:root {
  --bg-app: #08090b;
  --bg-sidebar: #0f1115;
  --bg-card: rgba(255, 255, 255, 0.03);
  --bg-input: #161920;
  --bg-input-hover: #1c202a;
  
  --border-color: rgba(255, 255, 255, 0.08);
  --border-focus: #38bdf8;
  
  --text-primary: #f8fafc;
  --text-secondary: #94a3b8;
  --text-muted: #64748b;
  
  --accent: #38bdf8;
  --accent-hover: #0ea5e9;
  --accent-glow: rgba(56, 189, 248, 0.2);
  
  --radius-sm: 6px;
  --radius-md: 10px;
  --radius-lg: 14px;
}

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

body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
  background-color: var(--bg-app);
  color: var(--text-primary);
  min-height: 100vh;
  height: 100vh;
  overflow: hidden;
  display: flex;
  flex-direction: column;
}

/* App Header */
.app-header {
  height: 54px;
  min-height: 54px;
  background-color: var(--bg-sidebar);
  border-bottom: 1px solid var(--border-color);
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 0 1.5rem;
  z-index: 10;
}

.brand-group {
  display: flex;
  align-items: center;
  gap: 0.5rem;
}

.brand {
  font-family: "Noto Sans", -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
  font-size: 1.12rem;
  font-weight: 800;
  letter-spacing: 0.07em;
  text-decoration: none;
  color: var(--text-primary);
  display: flex;
  align-items: center;
  transition: color 0.15s ease;
}

.brand:hover {
  color: var(--accent);
}

.unsaved-tag {
  font-family: "Noto Sans", -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
  color: #ef4444;
  font-size: 0.72rem;
  font-weight: 800;
  letter-spacing: 0.06em;
  padding: 1px 6px;
  border-radius: 4px;
  background: rgba(239, 68, 68, 0.12);
  border: 1px solid rgba(239, 68, 68, 0.3);
  display: inline-flex;
  align-items: center;
  user-select: none;
  opacity: 0;
  visibility: hidden;
  transition: opacity 0.18s ease, visibility 0.18s ease;
}

.unsaved-tag.visible {
  opacity: 1;
  visibility: visible;
}

.header-actions {
  display: flex;
  align-items: center;
  gap: 0.65rem;
}

.config-actions {
  display: flex;
  align-items: center;
  gap: 0.35rem;
}

.header-action-btn {
  background: rgba(255, 255, 255, 0.04);
  border: 1px solid var(--border-color);
  color: var(--text-secondary);
  font-family: ui-monospace, SFMono-Regular, Menlo, Monaco, Consolas, monospace;
  font-size: 0.76rem;
  font-weight: 600;
  letter-spacing: 0.02em;
  padding: 5px 9px;
  border-radius: var(--radius-sm);
  cursor: pointer;
  display: inline-flex;
  align-items: center;
  gap: 5px;
  transition: all 0.15s cubic-bezier(0.4, 0, 0.2, 1);
  user-select: none;
  text-decoration: none;
  white-space: nowrap;
}

.header-action-btn:hover {
  background: rgba(56, 189, 248, 0.1);
  border-color: rgba(56, 189, 248, 0.4);
  color: var(--text-primary);
  transform: translateY(-1px);
}

.header-action-btn:active {
  transform: translateY(0);
  background: rgba(56, 189, 248, 0.18);
}

.header-action-btn svg {
  color: var(--accent);
  opacity: 0.9;
  flex-shrink: 0;
}

/* Export Dropdown Button & Menu */
.export-dropdown-wrapper {
  position: relative;
}

.header-action-btn.export-btn {
  background: rgba(56, 189, 248, 0.12);
  border-color: rgba(56, 189, 248, 0.35);
  color: var(--accent);
  font-weight: 700;
}

.header-action-btn.export-btn:hover {
  background: rgba(56, 189, 248, 0.22);
  border-color: var(--accent);
  color: #ffffff;
  box-shadow: 0 0 12px var(--accent-glow);
}

.dropdown-chevron {
  transition: transform 0.2s ease;
  margin-left: 2px;
}

.export-dropdown-wrapper.open .dropdown-chevron {
  transform: rotate(180deg);
}

.export-menu {
  position: absolute;
  top: calc(100% + 8px);
  right: 0;
  width: 240px;
  background: rgba(18, 20, 26, 0.95);
  backdrop-filter: blur(16px);
  -webkit-backdrop-filter: blur(16px);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-md);
  box-shadow: 0 12px 30px rgba(0, 0, 0, 0.6), 0 0 0 1px rgba(255, 255, 255, 0.05);
  padding: 6px;
  display: flex;
  flex-direction: column;
  gap: 4px;
  z-index: 100;
  opacity: 0;
  visibility: hidden;
  transform: translateY(-6px);
  transition: opacity 0.18s ease, transform 0.18s ease, visibility 0.18s ease;
}

.export-dropdown-wrapper.open .export-menu {
  opacity: 1;
  visibility: visible;
  transform: translateY(0);
}

.export-item {
  width: 100%;
  display: flex;
  align-items: center;
  gap: 10px;
  padding: 8px 10px;
  background: transparent;
  border: 1px solid transparent;
  border-radius: var(--radius-sm);
  color: var(--text-primary);
  text-align: left;
  cursor: pointer;
  transition: background-color 0.15s ease, border-color 0.15s ease;
}

.export-item:hover {
  background: rgba(255, 255, 255, 0.06);
  border-color: rgba(255, 255, 255, 0.1);
}

.export-format-badge {
  font-family: ui-monospace, SFMono-Regular, Menlo, Monaco, Consolas, monospace;
  font-size: 0.72rem;
  font-weight: 700;
  padding: 3px 6px;
  border-radius: 4px;
  background: rgba(56, 189, 248, 0.15);
  color: var(--accent);
  border: 1px solid rgba(56, 189, 248, 0.3);
  flex-shrink: 0;
  min-width: 38px;
  text-align: center;
}

.export-format-badge.jpg {
  background: rgba(234, 179, 8, 0.15);
  color: #facc15;
  border-color: rgba(234, 179, 8, 0.3);
}

.export-format-badge.svg {
  background: rgba(168, 85, 247, 0.15);
  color: #c084fc;
  border-color: rgba(168, 85, 247, 0.3);
}

.export-item-info {
  display: flex;
  flex-direction: column;
  gap: 1px;
}

.export-item-info strong {
  font-size: 0.82rem;
  font-weight: 600;
  color: var(--text-primary);
}

.export-item-info span {
  font-size: 0.72rem;
  color: var(--text-muted);
}

.header-divider {
  width: 1px;
  height: 20px;
  background-color: var(--border-color);
  margin: 0 0.1rem;
}

.back-link {
  color: var(--text-secondary);
  text-decoration: none;
  font-size: 0.85rem;
  transition: color 0.15s ease;
  white-space: nowrap;
}

.back-link:hover {
  color: var(--text-primary);
}

/* Workspace Layout */
.app-workspace {
  flex: 1;
  display: flex;
  overflow: hidden;
  height: calc(100vh - 54px);
}

/* Left: Preview Area (Fluid ~60%) */
.preview-area {
  flex: 1 1 60%;
  position: relative;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  padding: 2rem;
  background-color: var(--bg-app);
  background-image: 
    radial-gradient(rgba(255, 255, 255, 0.05) 1px, transparent 1px);
  background-size: 24px 24px;
  overflow: hidden;
}

.preview-toolbar {
  position: absolute;
  top: 1rem;
  left: 1rem;
  display: flex;
  align-items: center;
  gap: 0.75rem;
  z-index: 5;
}

.preview-badge {
  background: rgba(15, 17, 21, 0.85);
  backdrop-filter: blur(8px);
  border: 1px solid var(--border-color);
  padding: 5px 12px;
  border-radius: var(--radius-sm);
  font-size: 0.78rem;
  color: var(--text-secondary);
  display: flex;
  align-items: center;
  gap: 6px;
}

.preview-badge strong {
  color: var(--text-primary);
  font-weight: 600;
}

.preview-badge .aspect-pill {
  background: rgba(56, 189, 248, 0.15);
  color: var(--accent);
  padding: 2px 6px;
  border-radius: 4px;
  font-size: 0.72rem;
  font-weight: 600;
}

.preview-viewport {
  position: relative;
  width: 100%;
  height: 100%;
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 1rem;
}

.wallpaper-canvas-container {
  position: relative;
  max-width: 100%;
  max-height: 100%;
  display: flex;
  align-items: center;
  justify-content: center;
  box-shadow: 
    0 25px 50px -12px rgba(0, 0, 0, 0.65),
    0 0 0 1px var(--border-color);
  border-radius: 6px;
  overflow: hidden;
  transition: all 0.2s cubic-bezier(0.4, 0, 0.2, 1);
}

#wallpaper-svg {
  display: block;
  width: 100%;
  height: 100%;
  object-fit: contain;
}

/* Right: Options Sidebar (40%) */
.sidebar {
  width: 40%;
  min-width: 350px;
  max-width: 520px;
  background-color: var(--bg-sidebar);
  border-left: 1px solid var(--border-color);
  display: flex;
  flex-direction: column;
  height: 100%;
  overflow-y: auto;
}

.sidebar-header {
  padding: 1.25rem 1.5rem;
  border-bottom: 1px solid var(--border-color);
}

.sidebar-header h2 {
  font-size: 1.1rem;
  font-weight: 600;
  color: var(--text-primary);
}

.sidebar-header p {
  font-size: 0.82rem;
  color: var(--text-muted);
  margin-top: 2px;
}

.sidebar-content {
  padding: 1.5rem;
  display: flex;
  flex-direction: column;
  gap: 1rem;
  flex: 1;
}

/* Control Sections (Collapsible) */
.control-section {
  display: flex;
  flex-direction: column;
  background: var(--bg-card);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-md);
  overflow: hidden;
  transition: border-color 0.2s ease, background-color 0.2s ease;
}

.control-section:hover {
  border-color: rgba(255, 255, 255, 0.15);
}

.control-section.open {
  border-color: rgba(56, 189, 248, 0.3);
  background: rgba(255, 255, 255, 0.02);
}

.section-header-btn {
  width: 100%;
  padding: 1rem 1.15rem;
  background: transparent;
  border: none;
  color: var(--text-primary);
  display: flex;
  align-items: center;
  justify-content: space-between;
  cursor: pointer;
  text-align: left;
  user-select: none;
  transition: background-color 0.15s ease;
}

.section-header-btn:hover {
  background: rgba(255, 255, 255, 0.03);
}

.section-header-left {
  display: flex;
  flex-direction: column;
  gap: 2px;
}

.section-title {
  font-size: 0.88rem;
  font-weight: 700;
  color: var(--text-primary);
  display: flex;
  align-items: center;
  gap: 8px;
}

.section-summary {
  font-size: 0.75rem;
  color: var(--text-muted);
  display: flex;
  align-items: center;
  gap: 6px;
}

.section-summary .summary-color-dot {
  width: 10px;
  height: 10px;
  border-radius: 50%;
  display: inline-block;
  border: 1px solid var(--border-color);
}

.section-chevron {
  color: var(--text-muted);
  transition: transform 0.25s cubic-bezier(0.4, 0, 0.2, 1), color 0.15s ease;
  flex-shrink: 0;
}

.section-header-btn:hover .section-chevron {
  color: var(--text-primary);
}

.control-section.open .section-chevron {
  transform: rotate(180deg);
  color: var(--accent);
}

/* Collapsible Body */
.control-card-body {
  padding: 1.15rem;
  display: flex;
  flex-direction: column;
  gap: 1.1rem;
  border-top: 1px solid var(--border-color);
}

.control-section:not(.open) .control-card-body {
  display: none;
}

/* Form Controls */
.form-group {
  display: flex;
  flex-direction: column;
  gap: 0.4rem;
}

.form-label {
  font-size: 0.82rem;
  font-weight: 500;
  color: var(--text-secondary);
  display: flex;
  justify-content: space-between;
  align-items: center;
}

.form-select, .form-input {
  background: var(--bg-input);
  border: 1px solid var(--border-color);
  color: var(--text-primary);
  border-radius: var(--radius-sm);
  padding: 0.55rem 0.75rem;
  font-size: 0.88rem;
  outline: none;
  transition: border-color 0.15s ease, background-color 0.15s ease;
  width: 100%;
}

.form-select:hover, .form-input:hover {
  background: var(--bg-input-hover);
}

.form-select:focus, .form-input:focus {
  border-color: var(--border-focus);
  box-shadow: 0 0 0 2px rgba(56, 189, 248, 0.2);
}

.dimensions-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 0.75rem;
}

.dimension-input-wrapper {
  position: relative;
}

.dimension-input-wrapper span.unit {
  position: absolute;
  right: 0.75rem;
  top: 50%;
  transform: translateY(-50%);
  font-size: 0.75rem;
  color: var(--text-muted);
  pointer-events: none;
}

.dimension-input-wrapper .form-input {
  padding-right: 2rem;
}

/* Aspect Ratio Indicator (Read-only) */
.readonly-aspect-box {
  background: rgba(255, 255, 255, 0.02);
  border: 1px dashed var(--border-color);
  border-radius: var(--radius-sm);
  padding: 0.65rem 0.85rem;
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.readonly-aspect-box .aspect-label {
  font-size: 0.8rem;
  color: var(--text-secondary);
}

.readonly-aspect-box .aspect-value {
  display: flex;
  align-items: center;
  gap: 6px;
  font-size: 0.85rem;
  font-weight: 700;
  color: var(--accent);
  background: rgba(56, 189, 248, 0.1);
  padding: 3px 8px;
  border-radius: 4px;
  border: 1px solid rgba(56, 189, 248, 0.2);
}

/* Color Controls */
.color-picker-row {
  display: flex;
  align-items: center;
  gap: 0.75rem;
}

.color-swatch-wrapper {
  position: relative;
  width: 42px;
  height: 42px;
  border-radius: var(--radius-sm);
  border: 1px solid var(--border-color);
  overflow: hidden;
  flex-shrink: 0;
  cursor: pointer;
}

.color-input-native {
  position: absolute;
  top: -10px;
  left: -10px;
  width: 60px;
  height: 60px;
  border: none;
  cursor: pointer;
  background: none;
}

.color-hex-input {
  flex: 1;
  font-family: ui-monospace, SFMono-Regular, Menlo, Monaco, Consolas, monospace;
  text-transform: uppercase;
}

.palette-swatches {
  display: grid;
  grid-template-columns: repeat(8, 1fr);
  gap: 6px;
}

.palette-btn {
  aspect-ratio: 1;
  border-radius: 6px;
  border: 1px solid var(--border-color);
  cursor: pointer;
  padding: 0;
  transition: transform 0.12s ease, border-color 0.12s ease;
}

.palette-btn:hover {
  transform: scale(1.15);
  border-color: #fff;
  z-index: 2;
}

.palette-btn.active {
  border: 2px solid var(--accent);
  transform: scale(1.1);
}

/* Range Slider Styling */
.slider-group {
  display: flex;
  flex-direction: column;
  gap: 0.5rem;
}

.slider-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  font-size: 0.82rem;
  color: var(--text-secondary);
}

.slider-value-badge {
  font-family: ui-monospace, SFMono-Regular, Menlo, Monaco, Consolas, monospace;
  font-size: 0.78rem;
  color: var(--accent);
  background: rgba(56, 189, 248, 0.1);
  padding: 2px 7px;
  border-radius: 4px;
  border: 1px solid rgba(56, 189, 248, 0.2);
  font-weight: 600;
}

.slider-input-badge-wrapper {
  display: inline-flex;
  align-items: center;
  gap: 2px;
  background: rgba(56, 189, 248, 0.08);
  border: 1px solid rgba(56, 189, 248, 0.25);
  border-radius: var(--radius-sm);
  padding: 1px 6px 1px 4px;
  transition: all 0.15s ease;
}

.slider-input-badge-wrapper:focus-within {
  border-color: var(--accent);
  background: rgba(56, 189, 248, 0.15);
  box-shadow: 0 0 0 2px rgba(56, 189, 248, 0.2);
}

.slider-number-input {
  width: 48px;
  background: transparent;
  border: none;
  color: var(--accent);
  font-family: ui-monospace, SFMono-Regular, Menlo, Monaco, Consolas, monospace;
  font-size: 0.78rem;
  font-weight: 700;
  text-align: right;
  outline: none;
  padding: 2px 2px;
  -moz-appearance: textfield;
}

.slider-number-input::-webkit-inner-spin-button,
.slider-number-input::-webkit-outer-spin-button {
  -webkit-appearance: none;
  margin: 0;
}

.slider-input-badge-wrapper .unit {
  font-size: 0.72rem;
  color: var(--text-muted);
  font-weight: 600;
}

.form-range {
  -webkit-appearance: none;
  appearance: none;
  width: 100%;
  height: 6px;
  background: var(--bg-input);
  border-radius: 999px;
  outline: none;
  cursor: pointer;
  transition: background 0.15s ease;
}

.form-range:hover {
  background: var(--bg-input-hover);
}

.form-range::-webkit-slider-thumb {
  -webkit-appearance: none;
  appearance: none;
  width: 16px;
  height: 16px;
  border-radius: 50%;
  background: var(--accent);
  cursor: pointer;
  box-shadow: 0 0 10px rgba(56, 189, 248, 0.4);
  transition: transform 0.1s ease, background-color 0.1s ease;
}

.form-range::-webkit-slider-thumb:hover {
  transform: scale(1.2);
  background: #ffffff;
}

.form-range::-moz-range-thumb {
  width: 16px;
  height: 16px;
  border: none;
  border-radius: 50%;
  background: var(--accent);
  cursor: pointer;
  box-shadow: 0 0 10px rgba(56, 189, 248, 0.4);
  transition: transform 0.1s ease;
}

.form-range::-moz-range-thumb:hover {
  transform: scale(1.2);
  background: #ffffff;
}

/* Modern Toggle Switch */
.toggle-row {
  display: flex;
  align-items: center;
  justify-content: space-between;
  cursor: pointer;
  user-select: none;
}

.toggle-label-text {
  font-size: 0.85rem;
  font-weight: 600;
  color: var(--text-primary);
}

.switch {
  position: relative;
  display: inline-block;
  width: 42px;
  height: 24px;
}

.switch input {
  opacity: 0;
  width: 0;
  height: 0;
}

.switch-slider {
  position: absolute;
  cursor: pointer;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  background-color: var(--bg-input);
  border: 1px solid var(--border-color);
  transition: 0.25s cubic-bezier(0.4, 0, 0.2, 1);
  border-radius: 24px;
}

.switch-slider:before {
  position: absolute;
  content: "";
  height: 16px;
  width: 16px;
  left: 3px;
  bottom: 3px;
  background-color: var(--text-muted);
  transition: 0.25s cubic-bezier(0.4, 0, 0.2, 1);
  border-radius: 50%;
}

input:checked + .switch-slider {
  background-color: rgba(56, 189, 248, 0.2);
  border-color: var(--accent);
}

input:checked + .switch-slider:before {
  transform: translateX(18px);
  background-color: var(--accent);
  box-shadow: 0 0 8px rgba(56, 189, 248, 0.5);
}

/* Segmented Button Group */
.segmented-control {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  background: var(--bg-input);
  padding: 3px;
  border-radius: var(--radius-sm);
  border: 1px solid var(--border-color);
  gap: 3px;
}

.segmented-control.three-col {
  grid-template-columns: repeat(3, 1fr);
}

.segment-btn {
  background: transparent;
  border: none;
  color: var(--text-secondary);
  padding: 0.45rem 0.5rem;
  font-size: 0.8rem;
  font-weight: 500;
  border-radius: 4px;
  cursor: pointer;
  transition: all 0.15s ease;
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 4px;
  text-align: center;
}

.segment-btn:hover {
  color: var(--text-primary);
}

.segment-btn.active {
  background: rgba(255, 255, 255, 0.08);
  color: var(--text-primary);
  font-weight: 600;
  box-shadow: 0 1px 3px rgba(0,0,0,0.3);
}

/* File Upload Component for Custom SVG */
.file-upload-zone {
  position: relative;
  background: var(--bg-input);
  border: 1px dashed var(--border-color);
  border-radius: var(--radius-sm);
  padding: 1rem 0.75rem;
  text-align: center;
  cursor: pointer;
  transition: border-color 0.2s ease, background-color 0.2s ease;
}

.file-upload-zone:hover {
  border-color: var(--accent);
  background: var(--bg-input-hover);
}

.file-upload-zone input[type="file"] {
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  opacity: 0;
  cursor: pointer;
}

.upload-prompt {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 0.35rem;
  color: var(--text-secondary);
  font-size: 0.8rem;
}

.upload-prompt svg {
  color: var(--accent);
  margin-bottom: 2px;
}

.upload-prompt strong {
  color: var(--text-primary);
}

.uploaded-file-status {
  display: flex;
  align-items: center;
  justify-content: space-between;
  background: rgba(56, 189, 248, 0.08);
  border: 1px solid rgba(56, 189, 248, 0.25);
  border-radius: var(--radius-sm);
  padding: 0.5rem 0.75rem;
  font-size: 0.8rem;
  color: var(--text-primary);
}

.uploaded-file-status .file-name {
  max-width: 180px;
  overflow: hidden;
  text-overflow: ellipsis;
  white-space: nowrap;
}

.uploaded-file-status .remove-file-btn {
  background: none;
  border: none;
  color: var(--text-muted);
  cursor: pointer;
  font-size: 1rem;
  padding: 2px 6px;
  border-radius: 4px;
}

.uploaded-file-status .remove-file-btn:hover {
  color: #ef4444;
  background: rgba(239, 68, 68, 0.1);
}

/* Collapsible sub-controls container */
.subcontrols-group {
  display: flex;
  flex-direction: column;
  gap: 1.1rem;
  transition: opacity 0.2s ease;
}

.subcontrols-group.disabled {
  opacity: 0.35;
  pointer-events: none;
  user-select: none;
}

/* Interactive Cutting Mat Cell Targets */
.grid-cell-target {
  cursor: pointer;
  fill: transparent;
  stroke: transparent;
  transition: fill 0.1s ease, stroke 0.1s ease;
}

.grid-cell-target:hover {
  fill: rgba(56, 189, 248, 0.14);
  stroke: rgba(56, 189, 248, 0.4);
  stroke-width: 1.5px;
}

.grid-cell-target.cell-cleared:hover {
  fill: rgba(74, 222, 128, 0.15);
  stroke: rgba(74, 222, 128, 0.5);
  stroke-width: 1.5px;
}

/* Toast Notifications */
.toast-notification {
  position: fixed;
  bottom: 2rem;
  left: 50%;
  transform: translateX(-50%) translateY(30px);
  background: rgba(15, 17, 22, 0.94);
  backdrop-filter: blur(14px);
  -webkit-backdrop-filter: blur(14px);
  border: 1px solid rgba(56, 189, 248, 0.4);
  color: #ffffff;
  font-size: 0.84rem;
  font-weight: 500;
  padding: 0.65rem 1.25rem;
  border-radius: 999px;
  box-shadow: 0 12px 30px rgba(0, 0, 0, 0.6), 0 0 16px var(--accent-glow);
  pointer-events: none;
  opacity: 0;
  visibility: hidden;
  transition: transform 0.25s cubic-bezier(0.34, 1.56, 0.64, 1), opacity 0.2s ease, visibility 0.2s ease;
  z-index: 9999;
  display: flex;
  align-items: center;
  gap: 8px;
}

.toast-notification.show {
  transform: translateX(-50%) translateY(0);
  opacity: 1;
  visibility: visible;
}

/* Responsive adjustments */
@media (max-width: 900px) {
  body {
    overflow-y: auto;
    height: auto;
  }

  .app-workspace {
    flex-direction: column;
    height: auto;
  }

  .preview-area {
    min-height: 420px;
    height: 55vh;
  }

  .sidebar {
    width: 100%;
    max-width: 100%;
    min-width: unset;
    border-left: none;
    border-top: 1px solid var(--border-color);
  }
}

@media (max-width: 640px) {
  .app-header {
    padding: 0 0.85rem;
    gap: 0.5rem;
  }

  .brand {
    font-size: 1rem;
    letter-spacing: 0.05em;
  }

  .header-actions {
    gap: 0.35rem;
  }

  .header-action-btn {
    padding: 4px 7px;
    font-size: 0.72rem;
  }

  .back-link {
    font-size: 0.78rem;
  }
}