/* ===================================================
   DFA Practice Website — Design System & Styles
   =================================================== */

@import url('https://fonts.googleapis.com/css2?family=Inter:wght@400;500;600;700;800&display=swap');

/* ----- Custom Properties ----- */
:root {
  /* Colors */
  --color-bg: #f0f4fa;
  --color-surface: #ffffff;
  --color-surface-alt: #f8fafd;
  --color-primary: #4f6ef7;
  --color-primary-light: #8da2fb;
  --color-primary-dark: #3a56d4;
  --color-primary-bg: #eef2ff;
  --color-accent-green: #22c55e;
  --color-accent-green-bg: #ecfdf5;
  --color-accent-red: #ef4444;
  --color-accent-red-bg: #fef2f2;
  --color-accent-amber: #f59e0b;
  --color-accent-amber-bg: #fffbeb;
  --color-text: #1e293b;
  --color-text-secondary: #64748b;
  --color-text-muted: #94a3b8;
  --color-border: #e2e8f0;
  --color-border-light: #f1f5f9;

  /* Canvas colors */
  --canvas-bg: #fafcff;
  --canvas-grid: #e8edf5;
  --state-fill: #ffffff;
  --state-stroke: #4f6ef7;
  --state-stroke-selected: #3a56d4;
  --state-text: #1e293b;
  --transition-stroke: #64748b;
  --transition-label-bg: #ffffff;
  --start-arrow: #4f6ef7;
  --highlight-color: #fbbf24;

  /* Spacing */
  --space-xs: 4px;
  --space-sm: 8px;
  --space-md: 12px;
  --space-lg: 16px;
  --space-xl: 24px;
  --space-2xl: 32px;
  --space-3xl: 48px;

  /* Radii */
  --radius-sm: 8px;
  --radius-md: 12px;
  --radius-lg: 16px;
  --radius-xl: 24px;
  --radius-full: 9999px;

  /* Shadows */
  --shadow-sm: 0 1px 3px rgba(0,0,0,0.06), 0 1px 2px rgba(0,0,0,0.04);
  --shadow-md: 0 4px 12px rgba(0,0,0,0.07), 0 2px 4px rgba(0,0,0,0.04);
  --shadow-lg: 0 10px 30px rgba(0,0,0,0.1), 0 4px 8px rgba(0,0,0,0.05);
  --shadow-xl: 0 20px 50px rgba(0,0,0,0.12);
  --shadow-primary: 0 4px 14px rgba(79,110,247,0.3);

  /* Typography */
  --font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
  --font-size-xs: 0.75rem;
  --font-size-sm: 0.8125rem;
  --font-size-base: 0.875rem;
  --font-size-md: 1rem;
  --font-size-lg: 1.125rem;
  --font-size-xl: 1.25rem;
  --font-size-2xl: 1.5rem;
  --font-size-3xl: 2rem;

  /* Transitions */
  --transition-fast: 150ms ease;
  --transition-base: 250ms ease;
  --transition-slow: 400ms cubic-bezier(0.4, 0, 0.2, 1);
}

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

html {
  font-size: 16px;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

body {
  font-family: var(--font-family);
  background: var(--color-bg);
  color: var(--color-text);
  line-height: 1.6;
  min-height: 100vh;
  overflow: hidden;
}

/* ----- App Layout ----- */
.app-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: var(--space-md) var(--space-xl);
  background: var(--color-surface);
  border-bottom: 1px solid var(--color-border);
  box-shadow: var(--shadow-sm);
  z-index: 100;
  position: relative;
}

.app-logo {
  display: flex;
  align-items: center;
  gap: var(--space-sm);
  font-size: var(--font-size-lg);
  font-weight: 700;
  color: var(--color-primary);
}

.app-logo svg {
  width: 28px;
  height: 28px;
}

.problem-selector {
  display: flex;
  align-items: center;
  gap: var(--space-sm);
}

.header-controls {
  display: flex;
  align-items: center;
  gap: var(--space-lg);
}

.user-menu {
  display: flex;
  align-items: center;
  gap: var(--space-md);
  padding-left: var(--space-lg);
  border-left: 1px solid var(--color-border);
}

.user-info {
  display: flex;
  align-items: center;
  gap: var(--space-sm);
}

.user-avatar {
  display: flex;
  align-items: center;
  justify-content: center;
  width: 32px;
  height: 32px;
  border-radius: var(--radius-full);
  background: var(--color-primary-bg);
  color: var(--color-primary);
  font-size: var(--font-size-sm);
  font-weight: 700;
  flex-shrink: 0;
}

.user-details {
  display: flex;
  flex-direction: column;
  line-height: 1.3;
}

.user-name {
  font-size: var(--font-size-sm);
  font-weight: 600;
  color: var(--color-text);
}

.user-role {
  font-size: var(--font-size-xs);
  color: var(--color-text-muted);
}

.automaton-type-toggle {
  display: inline-flex;
  padding: 3px;
  background: var(--color-surface-alt);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-full);
}

.automaton-type-toggle .type-btn {
  border: none;
  background: transparent;
  color: var(--color-text-secondary);
  font-family: var(--font-family);
  font-size: var(--font-size-sm);
  font-weight: 600;
  padding: var(--space-xs) var(--space-md);
  border-radius: var(--radius-full);
  cursor: pointer;
  transition: background var(--transition-fast), color var(--transition-fast), box-shadow var(--transition-fast);
}

.automaton-type-toggle .type-btn:hover {
  color: var(--color-text);
}

.automaton-type-toggle .type-btn.active {
  background: var(--color-surface);
  color: var(--color-primary);
  box-shadow: var(--shadow-sm);
}

.problem-selector label {
  font-size: var(--font-size-sm);
  font-weight: 600;
  color: var(--color-text-secondary);
}

.problem-selector select {
  min-width: 180px;
  max-width: 260px;
  padding: var(--space-sm) var(--space-lg);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-full);
  font-family: var(--font-family);
  font-size: var(--font-size-sm);
  font-weight: 500;
  color: var(--color-text);
  background: var(--color-surface);
  cursor: pointer;
  outline: none;
  transition: border-color var(--transition-fast), box-shadow var(--transition-fast);
  appearance: none;
  -webkit-appearance: none;
  background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='12' height='12' fill='%2364748b' viewBox='0 0 16 16'%3E%3Cpath d='M8 11L3 6h10z'/%3E%3C/svg%3E");
  background-repeat: no-repeat;
  background-position: right 12px center;
  padding-right: 32px;
}

.problem-selector select:focus {
  border-color: var(--color-primary);
  box-shadow: 0 0 0 3px var(--color-primary-bg);
}

/* ----- Custom Practice Problems ----- */
.custom-problem-badge {
  display: inline-block;
  padding: var(--space-xs) var(--space-md);
  margin-bottom: var(--space-md);
  background: var(--color-accent-amber-bg);
  color: var(--color-accent-amber);
  border-radius: var(--radius-full);
  font-size: var(--font-size-xs);
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.04em;
}

.custom-type-hint {
  font-size: var(--font-size-sm);
  color: var(--color-text-secondary);
  margin-bottom: var(--space-lg);
  padding: var(--space-sm) var(--space-md);
  background: var(--color-primary-bg);
  border-radius: var(--radius-sm);
  border-left: 3px solid var(--color-primary);
}

.custom-problem-actions {
  display: flex;
  gap: var(--space-sm);
  margin-top: var(--space-lg);
  padding-top: var(--space-lg);
  border-top: 1px solid var(--color-border-light);
}

.btn-danger-outline {
  border-color: var(--color-accent-red);
  color: var(--color-accent-red);
}

.btn-danger-outline:hover {
  background: var(--color-accent-red-bg);
}

.custom-problem-modal {
  max-width: 520px;
  max-height: 90vh;
  overflow-y: auto;
}

.custom-problem-subtitle {
  font-size: var(--font-size-sm);
  color: var(--color-text-secondary);
  margin-bottom: var(--space-xl);
  line-height: 1.5;
}

.custom-problem-form {
  display: flex;
  flex-direction: column;
  gap: var(--space-lg);
}

.form-group {
  display: flex;
  flex-direction: column;
  gap: var(--space-xs);
}

.form-group label {
  font-size: var(--font-size-sm);
  font-weight: 600;
  color: var(--color-text);
}

.form-group input[type="text"],
.form-group textarea {
  padding: var(--space-sm) var(--space-md);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-sm);
  font-family: var(--font-family);
  font-size: var(--font-size-sm);
  color: var(--color-text);
  background: var(--color-surface);
  outline: none;
  transition: border-color var(--transition-fast), box-shadow var(--transition-fast);
  resize: vertical;
}

.form-group input[type="text"]:focus,
.form-group textarea:focus {
  border-color: var(--color-primary);
  box-shadow: 0 0 0 3px var(--color-primary-bg);
}

.form-hint {
  font-size: var(--font-size-xs);
  color: var(--color-text-muted);
}

.cp-alphabet-display {
  display: inline-flex;
  align-items: center;
  padding: var(--space-xs) var(--space-md);
  background: var(--color-primary-bg);
  border-radius: var(--radius-full);
  font-size: var(--font-size-sm);
  font-weight: 600;
  color: var(--color-primary);
  font-family: 'Courier New', monospace;
}

.cp-type-toggle {
  display: inline-flex;
  gap: var(--space-sm);
}

.cp-type-option {
  display: inline-flex;
  align-items: center;
  gap: var(--space-xs);
  padding: var(--space-sm) var(--space-lg);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-full);
  font-size: var(--font-size-sm);
  font-weight: 600;
  cursor: pointer;
  transition: all var(--transition-fast);
}

.cp-type-option:has(input:checked) {
  border-color: var(--color-primary);
  background: var(--color-primary-bg);
  color: var(--color-primary);
}

.cp-type-option input {
  accent-color: var(--color-primary);
}

.cp-form-error {
  padding: var(--space-sm) var(--space-md);
  background: var(--color-accent-red-bg);
  color: var(--color-accent-red);
  border-radius: var(--radius-sm);
  font-size: var(--font-size-sm);
  line-height: 1.5;
}

.cp-form-error.hidden {
  display: none;
}

.app-main {
  display: grid;
  grid-template-columns: 300px 1fr 320px;
  height: calc(100vh - 57px);
  overflow: hidden;
}

/* ----- Panel Base ----- */
.panel {
  display: flex;
  flex-direction: column;
  overflow: hidden;
}

.panel-header {
  padding: var(--space-lg) var(--space-xl);
  border-bottom: 1px solid var(--color-border-light);
  flex-shrink: 0;
}

.panel-header h2 {
  font-size: var(--font-size-md);
  font-weight: 700;
  color: var(--color-text);
  display: flex;
  align-items: center;
  gap: var(--space-sm);
}

.panel-header h2 svg {
  width: 18px;
  height: 18px;
  color: var(--color-primary);
}

.panel-body {
  flex: 1;
  overflow-y: auto;
  padding: var(--space-lg) var(--space-xl);
}

.panel-body::-webkit-scrollbar {
  width: 5px;
}

.panel-body::-webkit-scrollbar-track {
  background: transparent;
}

.panel-body::-webkit-scrollbar-thumb {
  background: var(--color-border);
  border-radius: var(--radius-full);
}

/* ----- Problem Panel (Left) ----- */
.problem-panel {
  background: var(--color-surface);
  border-right: 1px solid var(--color-border);
}

.problem-title {
  font-size: var(--font-size-lg);
  font-weight: 700;
  color: var(--color-text);
  margin-bottom: var(--space-md);
  line-height: 1.4;
}

.problem-description {
  font-size: var(--font-size-base);
  color: var(--color-text-secondary);
  line-height: 1.7;
  margin-bottom: var(--space-xl);
}

.problem-alphabet {
  display: inline-flex;
  align-items: center;
  gap: var(--space-xs);
  padding: var(--space-xs) var(--space-md);
  background: var(--color-primary-bg);
  border-radius: var(--radius-full);
  font-size: var(--font-size-sm);
  font-weight: 600;
  color: var(--color-primary);
  margin-bottom: var(--space-xl);
}

.problem-alphabet .symbol {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 24px;
  height: 24px;
  background: var(--color-primary);
  color: white;
  border-radius: var(--radius-sm);
  font-size: var(--font-size-xs);
  font-weight: 700;
  font-family: 'Courier New', monospace;
}

.examples-section {
  margin-bottom: var(--space-xl);
}

.examples-section h3 {
  font-size: var(--font-size-sm);
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  margin-bottom: var(--space-sm);
  display: flex;
  align-items: center;
  gap: var(--space-xs);
}

.examples-section h3.accepted {
  color: var(--color-accent-green);
}

.examples-section h3.rejected {
  color: var(--color-accent-red);
}

.examples-list {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-xs);
}

.example-chip {
  display: inline-flex;
  align-items: center;
  padding: var(--space-xs) var(--space-md);
  border-radius: var(--radius-full);
  font-size: var(--font-size-sm);
  font-weight: 500;
  font-family: 'Courier New', monospace;
  letter-spacing: 0.03em;
}

.example-chip.accepted {
  background: var(--color-accent-green-bg);
  color: #15803d;
  border: 1px solid #bbf7d0;
}

.example-chip.rejected {
  background: var(--color-accent-red-bg);
  color: #dc2626;
  border: 1px solid #fecaca;
}

.example-chip.empty-string {
  font-style: italic;
  font-family: var(--font-family);
}

/* ----- Center Panel (Canvas + Toolbar) ----- */
.center-panel {
  display: flex;
  flex-direction: column;
  background: var(--color-bg);
  overflow: hidden;
}

/* ----- Toolbar ----- */
.toolbar {
  display: flex;
  align-items: center;
  gap: var(--space-sm);
  padding: var(--space-sm) var(--space-lg);
  background: var(--color-surface);
  border-bottom: 1px solid var(--color-border);
  flex-shrink: 0;
  flex-wrap: wrap;
}

.toolbar-group {
  display: flex;
  align-items: center;
  gap: var(--space-xs);
}

.toolbar-divider {
  width: 1px;
  height: 28px;
  background: var(--color-border);
  margin: 0 var(--space-sm);
}

.tool-btn {
  display: inline-flex;
  align-items: center;
  gap: var(--space-xs);
  padding: var(--space-sm) var(--space-md);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  background: var(--color-surface);
  color: var(--color-text-secondary);
  font-family: var(--font-family);
  font-size: var(--font-size-sm);
  font-weight: 500;
  cursor: pointer;
  transition: all var(--transition-fast);
  white-space: nowrap;
  user-select: none;
}

.tool-btn svg {
  width: 16px;
  height: 16px;
  flex-shrink: 0;
}

.tool-btn:hover {
  background: var(--color-surface-alt);
  border-color: var(--color-primary-light);
  color: var(--color-primary);
  transform: translateY(-1px);
  box-shadow: var(--shadow-sm);
}

.tool-btn.active {
  background: var(--color-primary-bg);
  border-color: var(--color-primary);
  color: var(--color-primary);
  box-shadow: var(--shadow-primary);
}

.tool-btn:disabled {
  opacity: 0.45;
  cursor: not-allowed;
  pointer-events: none;
  transform: none;
  box-shadow: none;
}

.tool-btn.danger:hover {
  border-color: var(--color-accent-red);
  color: var(--color-accent-red);
  background: var(--color-accent-red-bg);
}

.tool-btn.success {
  background: var(--color-primary);
  border-color: var(--color-primary);
  color: white;
  font-weight: 600;
}

.tool-btn.success:hover {
  background: var(--color-primary-dark);
  transform: translateY(-1px);
  box-shadow: var(--shadow-primary);
}

/* ----- DFA Canvas ----- */
.canvas-container {
  flex: 1;
  position: relative;
  overflow: hidden;
  background: var(--canvas-bg);
  /* Dot grid background */
  background-image: radial-gradient(circle, var(--canvas-grid) 1px, transparent 1px);
  background-size: 24px 24px;
}

.dfa-canvas {
  width: 100%;
  height: 100%;
  cursor: default;
}

.dfa-canvas.tool-add-state {
  cursor: crosshair;
}

.dfa-canvas.tool-add-transition {
  cursor: pointer;
}

.dfa-canvas.tool-delete {
  cursor: not-allowed;
}

.canvas-hint {
  position: absolute;
  bottom: var(--space-lg);
  left: 50%;
  transform: translateX(-50%);
  padding: var(--space-sm) var(--space-xl);
  background: var(--color-text);
  color: white;
  border-radius: var(--radius-full);
  font-size: var(--font-size-sm);
  font-weight: 500;
  opacity: 0.85;
  pointer-events: none;
  transition: opacity var(--transition-base);
  white-space: nowrap;
  z-index: 10;
}

.canvas-hint.hidden {
  opacity: 0;
}

/* SVG State Styles */
.state-group {
  cursor: grab;
  transition: filter var(--transition-fast);
}

.state-group:hover .state-circle {
  filter: drop-shadow(0 2px 8px rgba(79,110,247,0.3));
}

.state-group.dragging {
  cursor: grabbing;
}

.state-circle {
  fill: var(--state-fill);
  stroke: var(--state-stroke);
  stroke-width: 2.5;
  transition: stroke var(--transition-fast), fill var(--transition-fast);
}

.state-circle-accept {
  fill: none;
  stroke: var(--state-stroke);
  stroke-width: 2;
}

.state-group.selected .state-circle {
  stroke: var(--state-stroke-selected);
  stroke-width: 3;
  fill: var(--color-primary-bg);
}

.state-group.highlighted .state-circle {
  stroke: var(--highlight-color);
  stroke-width: 3.5;
  fill: #fef9c3;
  animation: pulse-highlight 0.5s ease;
}

.state-group.drag-hover .state-circle {
  stroke: var(--color-primary);
  stroke-width: 3.5;
  fill: #e0e7ff;
  filter: drop-shadow(0 0 12px rgba(79, 110, 247, 0.6));
}

.drag-preview-line {
  stroke: var(--color-primary);
  stroke-width: 2.5;
  stroke-dasharray: 6 4;
  animation: dashOffset 0.5s linear infinite;
}

@keyframes dashOffset {
  to {
    stroke-dashoffset: -10;
  }
}

.state-label {
  fill: var(--state-text);
  font-family: var(--font-family);
  font-size: 13px;
  font-weight: 600;
  text-anchor: middle;
  dominant-baseline: central;
  pointer-events: none;
  user-select: none;
}

/* Start arrow */
.start-arrow {
  stroke: var(--start-arrow);
  stroke-width: 2.5;
  fill: none;
  marker-end: url(#arrowhead-start);
}

/* Transition Styles */
.transition-group {
  cursor: pointer;
}

.transition-path {
  fill: none;
  stroke: var(--transition-stroke);
  stroke-width: 2;
  transition: stroke var(--transition-fast);
}

.transition-group:hover .transition-path {
  stroke: var(--color-primary);
  stroke-width: 2.5;
}

.transition-group.selected .transition-path {
  stroke: var(--color-primary);
  stroke-width: 2.5;
}

.transition-group.highlighted .transition-path {
  stroke: var(--highlight-color);
  stroke-width: 3;
  animation: pulse-highlight 0.5s ease;
}

.transition-label-bg {
  fill: var(--canvas-bg);
  rx: 4;
  ry: 4;
}

.transition-label {
  fill: var(--color-text);
  font-family: var(--font-family);
  font-size: 12px;
  font-weight: 600;
  text-anchor: middle;
  dominant-baseline: central;
  pointer-events: none;
  user-select: none;
}

.transition-hit-area {
  fill: none;
  stroke: transparent;
  stroke-width: 16;
  pointer-events: stroke;
  cursor: pointer;
}

/* ----- Context Menu ----- */
.context-menu {
  position: fixed;
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  box-shadow: var(--shadow-lg);
  padding: var(--space-xs) 0;
  z-index: 1000;
  min-width: 180px;
  animation: contextMenuIn 0.15s ease;
  display: none;
}

.context-menu.visible {
  display: block;
}

.context-menu-item {
  display: flex;
  align-items: center;
  gap: var(--space-sm);
  padding: var(--space-sm) var(--space-lg);
  font-size: var(--font-size-sm);
  font-weight: 500;
  color: var(--color-text);
  cursor: pointer;
  transition: background var(--transition-fast);
  border: none;
  background: none;
  width: 100%;
  text-align: left;
  font-family: var(--font-family);
}

.context-menu-item svg {
  width: 15px;
  height: 15px;
  color: var(--color-text-secondary);
}

.context-menu-item:hover {
  background: var(--color-primary-bg);
  color: var(--color-primary);
}

.context-menu-item:hover svg {
  color: var(--color-primary);
}

.context-menu-item.danger:hover {
  background: var(--color-accent-red-bg);
  color: var(--color-accent-red);
}

.context-menu-item.danger:hover svg {
  color: var(--color-accent-red);
}

.context-menu-divider {
  height: 1px;
  background: var(--color-border-light);
  margin: var(--space-xs) 0;
}

/* ----- State Quick Floating Toolbar ----- */
.state-quick-toolbar {
  position: absolute;
  transform: translate(-50%, -100%);
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-full);
  box-shadow: var(--shadow-md);
  padding: 3px 6px;
  display: flex;
  align-items: center;
  gap: 4px;
  z-index: 90;
  animation: slideUp 0.15s ease;
  pointer-events: auto;
}

.state-quick-toolbar.hidden {
  display: none;
}

.quick-btn {
  display: inline-flex;
  align-items: center;
  gap: 4px;
  padding: 4px 10px;
  border: none;
  background: transparent;
  border-radius: var(--radius-full);
  font-family: var(--font-family);
  font-size: 12px;
  font-weight: 600;
  color: var(--color-text);
  cursor: pointer;
  transition: all var(--transition-fast);
  white-space: nowrap;
}

.quick-btn svg {
  width: 14px;
  height: 14px;
}

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

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

.quick-btn.active:hover {
  background: var(--color-primary-dark);
}

.quick-btn.danger:hover {
  background: var(--color-accent-red-bg);
  color: var(--color-accent-red);
}

/* ----- Right Panel (Test & Submission) ----- */
.right-panel {
  background: var(--color-surface);
  border-left: 1px solid var(--color-border);
}

/* String Simulator */
.simulator-section {
  margin-bottom: var(--space-xl);
}

.simulator-input-row {
  display: flex;
  gap: var(--space-sm);
  margin-bottom: var(--space-md);
}

.simulator-input {
  flex: 1;
  padding: var(--space-sm) var(--space-md);
  border: 1.5px solid var(--color-border);
  border-radius: var(--radius-md);
  font-family: 'Courier New', monospace;
  font-size: var(--font-size-base);
  font-weight: 500;
  color: var(--color-text);
  outline: none;
  transition: border-color var(--transition-fast), box-shadow var(--transition-fast);
}

.simulator-input:focus {
  border-color: var(--color-primary);
  box-shadow: 0 0 0 3px var(--color-primary-bg);
}

.simulator-input::placeholder {
  color: var(--color-text-muted);
  font-family: var(--font-family);
  font-weight: 400;
}

.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: var(--space-xs);
  padding: var(--space-sm) var(--space-lg);
  border: 1.5px solid var(--color-border);
  border-radius: var(--radius-md);
  font-family: var(--font-family);
  font-size: var(--font-size-sm);
  font-weight: 600;
  cursor: pointer;
  transition: all var(--transition-fast);
  white-space: nowrap;
  background: var(--color-surface);
  color: var(--color-text-secondary);
}

.btn:hover {
  transform: translateY(-1px);
  box-shadow: var(--shadow-sm);
}

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

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

.btn-success {
  background: var(--color-accent-green);
  border-color: var(--color-accent-green);
  color: white;
}

.btn-success:hover {
  background: #16a34a;
  box-shadow: 0 4px 14px rgba(34,197,94,0.3);
}

.btn-sm {
  padding: var(--space-xs) var(--space-md);
  font-size: var(--font-size-xs);
}

.btn svg {
  width: 14px;
  height: 14px;
}

/* Simulation Result */
.sim-result {
  animation: slideUp 0.3s ease;
}

.sim-path {
  padding: var(--space-md);
  background: var(--color-surface-alt);
  border-radius: var(--radius-md);
  border: 1px solid var(--color-border-light);
  margin-bottom: var(--space-md);
}

.sim-path-label {
  font-size: var(--font-size-xs);
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  color: var(--color-text-muted);
  margin-bottom: var(--space-xs);
}

.sim-path-content {
  font-family: 'Courier New', monospace;
  font-size: var(--font-size-sm);
  font-weight: 500;
  color: var(--color-text);
  word-break: break-all;
  line-height: 1.8;
}

.sim-path-content .arrow {
  color: var(--color-text-muted);
  margin: 0 2px;
}

.sim-verdict {
  display: flex;
  align-items: center;
  gap: var(--space-sm);
  padding: var(--space-md);
  border-radius: var(--radius-md);
  font-size: var(--font-size-base);
  font-weight: 700;
}

.sim-verdict.accepted {
  background: var(--color-accent-green-bg);
  color: #15803d;
  border: 1px solid #bbf7d0;
}

.sim-verdict.rejected {
  background: var(--color-accent-red-bg);
  color: #dc2626;
  border: 1px solid #fecaca;
}

.sim-verdict svg {
  width: 18px;
  height: 18px;
}

/* ----- Validation Messages ----- */
.validation-messages {
  margin-bottom: var(--space-lg);
  animation: slideUp 0.3s ease;
}

.validation-msg {
  display: flex;
  align-items: flex-start;
  gap: var(--space-sm);
  padding: var(--space-sm) var(--space-md);
  border-radius: var(--radius-sm);
  font-size: var(--font-size-sm);
  margin-bottom: var(--space-xs);
  animation: slideUp 0.2s ease;
}

.validation-msg svg {
  width: 14px;
  height: 14px;
  flex-shrink: 0;
  margin-top: 2px;
}

.validation-msg.error {
  background: var(--color-accent-red-bg);
  color: #dc2626;
  border: 1px solid #fecaca;
}

.validation-msg.success {
  background: var(--color-accent-green-bg);
  color: #15803d;
  border: 1px solid #bbf7d0;
}

.validation-msg.warning {
  background: var(--color-accent-amber-bg);
  color: #b45309;
  border: 1px solid #fde68a;
}

/* ----- Submission Section ----- */
.submission-section {
  border-top: 1px solid var(--color-border-light);
  padding-top: var(--space-lg);
}

.submit-btn {
  width: 100%;
  padding: var(--space-md) var(--space-xl);
  font-size: var(--font-size-md);
  border-radius: var(--radius-lg);
}

/* Submission Result */
.submission-result {
  margin-top: var(--space-lg);
  animation: slideUp 0.4s ease;
}

.result-card {
  padding: var(--space-xl);
  border-radius: var(--radius-lg);
  text-align: center;
}

.result-card.correct {
  background: linear-gradient(135deg, #ecfdf5, #dcfce7);
  border: 2px solid #86efac;
}

.result-card.incorrect {
  background: linear-gradient(135deg, #fef2f2, #fee2e2);
  border: 2px solid #fca5a5;
}

.result-icon {
  width: 56px;
  height: 56px;
  margin: 0 auto var(--space-md);
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
}

.result-card.correct .result-icon {
  background: var(--color-accent-green);
}

.result-card.incorrect .result-icon {
  background: var(--color-accent-red);
}

.result-icon svg {
  width: 28px;
  height: 28px;
  color: white;
}

.result-title {
  font-size: var(--font-size-xl);
  font-weight: 800;
  margin-bottom: var(--space-xs);
}

.result-card.correct .result-title {
  color: #15803d;
}

.result-card.incorrect .result-title {
  color: #dc2626;
}

.result-score {
  font-size: var(--font-size-2xl);
  font-weight: 800;
  margin-bottom: var(--space-md);
}

.result-card.correct .result-score {
  color: #16a34a;
}

.result-card.incorrect .result-score {
  color: #ef4444;
}

.result-message {
  font-size: var(--font-size-sm);
  color: var(--color-text-secondary);
  line-height: 1.6;
}

.counterexample-box {
  margin-top: var(--space-lg);
  padding: var(--space-md);
  background: rgba(255,255,255,0.7);
  border-radius: var(--radius-md);
  text-align: left;
}

.counterexample-box h4 {
  font-size: var(--font-size-sm);
  font-weight: 700;
  color: var(--color-accent-red);
  margin-bottom: var(--space-sm);
}

.counterexample-row {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: var(--space-xs) 0;
  font-size: var(--font-size-sm);
  border-bottom: 1px solid var(--color-border-light);
}

.counterexample-row:last-child {
  border-bottom: none;
}

.counterexample-row .label {
  color: var(--color-text-secondary);
  font-weight: 500;
}

.counterexample-row .value {
  font-weight: 700;
  font-family: 'Courier New', monospace;
}

/* ----- Inline Rename Input ----- */
.inline-rename {
  position: absolute;
  z-index: 500;
  transform: translate(-50%, -50%);
}

.inline-rename input {
  width: 72px;
  padding: 2px 6px;
  border: 2px solid var(--color-primary);
  border-radius: var(--radius-sm);
  font-family: var(--font-family);
  font-size: 13px;
  font-weight: 600;
  text-align: center;
  outline: none;
  background: white;
  box-shadow: var(--shadow-md);
}

/* ----- Transition Label Input ----- */
.transition-label-input {
  position: absolute;
  z-index: 500;
  transform: translate(-50%, -50%);
}

.transition-label-input input {
  width: 56px;
  padding: 2px 6px;
  border: 2px solid var(--color-primary);
  border-radius: var(--radius-sm);
  font-family: 'Courier New', monospace;
  font-size: 13px;
  font-weight: 600;
  text-align: center;
  outline: none;
  background: white;
  box-shadow: var(--shadow-md);
}

/* ----- Modal Overlay ----- */
.modal-overlay {
  position: fixed;
  inset: 0;
  background: rgba(0,0,0,0.4);
  backdrop-filter: blur(4px);
  display: flex;
  align-items: center;
  justify-content: center;
  z-index: 2000;
  animation: fadeIn 0.2s ease;
}

.modal-overlay.hidden {
  display: none;
}

.modal {
  background: var(--color-surface);
  border-radius: var(--radius-xl);
  box-shadow: var(--shadow-xl);
  max-width: 420px;
  width: 90%;
  padding: var(--space-2xl);
  animation: modalIn 0.3s cubic-bezier(0.34, 1.56, 0.64, 1);
}

.modal h3 {
  font-size: var(--font-size-lg);
  font-weight: 700;
  margin-bottom: var(--space-md);
}

.modal-actions {
  display: flex;
  justify-content: flex-end;
  gap: var(--space-sm);
  margin-top: var(--space-xl);
}

/* ----- Toast Notifications ----- */
.toast-container {
  position: fixed;
  bottom: var(--space-xl);
  right: var(--space-xl);
  z-index: 3000;
  display: flex;
  flex-direction: column;
  gap: var(--space-sm);
}

.toast {
  padding: var(--space-md) var(--space-xl);
  border-radius: var(--radius-md);
  font-size: var(--font-size-sm);
  font-weight: 500;
  box-shadow: var(--shadow-lg);
  animation: toastIn 0.4s cubic-bezier(0.34, 1.56, 0.64, 1);
  display: flex;
  align-items: center;
  gap: var(--space-sm);
}

.toast.info {
  background: var(--color-primary);
  color: white;
}

.toast.success {
  background: var(--color-accent-green);
  color: white;
}

.toast.error {
  background: var(--color-accent-red);
  color: white;
}

.toast.warning {
  background: var(--color-accent-amber);
  color: white;
}

.toast.removing {
  animation: toastOut 0.3s ease forwards;
}

/* ----- Confetti ----- */
.confetti-container {
  position: fixed;
  inset: 0;
  pointer-events: none;
  z-index: 4000;
  overflow: hidden;
}

.confetti-piece {
  position: absolute;
  width: 10px;
  height: 10px;
  border-radius: 2px;
  animation: confettiFall 2.5s cubic-bezier(0.25, 0.46, 0.45, 0.94) forwards;
}

/* ----- Animations ----- */
@keyframes fadeIn {
  from { opacity: 0; }
  to { opacity: 1; }
}

@keyframes slideUp {
  from { opacity: 0; transform: translateY(8px); }
  to { opacity: 1; transform: translateY(0); }
}

@keyframes modalIn {
  from { opacity: 0; transform: scale(0.9); }
  to { opacity: 1; transform: scale(1); }
}

@keyframes contextMenuIn {
  from { opacity: 0; transform: scale(0.95) translateY(-4px); }
  to { opacity: 1; transform: scale(1) translateY(0); }
}

@keyframes toastIn {
  from { opacity: 0; transform: translateX(40px); }
  to { opacity: 1; transform: translateX(0); }
}

@keyframes toastOut {
  from { opacity: 1; transform: translateX(0); }
  to { opacity: 0; transform: translateX(40px); }
}

@keyframes pulse-highlight {
  0% { transform: scale(1); }
  50% { transform: scale(1.08); }
  100% { transform: scale(1); }
}

@keyframes confettiFall {
  0% {
    transform: translateY(-20px) rotate(0deg);
    opacity: 1;
  }
  100% {
    transform: translateY(100vh) rotate(720deg);
    opacity: 0;
  }
}

/* ----- Responsive ----- */
@media (max-width: 1100px) {
  .app-main {
    grid-template-columns: 1fr;
    grid-template-rows: auto 1fr auto;
    height: calc(100vh - 57px);
    overflow-y: auto;
  }

  .problem-panel {
    border-right: none;
    border-bottom: 1px solid var(--color-border);
    max-height: 200px;
  }

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

  .right-panel {
    border-left: none;
    border-top: 1px solid var(--color-border);
  }
}

@media (max-width: 768px) {
  .app-header {
    flex-direction: column;
    gap: var(--space-sm);
    padding: var(--space-sm) var(--space-md);
  }

  .header-controls {
    flex-wrap: wrap;
    justify-content: center;
  }

  .user-menu {
    border-left: none;
    padding-left: 0;
    width: 100%;
    justify-content: center;
    padding-top: var(--space-sm);
    border-top: 1px solid var(--color-border-light);
  }

  .toolbar {
    padding: var(--space-xs) var(--space-sm);
  }

  .tool-btn span {
    display: none;
  }

  .tool-btn {
    padding: var(--space-sm);
  }

  .panel-body {
    padding: var(--space-md);
  }
}