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

:root {
  --primary: #1a73e8;
  --primary-light: #e8f0fe;
  --primary-dark: #1557b0;
  --bg: #ffffff;
  --bg-secondary: #f8f9fa;
  --bg-tertiary: #f1f3f4;
  --text: #333333;
  --text-secondary: #5f6368;
  --text-tertiary: #9aa0a6;
  --border: #e1e4e8;
  --border-light: #f0f0f0;
  --code-bg: #f6f8fa;
  --shadow: 0 1px 3px rgba(0, 0, 0, 0.08);
  --shadow-lg: 0 4px 12px rgba(0, 0, 0, 0.1);
  --radius: 6px;
  --toolbar-height: 44px;
  --statusbar-height: 28px;
  --sidebar-width: 240px;
  --sidebar-bg: var(--bg-secondary);
  --sidebar-border: var(--border);
  --sidebar-hover: var(--bg-tertiary);
  --sidebar-active: var(--primary-light);
  --search-bg: var(--bg-secondary);
  --search-border: var(--border);
  --font-ui: system-ui, -apple-system, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
  --font-mono: "Cascadia Code", "Fira Code", "JetBrains Mono", Consolas, "Courier New", monospace;
}

/* ===== Dark Theme ===== */
:root.dark {
  --primary: #8ab4f8;
  --primary-light: #1a3a5c;
  --primary-dark: #aecbfa;
  --bg: #1e1e1e;
  --bg-secondary: #252526;
  --bg-tertiary: #2d2d2d;
  --text: #d4d4d4;
  --text-secondary: #9e9e9e;
  --text-tertiary: #6e6e6e;
  --border: #3e3e3e;
  --border-light: #333333;
  --code-bg: #2d2d2d;
  --shadow: 0 1px 3px rgba(0, 0, 0, 0.3);
  --shadow-lg: 0 4px 12px rgba(0, 0, 0, 0.4);
}

html, body {
  height: 100%;
  font-family: var(--font-ui);
  font-size: 14px;
  color: var(--text);
  background: var(--bg);
  overflow: hidden;
  user-select: none;
}

#app {
  display: flex;
  flex-direction: column;
  height: 100vh;
}

/* ===== Toolbar ===== */
#toolbar {
  height: var(--toolbar-height);
  background: var(--bg);
  border-bottom: 1px solid var(--border);
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 0 8px;
  flex-shrink: 0;
  z-index: 10;
}

.toolbar-left,
.toolbar-right {
  display: flex;
  align-items: center;
  gap: 2px;
}

.toolbar-btn {
  display: flex;
  align-items: center;
  gap: 5px;
  padding: 6px 12px;
  border: none;
  background: transparent;
  color: var(--text-secondary);
  font-size: 13px;
  font-family: var(--font-ui);
  border-radius: var(--radius);
  cursor: pointer;
  transition: all 0.15s ease;
  white-space: nowrap;
}

.toolbar-btn:hover {
  background: var(--bg-tertiary);
  color: var(--text);
}

.toolbar-btn.active {
  background: var(--primary-light);
  color: var(--primary);
}

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

.toolbar-divider {
  width: 1px;
  height: 24px;
  background: var(--border);
  margin: 0 6px;
}

/* ===== Modified Banner ===== */
#modified-banner {
  display: flex;
  align-items: center;
  gap: 12px;
  padding: 6px 12px;
  background: #fff3cd;
  border-bottom: 1px solid #ffc107;
  font-size: 13px;
  color: #856404;
  flex-shrink: 0;
}

:root.dark #modified-banner {
  background: #3a3000;
  border-bottom-color: #665500;
  color: #ffd54f;
}

#modified-banner.hidden {
  display: none;
}

.banner-btn {
  padding: 2px 10px;
  border: 1px solid #ffc107;
  border-radius: 4px;
  background: transparent;
  color: #856404;
  font-size: 12px;
  cursor: pointer;
  font-family: var(--font-ui);
}

:root.dark .banner-btn {
  border-color: #665500;
  color: #ffd54f;
}

.banner-btn:hover {
  background: #ffc107;
  color: #000;
}

:root.dark .banner-btn:hover {
  background: #665500;
  color: #fff;
}

/* ===== Tab Bar ===== */
#tab-bar {
  height: 36px;
  background: var(--bg-secondary);
  border-bottom: 1px solid var(--border);
  display: flex;
  align-items: flex-end;
  padding: 0 4px;
  flex-shrink: 0;
  overflow-x: auto;
  overflow-y: hidden;
}

#tab-bar::-webkit-scrollbar {
  height: 0;
}

#tab-list {
  display: flex;
  align-items: flex-end;
  gap: 1px;
  flex: 1;
  min-width: 0;
  overflow-x: auto;
  overflow-y: hidden;
}

#tab-list::-webkit-scrollbar {
  height: 0;
}

.tab-item {
  display: flex;
  align-items: center;
  gap: 6px;
  padding: 6px 12px;
  background: transparent;
  border: none;
  border-bottom: 2px solid transparent;
  color: var(--text-secondary);
  font-size: 12px;
  font-family: var(--font-ui);
  cursor: pointer;
  white-space: nowrap;
  max-width: 180px;
  min-width: 60px;
  flex-shrink: 0;
  transition: all 0.15s ease;
  position: relative;
}

.tab-item:hover {
  color: var(--text);
  background: var(--bg-tertiary);
}

.tab-item.active {
  color: var(--text);
  background: var(--bg);
  border-bottom-color: var(--primary);
}

.tab-item.modified .tab-name::after {
  content: ' •';
  color: var(--primary);
}

.tab-name {
  overflow: hidden;
  text-overflow: ellipsis;
  pointer-events: none;
}

.tab-close {
  display: flex;
  align-items: center;
  justify-content: center;
  width: 16px;
  height: 16px;
  border: none;
  background: transparent;
  color: var(--text-tertiary);
  border-radius: 3px;
  cursor: pointer;
  flex-shrink: 0;
  padding: 0;
  opacity: 0;
  transition: all 0.1s ease;
}

.tab-item:hover .tab-close,
.tab-item.active .tab-close {
  opacity: 1;
}

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

.tab-add-btn {
  display: flex;
  align-items: center;
  justify-content: center;
  width: 28px;
  height: 28px;
  border: none;
  background: transparent;
  color: var(--text-secondary);
  border-radius: var(--radius);
  cursor: pointer;
  margin-left: 2px;
  margin-bottom: 4px;
  flex-shrink: 0;
  transition: all 0.15s ease;
}

.tab-add-btn:hover {
  background: var(--bg-tertiary);
  color: var(--text);
}

/* ===== Main Content ===== */
#main-content {
  flex: 1;
  display: flex;
  overflow: hidden;
  position: relative;
}

/* ===== Editor Panel ===== */
#editor-panel {
  flex: 1;
  display: flex;
  flex-direction: column;
  min-width: 0;
  border-right: 1px solid var(--border);
}

#editor-wrapper {
  flex: 1;
  display: flex;
  overflow: hidden;
  position: relative;
}

#line-numbers {
  width: 50px;
  background: var(--bg-secondary);
  border-right: 1px solid var(--border-light);
  padding: 12px 0;
  text-align: right;
  font-family: var(--font-mono);
  font-size: 13px;
  line-height: 1.6;
  color: var(--text-tertiary);
  overflow: hidden;
  user-select: none;
  flex-shrink: 0;
}

#line-numbers .line-num {
  padding-right: 12px;
  height: 20.8px;
}

#editor {
  flex: 1;
  width: 100%;
  padding: 12px 16px;
  border: none;
  outline: none;
  resize: none;
  font-family: var(--font-mono);
  font-size: 13px;
  line-height: 1.6;
  color: var(--text);
  background: var(--bg);
  tab-size: 4;
  overflow-y: auto;
  user-select: text;
}

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

/* ===== Resizer ===== */
#resizer {
  width: 4px;
  background: var(--border);
  cursor: col-resize;
  transition: background 0.15s ease;
  flex-shrink: 0;
}

#resizer:hover,
#resizer.active {
  background: var(--primary);
}

/* ===== Preview Panel ===== */
#preview-panel {
  flex: 1;
  overflow-y: auto;
  min-width: 0;
  background: var(--bg);
}

#preview {
  padding: 24px 32px;
  max-width: 900px;
  margin: 0 auto;
  user-select: text;
  cursor: text;
}

/* ===== Markdown Body Styles ===== */
.markdown-body {
  font-family: var(--font-ui);
  font-size: 15px;
  line-height: 1.7;
  color: var(--text);
  word-wrap: break-word;
}

.markdown-body h1,
.markdown-body h2,
.markdown-body h3,
.markdown-body h4,
.markdown-body h5,
.markdown-body h6 {
  margin-top: 24px;
  margin-bottom: 16px;
  font-weight: 600;
  line-height: 1.25;
  color: var(--text);
}

.markdown-body h1 {
  font-size: 2em;
  padding-bottom: 0.3em;
  border-bottom: 1px solid var(--border);
}

.markdown-body h2 {
  font-size: 1.5em;
  padding-bottom: 0.3em;
  border-bottom: 1px solid var(--border-light);
}

.markdown-body h3 { font-size: 1.25em; }
.markdown-body h4 { font-size: 1em; }
.markdown-body h5 { font-size: 0.875em; }
.markdown-body h6 { font-size: 0.85em; color: var(--text-secondary); }

.markdown-body p {
  margin-top: 0;
  margin-bottom: 16px;
}

.markdown-body a {
  color: var(--primary);
  text-decoration: none;
  cursor: pointer;
}

.markdown-body a:hover {
  text-decoration: underline;
}

.markdown-body strong { font-weight: 600; }

.markdown-body img {
  max-width: 100%;
  height: auto;
  border-radius: var(--radius);
  margin: 8px 0;
}

.markdown-body hr {
  height: 2px;
  background: var(--border);
  border: none;
  margin: 24px 0;
  border-radius: 1px;
}

.markdown-body blockquote {
  margin: 0 0 16px 0;
  padding: 4px 16px;
  border-left: 4px solid var(--primary);
  color: var(--text-secondary);
  background: var(--bg-secondary);
  border-radius: 0 var(--radius) var(--radius) 0;
}

.markdown-body blockquote p:last-child {
  margin-bottom: 0;
}

.markdown-body ul,
.markdown-body ol {
  margin-top: 0;
  margin-bottom: 16px;
  padding-left: 2em;
}

.markdown-body li {
  margin-top: 4px;
}

.markdown-body li + li {
  margin-top: 4px;
}

.markdown-body code {
  font-family: var(--font-mono);
  font-size: 0.9em;
  background: var(--code-bg);
  padding: 2px 6px;
  border-radius: 4px;
  color: #e83e8c;
}

:root.dark .markdown-body code {
  color: #f48fb1;
}

.markdown-body pre {
  margin-top: 0;
  margin-bottom: 16px;
  padding: 16px;
  background: var(--code-bg);
  border-radius: var(--radius);
  overflow-x: auto;
  border: 1px solid var(--border-light);
}

.markdown-body pre code {
  padding: 0;
  background: transparent;
  color: inherit;
  font-size: 13px;
  line-height: 1.5;
}

.markdown-body table {
  border-collapse: collapse;
  width: 100%;
  margin-bottom: 16px;
  overflow-x: auto;
  display: block;
}

.markdown-body table th,
.markdown-body table td {
  padding: 8px 16px;
  border: 1px solid var(--border);
  text-align: left;
}

.markdown-body table th {
  font-weight: 600;
  background: var(--bg-secondary);
}

.markdown-body table tr:nth-child(even) {
  background: var(--bg-secondary);
}

.markdown-body input[type="checkbox"] {
  margin-right: 6px;
  accent-color: var(--primary);
}

/* ===== Status Bar ===== */
#statusbar {
  height: var(--statusbar-height);
  background: var(--bg-secondary);
  border-top: 1px solid var(--border);
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 0 12px;
  font-size: 12px;
  color: var(--text-secondary);
  flex-shrink: 0;
}

.status-left,
.status-right {
  display: flex;
  align-items: center;
  gap: 8px;
}

.status-divider {
  color: var(--border);
}

.status-size-divider {
  display: none;
}

.status-size-divider.visible {
  display: inline;
}

/* ===== Drop Overlay ===== */
#drop-overlay {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  background: rgba(26, 115, 232, 0.1);
  backdrop-filter: blur(4px);
  display: flex;
  align-items: center;
  justify-content: center;
  z-index: 1000;
  border: 3px dashed var(--primary);
  margin: 8px;
  border-radius: 12px;
}

#drop-overlay.hidden {
  display: none;
}

.drop-content {
  text-align: center;
  color: var(--primary);
}

.drop-content svg {
  margin-bottom: 12px;
  opacity: 0.7;
}

.drop-content p {
  font-size: 18px;
  font-weight: 500;
}

/* ===== Welcome Screen ===== */
#welcome-screen {
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  display: flex;
  align-items: center;
  justify-content: center;
  background: var(--bg);
  z-index: 5;
}

#welcome-screen.hidden {
  display: none;
}

.welcome-content {
  text-align: center;
  max-width: 480px;
  padding: 40px;
}

.welcome-icon {
  margin-bottom: 24px;
}

.welcome-content h1 {
  font-size: 28px;
  font-weight: 600;
  color: var(--text);
  margin-bottom: 8px;
}

.welcome-content > p {
  font-size: 16px;
  color: var(--text-secondary);
  margin-bottom: 32px;
}

.welcome-actions {
  display: flex;
  gap: 12px;
  justify-content: center;
  margin-bottom: 32px;
}

.welcome-btn {
  display: flex;
  align-items: center;
  gap: 8px;
  padding: 10px 24px;
  border: none;
  border-radius: var(--radius);
  font-size: 14px;
  font-family: var(--font-ui);
  font-weight: 500;
  cursor: pointer;
  transition: all 0.15s ease;
}

.welcome-btn.primary {
  background: var(--primary);
  color: white;
}

.welcome-btn.primary:hover {
  background: var(--primary-dark);
  box-shadow: var(--shadow-lg);
}

.welcome-btn.secondary {
  background: var(--bg-secondary);
  color: var(--text);
  border: 1px solid var(--border);
}

.welcome-btn.secondary:hover {
  background: var(--bg-tertiary);
}

.welcome-tips {
  text-align: left;
  background: var(--bg-secondary);
  border-radius: var(--radius);
  padding: 16px 20px;
  border: 1px solid var(--border-light);
}

.welcome-tips p {
  font-size: 13px;
  color: var(--text-secondary);
  margin-bottom: 6px;
}

.welcome-tips p:last-child {
  margin-bottom: 0;
}

/* ===== Sidebar ===== */
#sidebar {
  width: var(--sidebar-width);
  min-width: 180px;
  max-width: 500px;
  background: var(--sidebar-bg);
  border-right: 1px solid var(--sidebar-border);
  display: flex;
  flex-direction: column;
  flex-shrink: 0;
  overflow: hidden;
  user-select: none;
}

#sidebar.collapsed {
  display: none;
}

#sidebar-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 8px 12px;
  border-bottom: 1px solid var(--sidebar-border);
  flex-shrink: 0;
}

#sidebar-title {
  font-size: 12px;
  font-weight: 600;
  color: var(--text-secondary);
  text-transform: uppercase;
  letter-spacing: 0.5px;
}

.sidebar-header-btn {
  display: flex;
  align-items: center;
  justify-content: center;
  width: 24px;
  height: 24px;
  border: none;
  background: transparent;
  color: var(--text-secondary);
  border-radius: 4px;
  cursor: pointer;
  transition: all 0.15s ease;
}

.sidebar-header-btn:hover {
  background: var(--sidebar-hover);
  color: var(--text);
}

#sidebar-tree {
  flex: 1;
  overflow-y: auto;
  overflow-x: hidden;
  padding: 4px 0;
}

.tree-item {
  display: flex;
  align-items: center;
  padding: 3px 8px 3px 0;
  cursor: pointer;
  font-size: 13px;
  color: var(--text);
  white-space: nowrap;
  transition: background 0.1s ease;
  border-radius: 0;
}

.tree-item:hover {
  background: var(--sidebar-hover);
}

.tree-item.active {
  background: var(--sidebar-active);
  color: var(--primary);
  font-weight: 500;
}

.tree-indent {
  flex-shrink: 0;
}

.tree-arrow {
  display: flex;
  align-items: center;
  justify-content: center;
  width: 16px;
  height: 16px;
  flex-shrink: 0;
  color: var(--text-tertiary);
  transition: transform 0.15s ease;
}

.tree-arrow.expanded {
  transform: rotate(90deg);
}

.tree-icon {
  display: flex;
  align-items: center;
  justify-content: center;
  width: 16px;
  height: 16px;
  flex-shrink: 0;
  margin-right: 4px;
}

.tree-icon svg {
  width: 14px;
  height: 14px;
}

.tree-name {
  overflow: hidden;
  text-overflow: ellipsis;
}

/* ===== Search & Replace Bar ===== */
#search-bar {
  background: var(--search-bg);
  border-bottom: 1px solid var(--search-border);
  padding: 6px 10px;
  flex-shrink: 0;
}

#search-bar.hidden {
  display: none;
}

.search-row,
#replace-row {
  display: flex;
  align-items: center;
  gap: 4px;
}

#replace-row {
  margin-top: 4px;
}

#replace-row.hidden {
  display: none;
}

#search-input,
#replace-input {
  flex: 1;
  min-width: 0;
  height: 26px;
  padding: 0 8px;
  border: 1px solid var(--border);
  border-radius: 4px;
  background: var(--bg);
  color: var(--text);
  font-size: 13px;
  font-family: var(--font-ui);
  outline: none;
  transition: border-color 0.15s ease;
}

#search-input:focus,
#replace-input:focus {
  border-color: var(--primary);
}

#search-count {
  font-size: 11px;
  color: var(--text-tertiary);
  white-space: nowrap;
  min-width: 40px;
  text-align: center;
}

.search-opt-btn {
  display: flex;
  align-items: center;
  justify-content: center;
  min-width: 26px;
  height: 26px;
  padding: 0 4px;
  border: 1px solid var(--border);
  border-radius: 4px;
  background: transparent;
  color: var(--text-secondary);
  font-size: 11px;
  font-weight: 600;
  font-family: var(--font-mono);
  cursor: pointer;
  transition: all 0.15s ease;
}

.search-opt-btn:hover {
  background: var(--bg-tertiary);
}

.search-opt-btn.active {
  background: var(--primary-light);
  color: var(--primary);
  border-color: var(--primary);
}

.search-nav-btn {
  display: flex;
  align-items: center;
  justify-content: center;
  width: 26px;
  height: 26px;
  border: none;
  background: transparent;
  color: var(--text-secondary);
  border-radius: 4px;
  cursor: pointer;
  font-size: 14px;
  transition: all 0.15s ease;
}

.search-nav-btn:hover {
  background: var(--bg-tertiary);
  color: var(--text);
}

.replace-btn {
  height: 26px;
  padding: 0 10px;
  border: 1px solid var(--border);
  border-radius: 4px;
  background: transparent;
  color: var(--text-secondary);
  font-size: 12px;
  font-family: var(--font-ui);
  cursor: pointer;
  white-space: nowrap;
  transition: all 0.15s ease;
}

.replace-btn:hover {
  background: var(--bg-tertiary);
  color: var(--text);
}

/* ===== Search Highlight Overlays ===== */
.search-hl {
  background: rgba(255, 220, 0, 0.35);
  border-radius: 2px;
}

.search-hl.current {
  background: rgba(255, 150, 0, 0.55);
}

:root.dark .search-hl {
  background: rgba(255, 220, 0, 0.25);
}

:root.dark .search-hl.current {
  background: rgba(255, 150, 0, 0.4);
}

/* ===== View Modes ===== */
#app.mode-editor #preview-panel,
#app.mode-editor #resizer {
  display: none;
}

#app.mode-preview #editor-panel,
#app.mode-preview #resizer {
  display: none;
}

/* ===== Scrollbar ===== */
::-webkit-scrollbar {
  width: 8px;
  height: 8px;
}

::-webkit-scrollbar-track {
  background: transparent;
}

::-webkit-scrollbar-thumb {
  background: var(--border);
  border-radius: 4px;
}

::-webkit-scrollbar-thumb:hover {
  background: var(--text-tertiary);
}

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

.welcome-content {
  animation: fadeIn 0.3s ease;
}