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

:root {
  --bg: #f8f9fb;
  --surface: #ffffff;
  --border: #e8eaed;
  --text: #1a1d21;
  --text-secondary: #5f6368;
  --text-muted: #9aa0a6;
  --primary: #2563eb;
  --primary-hover: #1d4ed8;
  --primary-light: #eff6ff;
  --danger: #dc2626;
  --danger-hover: #b91c1c;
  --sidebar-bg: #f1f3f5;
  --sidebar-width: 260px;
  --radius: 8px;
  --radius-sm: 6px;
  --shadow-sm: 0 1px 2px rgba(0,0,0,0.05);
  --shadow: 0 1px 3px rgba(0,0,0,0.1), 0 1px 2px rgba(0,0,0,0.06);
  --transition: 0.2s ease;
}

body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Noto Sans SC", "PingFang SC", "Microsoft YaHei", sans-serif;
  background: var(--bg);
  color: var(--text);
  line-height: 1.6;
  height: 100vh;
  overflow: hidden;
}

.app {
  display: flex;
  height: 100vh;
}

/* Sidebar */
.sidebar {
  width: var(--sidebar-width);
  background: var(--sidebar-bg);
  border-right: 1px solid var(--border);
  display: flex;
  flex-direction: column;
  flex-shrink: 0;
  transition: transform var(--transition);
}

.sidebar-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 1.25rem 1rem 0.75rem;
}

.logo {
  font-size: 1.2rem;
  font-weight: 700;
  color: var(--text);
  letter-spacing: -0.02em;
}

.sidebar-close { display: none; }

.categories {
  flex: 1;
  overflow-y: auto;
  padding: 0.5rem;
}

.category-list {
  display: flex;
  flex-direction: column;
  gap: 2px;
}

.category-item {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  padding: 0.5rem 0.75rem;
  border: none;
  background: transparent;
  border-radius: var(--radius-sm);
  cursor: pointer;
  font-size: 0.875rem;
  color: var(--text-secondary);
  text-align: left;
  transition: all var(--transition);
  width: 100%;
}

.category-item:hover {
  background: rgba(0,0,0,0.04);
  color: var(--text);
}

.category-item.active {
  background: var(--surface);
  color: var(--primary);
  font-weight: 500;
  box-shadow: var(--shadow-sm);
}

.category-item .count {
  margin-left: auto;
  font-size: 0.75rem;
  color: var(--text-muted);
  background: rgba(0,0,0,0.04);
  padding: 0.1rem 0.4rem;
  border-radius: 10px;
}

.btn-add-category {
  display: flex;
  align-items: center;
  gap: 0.4rem;
  padding: 0.5rem 0.75rem;
  margin-top: 0.5rem;
  border: none;
  background: transparent;
  border-radius: var(--radius-sm);
  cursor: pointer;
  font-size: 0.8rem;
  color: var(--text-muted);
  transition: all var(--transition);
}

.btn-add-category:hover {
  color: var(--primary);
  background: var(--primary-light);
}

.sidebar-footer {
  padding: 0.75rem 1rem;
  border-top: 1px solid var(--border);
}

.storage-info {
  display: flex;
  align-items: center;
  gap: 0.4rem;
  font-size: 0.7rem;
  color: var(--text-muted);
}

/* Main */
.main {
  flex: 1;
  display: flex;
  flex-direction: column;
  min-width: 0;
}

.main-header {
  display: flex;
  align-items: center;
  gap: 0.75rem;
  padding: 0.75rem 1.5rem;
  background: var(--surface);
  border-bottom: 1px solid var(--border);
}

.menu-btn { display: none; }

.search-box {
  flex: 1;
  display: flex;
  align-items: center;
  gap: 0.5rem;
  padding: 0.5rem 0.75rem;
  background: var(--bg);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  transition: border-color var(--transition);
}

.search-box:focus-within {
  border-color: var(--primary);
}

.search-box svg { color: var(--text-muted); flex-shrink: 0; }

.search-box input {
  flex: 1;
  border: none;
  background: transparent;
  font-size: 0.875rem;
  color: var(--text);
  outline: none;
}

.search-box input::placeholder { color: var(--text-muted); }

.btn-primary {
  display: flex;
  align-items: center;
  gap: 0.4rem;
  padding: 0.5rem 1rem;
  background: var(--primary);
  color: white;
  border: none;
  border-radius: var(--radius);
  font-size: 0.875rem;
  font-weight: 500;
  cursor: pointer;
  transition: background var(--transition);
  white-space: nowrap;
}

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

.btn-secondary {
  padding: 0.5rem 1rem;
  background: var(--bg);
  color: var(--text-secondary);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  font-size: 0.875rem;
  cursor: pointer;
  transition: all var(--transition);
}

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

.btn-icon {
  display: flex;
  align-items: center;
  justify-content: center;
  width: 36px;
  height: 36px;
  border: none;
  background: transparent;
  border-radius: var(--radius-sm);
  cursor: pointer;
  color: var(--text-secondary);
  transition: all var(--transition);
  flex-shrink: 0;
}

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

/* Content */
.content {
  flex: 1;
  overflow: hidden;
  display: flex;
  flex-direction: column;
}

.note-list-view {
  flex: 1;
  overflow-y: auto;
  padding: 1.5rem;
}

.note-list-header {
  display: flex;
  align-items: baseline;
  justify-content: space-between;
  margin-bottom: 1rem;
}

.note-list-header h2 {
  font-size: 1.1rem;
  font-weight: 600;
}

.note-count {
  font-size: 0.8rem;
  color: var(--text-muted);
}

.note-list {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
  gap: 1rem;
}

.note-card {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 1.25rem;
  cursor: pointer;
  transition: all var(--transition);
}

.note-card:hover {
  border-color: var(--primary);
  box-shadow: var(--shadow);
  transform: translateY(-1px);
}

.note-card-title {
  font-size: 0.95rem;
  font-weight: 600;
  margin-bottom: 0.5rem;
  color: var(--text);
  display: -webkit-box;
  -webkit-line-clamp: 2;
  -webkit-box-orient: vertical;
  overflow: hidden;
}

.note-card-preview {
  font-size: 0.8rem;
  color: var(--text-secondary);
  line-height: 1.5;
  display: -webkit-box;
  -webkit-line-clamp: 3;
  -webkit-box-orient: vertical;
  overflow: hidden;
  margin-bottom: 0.75rem;
}

.note-card-footer {
  display: flex;
  align-items: center;
  justify-content: space-between;
  font-size: 0.7rem;
  color: var(--text-muted);
}

.note-card-category {
  background: var(--primary-light);
  color: var(--primary);
  padding: 0.15rem 0.5rem;
  border-radius: 10px;
  font-weight: 500;
}

.empty-state {
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  padding: 4rem 2rem;
  color: var(--text-muted);
  text-align: center;
}

.empty-state p { margin-top: 1rem; font-size: 0.95rem; }
.empty-hint { font-size: 0.8rem !important; margin-top: 0.5rem !important; }

/* Editor */
.editor-view {
  flex: 1;
  display: flex;
  flex-direction: column;
  padding: 1rem 1.5rem;
  overflow: hidden;
}

.editor-toolbar {
  display: flex;
  align-items: center;
  gap: 0.75rem;
  margin-bottom: 1rem;
  flex-shrink: 0;
}

.editor-meta {
  display: flex;
  align-items: center;
  gap: 1rem;
  flex: 1;
}

.category-select {
  padding: 0.3rem 0.6rem;
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  font-size: 0.8rem;
  color: var(--text-secondary);
  background: var(--surface);
  cursor: pointer;
  outline: none;
}

.category-select:focus { border-color: var(--primary); }

.editor-date {
  font-size: 0.75rem;
  color: var(--text-muted);
}

.editor-actions {
  display: flex;
  align-items: center;
  gap: 0.5rem;
}

.btn-save {
  padding: 0.4rem 1.2rem;
}

.editor-title {
  width: 100%;
  border: none;
  font-size: 1.5rem;
  font-weight: 700;
  color: var(--text);
  background: transparent;
  outline: none;
  padding: 0.5rem 0;
  margin-bottom: 0.5rem;
  flex-shrink: 0;
}

.editor-title::placeholder { color: var(--text-muted); }

.editor-content {
  flex: 1;
  width: 100%;
  border: none;
  font-size: 0.95rem;
  color: var(--text);
  background: transparent;
  outline: none;
  resize: none;
  line-height: 1.8;
  font-family: inherit;
}

.editor-content::placeholder { color: var(--text-muted); }

/* Modal */
.modal-overlay {
  position: fixed;
  inset: 0;
  background: rgba(0,0,0,0.4);
  display: flex;
  align-items: center;
  justify-content: center;
  z-index: 100;
}

.modal {
  background: var(--surface);
  border-radius: var(--radius);
  padding: 1.5rem;
  width: 90%;
  max-width: 360px;
  box-shadow: 0 20px 60px rgba(0,0,0,0.15);
}

.modal h3 {
  font-size: 1rem;
  margin-bottom: 1rem;
}

.modal-input {
  width: 100%;
  padding: 0.6rem 0.75rem;
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  font-size: 0.875rem;
  outline: none;
  margin-bottom: 1rem;
}

.modal-input:focus { border-color: var(--primary); }

.modal-actions {
  display: flex;
  justify-content: flex-end;
  gap: 0.5rem;
}

/* Responsive */
@media (max-width: 768px) {
  .sidebar {
    position: fixed;
    left: 0;
    top: 0;
    bottom: 0;
    z-index: 50;
    transform: translateX(-100%);
    box-shadow: 4px 0 20px rgba(0,0,0,0.1);
  }

  .sidebar.open { transform: translateX(0); }
  .sidebar-close { display: flex; }
  .menu-btn { display: flex; }

  .note-list {
    grid-template-columns: 1fr;
  }

  .main-header { padding: 0.75rem 1rem; }
  .note-list-view { padding: 1rem; }
  .editor-view { padding: 1rem; }

  .btn-primary span { display: none; }
}

@media (max-width: 480px) {
  .editor-meta { flex-direction: column; align-items: flex-start; gap: 0.4rem; }
}