear-gradient(#fff 0 0);
  -webkit-mask-composite: xor;
  mask-composite: exclude;
  opacity: 0;
  transition: opacity var(--transition-fast);
}

.hero__theme-toggle:hover::before {
  opacity: 1;
}

.hero__theme-toggle:hover,
.hero__theme-toggle:focus-visible {
  background: var(--color-accent);
  color: var(--color-bg-primary);
  border-color: var(--color-accent);
  outline: 2px solid var(--color-accent);
  outline-offset: 2px;
  transform: translateY(-2px);
  box-shadow: 0 4px 12px rgba(0, 0, 0, 0.15);
}

.hero__theme-toggle:active {
  transform: translateY(0);
  box-shadow: 0 2px 6px rgba(0, 0, 0, 0.1);
}

/* Theme Icon Wrapper */
.hero__theme-icon-wrapper {
  position: relative;
  width: 20px;
  height: 20px;
  display: flex;
  align-items: center;
  justify-content: center;
}

/* Theme Icons */
.hero__theme-icon {
  position: absolute;
  transition: all 0.4s cubic-bezier(0.4, 0, 0.2, 1);
}

.hero__theme-icon--sun {
  opacity: 0;
  transform: rotate(-90deg) scale(0.8);
}

.hero__theme-icon--moon {
  opacity: 1;
  transform: rotate(0deg) scale(1);
}

/* Light theme icon states */
html[data-theme="light"] .hero__theme-icon--sun {
  opacity: 1;
  transform: rotate(0deg) scale(1);
}

html[data-theme="light"] .hero__theme-icon--moon {
  opacity: 0;
  transform: rotate(90deg) scale(0.8);
}

/* Animated glow effect on hover */
.hero__theme-toggle:hover .hero__theme-icon--sun,
.hero__theme-toggle:hover .hero__theme-icon--moon {
  filter: drop-shadow(0 0 6px currentColor);
}

/* Theme Text */
.hero__theme-text {
  font-weight: var(--font-weight-medium);
  letter-spacing: 0.5px;
}

/* ================================
   Hero Content - BEM Element
   ================================ */
.hero__content {
  width: 100%;
  max-width: 50%;
  padding: var(--spacing-xl);
  margin-top: var(--spacing-2xl);
}

.hero__title {
  font-size: clamp(2.5rem, 8vw, 6rem);
  font-weight: var(--font-weight-bold);
  letter-spacing: 2px;
  text-transform: uppercase;
  margin: 0 0 var(--spacing-lg) 0;
  line-height: 1.1;
  color: var(--color-text-primary);
}

.hero__description {
  max-width: 420px;
  line-height: var(--line-height-base);
  margin: var(--spacing-lg) 0;
  color: var(--color-text-secondary);
  font-size: var(--font-size-base);
}

.hero__cta {
  font-size: var(--font-size-lg);
  font-weight: var(--font-weight-medium);
  font-family: var(--font-family-base);
  padding: 12px 28px;
  border-radius: var(--radius-full);
  border: 2px solid transparent;
  background: var(--color-accent);
  color: var(--color-bg-primary);
  cursor: pointer;
  transition: all 0.25s ease;
  display: inline-block;
  text-decoration: none;
}

.hero__cta:hover,
.hero__cta:focus-visible {
  background: transparent;
  color: var(--color-text-primary);
  border-color: var(--color-accent);
  outline: 2px solid var(--color-accent);
  outline-offset: 2px;
  transform: translateY(-2px);
  box-shadow: var(--shadow-md);
}

.hero__cta:active {
  transform: translateY(0);
}

/* ================================
   Responsive Design
   ================================ */

/* Tablet (1024px and below) */
@media (max-width: 1024px) {
  .hero__content {
    max-width: 70%;
  }
}

/* Mobile Landscape & Tablet Portrait (768px and below) */
@media (max-width: 768px) {
  .hero {
    min-height: auto;
    padding-bottom: var(--spacing-xl);
  }

  .hero__header {
    flex-direction: column;
    align-items: center;
    gap: var(--spacing-md);
  }

  .hero__nav {
    width: 100%;
  }

  .hero__menu {
    flex-wrap: wrap;
    justify-content: center;
    gap: var(--spacing-md);
  }

  .hero__content {
    max-width: 100%;
    margin-top: var(--spacing-md);
    padding: var(--spacing-lg);
  }

  .hero__title {
    font-size: clamp(2rem, 10vw, 3.5rem);
  }

  .hero__description {
    max-width: 100%;
  }
}

/* Small Mobile (480px and below) */
@media (max-width: 480px) {
  .page {
    padding: var(--spacing-sm);
  }

  .hero {
    border-radius: var(--radius-sm);
  }

  .hero__header {
    padding: var(--spacing-md);
  }

  .hero__menu {
    gap: var(--spacing-sm);
    font-size: var(--font-size-sm);
  }

  .hero__content {
    padding: var(--spacing-md);
  }

  .hero__cta {
    width: 100%;
    text-align: center;
  }

  .hero__theme-toggle {
    width: 100%;
    justify-content: center;
    padding: 12px 20px;
  }

  .hero__theme-text {
    display: inline;
  }
}

/* Extra Small Mobile (360px and below) */
@media (max-width: 360px) {
  .hero__logo {
    font-size: 1.25rem;
    letter-spacing: 2px;
  }

  .hero__title {
    font-size: 2rem;
    letter-spacing: 1px;
  }
}

/* ================================
   Print Styles
   ================================ */
@media print {
  .hero__theme-toggle,
  .hero__cta {
    display: none;
  }

  .hero {
    background: white;
    color: black;
    box-shadow: none;
  }

  .hero__header,
  .hero__content {
    padding: var(--spacing-md);
  }
}

/* ================================
   Reduced Motion Preference
   ================================ */
@media (prefers-reduced-motion: reduce) {
  *,
  *::before,
  *::after {
    animation-duration: 0.01ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.01ms !important;
    scroll-behavior: auto !important;
  }

  .hero:hover {
    transform: none;
  }
}

/* ================================
   High Contrast Mode Support
   ================================ */
@media (prefers-contrast: high) {
  .hero__menu-link,
  .hero__theme-toggle,
  .hero__cta {
    border-width: 3px;
  }

  .hero__menu-link:focus-visible,
  .hero__theme-toggle:focus-visible,
  .hero__cta:focus-visible {
    outline-width: 4px;
  }
}

/* ================================
   Focus Visible Styles
   ================================ */
:focus-visible {
  outline: 2px solid var(--color-accent);
  outline-offset: 2px;
  border-radius: var(--radius-sm);
}