:root {
  --primary: #4f46e5;
  --primary-hover: #4338ca;
  --primary-light: #eef2ff;
  --danger: #ef4444;
  --danger-hover: #dc2626;
  --success: #10b981;
  --bg: #f8fafc;
  --surface: #ffffff;
  --border: #e2e8f0;
  --text: #1e293b;
  --text-muted: #64748b;
  --shadow-sm: 0 1px 3px rgba(0, 0, 0, 0.1);
  --shadow-md:
    0 4px 6px -1px rgba(0, 0, 0, 0.1), 0 2px 4px -1px rgba(0, 0, 0, 0.06);
  --shadow-lg:
    0 10px 15px -3px rgba(0, 0, 0, 0.1), 0 4px 6px -2px rgba(0, 0, 0, 0.05);
  --radius: 12px;
  --radius-sm: 8px;
  --transition: all 0.2s ease;
}

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

body {
  font-family:
    "Inter",
    -apple-system,
    BlinkMacSystemFont,
    "Segoe UI",
    sans-serif;
  background: var(--bg);
  color: var(--text);
  min-height: 100vh;
  line-height: 1.5;
}

.app {
  max-width: 1400px;
  margin: 0 auto;
  padding: 20px;
  min-height: 100vh;
  display: flex;
  flex-direction: column;
}

/* Header */
.app-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 16px 24px;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  box-shadow: var(--shadow-sm);
  margin-bottom: 20px;
}

.logo {
  display: flex;
  align-items: center;
  gap: 12px;
}

.logo svg {
  width: 32px;
  height: 32px;
  color: var(--primary);
}

.logo h1 {
  font-size: 1.5rem;
  font-weight: 700;
  letter-spacing: -0.02em;
}

.logo h1 span {
  color: var(--primary);
  font-weight: 600;
}

.header-actions {
  display: flex;
  gap: 8px;
}

/* Buttons */
.btn {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 10px 16px;
  border: none;
  border-radius: var(--radius-sm);
  font-family: inherit;
  font-size: 0.875rem;
  font-weight: 500;
  cursor: pointer;
  transition: var(--transition);
  text-decoration: none;
}

.btn svg {
  width: 16px;
  height: 16px;
}

.btn:active {
  transform: scale(0.97);
}

.btn:disabled {
  opacity: 0.5;
  cursor: not-allowed;
  transform: none;
}

.btn-outline {
  background: transparent;
  border: 1px solid var(--border);
  color: var(--text);
}

.btn-outline:hover:not(:disabled) {
  background: var(--primary-light);
  border-color: var(--primary);
  color: var(--primary);
}

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

.btn-danger:hover:not(:disabled) {
  background: var(--danger-hover);
}

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

.btn-secondary:hover:not(:disabled) {
  background: var(--bg);
  border-color: var(--text-muted);
}

/* Main Layout */
.main-content {
  display: flex;
  gap: 20px;
  flex: 1;
}

/* Sidebar */
.sidebar {
  width: 280px;
  flex-shrink: 0;
  display: flex;
  flex-direction: column;
  gap: 16px;
}

.panel {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  box-shadow: var(--shadow-sm);
  padding: 20px;
}

.panel-title {
  font-size: 0.75rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  color: var(--text-muted);
  margin-bottom: 16px;
}

.tool-group {
  margin-bottom: 20px;
}

.tool-group:last-child {
  margin-bottom: 0;
}

.tool-label {
  display: block;
  font-size: 0.875rem;
  font-weight: 500;
  color: var(--text);
  margin-bottom: 8px;
}

/* Mode Buttons */
.mode-buttons {
  display: flex;
  flex-direction: column;
  gap: 8px;
}

.mode-btn {
  display: flex;
  align-items: center;
  gap: 10px;
  padding: 10px 12px;
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  background: var(--surface);
  color: var(--text);
  font-family: inherit;
  font-size: 0.875rem;
  font-weight: 500;
  cursor: pointer;
  transition: var(--transition);
  text-align: left;
}

.mode-btn svg {
  width: 18px;
  height: 18px;
  color: var(--text-muted);
  transition: var(--transition);
}

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

.mode-btn:hover svg {
  color: var(--primary);
}

.mode-btn.active {
  background: var(--primary);
  border-color: var(--primary);
  color: white;
}

.mode-btn.active svg {
  color: white;
}

/* Color Picker */
.color-row {
  display: flex;
  align-items: center;
  gap: 12px;
}

#colorPicker {
  width: 48px;
  height: 48px;
  border: none;
  border-radius: var(--radius-sm);
  cursor: pointer;
  padding: 0;
  background: transparent;
}

#colorPicker::-webkit-color-swatch-wrapper {
  padding: 0;
}

#colorPicker::-webkit-color-swatch {
  border: 2px solid var(--border);
  border-radius: var(--radius-sm);
}

.color-preview {
  width: 32px;
  height: 32px;
  border-radius: 50%;
  border: 2px solid var(--border);
  background: var(--primary);
  transition: var(--transition);
}

/* Range Slider */
#gridSize {
  width: 100%;
  height: 6px;
  -webkit-appearance: none;
  appearance: none;
  background: var(--border);
  border-radius: 3px;
  outline: none;
  cursor: pointer;
}

#gridSize::-webkit-slider-thumb {
  -webkit-appearance: none;
  appearance: none;
  width: 18px;
  height: 18px;
  border-radius: 50%;
  background: var(--primary);
  border: 3px solid white;
  box-shadow: var(--shadow-sm);
  cursor: pointer;
  transition: var(--transition);
}

#gridSize::-webkit-slider-thumb:hover {
  transform: scale(1.1);
  background: var(--primary-hover);
}

#gridSize::-moz-range-thumb {
  width: 18px;
  height: 18px;
  border-radius: 50%;
  background: var(--primary);
  border: 3px solid white;
  box-shadow: var(--shadow-sm);
  cursor: pointer;
}

.range-labels {
  display: flex;
  justify-content: space-between;
  font-size: 0.75rem;
  color: var(--text-muted);
  margin-top: 4px;
}

/* Toggle Switch */
.option-row {
  display: flex;
  align-items: center;
  gap: 12px;
  margin-bottom: 12px;
  font-size: 0.875rem;
  color: var(--text);
}

.option-row:last-child {
  margin-bottom: 0;
}

.switch {
  position: relative;
  display: inline-block;
  width: 40px;
  height: 22px;
  flex-shrink: 0;
}

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

.slider {
  position: absolute;
  cursor: pointer;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  background-color: var(--border);
  transition: var(--transition);
  border-radius: 22px;
}

.slider:before {
  position: absolute;
  content: "";
  height: 16px;
  width: 16px;
  left: 3px;
  bottom: 3px;
  background-color: white;
  transition: var(--transition);
  border-radius: 50%;
  box-shadow: var(--shadow-sm);
}

.switch input:checked + .slider {
  background-color: var(--primary);
}

.switch input:checked + .slider:before {
  transform: translateX(18px);
}

.switch input:focus + .slider {
  box-shadow: 0 0 1px var(--primary);
}

/* Action Buttons */
.action-buttons {
  display: flex;
  flex-direction: column;
  gap: 8px;
}

.action-buttons .btn {
  justify-content: center;
  width: 100%;
}

/* Canvas Area */
.canvas-area {
  flex: 1;
  display: flex;
  flex-direction: column;
  gap: 12px;
  min-width: 0;
}

.canvas-frame {
  flex: 1;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  box-shadow: var(--shadow-md);
  padding: 20px;
  display: flex;
  align-items: center;
  justify-content: center;
  min-height: 600px;
}

#container {
  display: grid;
  width: 100%;
  max-width: 800px;
  aspect-ratio: 1;
  background: white;
  border: 1px solid var(--border);
  border-radius: 4px;
  overflow: hidden;
  box-shadow: var(--shadow-sm);
}

.cell {
  background: white;
  transition: background-color 0.05s ease;
  user-select: none;
  -webkit-user-select: none;
}

.cell.grid-line {
  border: 0.5px solid rgba(226, 232, 240, 0.5);
}

.cell:hover {
  cursor: crosshair;
}

.canvas-status {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 8px 16px;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  font-size: 0.75rem;
  color: var(--text-muted);
}

/* Developer Credit */
.developer-credit {
  padding: 12px 20px;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  box-shadow: var(--shadow-sm);
  font-size: 0.875rem;
  color: var(--text-muted);
  text-align: center;
}

.developer-credit p {
  margin: 0;
}

.developer-credit a {
  color: var(--primary);
  text-decoration: none;
  font-weight: 500;
  transition: var(--transition);
}

.developer-credit a:hover {
  color: var(--primary-hover);
  text-decoration: underline;
}

/* Responsive */
@media (max-width: 1024px) {
  .main-content {
    flex-direction: column;
  }

  .sidebar {
    width: 100%;
    flex-direction: row;
    flex-wrap: wrap;
  }

  .panel {
    flex: 1;
    min-width: 250px;
  }

  .canvas-frame {
    min-height: 400px;
  }
}

@media (max-width: 640px) {
  .app {
    padding: 12px;
  }

  .app-header {
    flex-direction: column;
    gap: 12px;
    text-align: center;
  }

  .logo {
    justify-content: center;
  }

  .panel {
    min-width: 100%;
  }

  .canvas-frame {
    padding: 12px;
    min-height: 300px;
  }
}