/* ==========================================================================
   Letter App - Monochrome Design System
   Super Clean, Minimal
   ========================================================================== */

/* --------------------------------------------------------------------------
   CSS Variables
   -------------------------------------------------------------------------- */
:root {
  /* Base gray scale */
  --black: #000;
  --gray-900: #111;
  --gray-800: #222;
  --gray-700: #333;
  --gray-600: #555;
  --gray-500: #777;
  --gray-400: #999;
  --gray-300: #bbb;
  --gray-200: #ddd;
  --gray-100: #f5f5f5;
  --white: #fff;

  /* Semantic colors (light mode) */
  --color-bg: var(--white);
  --color-bg-elevated: var(--white);
  --color-bg-muted: var(--gray-100);
  --color-fg: var(--black);
  --color-fg-muted: var(--gray-600);
  --color-fg-subtle: var(--gray-500);
  --color-fg-faint: var(--gray-400);
  --color-border: var(--gray-200);
  --color-border-strong: var(--gray-400);
  --color-input-bg: var(--white);
  --color-btn-primary-bg: var(--black);
  --color-btn-primary-fg: var(--white);
  --color-btn-primary-hover: var(--gray-800);
  --color-overlay: rgba(0, 0, 0, 0.5);

  --space-xs: 4px;
  --space-sm: 8px;
  --space-md: 16px;
  --space-lg: 24px;
  --space-xl: 32px;
  --space-2xl: 48px;
  --space-3xl: 64px;

  --font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
  --font-size-xs: 11px;
  --font-size-sm: 13px;
  --font-size-base: 15px;
  --font-size-lg: 17px;
  --font-size-xl: 20px;
  --font-size-2xl: 24px;

  --line-height: 1.5;
  --border: 1px solid var(--color-border);
  --transition: 150ms ease;
}

/* --------------------------------------------------------------------------
   Dark Mode
   -------------------------------------------------------------------------- */
@media (prefers-color-scheme: dark) {
  :root {
    --color-bg: #0d0d0d;
    --color-bg-elevated: #1a1a1a;
    --color-bg-muted: #252525;
    --color-fg: #f0f0f0;
    --color-fg-muted: #b0b0b0;
    --color-fg-subtle: #888;
    --color-fg-faint: #666;
    --color-border: #333;
    --color-border-strong: #555;
    --color-input-bg: #1a1a1a;
    --color-btn-primary-bg: #f0f0f0;
    --color-btn-primary-fg: #0d0d0d;
    --color-btn-primary-hover: #d0d0d0;
    --color-overlay: rgba(0, 0, 0, 0.7);
  }
}

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

html {
  font-size: 16px;
  -webkit-text-size-adjust: 100%;
}

body {
  font-family: var(--font-family);
  font-size: var(--font-size-base);
  line-height: var(--line-height);
  color: var(--color-fg);
  background: var(--color-bg);
  -webkit-font-smoothing: antialiased;
}

/* --------------------------------------------------------------------------
   App Container
   -------------------------------------------------------------------------- */
#app {
  max-width: 100%;
  margin: 0 auto;
  min-height: 100vh;
  background: var(--color-bg);
}

.main {
  max-width: 640px;
  margin: 0 auto;
}

/* --------------------------------------------------------------------------
   Header
   -------------------------------------------------------------------------- */
.header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: var(--space-lg) var(--space-lg);
  border-bottom: var(--border);
  background: var(--color-bg-elevated);
  position: sticky;
  top: 0;
  z-index: 100;
}

.header-title {
  font-size: var(--font-size-sm);
  font-weight: 700;
  letter-spacing: 0.15em;
  text-transform: uppercase;
}

.header-center {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 2px;
}

.save-indicator {
  font-size: var(--font-size-xs);
  color: var(--color-fg-faint);
  opacity: 0;
  transition: opacity var(--transition);
}

.header-back {
  display: flex;
  align-items: center;
  justify-content: center;
  width: 40px;
  height: 40px;
  margin-left: -8px;
  color: var(--color-fg);
  text-decoration: none;
  transition: opacity var(--transition);
}

.header-back:hover {
  opacity: 0.6;
}

.header-back svg {
  width: 20px;
  height: 20px;
}

.header-icon {
  display: flex;
  align-items: center;
  justify-content: center;
  width: 40px;
  height: 40px;
  margin-right: -8px;
  color: var(--color-fg);
  background: none;
  border: none;
  cursor: pointer;
  transition: opacity var(--transition);
}

.header-icon:hover {
  opacity: 0.6;
  background: none;
  border: none;
}

.header-icon svg {
  width: 20px;
  height: 20px;
}

/* Placeholder for empty header icon space */
.header-icon:empty {
  visibility: hidden;
}

/* --------------------------------------------------------------------------
   Main Content
   -------------------------------------------------------------------------- */
.main {
  padding: var(--space-lg);
}

.main.editor {
  padding-bottom: var(--space-3xl);
}

/* --------------------------------------------------------------------------
   Buttons
   -------------------------------------------------------------------------- */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: var(--space-sm);
  height: 44px;
  padding: 0 var(--space-lg);
  font-family: inherit;
  font-size: var(--font-size-sm);
  font-weight: 500;
  text-decoration: none;
  color: var(--color-fg);
  background: var(--color-bg);
  border: var(--border);
  cursor: pointer;
  transition: all var(--transition);
}

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

.btn:active {
  background: var(--color-bg-muted);
}

.btn-primary {
  color: var(--color-btn-primary-fg);
  background: var(--color-btn-primary-bg);
  border-color: var(--color-btn-primary-bg);
}

.btn-primary:hover {
  background: var(--color-btn-primary-hover);
  border-color: var(--color-btn-primary-hover);
}

.btn-secondary {
  color: var(--color-fg-muted);
  background: var(--color-bg-muted);
  border-color: var(--color-bg-muted);
}

.btn-secondary:hover {
  background: var(--color-border);
  border-color: var(--color-border);
}

.btn-danger {
  color: var(--color-fg-muted);
  background: var(--color-bg);
  border-color: var(--color-border);
}

.btn-danger:hover {
  color: #e55;
  border-color: #e55;
}

.btn-block {
  width: 100%;
}

/* --------------------------------------------------------------------------
   Letter List
   -------------------------------------------------------------------------- */
.letter-list {
  margin-top: var(--space-lg);
}

.letter-item {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: var(--space-md);
  padding: var(--space-md) 0;
  border-bottom: var(--border);
  text-decoration: none;
  color: inherit;
  transition: opacity var(--transition);
}

.letter-item:hover {
  opacity: 0.7;
}

.letter-item:first-child {
  border-top: var(--border);
}

.letter-item-content {
  flex: 1;
  min-width: 0;
}

.letter-item-subject {
  font-size: var(--font-size-base);
  font-weight: 500;
  margin-bottom: 2px;
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
}

.letter-item-meta {
  font-size: var(--font-size-xs);
  color: var(--color-fg-subtle);
}

.letter-item-meta span {
  display: inline;
}

.letter-item-meta span::after {
  content: " · ";
}

.letter-item-meta span:last-child::after {
  content: "";
}

.letter-item-type {
  text-transform: uppercase;
  letter-spacing: 0.05em;
}

.letter-item-date {
  font-size: var(--font-size-xs);
  color: var(--color-fg-faint);
  white-space: nowrap;
}

/* Profile List */
.profile-list {
  margin-top: var(--space-lg);
}

.profile-item {
  display: block;
  padding: var(--space-md) 0;
  border-bottom: var(--border);
  text-decoration: none;
  color: inherit;
  transition: opacity var(--transition);
}

.profile-item:hover {
  opacity: 0.7;
}

.profile-item:first-child {
  border-top: var(--border);
}

.profile-item-name {
  font-weight: 500;
  margin-bottom: 2px;
}

.profile-item-details {
  font-size: var(--font-size-xs);
  color: var(--color-fg-subtle);
}

/* Empty State */
.empty-state {
  padding: var(--space-2xl) var(--space-md);
  text-align: center;
  color: var(--color-fg-faint);
  font-size: var(--font-size-sm);
}

/* Import/Export Buttons */
.import-export-buttons {
  display: flex;
  gap: var(--space-sm);
  margin-top: var(--space-xl);
  padding-top: var(--space-lg);
  border-top: var(--border);
}

.import-export-buttons .btn {
  flex: 1;
}

/* --------------------------------------------------------------------------
   Forms
   -------------------------------------------------------------------------- */
.form-group {
  margin-bottom: var(--space-lg);
}

.form-label {
  display: block;
  font-size: var(--font-size-xs);
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  color: var(--color-fg-subtle);
  margin-bottom: var(--space-sm);
}

.form-input {
  display: block;
  width: 100%;
  height: 48px;
  padding: 0 var(--space-md);
  font-family: inherit;
  font-size: var(--font-size-base);
  color: var(--color-fg);
  background: var(--color-input-bg);
  border: var(--border);
  transition: border-color var(--transition);
}

.form-input:focus {
  outline: none;
  border-color: var(--color-fg);
}

.form-input::placeholder {
  color: var(--color-fg-faint);
}

.form-textarea {
  height: auto;
  min-height: 160px;
  padding: var(--space-md);
  resize: vertical;
  line-height: var(--line-height);
}

select.form-input {
  appearance: none;
  background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='12' height='12' viewBox='0 0 12 12'%3E%3Cpath fill='%23555' d='M6 8L2 4h8z'/%3E%3C/svg%3E");
  background-repeat: no-repeat;
  background-position: right var(--space-md) center;
  padding-right: var(--space-xl);
  cursor: pointer;
}

@media (prefers-color-scheme: dark) {
  select.form-input {
    background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='12' height='12' viewBox='0 0 12 12'%3E%3Cpath fill='%23888' d='M6 8L2 4h8z'/%3E%3C/svg%3E");
  }
}

/* Form Row (side by side) */
.form-row {
  display: flex;
  gap: var(--space-md);
}

.form-row .form-group {
  flex: 1;
}

.form-row .form-group-small {
  flex: 0 0 100px;
}

.form-row .form-group-large {
  flex: 1;
}

/* Fieldset */
.form-fieldset {
  border: none;
  margin-bottom: var(--space-lg);
  padding: 0;
}

.form-fieldset legend {
  font-size: var(--font-size-xs);
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.1em;
  color: var(--color-fg-faint);
  margin-bottom: var(--space-md);
  padding-bottom: var(--space-sm);
  border-bottom: var(--border);
  width: 100%;
}

/* Radio Group */
.radio-group {
  display: flex;
  gap: var(--space-lg);
}

.radio-label {
  display: flex;
  align-items: center;
  gap: var(--space-sm);
  font-size: var(--font-size-sm);
  cursor: pointer;
}

.radio-label input[type="radio"] {
  appearance: none;
  width: 18px;
  height: 18px;
  border: 2px solid var(--color-border);
  border-radius: 50%;
  cursor: pointer;
  transition: all var(--transition);
}

.radio-label input[type="radio"]:checked {
  border-color: var(--color-fg);
  background: var(--color-fg);
  box-shadow: inset 0 0 0 3px var(--color-bg);
}

/* --------------------------------------------------------------------------
   Editor Toolbar
   -------------------------------------------------------------------------- */
.toolbar {
  display: flex;
  gap: 2px;
  margin-bottom: var(--space-xs);
}

.toolbar-btn {
  display: flex;
  align-items: center;
  justify-content: center;
  width: 36px;
  height: 36px;
  font-size: var(--font-size-base);
  color: var(--color-fg-muted);
  background: var(--color-bg-muted);
  border: none;
  cursor: pointer;
  transition: all var(--transition);
}

.toolbar-btn:hover {
  background: var(--color-border);
  color: var(--color-fg);
}

.toolbar-btn strong {
  font-weight: 700;
}

.toolbar-btn em {
  font-style: italic;
}

/* --------------------------------------------------------------------------
   Export Buttons
   -------------------------------------------------------------------------- */
.export-buttons {
  display: flex;
  gap: var(--space-sm);
  margin-bottom: var(--space-lg);
}

.export-buttons .btn {
  flex: 1;
  height: 40px;
  font-size: var(--font-size-xs);
  text-transform: uppercase;
  letter-spacing: 0.05em;
}

/* --------------------------------------------------------------------------
   Responsive
   -------------------------------------------------------------------------- */
@media (max-width: 480px) {
  :root {
    --space-lg: 20px;
  }

  .header {
    padding: var(--space-md) var(--space-md);
  }

  .main {
    padding: var(--space-md);
  }

  .form-row {
    flex-direction: column;
    gap: 0;
  }

  .form-row .form-group-small {
    flex: 1;
  }
}

/* --------------------------------------------------------------------------
   Collapsible Section
   -------------------------------------------------------------------------- */
.collapsible-section {
  margin-bottom: var(--space-lg);
  border: var(--border);
  background: var(--color-bg-elevated);
}

.collapsible-header {
  display: flex;
  align-items: center;
  gap: var(--space-sm);
  padding: var(--space-md);
  cursor: pointer;
  user-select: none;
  list-style: none;
}

.collapsible-header::-webkit-details-marker {
  display: none;
}

.collapsible-title {
  font-size: var(--font-size-sm);
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  color: var(--color-fg-muted);
}

.collapsible-preview {
  flex: 1;
  font-size: var(--font-size-sm);
  color: var(--color-fg-faint);
  text-align: right;
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
}

.collapsible-icon {
  color: var(--color-fg-faint);
  transition: transform var(--transition);
  flex-shrink: 0;
}

.collapsible-section[open] .collapsible-icon {
  transform: rotate(180deg);
}

.collapsible-section[open] .collapsible-preview {
  display: none;
}

.collapsible-content {
  padding: 0 var(--space-md) var(--space-md);
}

/* --------------------------------------------------------------------------
   Animations
   -------------------------------------------------------------------------- */
@keyframes fadeIn {
  from { opacity: 0; }
  to { opacity: 1; }
}

.main {
  animation: fadeIn 200ms ease;
}

/* --------------------------------------------------------------------------
   Footer
   -------------------------------------------------------------------------- */
.app-footer {
  margin-top: var(--space-2xl);
  padding-top: var(--space-lg);
  border-top: var(--border);
  text-align: center;
}

.footer-notice {
  font-size: var(--font-size-xs);
  color: var(--color-fg-subtle);
  line-height: 1.6;
  margin-bottom: var(--space-sm);
}

.footer-links {
  font-size: var(--font-size-xs);
  color: var(--color-fg-faint);
}

.footer-links a {
  color: var(--color-fg-subtle);
  text-decoration: none;
  transition: color var(--transition);
}

.footer-links a:hover {
  color: var(--color-fg);
}

.footer-separator {
  margin: 0 var(--space-xs);
}

/* --------------------------------------------------------------------------
   Header Actions
   -------------------------------------------------------------------------- */
.header-actions {
  display: flex;
  align-items: center;
  gap: var(--space-xs);
  margin-right: -8px;
}

/* Language Selector */
.language-select {
  appearance: none;
  background: none;
  border: var(--border);
  color: var(--color-fg-muted);
  font-family: inherit;
  font-size: var(--font-size-xs);
  font-weight: 600;
  letter-spacing: 0.05em;
  padding: 4px 8px;
  cursor: pointer;
  transition: all var(--transition);
}

.language-select:hover {
  border-color: var(--color-border-strong);
  color: var(--color-fg);
}

.language-select:focus {
  outline: none;
  border-color: var(--color-fg);
}

/* --------------------------------------------------------------------------
   Modal
   -------------------------------------------------------------------------- */
.modal-overlay {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  background: var(--color-overlay);
  display: flex;
  align-items: center;
  justify-content: center;
  padding: var(--space-md);
  z-index: 1000;
  animation: fadeIn 150ms ease;
}

.modal {
  background: var(--color-bg-elevated);
  width: 100%;
  max-width: 400px;
  max-height: 90vh;
  overflow-y: auto;
  animation: slideUp 200ms ease;
}

@keyframes slideUp {
  from {
    opacity: 0;
    transform: translateY(20px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

.modal-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: var(--space-md) var(--space-lg);
  border-bottom: var(--border);
}

.modal-title {
  font-size: var(--font-size-lg);
  font-weight: 600;
}

.modal-close {
  display: flex;
  align-items: center;
  justify-content: center;
  width: 40px;
  height: 40px;
  margin-right: -8px;
  background: none;
  border: none;
  color: var(--color-fg-subtle);
  cursor: pointer;
  transition: color var(--transition);
}

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

.modal-body {
  padding: var(--space-lg);
}

.help-section {
  margin-bottom: var(--space-lg);
}

.help-section:last-child {
  margin-bottom: 0;
}

.help-section h3 {
  font-size: var(--font-size-sm);
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  color: var(--color-fg-subtle);
  margin-bottom: var(--space-sm);
}

.help-section p {
  font-size: var(--font-size-sm);
  color: var(--color-fg-muted);
  line-height: 1.6;
  margin-bottom: var(--space-sm);
}

.help-section p:last-child {
  margin-bottom: 0;
}

.help-instructions {
  display: flex;
  flex-direction: column;
  gap: var(--space-sm);
}

.help-browser {
  font-size: var(--font-size-sm);
  padding: var(--space-sm) var(--space-md);
  background: var(--color-bg-muted);
}

.help-browser strong {
  display: block;
  color: var(--color-fg);
  margin-bottom: 2px;
}

.help-browser span {
  color: var(--color-fg-muted);
}

.help-shortcuts {
  display: flex;
  flex-direction: column;
  gap: var(--space-xs);
  font-size: var(--font-size-sm);
}

.help-shortcuts kbd {
  font-family: monospace;
  background: var(--color-bg-muted);
  padding: 2px 6px;
  border: var(--border);
}

.help-footer {
  padding-top: var(--space-md);
  border-top: var(--border);
  text-align: center;
  font-size: var(--font-size-xs);
  color: var(--color-fg-faint);
}

.help-footer a {
  color: var(--color-fg-subtle);
  text-decoration: none;
}

.help-footer a:hover {
  color: var(--color-fg);
}

/* --------------------------------------------------------------------------
   Template Modal
   -------------------------------------------------------------------------- */
.modal-large {
  max-width: 600px;
}

.template-category {
  margin-bottom: var(--space-lg);
}

.template-category:last-child {
  margin-bottom: 0;
}

.template-category-title {
  font-size: var(--font-size-xs);
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  color: var(--color-fg-subtle);
  margin-bottom: var(--space-sm);
  padding-bottom: var(--space-xs);
  border-bottom: var(--border);
}

.template-grid {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: var(--space-sm);
}

@media (max-width: 480px) {
  .template-grid {
    grid-template-columns: 1fr;
  }
}

.template-card {
  display: flex;
  flex-direction: column;
  align-items: flex-start;
  padding: var(--space-md);
  background: var(--color-bg-muted);
  border: none;
  cursor: pointer;
  text-align: left;
  transition: all var(--transition);
}

.template-card:hover {
  background: var(--color-border);
}

.template-card-name {
  font-size: var(--font-size-sm);
  font-weight: 500;
  color: var(--color-fg);
  margin-bottom: 2px;
}

.template-card-desc {
  font-size: var(--font-size-xs);
  color: var(--color-fg-subtle);
}