/* {{RIPER-5:
   Action: "Added"
   Task_ID: "344451e0-d7ca-4c15-bf86-b5a727a8125b"
   Timestamp: "2025-11-04T12:48:00+08:00"
   Authoring_Role: "LD"
   Principle_Applied: "Aether-Design-Glass-Effect, Aether-Design-Universal-Softness, Aether-Design-Fluid-Animation, Aether-Engineering-SOLID-S, DRY"
   Quality_Check: "CSS 验证通过。所有圆角规则遵循以太设计哲学。"
}} */

/* ============================================
   LinguaMind AI - Aether Design System
   A Liquid Glass Design Language
   ============================================ */

/* ====== CSS Custom Properties (Design Tokens) ====== */
:root {
  /* Aether-Design-Universal-Softness: Rounded Corner System */
  --radius-2xl: 1rem;           /* For all containers, buttons, inputs, cards */
  --radius-full: 9999px;        /* For avatars, badges, circular elements */
  
  /* Aether-Design-Glass-Effect: Glass Morphism Variables */
  --glass-bg: rgba(255, 255, 255, 0.1);
  --glass-border: rgba(255, 255, 255, 0.2);
  --glass-blur: blur(20px) saturate(180%) brightness(110%);
  --glass-shadow: 0 8px 32px rgba(0, 0, 0, 0.1);
  --glass-inset-glow: inset 0 0 20px rgba(255, 255, 255, 0.1);
  
  /* Color System: Blue-Purple Tech Gradient */
  --gradient-primary: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
  --gradient-secondary: linear-gradient(135deg, #f093fb 0%, #f5576c 100%);
  --color-primary: #667eea;
  --color-secondary: #764ba2;
  --color-accent: #f093fb;
  
  /* Semantic Colors */
  --color-success: #10b981;
  --color-warning: #f59e0b;
  --color-error: #ef4444;
  --color-info: #3b82f6;
  
  /* Typography */
  --font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', 'Segoe UI Symbol';
  --font-mono: 'SF Mono', 'Monaco', 'Cascadia Code', 'Roboto Mono', 'Courier New', monospace;
  
  /* Aether-Design-Fluid-Animation: Natural Easing Curves */
  --ease-natural: cubic-bezier(0.4, 0, 0.2, 1);
  --ease-in-out: cubic-bezier(0.645, 0.045, 0.355, 1);
  --ease-bounce: cubic-bezier(0.68, -0.55, 0.265, 1.55);
  --transition-base: 0.3s var(--ease-natural);
  --transition-slow: 0.6s var(--ease-natural);
  
  /* Spacing System */
  --spacing-xs: 0.25rem;
  --spacing-sm: 0.5rem;
  --spacing-md: 1rem;
  --spacing-lg: 1.5rem;
  --spacing-xl: 2rem;
  --spacing-2xl: 3rem;
  
  /* Z-index Layers */
  --z-base: 1;
  --z-dropdown: 100;
  --z-sticky: 200;
  --z-modal: 300;
  --z-tooltip: 400;
}

/* ====== Global Reset & Base Styles ====== */
* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

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

body {
  font-family: var(--font-family);
  background: var(--gradient-primary);
  background-attachment: fixed;
  color: #ffffff;
  line-height: 1.6;
  overflow-x: hidden;
  min-height: 100vh;
}

body.loaded {
  animation: fadeIn 0.5s var(--ease-natural);
}

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

/* Typography Base */
h1, h2, h3, h4, h5, h6 {
  font-weight: 700;
  line-height: 1.2;
  margin-bottom: var(--spacing-md);
}

h1 { font-size: 3.5rem; }
h2 { font-size: 2.5rem; }
h3 { font-size: 2rem; }
h4 { font-size: 1.5rem; }
h5 { font-size: 1.25rem; }
h6 { font-size: 1rem; }

p {
  margin-bottom: var(--spacing-md);
  font-size: 1.125rem;
  line-height: 1.8;
}

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

a:hover {
  opacity: 0.8;
}

/* ====== Glass Morphism Components ====== */

/* Glass Card - Aether-Design-Glass-Effect + Aether-Design-Universal-Softness */
.glass-card {
  background: var(--glass-bg);
  backdrop-filter: var(--glass-blur);
  -webkit-backdrop-filter: var(--glass-blur);
  border: 1px solid var(--glass-border);
  border-radius: var(--radius-2xl);
  padding: var(--spacing-xl);
  box-shadow: var(--glass-shadow);
  transition: all var(--transition-base);
  will-change: transform, box-shadow;
}

.glass-card:hover {
  box-shadow: var(--glass-inset-glow), var(--glass-shadow);
  transform: translateY(-4px);
}

/* Glass Button - Universal Component */
.glass-button {
  background: var(--glass-bg);
  backdrop-filter: var(--glass-blur);
  -webkit-backdrop-filter: var(--glass-blur);
  border: 1px solid var(--glass-border);
  border-radius: var(--radius-2xl);
  padding: 0.75rem 2rem;
  font-size: 1rem;
  font-weight: 600;
  color: #ffffff;
  cursor: pointer;
  transition: all var(--transition-base);
  will-change: transform, box-shadow;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 0.5rem;
}

.glass-button:hover {
  box-shadow: var(--glass-inset-glow), var(--glass-shadow);
  transform: translateY(-2px);
}

.glass-button:active {
  transform: translateY(0);
}

.glass-button.primary {
  background: linear-gradient(135deg, rgba(102, 126, 234, 0.3), rgba(118, 75, 162, 0.3));
  border-color: var(--color-primary);
}

.glass-button.large {
  padding: 1rem 2.5rem;
  font-size: 1.125rem;
}

/* Glass Input - Form Elements */
.glass-input,
.glass-textarea {
  background: var(--glass-bg);
  backdrop-filter: var(--glass-blur);
  -webkit-backdrop-filter: var(--glass-blur);
  border: 1px solid var(--glass-border);
  border-radius: var(--radius-2xl);
  padding: 0.875rem 1.25rem;
  font-size: 1rem;
  font-family: var(--font-family);
  color: #ffffff;
  width: 100%;
  transition: all var(--transition-base);
  outline: none;
}

.glass-input::placeholder,
.glass-textarea::placeholder {
  color: rgba(255, 255, 255, 0.6);
}

.glass-input:focus,
.glass-textarea:focus {
  border-color: var(--color-primary);
  box-shadow: var(--glass-inset-glow), 0 0 0 3px rgba(102, 126, 234, 0.2);
}

.glass-textarea {
  resize: vertical;
  min-height: 120px;
}

/* Glass Navigation - Fixed Header */
.glass-nav {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  background: var(--glass-bg);
  backdrop-filter: var(--glass-blur);
  -webkit-backdrop-filter: var(--glass-blur);
  border-bottom: 1px solid var(--glass-border);
  padding: 1rem 2rem;
  z-index: var(--z-sticky);
  transition: all var(--transition-base);
}

.glass-nav .container {
  display: flex;
  justify-content: space-between;
  align-items: center;
}

/* Glass Footer */
.glass-footer {
  background: var(--glass-bg);
  backdrop-filter: var(--glass-blur);
  -webkit-backdrop-filter: var(--glass-blur);
  border-top: 1px solid var(--glass-border);
  padding: 2rem;
  margin-top: 4rem;
}

/* ====== Browser Compatibility Fallback ====== */
@supports not (backdrop-filter: blur(20px)) {
  .glass-card,
  .glass-button,
  .glass-input,
  .glass-textarea,
  .glass-nav,
  .glass-footer {
    background: rgba(255, 255, 255, 0.25);
    backdrop-filter: none;
  }
}

/* ====== Utility Classes ====== */

/* Container - Max Width Constraint */
.container {
  max-width: 1280px;
  margin: 0 auto;
  padding: 0 2rem;
}

/* Badge - Aether-Design-Universal-Softness (rounded-full) */
.badge {
  background: var(--glass-bg);
  backdrop-filter: var(--glass-blur);
  -webkit-backdrop-filter: var(--glass-blur);
  border: 1px solid var(--glass-border);
  border-radius: var(--radius-full);
  padding: 0.25rem 0.75rem;
  font-size: 0.875rem;
  font-weight: 600;
  display: inline-flex;
  align-items: center;
  gap: 0.25rem;
}

/* Avatar - Aether-Design-Universal-Softness (rounded-full) */
.avatar {
  border-radius: var(--radius-full);
  overflow: hidden;
  display: inline-block;
  border: 2px solid var(--glass-border);
}

.avatar img {
  width: 100%;
  height: 100%;
  object-fit: cover;
}

/* Text Utilities */
.text-center { text-align: center; }
.text-gradient {
  background: var(--gradient-primary);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

/* ====== Animation Classes ====== */

/* Scroll Animation - Aether-Design-Fluid-Animation */
.animate-on-scroll {
  opacity: 0;
  transform: translateY(20px);
  transition: opacity var(--transition-slow), transform var(--transition-slow);
}

.animate-on-scroll.animate-in {
  opacity: 1;
  transform: translateY(0);
}

/* Fade Animations */
.fade-in {
  animation: fadeIn 0.6s var(--ease-natural);
}

/* Pulse Animation for CTAs */
@keyframes pulse {
  0%, 100% { transform: scale(1); }
  50% { transform: scale(1.05); }
}

.pulse {
  animation: pulse 2s var(--ease-natural) infinite;
}

/* ====== Layout Sections ====== */

/* Section Spacing */
section {
  padding: 4rem 0;
}

.section-title {
  text-align: center;
  margin-bottom: 3rem;
}

/* Hero Section */
.hero-section {
  min-height: 100vh;
  display: flex;
  flex-direction: column;
  justify-content: center;
  align-items: center;
  text-align: center;
  padding: 6rem 2rem;
  position: relative;
}

.hero-section h1 {
  font-size: 4rem;
  margin-bottom: 1rem;
}

.hero-section p {
  font-size: 1.5rem;
  margin-bottom: 2rem;
  opacity: 0.9;
}

.hero-cta {
  display: flex;
  gap: 1rem;
  flex-wrap: wrap;
  justify-content: center;
}

/* Features Grid */
.features-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
  gap: 2rem;
  margin-top: 2rem;
}

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

.feature-icon {
  width: 64px;
  height: 64px;
  margin: 0 auto 1rem;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 2rem;
}

/* Stats Section */
.stats-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
  gap: 2rem;
  margin-top: 2rem;
}

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

.stat-number {
  font-size: 3rem;
  font-weight: 700;
  display: block;
  margin-bottom: 0.5rem;
}

.stat-label {
  font-size: 1rem;
  opacity: 0.8;
}

/* CTA Section */
.cta-section {
  text-align: center;
  padding: 6rem 2rem;
}

/* Form Layout */
.glass-form {
  display: flex;
  flex-direction: column;
  gap: 1.5rem;
}

.form-group {
  display: flex;
  flex-direction: column;
  gap: 0.5rem;
}

.form-label {
  font-weight: 600;
  font-size: 0.875rem;
  text-transform: uppercase;
  letter-spacing: 0.05em;
}

/* Navigation Links */
.nav-links {
  display: flex;
  gap: 2rem;
  list-style: none;
  align-items: center;
}

.nav-links a {
  font-weight: 500;
  transition: color var(--transition-base);
}

.nav-links a:hover {
  color: var(--color-accent);
}

/* Footer Layout */
.footer-content {
  display: flex;
  justify-content: space-between;
  align-items: center;
  flex-wrap: wrap;
  gap: 2rem;
}

.footer-links {
  display: flex;
  gap: 2rem;
  list-style: none;
}

.social-links {
  display: flex;
  gap: 1rem;
}

.social-icon {
  width: 40px;
  height: 40px;
  border-radius: var(--radius-full);
  background: var(--glass-bg);
  border: 1px solid var(--glass-border);
  display: flex;
  align-items: center;
  justify-content: center;
  transition: all var(--transition-base);
}

.social-icon:hover {
  transform: translateY(-2px);
  box-shadow: var(--glass-inset-glow);
}

/* ====== Responsive Breakpoints ====== */

/* Tablet: 640px - 1023px */
@media (min-width: 640px) and (max-width: 1023px) {
  h1 { font-size: 3rem; }
  h2 { font-size: 2rem; }
  
  .hero-section h1 {
    font-size: 3rem;
  }
  
  .features-grid {
    grid-template-columns: repeat(2, 1fr);
  }
}

/* Mobile: < 640px */
@media (max-width: 639px) {
  html {
    font-size: 14px;
  }
  
  h1 { font-size: 2.5rem; }
  h2 { font-size: 1.75rem; }
  
  .hero-section {
    padding: 4rem 1rem;
  }
  
  .hero-section h1 {
    font-size: 2.5rem;
  }
  
  .hero-section p {
    font-size: 1.125rem;
  }
  
  .hero-cta {
    flex-direction: column;
    width: 100%;
  }
  
  .glass-button {
    width: 100%;
  }
  
  .features-grid {
    grid-template-columns: 1fr;
  }
  
  .stats-grid {
    grid-template-columns: repeat(2, 1fr);
  }
  
  .nav-links {
    gap: 1rem;
    font-size: 0.875rem;
  }
  
  .container {
    padding: 0 1rem;
  }
  
  section {
    padding: 2rem 0;
  }
  
  .footer-content {
    flex-direction: column;
    text-align: center;
  }
}

/* Desktop: > 1024px */
@media (min-width: 1024px) {
  .features-grid {
    grid-template-columns: repeat(3, 1fr);
  }
  
  .stats-grid {
    grid-template-columns: repeat(4, 1fr);
  }
}

/* Accessibility - Reduced Motion */
@media (prefers-reduced-motion: reduce) {
  *,
  *::before,
  *::after {
    animation-duration: 0.01ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.01ms !important;
  }
  
  .glass-card,
  .glass-button,
  .glass-input,
  .glass-textarea,
  .glass-nav,
  .glass-footer {
    backdrop-filter: none;
    background: rgba(255, 255, 255, 0.3);
  }
}

/* Print Styles */
@media print {
  body {
    background: white;
    color: black;
  }
  
  .glass-nav,
  .glass-footer,
  .glass-button {
    display: none;
  }
}