/* ========================================
   鱼塘 Yutang - Modern UI Design System
   Style: Clean Minimalism with Glassmorphism
   ======================================== */

/* --- Design Tokens --- */
:root {
  /* Color System (Semantic Tokens) */
  --color-primary: #6366f1;
  --color-primary-hover: #4f46e5;
  --color-primary-active: #4338ca;
  --color-primary-subtle: rgba(99, 102, 241, 0.08);
  --color-primary-soft: rgba(99, 102, 241, 0.12);
  
  --color-surface: #ffffff;
  --color-surface-elevated: #ffffff;
  --color-background: #f1f5f9;
  --color-background-alt: #f8fafc;
  
  --color-text: #0f172a;
  --color-text-secondary: #475569;
  --color-text-tertiary: #94a3b8;
  --color-text-inverse: #ffffff;
  
  --color-border: #e2e8f0;
  --color-border-strong: #cbd5e1;
  
  --color-success: #10b981;
  --color-success-subtle: rgba(16, 185, 129, 0.1);
  --color-warning: #f59e0b;
  --color-warning-subtle: rgba(245, 158, 11, 0.1);
  --color-error: #ef4444;
  
  /* Typography Scale */
  --font-family: 'Inter', 'Noto Sans SC', -apple-system, BlinkMacSystemFont, sans-serif;
  --text-xs: 0.75rem;
  --text-sm: 0.875rem;
  --text-base: 1rem;
  --text-lg: 1.125rem;
  --text-xl: 1.25rem;
  --text-2xl: 1.5rem;
  --text-3xl: 1.875rem;
  
  --font-normal: 400;
  --font-medium: 500;
  --font-semibold: 600;
  --font-bold: 700;
  
  --leading-tight: 1.25;
  --leading-normal: 1.5;
  --leading-relaxed: 1.75;
  
  /* Spacing Scale (8dp system) */
  --space-1: 4px;
  --space-2: 8px;
  --space-3: 12px;
  --space-4: 16px;
  --space-5: 20px;
  --space-6: 24px;
  --space-8: 32px;
  --space-10: 40px;
  --space-12: 48px;
  
  /* Border Radius */
  --radius-sm: 8px;
  --radius-md: 12px;
  --radius-lg: 16px;
  --radius-xl: 20px;
  --radius-full: 9999px;
  
  /* Shadows (Elevation System) */
  --shadow-sm: 0 1px 2px rgba(0, 0, 0, 0.05);
  --shadow-md: 0 1px 3px rgba(0, 0, 0, 0.1), 0 1px 2px rgba(0, 0, 0, 0.06);
  --shadow-lg: 0 4px 6px -1px rgba(0, 0, 0, 0.1), 0 2px 4px -2px rgba(0, 0, 0, 0.1);
  --shadow-xl: 0 10px 15px -3px rgba(0, 0, 0, 0.1), 0 4px 6px -4px rgba(0, 0, 0, 0.1);
  --shadow-glow: 0 0 20px rgba(99, 102, 241, 0.15);
  
  /* Animation */
  --transition-fast: 150ms;
  --transition-normal: 200ms;
  --transition-slow: 300ms;
  --ease-out: cubic-bezier(0.16, 1, 0.3, 1);
  --ease-in-out: cubic-bezier(0.4, 0, 0.2, 1);
  
  /* Layout */
  --max-width: 720px;
  --header-height: 64px;
}

/* --- Dark Mode --- */
@media (prefers-color-scheme: dark) {
  :root {
    --color-primary: #818cf8;
    --color-primary-hover: #6366f1;
    --color-primary-active: #818cf8;
    --color-primary-subtle: rgba(129, 140, 248, 0.12);
    --color-primary-soft: rgba(129, 140, 248, 0.18);
    
    --color-surface: #1e293b;
    --color-surface-elevated: #334155;
    --color-background: #0f172a;
    --color-background-alt: #1e293b;
    
    --color-text: #f1f5f9;
    --color-text-secondary: #94a3b8;
    --color-text-tertiary: #64748b;
    
    --color-border: #334155;
    --color-border-strong: #475569;
    
    --shadow-sm: 0 1px 2px rgba(0, 0, 0, 0.3);
    --shadow-md: 0 1px 3px rgba(0, 0, 0, 0.4), 0 1px 2px rgba(0, 0, 0, 0.3);
    --shadow-lg: 0 4px 6px -1px rgba(0, 0, 0, 0.4), 0 2px 4px -2px rgba(0, 0, 0, 0.3);
    --shadow-xl: 0 10px 15px -3px rgba(0, 0, 0, 0.5), 0 4px 6px -4px rgba(0, 0, 0, 0.3);
    --shadow-glow: 0 0 24px rgba(129, 140, 248, 0.2);
  }
}

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

html {
  scroll-behavior: smooth;
  -webkit-text-size-adjust: 100%;
}

body {
  font-family: var(--font-family);
  font-size: var(--text-base);
  line-height: var(--leading-normal);
  color: var(--color-text);
  background: var(--color-background);
  min-height: 100dvh;
  display: flex;
  flex-direction: column;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

button {
  font-family: inherit;
  cursor: pointer;
  border: none;
  background: none;
  min-height: 44px;
  min-width: 44px;
}

textarea {
  font-family: inherit;
}

/* --- Layout --- */
.container {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 var(--space-4);
  width: 100%;
}

/* --- Header --- */
header {
  background: var(--color-surface);
  border-bottom: 1px solid var(--color-border);
  padding: var(--space-3) 0;
  position: sticky;
  top: 0;
  z-index: 100;
  backdrop-filter: blur(12px);
  background: color-mix(in srgb, var(--color-surface) 85%, transparent);
}

.header-content {
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: var(--space-4);
}

.logo-group {
  display: flex;
  align-items: center;
  gap: var(--space-3);
}

.logo-icon {
  color: var(--color-primary);
  flex-shrink: 0;
}

.logo-text {
  display: flex;
  align-items: baseline;
  gap: var(--space-2);
}

.logo {
  font-size: var(--text-xl);
  font-weight: var(--font-bold);
  color: var(--color-text);
  letter-spacing: -0.02em;
}

.subtitle {
  font-size: var(--text-xs);
  color: var(--color-text-tertiary);
  font-weight: var(--font-medium);
  text-transform: uppercase;
  letter-spacing: 0.05em;
}

nav {
  display: flex;
  gap: var(--space-1);
  background: var(--color-background);
  padding: var(--space-1);
  border-radius: var(--radius-md);
}

.nav-btn {
  display: flex;
  align-items: center;
  gap: var(--space-2);
  padding: var(--space-2) var(--space-3);
  border: none;
  background: transparent;
  color: var(--color-text-secondary);
  border-radius: var(--radius-sm);
  font-size: var(--text-sm);
  font-weight: var(--font-medium);
  transition: all var(--transition-fast) var(--ease-out);
  min-height: 36px;
}

.nav-btn:hover {
  color: var(--color-text);
  background: var(--color-surface);
}

.nav-btn.active {
  background: var(--color-surface);
  color: var(--color-primary);
  box-shadow: var(--shadow-sm);
}

.nav-btn svg {
  flex-shrink: 0;
}

/* --- Main --- */
main {
  flex: 1;
  padding: var(--space-8) 0 var(--space-6);
}

.view {
  display: none;
  animation: fadeIn var(--transition-slow) var(--ease-out);
}

.view.active {
  display: block;
}

@keyframes fadeIn {
  from { opacity: 0; transform: translateY(8px); }
  to { opacity: 1; transform: translateY(0); }
}

/* --- Section Header --- */
.section-header {
  display: flex;
  align-items: center;
  gap: var(--space-3);
  margin-bottom: var(--space-4);
}

.section-header h2 {
  font-size: var(--text-xl);
  font-weight: var(--font-semibold);
  color: var(--color-text);
  letter-spacing: -0.01em;
}

.section-count {
  font-size: var(--text-sm);
  color: var(--color-text-tertiary);
  background: var(--color-background);
  padding: var(--space-1) var(--space-3);
  border-radius: var(--radius-full);
  font-weight: var(--font-medium);
}

/* --- Translate Card --- */
.translate-card {
  background: var(--color-surface);
  border-radius: var(--radius-lg);
  box-shadow: var(--shadow-md);
  overflow: hidden;
  border: 1px solid var(--color-border);
}

.input-section {
  padding: var(--space-6);
}

/* Language Auto-Detect Indicator */
.lang-indicator {
  display: flex;
  align-items: center;
  gap: var(--space-2);
  margin-bottom: var(--space-4);
  font-size: var(--text-sm);
  color: var(--color-text-secondary);
}

.lang-dot {
  width: 8px;
  height: 8px;
  border-radius: 50%;
  background: var(--color-text-tertiary);
  transition: background var(--transition-normal) var(--ease-out);
}

.lang-dot.zh { background: var(--color-primary); }
.lang-dot.en { background: var(--color-success); }

/* Input Area */
.input-wrapper {
  position: relative;
  margin-bottom: var(--space-4);
}

#source-input {
  width: 100%;
  padding: var(--space-4);
  padding-bottom: var(--space-8);
  border: 2px solid var(--color-border);
  border-radius: var(--radius-md);
  font-size: var(--text-lg);
  resize: vertical;
  min-height: 100px;
  max-height: 200px;
  color: var(--color-text);
  background: var(--color-background-alt);
  transition: border-color var(--transition-fast) var(--ease-out),
              box-shadow var(--transition-fast) var(--ease-out),
              background-color var(--transition-fast) var(--ease-out);
  line-height: var(--leading-relaxed);
}

#source-input:focus {
  outline: none;
  border-color: var(--color-primary);
  box-shadow: var(--shadow-glow);
  background: var(--color-surface);
}

#source-input::placeholder {
  color: var(--color-text-tertiary);
}

.char-count {
  position: absolute;
  bottom: var(--space-3);
  right: var(--space-4);
  font-size: var(--text-xs);
  color: var(--color-text-tertiary);
  font-variant-numeric: tabular-nums;
}

/* Translate Button */
.primary-btn {
  width: 100%;
  padding: var(--space-4);
  background: var(--color-primary);
  color: var(--color-text-inverse);
  border: none;
  border-radius: var(--radius-md);
  font-size: var(--text-base);
  font-weight: var(--font-semibold);
  display: flex;
  align-items: center;
  justify-content: center;
  gap: var(--space-2);
  transition: all var(--transition-fast) var(--ease-out);
  min-height: 52px;
}

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

.primary-btn:active {
  background: var(--color-primary-active);
  transform: translateY(0);
  box-shadow: var(--shadow-md);
}

.primary-btn:disabled {
  opacity: 0.6;
  cursor: not-allowed;
  transform: none;
  box-shadow: none;
}

.btn-icon {
  flex-shrink: 0;
}

/* Spinner Animation */
.spinner {
  animation: spin 1s linear infinite;
}

@keyframes spin {
  from { transform: rotate(0deg); }
  to { transform: rotate(360deg); }
}

/* --- Result Section --- */
.result-section {
  border-top: 1px solid var(--color-border);
  padding: var(--space-6);
  animation: slideUp var(--transition-slow) var(--ease-out);
}

@keyframes slideUp {
  from { opacity: 0; transform: translateY(12px); }
  to { opacity: 1; transform: translateY(0); }
}

.result-header {
  display: flex;
  justify-content: space-between;
  align-items: flex-start;
  margin-bottom: var(--space-6);
  gap: var(--space-4);
}

.result-title-group {
  flex: 1;
}

.result-title-group h2 {
  font-size: var(--text-2xl);
  font-weight: var(--font-semibold);
  color: var(--color-text);
  letter-spacing: -0.02em;
  line-height: var(--leading-tight);
}

.register-tag {
  display: inline-block;
  margin-top: var(--space-2);
  font-size: var(--text-xs);
  color: var(--color-primary);
  background: var(--color-primary-subtle);
  padding: var(--space-1) var(--space-3);
  border-radius: var(--radius-full);
  font-weight: var(--font-medium);
}

.result-actions {
  display: flex;
  gap: var(--space-1);
  flex-shrink: 0;
}

.bookmark-btn, .copy-btn {
  display: flex;
  align-items: center;
  justify-content: center;
  padding: var(--space-2);
  border-radius: var(--radius-sm);
  transition: all var(--transition-fast) var(--ease-out);
  color: var(--color-text-tertiary);
  min-height: 44px;
  min-width: 44px;
}

.bookmark-btn:hover, .copy-btn:hover {
  background: var(--color-background);
  color: var(--color-text-secondary);
}

.bookmark-btn.active {
  color: var(--color-warning);
}

.bookmark-btn.active .bookmark-icon path {
  fill: var(--color-warning);
  stroke: var(--color-warning);
}

/* Result Content Sections */
.result-section h3 {
  font-size: var(--text-sm);
  font-weight: var(--font-semibold);
  text-transform: uppercase;
  letter-spacing: 0.05em;
  color: var(--color-text-tertiary);
  margin-bottom: var(--space-3);
  margin-top: var(--space-6);
}

.result-section h3:first-child {
  margin-top: 0;
}

/* Nuance List */
.nuance-list {
  list-style: none;
  padding: 0;
  display: flex;
  flex-direction: column;
  gap: var(--space-3);
}

.nuance-list li {
  padding: var(--space-3) var(--space-4);
  padding-left: var(--space-6);
  position: relative;
  background: var(--color-background-alt);
  border-radius: var(--radius-sm);
  font-size: var(--text-sm);
  line-height: var(--leading-relaxed);
  color: var(--color-text-secondary);
}

.nuance-list li::before {
  content: '';
  position: absolute;
  left: var(--space-4);
  top: 50%;
  transform: translateY(-50%);
  width: 6px;
  height: 6px;
  border-radius: 50%;
  background: var(--color-primary);
}

/* Example Cards */
.examples-grid {
  display: flex;
  flex-direction: column;
  gap: var(--space-3);
}

.example-card {
  background: var(--color-background-alt);
  border-radius: var(--radius-md);
  padding: var(--space-4);
  border: 1px solid var(--color-border);
  transition: all var(--transition-fast) var(--ease-out);
}

.example-card:hover {
  border-color: var(--color-border-strong);
  box-shadow: var(--shadow-sm);
}

.example-sentence {
  font-size: var(--text-base);
  font-weight: var(--font-medium);
  margin-bottom: var(--space-1);
  color: var(--color-text);
  line-height: var(--leading-tight);
}

.example-translation {
  color: var(--color-text-secondary);
  font-size: var(--text-sm);
  margin-bottom: var(--space-2);
  line-height: var(--leading-normal);
}

.example-context {
  font-size: var(--text-xs);
  color: var(--color-primary);
  background: var(--color-primary-subtle);
  padding: var(--space-1) var(--space-3);
  border-radius: var(--radius-full);
  display: inline-block;
  font-weight: var(--font-medium);
}

/* Usage Notes */
.usage-notes {
  background: var(--color-primary-subtle);
  padding: var(--space-4);
  border-radius: var(--radius-md);
  border-left: 3px solid var(--color-primary);
  font-size: var(--text-sm);
  line-height: var(--leading-relaxed);
  color: var(--color-text-secondary);
}

/* Related Expressions */
.related-list {
  list-style: none;
  padding: 0;
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-2);
}

.related-list li {
  background: var(--color-background-alt);
  padding: var(--space-2) var(--space-4);
  border-radius: var(--radius-full);
  font-size: var(--text-sm);
  color: var(--color-text-secondary);
  border: 1px solid var(--color-border);
  transition: all var(--transition-fast) var(--ease-out);
}

.related-list li:hover {
  border-color: var(--color-primary);
  color: var(--color-primary);
  background: var(--color-primary-subtle);
}

/* --- Translation List --- */
.translation-list {
  display: flex;
  flex-direction: column;
  gap: var(--space-3);
}

.translation-item {
  background: var(--color-surface);
  border-radius: var(--radius-md);
  padding: var(--space-4);
  box-shadow: var(--shadow-sm);
  border: 1px solid var(--color-border);
  cursor: pointer;
  transition: all var(--transition-fast) var(--ease-out);
}

.translation-item:hover {
  box-shadow: var(--shadow-md);
  border-color: var(--color-border-strong);
  transform: translateY(-1px);
}

.translation-item:active {
  transform: translateY(0);
}

.translation-item-header {
  display: flex;
  justify-content: space-between;
  align-items: flex-start;
  margin-bottom: var(--space-2);
  gap: var(--space-3);
}

.translation-source {
  font-size: var(--text-base);
  font-weight: var(--font-semibold);
  color: var(--color-text);
  line-height: var(--leading-tight);
}

.translation-date {
  font-size: var(--text-xs);
  color: var(--color-text-tertiary);
  white-space: nowrap;
  font-variant-numeric: tabular-nums;
}

.translation-result {
  color: var(--color-primary);
  font-size: var(--text-sm);
  font-weight: var(--font-medium);
}

.translation-item-footer {
  display: flex;
  align-items: center;
  gap: var(--space-2);
  margin-top: var(--space-2);
}

.bookmark-indicator {
  display: flex;
  align-items: center;
  gap: var(--space-1);
  font-size: var(--text-xs);
  color: var(--color-warning);
  font-weight: var(--font-medium);
}

.bookmark-indicator svg {
  width: 14px;
  height: 14px;
}

/* --- Skeleton Loading --- */
.skeleton-list {
  display: flex;
  flex-direction: column;
  gap: var(--space-3);
}

.skeleton-item {
  background: var(--color-surface);
  border-radius: var(--radius-md);
  padding: var(--space-4);
  border: 1px solid var(--color-border);
}

.skeleton-line {
  height: 12px;
  background: linear-gradient(90deg, var(--color-background) 25%, var(--color-background-alt) 50%, var(--color-background) 75%);
  background-size: 200% 100%;
  animation: shimmer 1.5s infinite;
  border-radius: var(--radius-sm);
}

.skeleton-sm { width: 40%; margin-bottom: var(--space-3); }
.skeleton-md { width: 70%; }

@keyframes shimmer {
  0% { background-position: 200% 0; }
  100% { background-position: -200% 0; }
}

/* --- Loading State --- */
.loading {
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  padding: var(--space-10);
  color: var(--color-text-tertiary);
  font-size: var(--text-sm);
  gap: var(--space-3);
}

.loading-spinner svg {
  color: var(--color-primary);
}

/* --- Empty State --- */
.empty-state {
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  padding: var(--space-12) var(--space-4);
  text-align: center;
  color: var(--color-text-tertiary);
}

.empty-state svg {
  color: var(--color-border-strong);
  margin-bottom: var(--space-4);
  opacity: 0.5;
}

.empty-state p {
  font-size: var(--text-base);
  font-weight: var(--font-medium);
  color: var(--color-text-secondary);
}

.empty-state .hint {
  font-size: var(--text-sm);
  color: var(--color-text-tertiary);
  margin-top: var(--space-2);
}

/* --- Load More Button --- */
.load-more-btn {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: var(--space-2);
  margin: var(--space-4) auto;
  padding: var(--space-3) var(--space-6);
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  font-size: var(--text-sm);
  font-weight: var(--font-medium);
  color: var(--color-text-secondary);
  transition: all var(--transition-fast) var(--ease-out);
  min-height: 44px;
}

.load-more-btn:hover {
  background: var(--color-background);
  border-color: var(--color-border-strong);
}

/* --- Footer --- */
footer {
  padding: var(--space-6) 0;
  text-align: center;
  color: var(--color-text-tertiary);
  font-size: var(--text-sm);
  border-top: 1px solid var(--color-border);
  margin-top: auto;
}

/* --- Modal --- */
.modal-overlay {
  position: fixed;
  inset: 0;
  z-index: 200;
  display: flex;
  justify-content: center;
  align-items: flex-start;
  padding: var(--space-12) var(--space-4) var(--space-4);
  overflow-y: auto;
  background: rgba(0, 0, 0, 0.4);
  backdrop-filter: blur(4px);
  animation: fadeIn var(--transition-slow) var(--ease-out);
}

.modal-overlay.active {
  display: flex;
}

.modal-content {
  background: var(--color-surface);
  border-radius: var(--radius-lg);
  max-width: 680px;
  width: 100%;
  padding: var(--space-6);
  box-shadow: var(--shadow-xl);
  position: relative;
  animation: slideUp var(--transition-slow) var(--ease-out);
  margin-bottom: var(--space-4);
}

.modal-close {
  position: absolute;
  top: var(--space-4);
  right: var(--space-4);
  padding: var(--space-2);
  border-radius: var(--radius-sm);
  color: var(--color-text-tertiary);
  transition: all var(--transition-fast) var(--ease-out);
  min-height: 44px;
  min-width: 44px;
  display: flex;
  align-items: center;
  justify-content: center;
}

.modal-close:hover {
  background: var(--color-background);
  color: var(--color-text);
}

/* --- Toast Notification --- */
.toast {
  position: fixed;
  bottom: var(--space-6);
  left: 50%;
  transform: translateX(-50%) translateY(100%);
  background: var(--color-text);
  color: var(--color-text-inverse);
  padding: var(--space-3) var(--space-5);
  border-radius: var(--radius-full);
  font-size: var(--text-sm);
  font-weight: var(--font-medium);
  box-shadow: var(--shadow-xl);
  z-index: 300;
  animation: toastIn var(--transition-slow) var(--ease-out) forwards;
  display: flex;
  align-items: center;
  gap: var(--space-2);
}

.toast.out {
  animation: toastOut var(--transition-slow) var(--ease-in-out) forwards;
}

@keyframes toastIn {
  from { transform: translateX(-50%) translateY(100%); opacity: 0; }
  to { transform: translateX(-50%) translateY(0); opacity: 1; }
}

@keyframes toastOut {
  from { transform: translateX(-50%) translateY(0); opacity: 1; }
  to { transform: translateX(-50%) translateY(100%); opacity: 0; }
}

/* --- Responsive --- */
@media (max-width: 640px) {
  .container {
    padding: 0 var(--space-3);
  }
  
  .header-content {
    flex-direction: column;
    gap: var(--space-3);
  }
  
  nav {
    width: 100%;
    justify-content: center;
  }
  
  .nav-btn span {
    display: none;
  }
  
  .nav-btn {
    padding: var(--space-2);
    min-width: 44px;
    justify-content: center;
  }
  
  .input-section {
    padding: var(--space-4);
  }
  
  .result-section {
    padding: var(--space-4);
  }
  
  .result-header {
    flex-direction: column;
    gap: var(--space-3);
  }
  
  .result-actions {
    align-self: flex-end;
  }
  
  .modal-content {
    padding: var(--space-4);
    margin-bottom: 0;
  }
}

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

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