/**
 * Book Code Builder - Stylesheet
 *
 * Architecture:
 * - CSS Custom Properties for theming
 * - Light/Dark mode via prefers-color-scheme
 * - Mobile-first responsive design
 * - BEM-like naming for components
 *
 * Sections:
 * 1. CSS Variables (Light/Dark themes)
 * 2. Base styles (html, body)
 * 3. Layout (container, panels)
 * 4. Components (buttons, tabs, inputs, etc.)
 * 5. Utility classes
 * 6. Mobile responsive overrides
 */

/* ========================================
   1. CSS VARIABLES - LIGHT THEME
   ======================================== */
/**
 * Light theme color palette
 * Applied when: prefers-color-scheme is light or not set
 */
:root {
  --bg: #fafafa;           /* Page background */
  --fg: #1f2937;           /* Primary text color */
  --muted: #6b7280;        /* Secondary text color */
  --accent: #0ea5e9;       /* Brand color (links, buttons) */
  --panel: #ffffff;        /* Card/panel background */
  --border: #e5e7eb;       /* Border color */
  --code: #111827;         /* Code text color */
  --hl: #fff7cc;           /* Highlight background */
  --error: #dc2626;        /* Error text color */
  --error-bg: #fee2e2;     /* Error background */
  --success: #16a34a;      /* Success text color */
  --success-bg: #dcfce7;   /* Success background */
  --warning: #ca8a04;      /* Warning text color */
  --warning-bg: #fef9c3;   /* Warning background */
}

/* ========================================
   DARK THEME
   ======================================== */
/**
 * Dark theme color palette
 * Applied when: prefers-color-scheme is dark
 *
 * Design notes:
 * - Reduced contrast for eye comfort
 * - Slightly desaturated colors
 * - Darker highlight to prevent glare
 */
@media (prefers-color-scheme: dark) {
  :root {
    --bg: #0f172a;           /* Dark slate background */
    --fg: #e2e8f0;           /* Light text */
    --muted: #94a3b8;        /* Muted text */
    --accent: #38bdf8;       /* Bright accent */
    --panel: #1e293b;        /* Elevated panel */
    --border: #334155;       /* Subtle border */
    --code: #f1f5f9;         /* Code text */
    --hl: #422006;           /* Dark highlight */
    --error: #f87171;        /* Soft red */
    --error-bg: #450a0a;     /* Dark red background */
    --success: #4ade80;      /* Soft green */
    --success-bg: #052e16;   /* Dark green background */
    --warning: #fbbf24;      /* Soft yellow */
    --warning-bg: #422006;   /* Dark yellow background */
  }
}

/* ========================================
   2. BASE STYLES
   ======================================== */
/**
 * Universal box-sizing for predictable layouts
 * Includes padding/border in element dimensions
 */
* { box-sizing: border-box; }

/**
 * Base styles for html and body
 * - System font stack for native look
 * - Japanese font support (Noto Sans JP, Hiragino, Meiryo)
 * - Comfortable line-height for readability
 */
html, body {
  margin: 0;
  padding: 0;
  background: var(--bg);
  color: var(--fg);
  font-family: system-ui, -apple-system, "Segoe UI", Roboto, "Noto Sans JP", "Hiragino Kaku Gothic ProN", "Meiryo", sans-serif;
  line-height: 1.6;
}

/* ========================================
   3. LAYOUT COMPONENTS
   ======================================== */

/**
 * App header - Site title and subtitle
 * Centered layout with generous top padding
 */
.app-header {
  padding: 24px 16px 8px;
  text-align: center;
}
.app-header h1 {
  margin: 0;
  font-size: 28px;
  letter-spacing: 0.2px;
}
.subtitle {
  margin: 6px 0 0;
  color: var(--muted);
  font-size: 14px;
}

/**
 * Main container - Centers content with max-width
 * Responsive: Full width on mobile, constrained on desktop
 */
.container {
  max-width: 980px;
  margin: 0 auto;
  padding: 16px;
}

/**
 * Panel - Card-like container for content sections
 * - Elevated appearance with subtle shadow
 * - Rounded corners for modern look
 * - Border for definition in light mode
 */
.panel {
  background: var(--panel);
  border: 1px solid var(--border);
  border-radius: 12px;
  padding: 16px;
  margin-bottom: 16px;
  box-shadow: 0 1px 0 rgba(0,0,0,0.02);
}

/* ========================================
   4. FORM CONTROLS
   ======================================== */

/**
 * Controls row - Flexible container for form inputs
 * - Wraps on small screens
 * - Even spacing between items
 * - Vertically aligned
 */
.controls {
  display: flex;
  flex-wrap: wrap;
  gap: 12px;
  align-items: center;
  margin: 8px 0 12px;
}
.controls label {
  font-size: 14px;
}
.controls input[type="number"] {
  width: 90px;
}

/**
 * Controls actions row - Right-aligned action buttons
 * - Min-width prevents layout shift when button text changes
 */
.controls-actions {
  display: flex;
  justify-content: flex-end;
  margin: 0 0 12px;
}
.controls-actions button {
  min-width: 160px;
}

/**
 * Textarea - Input/output areas for text
 * - Monospace font for cipher text readability
 * - Vertical resize only (horizontal locked to container)
 * - Fixed white background for consistency
 */
textarea {
  width: 100%;
  border: 1px solid var(--border);
  border-radius: 10px;
  padding: 12px;
  background: #fff;
  color: var(--fg);
  font-family: ui-monospace, SFMono-Regular, Menlo, Consolas, "Liberation Mono", monospace;
  font-size: 14px;
  resize: vertical;
}

/**
 * Input with sync button pattern
 * - Positioned absolutely above textarea
 * - On mobile: Stacks vertically via media query
 */
.input-with-sync {
  position: relative;
  margin-bottom: 12px;
}
.input-with-sync textarea {
  margin-bottom: 0;
}

/**
 * Sync button - Transfers cipher text between tabs
 * - Subtle styling to not compete with main buttons
 * - Hover state changes to accent color
 */
.sync-btn {
  position: absolute;
  top: -32px;
  right: 0;
  background: var(--bg);
  color: var(--fg);
  border: 1px solid var(--border);
  padding: 6px 12px;
  font-size: 13px;
  font-weight: 500;
  min-width: unset;
}
.sync-btn:hover:not(:disabled) {
  background: var(--accent);
  color: #fff;
  border-color: var(--accent);
}
.sync-btn:disabled {
  opacity: 0.5;
  cursor: not-allowed;
}
.sync-btn span {
  display: flex;
  align-items: center;
  gap: 4px;
}

/* Output with copy button */
.output-with-copy {
  position: relative;
  margin-bottom: 12px;
}
.output-with-copy textarea {
  margin-bottom: 0;
}
.copy-btn {
  position: absolute;
  top: -32px;
  right: 0;
  background: var(--bg);
  color: var(--fg);
  border: 1px solid var(--border);
  padding: 6px 12px;
  font-size: 13px;
  font-weight: 500;
  min-width: unset;
}
.copy-btn:hover:not(:disabled) {
  background: var(--accent);
  color: #fff;
  border-color: var(--accent);
}
.copy-btn span {
  display: flex;
  align-items: center;
  gap: 4px;
}

/* ========================================
   5. BUTTONS
   ======================================== */

/**
 * Primary button - Main action buttons
 * - Accent color for prominence
 * - Disabled state with reduced opacity
 * - Smooth transitions for hover/disabled states
 */
button {
  background: var(--accent);
  color: #fff;
  border: none;
  border-radius: 10px;
  padding: 10px 14px;
  cursor: pointer;
  font-weight: 600;
  transition: filter 0.2s, opacity 0.2s;
}
button:hover { filter: brightness(0.95); }
button:disabled {
  opacity: 0.6;
  cursor: not-allowed;
}

/**
 * Secondary button variant - Less prominent actions
 * - Neutral gray color
 * - Used for pagination, navigation
 */
button.secondary {
  background: #e5e7eb;
  color: var(--fg);
}
@media (prefers-color-scheme: dark) {
  button.secondary {
    background: #374151;
    color: var(--fg);
  }
}

.stats {
  margin-top: 12px;
  font-size: 14px;
  color: var(--muted);
}
.stats-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(120px, 1fr));
  gap: 12px;
  margin-top: 12px;
}
.stat-item {
  background: var(--bg);
  padding: 8px 12px;
  border-radius: 8px;
  font-size: 14px;
  color: var(--muted);
}
.stat-item strong {
  color: var(--fg);
  font-weight: 600;
}

/* ========================================
   6. TABS NAVIGATION
   ======================================== */

/**
 * Tab bar - Horizontal navigation
 * - Traditional tab appearance
 * - Wraps on small screens
 */
.tabs {
  display: flex;
  gap: 4px;
  margin: 16px 0 0;
  flex-wrap: wrap;
  border-bottom: none;
}

/**
 * Individual tab button
 * - Rounded top corners only
 * - Active tab connects visually to content panel
 * - Negative margin trick for seamless border
 */
.tab {
  background: var(--bg);
  color: var(--muted);
  border: 1px solid var(--border);
  border-bottom: none;
  padding: 12px 20px;
  border-radius: 12px 12px 0 0;
  cursor: pointer;
  font-weight: 600;
  transition: all 0.2s;
  position: relative;
  margin-bottom: 0;
}
.tab:hover {
  color: var(--fg);
  background: var(--panel);
}
.tab.active {
  background: var(--panel);
  color: var(--accent);
  border-bottom: 1px solid var(--panel);  /* Hides border to connect with panel */
  z-index: 1;
  margin-bottom: -1px;  /* Overlaps panel border */
}

/**
 * Tab content panels
 * - Hidden by default, shown when active
 * - Rounded corners except top-left (connected to tab)
 */
.tabcontent { display: none; }
.tabcontent.active {
  display: block;
  background: var(--panel);
  border: 1px solid var(--border);
  border-radius: 0 12px 12px 12px;
  padding: 20px;
  margin-bottom: 16px;
}

.viewer-controls {
  display: flex;
  gap: 12px;
  align-items: center;
  margin-bottom: 12px;
}
/* ========================================
   7. CODEBOOK VIEWER
   ======================================== */

/**
 * Viewer - Interactive codebook display
 * - Dashed border for distinction from textareas
 * - Scrollable with fixed max-height
 * - Monospace for coordinate alignment
 */
.viewer {
  border: 1px dashed var(--border);
  border-radius: 12px;
  background: var(--panel);
  padding: 12px;
  min-height: 200px;
  max-height: 500px;
  overflow-y: auto;
  font-family: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;
  white-space: pre-wrap;
}

/**
 * Line - One line in viewer
 * Prefixed with [p:l] coordinate
 */
.line {
  margin: 4px 0;
}

/**
 * Word - Clickable word in viewer
 * - Hover effect for interactivity
 * - Active state when clicked
 * - Smooth background transition
 */
.word {
  padding: 1px 3px;
  border-radius: 6px;
  transition: background 0.15s;
}
.word:hover { background: #eef6ff; }
.word.active { background: var(--hl); }

/* ========================================
   8. NOTIFICATION MESSAGES
   ======================================== */

/**
 * Notes - Status/feedback messages
 * Base styling for all note types
 */
.notes {
  margin-top: 8px;
  font-size: 13px;
  color: var(--muted);
  padding: 8px 12px;
  border-radius: 8px;
}

/* ========================================
   9. PRESET BUTTONS
   ======================================== */

/**
 * Preset button row - Quick sample/codebook selection
 * - Flexbox wrapping for responsive layout
 * - Label + buttons pattern
 */
.preset-buttons {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  align-items: center;
  margin-bottom: 12px;
}
.preset-label {
  font-size: 14px;
  color: var(--muted);
  font-weight: 600;
}

/**
 * Preset button - Individual preset selector
 * - Subtle default state
 * - Accent color on hover for clear affordance
 */
.preset-btn {
  background: var(--bg);
  color: var(--fg);
  border: 1px solid var(--border);
  padding: 6px 12px;
  font-size: 13px;
  font-weight: 500;
  transition: all 0.2s;
}
.preset-btn:hover {
  background: var(--accent);
  color: #fff;
  border-color: var(--accent);
}
.notes.error {
  color: var(--error);
  background: var(--error-bg);
  border-left: 3px solid var(--error);
}
.notes.success {
  color: var(--success);
  background: var(--success-bg);
  border-left: 3px solid var(--success);
}
.notes.warning {
  color: var(--warning);
  background: var(--warning-bg);
  border-left: 3px solid var(--warning);
}
.notes.info {
  color: var(--accent);
  background: #dbeafe;
  border-left: 3px solid var(--accent);
}
@media (prefers-color-scheme: dark) {
  .notes.info {
    background: #082f49;
  }
}

footer .footer {
  text-align: center;
  color: var(--muted);
  font-size: 14px;
  padding: 16px 0 24px;
}
footer a { color: var(--accent); text-decoration: none; }
footer a:hover { text-decoration: underline; }

/* Focus states for accessibility */
button:focus-visible,
input:focus-visible,
textarea:focus-visible {
  outline: 2px solid var(--accent);
  outline-offset: 2px;
}

/* Tooltip */
.tooltip {
  position: relative;
  display: inline-block;
  cursor: help;
  color: var(--accent);
  font-weight: 700;
  margin-left: 4px;
  width: 18px;
  height: 18px;
  border: 2px solid var(--accent);
  border-radius: 50%;
  text-align: center;
  line-height: 14px;
  font-size: 12px;
  background: var(--panel);
  transition: all 0.2s;
}
.tooltip:hover {
  background: var(--accent);
  color: var(--panel);
}
.tooltip .tooltiptext {
  visibility: hidden;
  width: 220px;
  background-color: var(--code);
  color: var(--panel);
  text-align: left;
  border-radius: 8px;
  padding: 8px 10px;
  position: absolute;
  z-index: 1;
  bottom: 125%;
  left: 50%;
  margin-left: -110px;
  opacity: 0;
  transition: opacity 0.3s;
  font-size: 12px;
  font-weight: normal;
  line-height: 1.4;
}
.tooltip:hover .tooltiptext {
  visibility: visible;
  opacity: 1;
}
.tooltip .tooltiptext::after {
  content: "";
  position: absolute;
  top: 100%;
  left: 50%;
  margin-left: -5px;
  border-width: 5px;
  border-style: solid;
  border-color: var(--code) transparent transparent transparent;
}

/* Viewer selection info */
.viewer-selection {
  margin-top: 12px;
  padding: 10px 14px;
  background: var(--bg);
  border-radius: 8px;
  font-size: 13px;
  color: var(--fg);
  font-family: ui-monospace, monospace;
  border: 1px solid var(--border);
  line-height: 1.6;
}
.viewer-selection strong {
  color: var(--accent);
}

/* ========================================
   10. ACCORDION (HELP SECTIONS)
   ======================================== */

/**
 * Accordion - Expandable/collapsible content sections
 * Used in Help tab for organized information
 * - Hover effect for interactivity
 * - Smooth transitions
 */
.accordion {
  background: var(--bg);
  border: 1px solid var(--border);
  border-radius: 10px;
  margin-bottom: 12px;
  overflow: hidden;
  transition: all 0.2s;
}
.accordion:hover {
  border-color: var(--accent);
}

/**
 * Accordion summary - Clickable header
 * - Custom arrow indicator (▶ rotates to ▼ when open)
 * - Removes default details marker
 * - Prevents text selection for cleaner UX
 */
.accordion summary {
  cursor: pointer;
  padding: 14px 16px;
  font-weight: 600;
  font-size: 15px;
  color: var(--fg);
  background: var(--bg);
  user-select: none;
  transition: all 0.2s;
  list-style: none;
  display: flex;
  align-items: center;
}
.accordion summary::-webkit-details-marker {
  display: none;
}
.accordion summary::before {
  content: "▶";
  display: inline-block;
  width: 20px;
  margin-right: 8px;
  font-size: 12px;
  transition: transform 0.2s;
  color: var(--accent);
}
.accordion[open] summary::before {
  transform: rotate(90deg);
}
.accordion summary:hover {
  background: var(--panel);
  color: var(--accent);
}

/**
 * Accordion content - Revealed content area
 * - Fade-in animation for smooth reveal
 * - Elevated background for hierarchy
 */
.accordion-content {
  padding: 16px;
  background: var(--panel);
  border-top: 1px solid var(--border);
  animation: fadeIn 0.3s ease-in;
}
@keyframes fadeIn {
  from {
    opacity: 0;
    transform: translateY(-10px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}
.accordion-content h3 {
  margin-top: 0;
  margin-bottom: 12px;
  font-size: 16px;
  color: var(--accent);
  border-bottom: 2px solid var(--border);
  padding-bottom: 6px;
}
.accordion-content h4 {
  margin-top: 16px;
  margin-bottom: 8px;
  font-size: 14px;
  color: var(--fg);
}
.accordion-content p {
  margin: 8px 0;
  line-height: 1.7;
}
.accordion-content ul, .accordion-content ol {
  margin: 8px 0;
  padding-left: 24px;
}
.accordion-content li {
  margin: 6px 0;
  line-height: 1.6;
}
.accordion-content code {
  background: var(--bg);
  padding: 2px 6px;
  border-radius: 4px;
  font-size: 13px;
  font-family: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;
  color: var(--code);
  border: 1px solid var(--border);
}
.note-box {
  padding: 12px 14px;
  border-radius: 8px;
  margin: 12px 0;
  line-height: 1.6;
}
.note-box.info {
  background: #dbeafe;
  border-left: 3px solid var(--accent);
  color: var(--code);
}
.note-box.warning {
  background: var(--warning-bg);
  border-left: 3px solid var(--warning);
  color: var(--code);
}
@media (prefers-color-scheme: dark) {
  .note-box.info {
    background: #082f49;
    color: var(--fg);
  }
  .note-box.warning {
    color: var(--fg);
  }
}

/* Mobile responsive styles */
/* ========================================
   11. UTILITY CLASSES
   ======================================== */

/**
 * Hidden - Visibility control (replaces inline style display:none)
 * Used for dynamic show/hide via classList
 */
.hidden {
  display: none;
}

/**
 * Line number - Muted color for coordinate prefixes
 * Used in viewer for [p:l] display
 */
.line-number {
  color: #9ca3af;
}

/**
 * Coordinate highlight - Emphasized coordinate display
 * Used in viewer selection info to highlight current coordinate
 */
.coord-highlight {
  background: var(--hl);
  padding: 2px 4px;
  border-radius: 3px;
}

/* ========================================
   12. RESPONSIVE DESIGN (MOBILE)
   ======================================== */

/**
 * Mobile breakpoint: 640px and below
 *
 * Changes:
 * - Stacked layouts instead of horizontal
 * - Full-width buttons
 * - Larger touch targets (min 44px)
 * - Font-size: 16px on inputs to prevent iOS zoom
 * - Repositioned floating buttons (sync, copy)
 */
@media (max-width: 640px) {
  .container {
    padding: 12px;
  }

  /* Stack controls vertically */
  .controls {
    flex-direction: column;
    align-items: stretch;
  }

  .controls label {
    width: 100%;
  }

  .controls input[type="number"] {
    width: 100%;
  }

  .controls-actions {
    justify-content: stretch;
  }

  .controls-actions button {
    width: 100%;
    min-width: unset;
    padding: 12px;  /* Larger touch target */
  }

  /* Tabs remain horizontal but adapt sizing */
  .tabs {
    flex-wrap: wrap;
    gap: 2px;
  }

  .tab {
    flex: 1 1 auto;
    padding: 12px 8px;
    min-height: 44px;  /* Minimum touch target size (Apple HIG) */
    text-align: center;
    font-size: 13px;
  }

  .viewer-controls {
    flex-direction: column;
    align-items: stretch;
  }

  .viewer-controls label {
    width: 100%;
  }

  .viewer-controls input {
    width: 100%;
  }

  .viewer-controls button {
    width: 100%;
    padding: 12px;
  }

  /* Prevent iOS auto-zoom on input focus */
  textarea {
    font-size: 16px; /* iOS zooms if font-size < 16px */
  }

  /* 2-column grid for stats on mobile */
  .stats-grid {
    grid-template-columns: 1fr 1fr;
  }

  /**
   * Reposition floating buttons on mobile
   * - Move from absolute (desktop) to static (mobile)
   * - Stack vertically above textareas
   * - column-reverse: Button appears above textarea
   */
  .sync-btn {
    position: static;
    width: 100%;
    margin-bottom: 8px;
  }

  .input-with-sync {
    display: flex;
    flex-direction: column-reverse;
  }

  .copy-btn {
    position: static;
    width: 100%;
    margin-bottom: 8px;
  }

  .output-with-copy {
    display: flex;
    flex-direction: column-reverse;
  }
}

/* ========================================
   END OF STYLESHEET
   ======================================== */