/* =====================================================
   AutomataLab — Design System & Global Styles
   Dark Theme + Glassmorphism + Premium Animations
   ===================================================== */

/* --- CSS Variables / Design Tokens --- */
:root {
  /* Colors */
  --bg-base:       #07070f;
  --bg-surface:    #0d0d1a;
  --bg-card:       rgba(255, 255, 255, 0.04);
  --bg-card-hover: rgba(255, 255, 255, 0.07);
  --bg-input:      rgba(255, 255, 255, 0.06);
  --bg-input-focus:rgba(255, 255, 255, 0.10);

  --border:        rgba(255, 255, 255, 0.09);
  --border-focus:  rgba(124, 58, 237, 0.6);

  --accent-1:      #7c3aed; /* violet */
  --accent-2:      #4f46e5; /* indigo */
  --accent-3:      #06b6d4; /* cyan */
  --accent-grad:   linear-gradient(135deg, #7c3aed, #4f46e5, #06b6d4);

  --text-primary:  #f1f5f9;
  --text-secondary:#94a3b8;
  --text-muted:    #475569;
  --text-code:     #a5f3fc;

  --success:       #10b981;
  --success-bg:    rgba(16, 185, 129, 0.12);
  --error:         #f43f5e;
  --error-bg:      rgba(244, 63, 94, 0.12);
  --warning:       #f59e0b;
  --warning-bg:    rgba(245, 158, 11, 0.12);
  --info:          #38bdf8;
  --info-bg:       rgba(56, 189, 248, 0.12);

  /* Spacing */
  --space-xs:  4px;
  --space-sm:  8px;
  --space-md:  16px;
  --space-lg:  24px;
  --space-xl:  32px;
  --space-2xl: 48px;
  --space-3xl: 64px;

  /* Radius */
  --radius-sm: 6px;
  --radius-md: 12px;
  --radius-lg: 16px;
  --radius-xl: 24px;

  /* Shadows */
  --shadow-sm: 0 2px 8px rgba(0,0,0,0.4);
  --shadow-md: 0 4px 20px rgba(0,0,0,0.5);
  --shadow-lg: 0 8px 40px rgba(0,0,0,0.6);
  --shadow-glow: 0 0 40px rgba(124, 58, 237, 0.2);

  /* Typography */
  --font-sans: 'Inter', system-ui, sans-serif;
  --font-mono: 'JetBrains Mono', 'Fira Code', monospace;

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

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

html { scroll-behavior: smooth; }

body {
  font-family: var(--font-sans);
  background-color: var(--bg-base);
  color: var(--text-primary);
  line-height: 1.6;
  min-height: 100vh;
  overflow-x: hidden;
  -webkit-font-smoothing: antialiased;
}

/* --- Animated Background Orbs --- */
.bg-orbs {
  position: fixed;
  inset: 0;
  z-index: 0;
  pointer-events: none;
  overflow: hidden;
}
.orb {
  position: absolute;
  border-radius: 50%;
  filter: blur(80px);
  opacity: 0.18;
  animation: orb-float 15s ease-in-out infinite;
}
.orb-1 {
  width: 600px; height: 600px;
  background: radial-gradient(circle, #7c3aed, transparent);
  top: -200px; left: -100px;
  animation-duration: 18s;
}
.orb-2 {
  width: 500px; height: 500px;
  background: radial-gradient(circle, #06b6d4, transparent);
  bottom: -150px; right: -100px;
  animation-duration: 22s;
  animation-delay: -5s;
}
.orb-3 {
  width: 400px; height: 400px;
  background: radial-gradient(circle, #4f46e5, transparent);
  top: 40%; left: 50%;
  animation-duration: 20s;
  animation-delay: -10s;
}
@keyframes orb-float {
  0%, 100% { transform: translate(0, 0) scale(1); }
  33%       { transform: translate(40px, -30px) scale(1.05); }
  66%       { transform: translate(-30px, 20px) scale(0.95); }
}

/* All content above z-index 0 */
header, nav, main, footer { position: relative; z-index: 1; }

/* --- Site Header --- */
.site-header {
  background: rgba(7, 7, 15, 0.8);
  border-bottom: 1px solid var(--border);
  backdrop-filter: blur(20px);
  -webkit-backdrop-filter: blur(20px);
  position: sticky;
  top: 0;
  z-index: 100;
}
.header-inner {
  max-width: 1400px;
  margin: 0 auto;
  padding: var(--space-md) var(--space-xl);
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: var(--space-md);
}
.logo {
  display: flex;
  align-items: center;
  gap: var(--space-md);
}
.logo-icon {
  width: 44px; height: 44px;
  background: var(--accent-grad);
  border-radius: var(--radius-md);
  display: flex; align-items: center; justify-content: center;
  padding: 8px;
  color: white;
  box-shadow: 0 0 20px rgba(124,58,237,0.4);
  flex-shrink: 0;
}
.logo-icon svg { width: 100%; height: 100%; }
.logo-text { display: flex; flex-direction: column; }
.logo-title {
  font-size: 1.25rem;
  font-weight: 800;
  background: var(--accent-grad);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
  line-height: 1.2;
  letter-spacing: -0.5px;
}
.logo-sub {
  font-size: 0.7rem;
  color: var(--text-muted);
  font-weight: 500;
  letter-spacing: 0.05em;
  text-transform: uppercase;
}
.header-badge {
  display: flex;
  align-items: center;
  gap: var(--space-sm);
  font-size: 0.8rem;
  color: var(--text-secondary);
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: 100px;
  padding: var(--space-xs) var(--space-md);
}
.badge-dot {
  width: 6px; height: 6px;
  border-radius: 50%;
  background: var(--accent-1);
  box-shadow: 0 0 8px var(--accent-1);
  animation: pulse-dot 2s ease-in-out infinite;
}
@keyframes pulse-dot {
  0%, 100% { opacity: 1; }
  50%       { opacity: 0.4; }
}

/* --- Tab Navigation --- */
.tab-nav {
  background: rgba(7, 7, 15, 0.6);
  border-bottom: 1px solid var(--border);
  backdrop-filter: blur(20px);
  -webkit-backdrop-filter: blur(20px);
  position: sticky;
  top: 73px;
  z-index: 99;
}
.tab-nav-inner {
  max-width: 1400px;
  margin: 0 auto;
  padding: 0 var(--space-xl);
  display: flex;
  align-items: stretch;
  position: relative;
  overflow-x: auto;
  scrollbar-width: none;
  gap: 2px;
}
.tab-nav-inner::-webkit-scrollbar { display: none; }

.tab-btn {
  display: flex;
  align-items: center;
  gap: var(--space-md);
  padding: var(--space-md) var(--space-lg);
  border: none;
  background: transparent;
  color: var(--text-muted);
  cursor: pointer;
  font-family: var(--font-sans);
  font-size: 0.875rem;
  transition: color var(--transition-base), background var(--transition-base);
  border-radius: var(--radius-sm) var(--radius-sm) 0 0;
  white-space: nowrap;
  position: relative;
  flex-shrink: 0;
}
.tab-btn::after {
  content: '';
  position: absolute;
  bottom: 0; left: 0; right: 0;
  height: 2px;
  background: var(--accent-grad);
  border-radius: 2px 2px 0 0;
  opacity: 0;
  transition: opacity var(--transition-base);
}
.tab-btn:hover { color: var(--text-secondary); background: rgba(255,255,255,0.03); }
.tab-btn.active { color: var(--text-primary); }
.tab-btn.active::after { opacity: 1; }

.tab-num {
  font-size: 0.65rem;
  font-weight: 700;
  letter-spacing: 0.1em;
  color: var(--accent-1);
  font-family: var(--font-mono);
  padding: 2px 6px;
  background: rgba(124,58,237,0.15);
  border-radius: 4px;
  border: 1px solid rgba(124,58,237,0.3);
  transition: var(--transition-base);
}
.tab-btn.active .tab-num { background: rgba(124,58,237,0.3); }

.tab-content-label { display: flex; flex-direction: column; text-align: left; }
.tab-title { font-weight: 600; font-size: 0.875rem; }
.tab-sub { font-size: 0.7rem; opacity: 0.6; margin-top: 1px; }

/* --- Main Content --- */
.main-content {
  max-width: 1400px;
  margin: 0 auto;
  padding: var(--space-2xl) var(--space-xl);
  min-height: calc(100vh - 200px);
}

/* --- Tab Panels --- */
.tab-panel {
  display: none;
  animation: panel-in var(--transition-slow) ease forwards;
}
.tab-panel.active { display: block; }

@keyframes panel-in {
  from { opacity: 0; transform: translateY(16px); }
  to   { opacity: 1; transform: translateY(0); }
}

/* --- Module Header --- */
.module-header {
  margin-bottom: var(--space-2xl);
}
.module-header h1,
.module-header h2 {
  font-size: clamp(1.5rem, 3vw, 2.2rem);
  font-weight: 800;
  background: var(--accent-grad);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
  letter-spacing: -0.5px;
  line-height: 1.2;
  margin-bottom: var(--space-sm);
}
.module-desc {
  color: var(--text-secondary);
  font-size: 0.95rem;
  max-width: 700px;
}

/* --- Module Layout --- */
.module-layout {
  display: grid;
  grid-template-columns: 380px 1fr;
  gap: var(--space-xl);
  align-items: start;
}
@media (max-width: 1024px) {
  .module-layout { grid-template-columns: 1fr; }
}

.panel-left  { display: flex; flex-direction: column; gap: var(--space-lg); }
.panel-right { display: flex; flex-direction: column; gap: var(--space-lg); }

/* --- Cards --- */
.card {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  backdrop-filter: blur(10px);
  -webkit-backdrop-filter: blur(10px);
  overflow: hidden;
  transition: border-color var(--transition-base), box-shadow var(--transition-base);
}
.card:hover { border-color: rgba(124,58,237,0.3); }
.card.hidden { display: none; }

.card-header {
  display: flex;
  align-items: center;
  gap: var(--space-sm);
  padding: var(--space-md) var(--space-lg);
  border-bottom: 1px solid var(--border);
  font-weight: 600;
  font-size: 0.875rem;
  color: var(--text-primary);
  background: rgba(255,255,255,0.02);
}
.card-icon { font-size: 1rem; }

.card-body {
  padding: var(--space-lg);
  display: flex;
  flex-direction: column;
  gap: var(--space-md);
}

/* --- Result Cards --- */
.result-card .card-header { color: var(--text-primary); }
.result-card.accepted { border-color: var(--success); }
.result-card.rejected { border-color: var(--error); }

/* --- Form Fields --- */
.field-group { display: flex; flex-direction: column; gap: var(--space-xs); }
.field-label {
  font-size: 0.8rem;
  font-weight: 600;
  color: var(--text-secondary);
  letter-spacing: 0.03em;
  display: flex;
  align-items: center;
  gap: var(--space-sm);
}
.field-label .hint {
  font-weight: 400;
  color: var(--text-muted);
  font-size: 0.72rem;
}
.field-input {
  background: var(--bg-input);
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  color: var(--text-primary);
  font-family: var(--font-sans);
  font-size: 0.875rem;
  padding: 10px 14px;
  transition: border-color var(--transition-fast), background var(--transition-fast), box-shadow var(--transition-fast);
  outline: none;
  width: 100%;
}
.field-input:focus {
  border-color: var(--border-focus);
  background: var(--bg-input-focus);
  box-shadow: 0 0 0 3px rgba(124,58,237,0.15);
}
.field-input.mono { font-family: var(--font-mono); letter-spacing: 0.05em; }
.field-textarea {
  background: var(--bg-input);
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  color: var(--text-primary);
  font-family: var(--font-mono);
  font-size: 0.875rem;
  padding: 10px 14px;
  transition: border-color var(--transition-fast), background var(--transition-fast), box-shadow var(--transition-fast);
  outline: none;
  resize: vertical;
  width: 100%;
  line-height: 1.6;
}
.field-textarea:focus {
  border-color: var(--border-focus);
  background: var(--bg-input-focus);
  box-shadow: 0 0 0 3px rgba(124,58,237,0.15);
}

/* --- Radio Group --- */
.radio-group { display: flex; gap: var(--space-lg); flex-wrap: wrap; }
.radio-label {
  display: flex;
  align-items: center;
  gap: var(--space-sm);
  cursor: pointer;
  font-size: 0.875rem;
  color: var(--text-secondary);
  transition: color var(--transition-fast);
}
.radio-label:hover { color: var(--text-primary); }
.radio-label input[type="radio"] { display: none; }
.radio-custom {
  width: 18px; height: 18px;
  border-radius: 50%;
  border: 2px solid var(--border);
  display: flex; align-items: center; justify-content: center;
  transition: border-color var(--transition-fast);
  flex-shrink: 0;
}
.radio-custom::after {
  content: '';
  width: 8px; height: 8px;
  border-radius: 50%;
  background: var(--accent-1);
  opacity: 0;
  transition: opacity var(--transition-fast), transform var(--transition-fast);
  transform: scale(0.5);
}
.radio-label input[type="radio"]:checked + .radio-custom {
  border-color: var(--accent-1);
}
.radio-label input[type="radio"]:checked + .radio-custom::after {
  opacity: 1;
  transform: scale(1);
}
.radio-label input[type="radio"]:checked ~ span { color: var(--text-primary); font-weight: 500; }

/* --- Buttons --- */
.btn-row { display: flex; gap: var(--space-sm); flex-wrap: wrap; }
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: var(--space-xs);
  padding: 10px 20px;
  border-radius: var(--radius-sm);
  border: none;
  font-family: var(--font-sans);
  font-size: 0.875rem;
  font-weight: 600;
  cursor: pointer;
  transition: all var(--transition-fast);
  white-space: nowrap;
}
.btn-primary {
  background: var(--accent-grad);
  color: white;
  box-shadow: 0 4px 15px rgba(124,58,237,0.3);
}
.btn-primary:hover {
  transform: translateY(-1px);
  box-shadow: 0 6px 20px rgba(124,58,237,0.4);
}
.btn-primary:active { transform: translateY(0); }
.btn-secondary {
  background: rgba(255,255,255,0.06);
  color: var(--text-secondary);
  border: 1px solid var(--border);
}
.btn-secondary:hover { background: rgba(255,255,255,0.10); color: var(--text-primary); }
.btn-ghost {
  background: transparent;
  color: var(--accent-1);
  border: 1px solid rgba(124,58,237,0.3);
  padding: 5px 12px;
  font-size: 0.75rem;
  margin-left: auto;
}
.btn-ghost:hover { background: rgba(124,58,237,0.1); }
.btn-sm { padding: 5px 12px; font-size: 0.78rem; }

/* --- Help & Info Text --- */
.help-text {
  font-size: 0.78rem;
  color: var(--text-muted);
  line-height: 1.6;
}
.help-text code {
  font-family: var(--font-mono);
  color: var(--text-code);
  background: rgba(165,243,252,0.1);
  padding: 1px 5px;
  border-radius: 3px;
  font-size: 0.85em;
}

/* --- Transition Table --- */
.trans-table-wrapper { overflow-x: auto; }
.trans-table {
  width: 100%;
  border-collapse: collapse;
  font-size: 0.825rem;
  font-family: var(--font-mono);
}
.trans-table th {
  background: rgba(124,58,237,0.15);
  color: var(--accent-1);
  padding: 8px 12px;
  text-align: center;
  border: 1px solid var(--border);
  font-size: 0.8rem;
  letter-spacing: 0.05em;
  white-space: nowrap;
}
.trans-table td {
  padding: 6px 8px;
  border: 1px solid var(--border);
  text-align: center;
}
.trans-table td:first-child { color: var(--text-secondary); font-weight: 500; text-align: left; }
.trans-table input {
  background: transparent;
  border: none;
  color: var(--text-primary);
  font-family: var(--font-mono);
  font-size: 0.825rem;
  text-align: center;
  width: 100%;
  outline: none;
  padding: 2px 4px;
}
.trans-table input:focus { background: rgba(124,58,237,0.1); border-radius: 3px; }
.state-indicator { display: flex; align-items: center; justify-content: flex-start; gap: 4px; }
.state-badge { font-size: 0.65rem; padding: 1px 4px; border-radius: 3px; }
.state-badge.start { background: rgba(16,185,129,0.2); color: var(--success); }
.state-badge.final { background: rgba(124,58,237,0.2); color: var(--accent-1); }

/* --- Trace / Step Display --- */
.trace-steps { display: flex; flex-direction: column; gap: var(--space-xs); }
.trace-step {
  display: flex;
  align-items: center;
  gap: var(--space-md);
  padding: 8px 12px;
  background: rgba(255,255,255,0.03);
  border-radius: var(--radius-sm);
  border-left: 3px solid transparent;
  font-size: 0.825rem;
  animation: step-in 0.3s ease forwards;
  opacity: 0;
}
.trace-step.accepted-step { border-left-color: var(--success); background: rgba(16,185,129,0.06); }
.trace-step.rejected-step { border-left-color: var(--error); background: rgba(244,63,94,0.06); }
.trace-step.normal-step { border-left-color: rgba(124,58,237,0.5); }

@keyframes step-in {
  from { opacity: 0; transform: translateX(-8px); }
  to   { opacity: 1; transform: translateX(0); }
}

.step-num {
  font-family: var(--font-mono);
  font-size: 0.7rem;
  color: var(--text-muted);
  min-width: 28px;
  text-align: right;
}
.step-state {
  font-family: var(--font-mono);
  font-weight: 600;
  color: var(--accent-3);
  min-width: 60px;
}
.step-input { font-family: var(--font-mono); color: var(--text-secondary); }
.step-arrow { color: var(--text-muted); }
.step-next { font-family: var(--font-mono); font-weight: 600; color: var(--text-primary); }
.step-symbol { 
  font-family: var(--font-mono);
  font-weight: 700;
  color: var(--warning);
  background: var(--warning-bg);
  padding: 1px 6px; border-radius: 3px;
  min-width: 24px; text-align: center;
}

/* --- Result Banner --- */
.result-banner {
  display: flex;
  align-items: center;
  gap: var(--space-md);
  padding: var(--space-md) var(--space-lg);
  border-radius: var(--radius-md);
  font-weight: 700;
  font-size: 1.1rem;
}
.result-banner.accepted { background: var(--success-bg); color: var(--success); border: 1px solid rgba(16,185,129,0.3); }
.result-banner.rejected  { background: var(--error-bg);   color: var(--error);   border: 1px solid rgba(244,63,94,0.3); }
.result-banner .banner-icon { font-size: 1.5rem; }
.result-banner .banner-text { display: flex; flex-direction: column; }
.result-banner .banner-label { font-size: 0.75rem; font-weight: 500; opacity: 0.8; }

/* --- Error Message --- */
.error-msg {
  display: flex;
  align-items: flex-start;
  gap: var(--space-sm);
  padding: var(--space-md);
  background: var(--error-bg);
  border: 1px solid rgba(244,63,94,0.3);
  border-radius: var(--radius-sm);
  color: var(--error);
  font-size: 0.85rem;
}
.error-msg::before { content: '⚠️'; flex-shrink: 0; }

/* --- Visualization Container --- */
.viz-body { padding: 0; }
.viz-container {
  min-height: 350px;
  width: 100%;
  position: relative;
  overflow: auto;
}
.viz-placeholder {
  position: absolute;
  inset: 0;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  gap: var(--space-md);
  color: var(--text-muted);
  font-size: 0.875rem;
  text-align: center;
  padding: var(--space-xl);
}
.viz-placeholder span { font-size: 3rem; opacity: 0.5; }

/* D3 Styles */
.d3-svg {
  width: 100%;
  overflow: visible;
}
.node circle {
  fill: rgba(124,58,237,0.2);
  stroke: var(--accent-1);
  stroke-width: 2;
  transition: all 0.3s;
  cursor: pointer;
}
.node circle.start-state { stroke: var(--success); fill: rgba(16,185,129,0.15); }
.node circle.final-state {
  stroke: var(--accent-1);
  fill: rgba(124,58,237,0.2);
}
.node circle.final-state.double {
  stroke: var(--accent-1);
  fill: rgba(124,58,237,0.2);
}
.node circle.active-state { fill: rgba(245,158,11,0.3); stroke: var(--warning); }
.node circle:hover { fill: rgba(124,58,237,0.4); }
.node text {
  fill: var(--text-primary);
  font-family: var(--font-mono);
  font-size: 12px;
  font-weight: 600;
  text-anchor: middle;
  dominant-baseline: central;
  pointer-events: none;
}
.link { stroke: var(--text-muted); stroke-width: 1.5; fill: none; }
.link.active-link { stroke: var(--warning); stroke-width: 2.5; }
.link-label {
  fill: var(--text-secondary);
  font-family: var(--font-mono);
  font-size: 11px;
}
.arrow-marker { fill: var(--text-muted); }
.arrow-marker-active { fill: var(--warning); }
.start-arrow { stroke: var(--success); stroke-width: 2; fill: none; }

/* Parse Tree Styles */
.tree-node circle {
  fill: rgba(124,58,237,0.25);
  stroke: var(--accent-1);
  stroke-width: 2;
}
.tree-node.terminal circle {
  fill: rgba(6,182,212,0.2);
  stroke: var(--accent-3);
}
.tree-node text {
  fill: var(--text-primary);
  font-family: var(--font-mono);
  font-size: 12px;
  font-weight: 600;
  text-anchor: middle;
  dominant-baseline: central;
}
.tree-link {
  stroke: var(--border);
  stroke-width: 1.5;
  fill: none;
}

/* --- RE Legend --- */
.re-legend {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-xs) var(--space-md);
  margin-top: var(--space-xs);
}
.legend-item {
  font-size: 0.72rem;
  color: var(--text-muted);
  display: flex;
  align-items: center;
  gap: 3px;
}
.legend-item code {
  font-family: var(--font-mono);
  color: var(--accent-3);
  background: rgba(6,182,212,0.1);
  padding: 1px 5px;
  border-radius: 3px;
}

/* --- Grammar Production Display --- */
.production-rule {
  display: flex;
  align-items: baseline;
  gap: var(--space-sm);
  padding: 6px 10px;
  border-radius: var(--radius-sm);
  background: rgba(255,255,255,0.03);
  font-family: var(--font-mono);
  font-size: 0.875rem;
  border-left: 3px solid rgba(124,58,237,0.4);
  flex-wrap: wrap;
}
.prod-lhs { color: var(--accent-1); font-weight: 600; }
.prod-arrow { color: var(--text-muted); }
.prod-rhs { color: var(--text-primary); }
.prod-rhs .terminal { color: var(--accent-3); }
.prod-rhs .nonterminal { color: var(--accent-1); }

/* --- CNF Steps --- */
.cnf-step {
  border: 1px solid var(--border);
  border-radius: var(--radius-md);
  overflow: hidden;
  margin-bottom: var(--space-md);
}
.cnf-step-header {
  display: flex;
  align-items: center;
  gap: var(--space-md);
  padding: 10px var(--space-md);
  background: rgba(255,255,255,0.04);
  border-bottom: 1px solid var(--border);
}
.cnf-step-num {
  display: flex; align-items: center; justify-content: center;
  width: 28px; height: 28px;
  border-radius: 50%;
  background: var(--accent-grad);
  color: white;
  font-size: 0.75rem;
  font-weight: 700;
  flex-shrink: 0;
}
.cnf-step-title { font-weight: 600; font-size: 0.875rem; }
.cnf-step-desc { font-size: 0.78rem; color: var(--text-secondary); margin-left: auto; }
.cnf-step-body { padding: var(--space-md); }
.grammar-block { display: flex; flex-direction: column; gap: 6px; }

/* --- Chomsky Hierarchy Visual --- */
.chomsky-hierarchy { width: 100%; }
.ch-level {
  padding: var(--space-md);
  border-radius: var(--radius-md);
  border: 2px solid transparent;
  transition: border-color var(--transition-base), background var(--transition-base);
}
.ch-0 { background: rgba(124,58,237,0.08); border-color: rgba(124,58,237,0.3); }
.ch-1 { background: rgba(79,70,229,0.08);  border-color: rgba(79,70,229,0.3);  margin-top: var(--space-sm); }
.ch-2 { background: rgba(6,182,212,0.08);  border-color: rgba(6,182,212,0.3);  margin-top: var(--space-sm); }
.ch-3 { background: rgba(16,185,129,0.08); border-color: rgba(16,185,129,0.3); margin-top: var(--space-sm); }
.ch-label {
  font-family: var(--font-mono);
  font-size: 0.7rem;
  font-weight: 700;
  letter-spacing: 0.05em;
  text-transform: uppercase;
  display: block;
}
.ch-0 .ch-label { color: var(--accent-1); }
.ch-1 .ch-label { color: #818cf8; }
.ch-2 .ch-label { color: var(--accent-3); }
.ch-3 .ch-label { color: var(--success); }
.ch-name {
  font-size: 0.8rem;
  color: var(--text-secondary);
  display: block;
  margin-top: 1px;
}
.ch-level.highlighted { box-shadow: 0 0 20px rgba(124,58,237,0.4); }
.ch-0.highlighted { border-color: var(--accent-1); background: rgba(124,58,237,0.2); }
.ch-1.highlighted { border-color: #818cf8; background: rgba(79,70,229,0.2); }
.ch-2.highlighted { border-color: var(--accent-3); background: rgba(6,182,212,0.2); }
.ch-3.highlighted { border-color: var(--success); background: rgba(16,185,129,0.2); }

/* --- Tags/Badges --- */
.tag {
  display: inline-flex;
  align-items: center;
  padding: 2px 8px;
  border-radius: 100px;
  font-size: 0.72rem;
  font-weight: 600;
  letter-spacing: 0.03em;
}
.tag-success { background: var(--success-bg); color: var(--success); }
.tag-error   { background: var(--error-bg);   color: var(--error); }
.tag-info    { background: var(--info-bg);     color: var(--info); }
.tag-warning { background: var(--warning-bg);  color: var(--warning); }
.tag-purple  { background: rgba(124,58,237,0.15); color: var(--accent-1); }

/* --- Subset Construction Table --- */
.subset-table {
  width: 100%;
  border-collapse: collapse;
  font-size: 0.8rem;
  font-family: var(--font-mono);
}
.subset-table th {
  background: rgba(124,58,237,0.15);
  color: var(--accent-1);
  padding: 7px 10px;
  border: 1px solid var(--border);
  text-align: center;
  font-weight: 600;
}
.subset-table td {
  padding: 6px 10px;
  border: 1px solid var(--border);
  text-align: center;
  color: var(--text-secondary);
}
.subset-table td.final-dfa { color: var(--accent-1); font-weight: 600; }

/* --- Derivation Steps --- */
.deriv-step {
  display: flex;
  flex-direction: column;
  gap: 4px;
  padding: 10px;
  border-radius: var(--radius-sm);
  background: rgba(255,255,255,0.02);
  border: 1px solid var(--border);
}
.deriv-step-label { font-size: 0.7rem; color: var(--text-muted); font-family: var(--font-mono); }
.deriv-step-form  { font-family: var(--font-mono); font-size: 0.9rem; color: var(--text-primary); }
.deriv-step-form .nt  { color: var(--accent-1); font-weight: 700; }
.deriv-step-form .t   { color: var(--accent-3); }
.deriv-arrow { color: var(--text-muted); font-size: 0.7rem; text-align: center; margin: 2px 0; }

/* --- NFA State Info --- */
.nfa-info-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: var(--space-sm);
}
.nfa-info-item { }
.nfa-info-label { font-size: 0.72rem; color: var(--text-muted); font-weight: 600; text-transform: uppercase; letter-spacing: 0.05em; margin-bottom: 4px; }
.nfa-info-value { font-family: var(--font-mono); font-size: 0.85rem; color: var(--text-primary); }

/* --- Site Footer --- */
.site-footer {
  background: rgba(7,7,15,0.8);
  border-top: 1px solid var(--border);
  padding: var(--space-xl);
  margin-top: var(--space-3xl);
}
.footer-inner {
  max-width: 1400px;
  margin: 0 auto;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: var(--space-md);
  flex-wrap: wrap;
}
.footer-info { }
.footer-info p { font-size: 0.8rem; color: var(--text-muted); line-height: 1.8; }
.footer-info strong { color: var(--text-secondary); }
.footer-modules {
  display: flex;
  align-items: center;
  gap: var(--space-sm);
  font-size: 0.75rem;
  color: var(--text-muted);
  flex-wrap: wrap;
  justify-content: flex-end;
}

/* --- Scrollbar --- */
::-webkit-scrollbar { width: 6px; height: 6px; }
::-webkit-scrollbar-track { background: transparent; }
::-webkit-scrollbar-thumb { background: rgba(255,255,255,0.12); border-radius: 3px; }
::-webkit-scrollbar-thumb:hover { background: rgba(255,255,255,0.22); }

/* --- Responsive --- */
@media (max-width: 768px) {
  .header-inner { padding: var(--space-md); }
  .tab-nav-inner { padding: 0 var(--space-md); }
  .main-content  { padding: var(--space-lg) var(--space-md); }
  .header-badge  { display: none; }
  .tab-btn { padding: var(--space-sm) var(--space-md); }
  .tab-sub { display: none; }
  .btn-row { flex-direction: column; }
  .btn { width: 100%; }
  .nfa-info-grid { grid-template-columns: 1fr; }
}

/* --- Utility --- */
.mono { font-family: var(--font-mono) !important; }
.text-success { color: var(--success); }
.text-error   { color: var(--error); }
.text-muted   { color: var(--text-muted); }
.text-accent  { color: var(--accent-1); }
.mt-sm { margin-top: var(--space-sm); }
.mt-md { margin-top: var(--space-md); }
.fw-600 { font-weight: 600; }
.fw-700 { font-weight: 700; }

/* --- Loading spinner --- */
.spinner {
  display: inline-block;
  width: 16px; height: 16px;
  border: 2px solid rgba(124,58,237,0.3);
  border-top-color: var(--accent-1);
  border-radius: 50%;
  animation: spin 0.6s linear infinite;
}
@keyframes spin { to { transform: rotate(360deg); } }

code {
  font-family: var(--font-mono);
  color: var(--text-code);
  background: rgba(165,243,252,0.1);
  padding: 1px 5px;
  border-radius: 3px;
  font-size: 0.85em;
}