:root {
  --bg-main: #07090e;
  --bg-panel: #0d111a;
  --bg-card: #131926;
  --bg-card-hover: #1b2436;
  --bg-input: #1a2234;
  --border: rgba(255, 255, 255, 0.08);
  --border-accent: rgba(255, 107, 53, 0.35);
  --accent: #ff6b35;
  --accent-cyan: #00d9ff;
  --accent-purple: #a78bfa;
  --accent-green: #10b981;
  --accent-yellow: #fbbf24;
  --accent-pink: #f43f5e;
  --text-main: #f3f4f6;
  --text-muted: #9ca3af;
  --font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
  --radius: 12px;
  --shadow: 0 10px 30px rgba(0, 0, 0, 0.5);
}

* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
  -webkit-tap-highlight-color: transparent;
}

body {
  background-color: var(--bg-main);
  color: var(--text-main);
  font-family: var(--font-family);
  min-height: 100vh;
  display: flex;
  flex-direction: column;
  overflow: hidden;
}

/* App Header */
header {
  height: 60px;
  background: var(--bg-panel);
  border-bottom: 1px solid var(--border);
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 0 1rem;
  z-index: 50;
  gap: 0.5rem;
}

.brand {
  display: flex;
  align-items: center;
  gap: 0.6rem;
  text-decoration: none;
  color: inherit;
  flex-shrink: 0;
}

.brand-icon {
  font-size: 1.4rem;
  background: linear-gradient(135deg, var(--accent), var(--accent-cyan));
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
}

.brand-text h1 {
  font-size: 1.05rem;
  font-weight: 700;
  letter-spacing: -0.5px;
}

.brand-text span {
  font-size: 0.65rem;
  color: var(--text-muted);
  text-transform: uppercase;
  letter-spacing: 1px;
  display: block;
}

.header-actions {
  display: flex;
  align-items: center;
  gap: 0.35rem;
  flex-wrap: nowrap;
  overflow-x: auto;
  scrollbar-width: none;
}

.header-actions::-webkit-scrollbar {
  display: none;
}

.btn {
  background: var(--bg-input);
  border: 1px solid var(--border);
  color: var(--text-main);
  padding: 0.4rem 0.75rem;
  border-radius: 8px;
  font-size: 0.75rem;
  font-weight: 600;
  cursor: pointer;
  display: inline-flex;
  align-items: center;
  gap: 0.35rem;
  transition: all 0.2s ease;
  user-select: none;
  white-space: nowrap;
  flex-shrink: 0;
}

.btn:hover {
  background: var(--bg-card);
  border-color: var(--accent);
  color: #fff;
  transform: translateY(-1px);
}

.btn:active {
  transform: translateY(0);
}

.btn-primary {
  background: var(--accent);
  border-color: var(--accent);
  color: #050609;
}

.btn-primary:hover {
  background: #ff8554;
  border-color: #ff8554;
  color: #000;
  box-shadow: 0 0 15px rgba(255, 107, 53, 0.4);
}

.btn-secondary {
  background: rgba(0, 217, 255, 0.15);
  border-color: var(--accent-cyan);
  color: var(--accent-cyan);
}

.btn-secondary:hover {
  background: var(--accent-cyan);
  color: #000;
  box-shadow: 0 0 15px rgba(0, 217, 255, 0.4);
}

.btn-icon {
  padding: 0.45rem;
  border-radius: 8px;
}

/* App Main Container */
.app-container {
  flex: 1;
  display: flex;
  height: calc(100vh - 60px);
  position: relative;
  overflow: hidden;
}

/* Left Sidebar: Categories & Drawing Library */
.sidebar-library {
  width: 340px;
  min-width: 260px;
  max-width: 480px;
  background: var(--bg-panel);
  border-right: 1px solid var(--border);
  display: flex;
  flex-direction: column;
  z-index: 40;
  transition: width 0.25s cubic-bezier(0.4, 0, 0.2, 1), transform 0.25s ease;
  position: relative;
}

.sidebar-library.collapsed {
  width: 0 !important;
  min-width: 0 !important;
  overflow: hidden;
  border-right: none;
}

.library-header {
  padding: 0.75rem 0.85rem;
  border-bottom: 1px solid var(--border);
  display: flex;
  flex-direction: column;
  gap: 0.5rem;
}

.library-header-top {
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.library-header h3 {
  font-size: 0.9rem;
  font-weight: 700;
  display: flex;
  align-items: center;
  gap: 0.4rem;
}

.search-box {
  position: relative;
  width: 100%;
}

.search-box input {
  width: 100%;
  background: var(--bg-input);
  border: 1px solid var(--border);
  color: var(--text-main);
  padding: 0.35rem 0.65rem 0.35rem 1.8rem;
  border-radius: 6px;
  font-size: 0.75rem;
  outline: none;
}

.search-box input:focus {
  border-color: var(--accent);
}

.search-box i {
  position: absolute;
  left: 0.6rem;
  top: 50%;
  transform: translateY(-50%);
  color: var(--text-muted);
  font-size: 0.7rem;
}

/* Categories Scroll */
.category-tabs {
  display: flex;
  gap: 0.3rem;
  overflow-x: auto;
  padding-bottom: 0.2rem;
  scrollbar-width: none;
}

.category-tabs::-webkit-scrollbar {
  display: none;
}

.tab-btn {
  background: var(--bg-input);
  border: 1px solid var(--border);
  color: var(--text-muted);
  padding: 0.3rem 0.55rem;
  border-radius: 6px;
  font-size: 0.7rem;
  font-weight: 600;
  cursor: pointer;
  white-space: nowrap;
  transition: all 0.2s ease;
}

.tab-btn.active, .tab-btn:hover {
  background: rgba(255, 107, 53, 0.15);
  border-color: var(--accent);
  color: var(--accent);
}

/* Drawing Library Cards */
.library-content {
  flex: 1;
  overflow-y: auto;
  padding: 0.75rem;
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 0.6rem;
  align-content: start;
}

.drawing-card {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: 8px;
  padding: 0.45rem;
  cursor: pointer;
  transition: all 0.2s cubic-bezier(0.4, 0, 0.2, 1);
  display: flex;
  flex-direction: column;
  align-items: center;
  text-align: center;
  position: relative;
  overflow: hidden;
}

.drawing-card:hover {
  border-color: var(--accent-cyan);
  transform: translateY(-2px);
  background: var(--bg-card-hover);
  box-shadow: 0 6px 16px rgba(0, 217, 255, 0.18);
}

.drawing-card.active {
  border-color: var(--accent);
  background: rgba(255, 107, 53, 0.12);
  box-shadow: 0 0 12px rgba(255, 107, 53, 0.35);
}

.drawing-card-badge {
  position: absolute;
  top: 0.35rem;
  right: 0.35rem;
  font-size: 0.55rem;
  font-weight: 700;
  padding: 0.1rem 0.35rem;
  border-radius: 4px;
  background: rgba(0, 0, 0, 0.65);
  color: var(--accent-yellow);
  backdrop-filter: blur(4px);
  z-index: 2;
}

.drawing-preview {
  width: 100%;
  aspect-ratio: 1;
  background: #ffffff;
  border-radius: 6px;
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 0.35rem;
  overflow: hidden;
  margin-bottom: 0.35rem;
  transition: transform 0.2s ease;
}

.drawing-card:hover .drawing-preview {
  transform: scale(1.04);
}

.drawing-preview svg {
  width: 100%;
  height: 100%;
  object-fit: contain;
}

.drawing-title {
  font-size: 0.7rem;
  font-weight: 600;
  color: var(--text-main);
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
  max-width: 100%;
}

.photo-to-coloring-banner {
  margin: 0.5rem 0.75rem;
  padding: 0.5rem;
  background: linear-gradient(135deg, rgba(255, 107, 53, 0.1), rgba(0, 217, 255, 0.1));
  border: 1px dashed var(--accent);
  border-radius: 6px;
  text-align: center;
  cursor: pointer;
  transition: all 0.2s ease;
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 0.5rem;
}

.photo-to-coloring-banner:hover {
  background: linear-gradient(135deg, rgba(255, 107, 53, 0.2), rgba(0, 217, 255, 0.2));
  transform: translateY(-1px);
}

/* Splitter Bar */
.splitter {
  width: 6px;
  background: transparent;
  cursor: col-resize;
  position: relative;
  z-index: 45;
  display: flex;
  align-items: center;
  justify-content: center;
  transition: background 0.2s ease;
}

.splitter:hover, .splitter.active {
  background: var(--accent);
}

.splitter-toggle-btn {
  position: absolute;
  top: 50%;
  transform: translateY(-50%);
  background: var(--bg-panel);
  border: 1px solid var(--border);
  color: var(--text-muted);
  width: 18px;
  height: 36px;
  border-radius: 4px;
  display: flex;
  align-items: center;
  justify-content: center;
  cursor: pointer;
  font-size: 0.65rem;
  z-index: 50;
  transition: all 0.2s ease;
}

.splitter-toggle-btn:hover {
  background: var(--accent);
  color: #000;
  border-color: var(--accent);
}

/* Canvas Area (Center Workspace) */
.workspace {
  flex: 1;
  background: #040508;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  position: relative;
  overflow: hidden;
  user-select: none;
  min-width: 320px;
}

.canvas-viewport {
  position: relative;
  display: flex;
  align-items: center;
  justify-content: center;
  transform-origin: center center;
  transition: transform 0.1s ease-out;
  box-shadow: 0 20px 50px rgba(0, 0, 0, 0.85);
  border-radius: 6px;
}

#art-canvas-container {
  background: #ffffff;
  position: relative;
  width: 700px;
  height: 700px;
  max-width: 90vw;
  max-height: 80vh;
  display: flex;
  align-items: center;
  justify-content: center;
  border-radius: 6px;
  overflow: hidden;
  transition: background 0.3s ease;
}

/* Paper Texture Classes */
#art-canvas-container.paper-white { background: #ffffff; }
#art-canvas-container.paper-kraft { background: #d7b58c; }
#art-canvas-container.paper-watercolor { background: #fbf8f1; background-image: radial-gradient(#e6dfd1 15%, transparent 16%); background-size: 8px 8px; }
#art-canvas-container.paper-dark { background: #161a24; }

#drawing-svg-layer {
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  z-index: 5;
  pointer-events: none;
}

#paint-canvas-layer {
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  z-index: 15;
  cursor: crosshair;
  pointer-events: auto;
  touch-action: none;
}

/* Floating Zoom & Controls Overlay */
.floating-controls {
  position: absolute;
  bottom: 1rem;
  left: 50%;
  transform: translateX(-50%);
  background: rgba(13, 17, 26, 0.9);
  backdrop-filter: blur(12px);
  border: 1px solid var(--border);
  padding: 0.3rem 0.65rem;
  border-radius: 30px;
  display: flex;
  align-items: center;
  gap: 0.5rem;
  z-index: 30;
  box-shadow: var(--shadow);
}

.zoom-indicator {
  font-size: 0.75rem;
  font-weight: 700;
  color: var(--accent-cyan);
  min-width: 45px;
  text-align: center;
}

/* Right Toolbar: Tools & Color Palette */
.sidebar-tools {
  width: 300px;
  min-width: 250px;
  max-width: 400px;
  background: var(--bg-panel);
  border-left: 1px solid var(--border);
  display: flex;
  flex-direction: column;
  padding: 0.85rem;
  gap: 1rem;
  z-index: 40;
  overflow-y: auto;
  transition: width 0.25s cubic-bezier(0.4, 0, 0.2, 1), transform 0.25s ease;
  position: relative;
}

.sidebar-tools.collapsed {
  width: 0 !important;
  min-width: 0 !important;
  overflow: hidden;
  border-left: none;
  padding: 0 !important;
}

.tool-group-title {
  font-size: 0.7rem;
  text-transform: uppercase;
  letter-spacing: 1px;
  color: var(--text-muted);
  margin-bottom: 0.4rem;
  font-weight: 700;
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.tools-grid {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 0.3rem;
}

.tool-btn {
  background: var(--bg-input);
  border: 1px solid var(--border);
  color: var(--text-main);
  padding: 0.45rem 0.15rem;
  border-radius: 6px;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 0.2rem;
  cursor: pointer;
  font-size: 0.65rem;
  font-weight: 600;
  transition: all 0.2s ease;
}

.tool-btn i {
  font-size: 0.95rem;
}

.tool-btn.active, .tool-btn:hover {
  background: rgba(255, 107, 53, 0.15);
  border-color: var(--accent);
  color: var(--accent);
}

/* Brush Size & Opacity Slider */
.param-slider {
  display: flex;
  flex-direction: column;
  gap: 0.2rem;
}

.param-label {
  display: flex;
  justify-content: space-between;
  font-size: 0.7rem;
  color: var(--text-muted);
}

input[type="range"] {
  width: 100%;
  accent-color: var(--accent);
  cursor: pointer;
}

/* Color Swatches & Palettes */
.swatches-grid {
  display: grid;
  grid-template-columns: repeat(6, 1fr);
  gap: 0.35rem;
}

.color-swatch {
  width: 100%;
  aspect-ratio: 1;
  border-radius: 6px;
  cursor: pointer;
  border: 2px solid transparent;
  transition: transform 0.15s ease;
  position: relative;
}

.color-swatch:hover {
  transform: scale(1.15);
  z-index: 2;
}

.color-swatch.active {
  border-color: #ffffff;
  box-shadow: 0 0 10px rgba(255, 255, 255, 0.9);
  transform: scale(1.1);
}

.custom-color-picker {
  display: flex;
  align-items: center;
  gap: 0.45rem;
  margin-top: 0.4rem;
  background: var(--bg-input);
  padding: 0.3rem 0.5rem;
  border-radius: 6px;
  border: 1px solid var(--border);
}

.custom-color-picker input[type="color"] {
  border: none;
  background: none;
  width: 24px;
  height: 24px;
  cursor: pointer;
  border-radius: 4px;
}

/* Advanced Features: Paper & Symmetry Buttons */
.feature-toggle-group {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 0.3rem;
}

.toggle-btn {
  background: var(--bg-input);
  border: 1px solid var(--border);
  color: var(--text-muted);
  padding: 0.35rem;
  border-radius: 6px;
  font-size: 0.65rem;
  font-weight: 600;
  cursor: pointer;
  text-align: center;
  transition: all 0.2s ease;
}

.toggle-btn.active {
  background: rgba(0, 217, 255, 0.15);
  border-color: var(--accent-cyan);
  color: var(--accent-cyan);
}

/* Mobile Bottom Navigation Bar */
.mobile-nav-bar {
  display: none;
  height: 50px;
  background: var(--bg-panel);
  border-top: 1px solid var(--border);
  z-index: 50;
}

.mobile-nav-btn {
  flex: 1;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  background: none;
  border: none;
  color: var(--text-muted);
  font-size: 0.65rem;
  gap: 0.2rem;
  cursor: pointer;
}

.mobile-nav-btn.active {
  color: var(--accent);
}

/* Print Sheet */
.print-sheet {
  display: none;
}

@media print {
  body * {
    visibility: hidden;
  }
  .print-sheet, .print-sheet * {
    visibility: visible;
  }
  .print-sheet {
    display: block;
    position: absolute;
    top: 0;
    left: 0;
    width: 100vw;
    height: 100vh;
    padding: 2cm;
    background: #fff;
    text-align: center;
  }
  .print-sheet svg {
    max-width: 100%;
    max-height: 75vh;
  }
}

/* Responsive Adjustments */
@media (max-width: 992px) {
  body {
    overflow-y: auto;
  }
  .app-container {
    height: calc(100vh - 110px);
  }
  .mobile-nav-bar {
    display: flex;
  }
  .splitter {
    display: none;
  }
  .sidebar-library, .sidebar-tools {
    position: absolute;
    top: 0;
    bottom: 0;
    width: 100% !important;
    max-width: 100% !important;
    z-index: 60;
    transform: translateX(-100%);
  }
  .sidebar-tools {
    right: 0;
    transform: translateX(100%);
  }
  .sidebar-library.mobile-active, .sidebar-tools.mobile-active {
    transform: translateX(0);
  }
  .workspace {
    width: 100%;
    height: 100%;
  }
  #art-canvas-container {
    width: 90vw;
    height: 90vw;
    max-width: 90vw;
    max-height: 90vw;
  }
}