/* ============================================================
   COMPILER CONSTRUCTION VISUAL LEARNING — GLOBAL DESIGN SYSTEM
   ============================================================ */

@import url('https://fonts.googleapis.com/css2?family=Inter:wght@300;400;500;600;700;800&family=JetBrains+Mono:wght@400;500;600;700&display=swap');

/* ─────────────────────────────────────────
   CSS VARIABLES
───────────────────────────────────────── */
:root {
  /* Core Palette */
  --bg:           #0b0b14;
  --bg-2:         #10101c;
  --surface:      #13131f;
  --surface-2:    #1a1a2e;
  --surface-3:    #21213a;
  --border:       rgba(255,255,255,0.07);
  --border-2:     rgba(255,255,255,0.12);

  /* Text */
  --text:         #e2e8f0;
  --text-muted:   #94a3b8;
  --text-dim:     #64748b;

  /* Brand */
  --primary:      #6c63ff;
  --primary-glow: rgba(108,99,255,0.25);
  --primary-dim:  rgba(108,99,255,0.15);

  /* Semantic Colors (parser operations) */
  --shift:        #22c55e;
  --shift-bg:     rgba(34,197,94,0.12);
  --shift-border: rgba(34,197,94,0.3);

  --goto:         #3b82f6;
  --goto-bg:      rgba(59,130,246,0.12);
  --goto-border:  rgba(59,130,246,0.3);

  --reduce:       #f97316;
  --reduce-bg:    rgba(249,115,22,0.12);
  --reduce-border:rgba(249,115,22,0.3);

  --lookahead:    #a855f7;
  --lookahead-bg: rgba(168,85,247,0.12);
  --lookahead-border:rgba(168,85,247,0.3);

  --conflict:     #ef4444;
  --conflict-bg:  rgba(239,68,68,0.12);
  --conflict-border:rgba(239,68,68,0.3);

  --accept:       #10b981;
  --accept-bg:    rgba(16,185,129,0.12);

  /* Code */
  --code-bg:      #0d0f18;

  /* Spacing */
  --nav-h:        64px;
  --gap:          24px;
  --radius:       12px;
  --radius-sm:    8px;
  --radius-lg:    16px;

  /* Transitions */
  --ease:         cubic-bezier(0.4, 0, 0.2, 1);
  --dur:          200ms;
}

/* ─────────────────────────────────────────
   RESET & BASE
───────────────────────────────────────── */
*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }

html {
  scroll-behavior: smooth;
  scroll-padding-top: calc(var(--nav-h) + 24px);
}

body {
  font-family: 'Inter', system-ui, sans-serif;
  background: var(--bg);
  color: var(--text);
  line-height: 1.7;
  font-size: 16px;
  min-height: 100vh;
  -webkit-font-smoothing: antialiased;
}

a { color: var(--primary); text-decoration: none; }
a:hover { text-decoration: underline; }

h1, h2, h3, h4, h5 {
  line-height: 1.25;
  font-weight: 700;
  letter-spacing: -0.02em;
}

h1 { font-size: clamp(2rem, 4vw, 3.5rem); }
h2 { font-size: clamp(1.5rem, 3vw, 2.25rem); }
h3 { font-size: 1.4rem; }
h4 { font-size: 1.1rem; font-weight: 600; }

p { color: var(--text-muted); margin-bottom: 0.75rem; }
p:last-child { margin-bottom: 0; }

code, pre, .mono {
  font-family: 'JetBrains Mono', 'Fira Code', monospace;
}

/* ─────────────────────────────────────────
   NAVBAR
───────────────────────────────────────── */
.navbar {
  position: fixed;
  top: 0; left: 0; right: 0;
  height: var(--nav-h);
  background: rgba(11,11,20,0.85);
  backdrop-filter: blur(16px);
  -webkit-backdrop-filter: blur(16px);
  border-bottom: 1px solid var(--border);
  z-index: 1000;
  display: flex;
  align-items: center;
}

.navbar-inner {
  width: 100%;
  max-width: 1400px;
  margin: 0 auto;
  padding: 0 24px;
  display: flex;
  align-items: center;
  gap: 8px;
  overflow-x: auto;
  scrollbar-width: none;
}
.navbar-inner::-webkit-scrollbar { display: none; }

.nav-brand {
  font-size: 0.9rem;
  font-weight: 700;
  color: var(--primary);
  white-space: nowrap;
  margin-right: 12px;
  font-family: 'JetBrains Mono', monospace;
  text-decoration: none;
}
.nav-brand:hover { text-decoration: none; opacity: 0.85; }

.nav-link {
  font-size: 0.78rem;
  font-weight: 500;
  color: var(--text-muted);
  padding: 6px 10px;
  border-radius: var(--radius-sm);
  white-space: nowrap;
  transition: color var(--dur) var(--ease), background var(--dur) var(--ease);
  text-decoration: none;
}
.nav-link:hover { color: var(--text); background: var(--surface-2); text-decoration: none; }
.nav-link.active { color: var(--primary); background: var(--primary-dim); }

/* ─────────────────────────────────────────
   PAGE LAYOUT
───────────────────────────────────────── */
.page-wrapper {
  padding-top: var(--nav-h);
  min-height: 100vh;
}

.container {
  max-width: 1100px;
  margin: 0 auto;
  padding: 0 24px;
}

.container-wide {
  max-width: 1300px;
  margin: 0 auto;
  padding: 0 24px;
}

/* ─────────────────────────────────────────
   PAGE HERO
───────────────────────────────────────── */
.page-hero {
  padding: 72px 24px 48px;
  text-align: center;
  position: relative;
  overflow: hidden;
}

.page-hero::before {
  content: '';
  position: absolute;
  top: -60px; left: 50%; transform: translateX(-50%);
  width: 600px; height: 300px;
  background: radial-gradient(ellipse, var(--primary-glow) 0%, transparent 70%);
  pointer-events: none;
}

.page-badge {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  font-size: 0.78rem;
  font-weight: 600;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--primary);
  background: var(--primary-dim);
  border: 1px solid rgba(108,99,255,0.25);
  padding: 5px 14px;
  border-radius: 999px;
  margin-bottom: 20px;
}

.page-hero h1 {
  margin-bottom: 16px;
  background: linear-gradient(135deg, #fff 30%, var(--primary) 100%);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.page-hero p {
  font-size: 1.1rem;
  max-width: 640px;
  margin: 0 auto;
  color: var(--text-muted);
}

/* ─────────────────────────────────────────
   CARDS & SECTIONS
───────────────────────────────────────── */
.section {
  padding: 56px 0;
  border-bottom: 1px solid var(--border);
}
.section:last-child { border-bottom: none; }

.section-header {
  margin-bottom: 32px;
}

.section-label {
  font-size: 0.72rem;
  font-weight: 700;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: var(--primary);
  margin-bottom: 8px;
}

.section-header h2 { margin-bottom: 12px; }
.section-header p { font-size: 1.05rem; max-width: 640px; }

.card {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  padding: 28px;
  transition: border-color var(--dur) var(--ease);
}
.card:hover { border-color: var(--border-2); }

.card-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
  gap: 20px;
}

/* ─────────────────────────────────────────
   GRAMMAR DISPLAY
───────────────────────────────────────── */
.grammar-box {
  background: var(--code-bg);
  border: 1px solid var(--border-2);
  border-radius: var(--radius);
  padding: 20px 24px;
  font-family: 'JetBrains Mono', monospace;
  font-size: 0.95rem;
  line-height: 2;
}

.grammar-box .prod { display: flex; align-items: baseline; gap: 12px; }
.grammar-box .nt   { color: #93c5fd; font-weight: 600; }
.grammar-box .arrow { color: var(--text-dim); }
.grammar-box .t    { color: #86efac; }
.grammar-box .dot  { color: var(--primary); font-weight: 700; font-size: 1.1em; }
.grammar-box .eps  { color: var(--text-dim); font-style: italic; }
.grammar-box .sep  { color: var(--text-dim); padding: 0 6px; }
.grammar-box .la   { color: var(--lookahead); }

/* Inline terminal/non-terminal badges */
.sym-t  { color: var(--shift); font-family: 'JetBrains Mono', monospace; font-weight: 600; }
.sym-nt { color: #93c5fd; font-family: 'JetBrains Mono', monospace; font-weight: 600; }
.sym-dot{ color: var(--primary); font-family: 'JetBrains Mono', monospace; font-weight: 700; }

/* ─────────────────────────────────────────
   ITEM SETS / CLOSURE DISPLAY
───────────────────────────────────────── */
.item-set {
  background: var(--code-bg);
  border: 1px solid var(--border-2);
  border-radius: var(--radius);
  padding: 0;
  overflow: hidden;
}

.item-set-header {
  background: var(--surface-2);
  padding: 10px 16px;
  font-size: 0.82rem;
  font-weight: 700;
  color: var(--text);
  font-family: 'JetBrains Mono', monospace;
  border-bottom: 1px solid var(--border-2);
  display: flex;
  align-items: center;
  gap: 8px;
}

.item-set-header .state-badge {
  background: var(--primary-dim);
  color: var(--primary);
  border-radius: 6px;
  padding: 2px 10px;
  font-size: 0.8rem;
}

.item-row {
  padding: 8px 16px;
  font-family: 'JetBrains Mono', monospace;
  font-size: 0.88rem;
  border-bottom: 1px solid rgba(255,255,255,0.04);
  display: flex;
  align-items: center;
  gap: 8px;
  transition: background var(--dur) var(--ease);
}
.item-row:last-child { border-bottom: none; }
.item-row:hover { background: rgba(255,255,255,0.03); }
.item-row.highlight { background: var(--primary-dim); border-left: 3px solid var(--primary); }
.item-row.new-item  { background: rgba(34,197,94,0.07); border-left: 3px solid var(--shift); }
.item-row.kernel    { background: rgba(108,99,255,0.07); }

.item-la {
  margin-left: auto;
  color: var(--lookahead);
  font-size: 0.78rem;
  padding: 2px 8px;
  background: var(--lookahead-bg);
  border-radius: 4px;
  border: 1px solid var(--lookahead-border);
}

/* ─────────────────────────────────────────
   PARSING TABLE
───────────────────────────────────────── */
.table-wrapper {
  overflow-x: auto;
  border-radius: var(--radius);
  border: 1px solid var(--border-2);
}

.parse-table {
  width: 100%;
  border-collapse: collapse;
  font-family: 'JetBrains Mono', monospace;
  font-size: 0.85rem;
}

.parse-table th {
  background: var(--surface-2);
  color: var(--text-muted);
  font-size: 0.75rem;
  font-weight: 700;
  letter-spacing: 0.06em;
  text-transform: uppercase;
  padding: 10px 14px;
  border-bottom: 1px solid var(--border-2);
  text-align: center;
  white-space: nowrap;
}

.parse-table th.section-goto { color: var(--goto); }
.parse-table th.section-action { color: var(--shift); }

.parse-table td {
  padding: 9px 14px;
  text-align: center;
  border-bottom: 1px solid var(--border);
  border-right: 1px solid var(--border);
  color: var(--text);
  transition: background var(--dur) var(--ease);
}
.parse-table td:last-child { border-right: none; }
.parse-table tr:last-child td { border-bottom: none; }
.parse-table tr:hover td { background: rgba(255,255,255,0.025); }

.parse-table td.state-col {
  background: var(--surface-2);
  color: var(--text-muted);
  font-weight: 700;
  font-size: 0.8rem;
  border-right: 2px solid var(--border-2);
}

/* Cell color coding */
.cell-shift    { color: var(--shift);    background: var(--shift-bg); }
.cell-reduce   { color: var(--reduce);   background: var(--reduce-bg); }
.cell-goto     { color: var(--goto);     background: var(--goto-bg); }
.cell-accept   { color: var(--accept);   background: var(--accept-bg); font-weight: 700; }
.cell-conflict { color: var(--conflict); background: var(--conflict-bg); font-weight: 700; animation: pulse-conflict 1.5s ease infinite; }
.cell-active   { outline: 2px solid var(--primary); outline-offset: -2px; }

@keyframes pulse-conflict {
  0%, 100% { background: var(--conflict-bg); }
  50% { background: rgba(239,68,68,0.22); }
}

/* Divider between ACTION and GOTO sections */
.parse-table .divider-col { border-left: 2px solid var(--goto-border); }

/* ─────────────────────────────────────────
   STACK SIMULATION
───────────────────────────────────────── */
.sim-container {
  background: var(--code-bg);
  border: 1px solid var(--border-2);
  border-radius: var(--radius-lg);
  overflow: hidden;
}

.sim-table-wrap { overflow-x: auto; }

.sim-table {
  width: 100%;
  border-collapse: collapse;
  font-family: 'JetBrains Mono', monospace;
  font-size: 0.88rem;
}

.sim-table th {
  background: var(--surface-3);
  color: var(--text-muted);
  font-size: 0.72rem;
  font-weight: 700;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  padding: 12px 16px;
  border-bottom: 1px solid var(--border-2);
  text-align: left;
}

.sim-table td {
  padding: 10px 16px;
  border-bottom: 1px solid var(--border);
  vertical-align: middle;
}

.sim-table .stack-cell { color: var(--text); max-width: 280px; word-break: break-all; }
.sim-table .input-cell { color: var(--text-muted); }
.sim-table .action-cell { font-weight: 600; }

.sim-row.active-row td { background: rgba(108,99,255,0.08); }
.sim-row.active-row .action-cell { color: var(--primary); }
.sim-row.past-row td { opacity: 0.45; }
.sim-row.accept-row td { background: var(--accept-bg); }
.sim-row.error-row  td { background: var(--conflict-bg); }

.action-shift  { color: var(--shift); }
.action-reduce { color: var(--reduce); }
.action-goto   { color: var(--goto); }
.action-accept { color: var(--accept); font-weight: 700; }
.action-error  { color: var(--conflict); }

/* ─────────────────────────────────────────
   ANIMATION CONTROLS
───────────────────────────────────────── */
.anim-controls {
  display: flex;
  align-items: center;
  gap: 10px;
  padding: 16px 20px;
  background: var(--surface-2);
  border-bottom: 1px solid var(--border);
  flex-wrap: wrap;
}

.anim-btn {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  padding: 8px 16px;
  border: 1px solid var(--border-2);
  border-radius: var(--radius-sm);
  background: var(--surface-3);
  color: var(--text);
  font-size: 0.82rem;
  font-weight: 600;
  cursor: pointer;
  transition: all var(--dur) var(--ease);
  font-family: 'Inter', sans-serif;
}
.anim-btn:hover:not(:disabled) {
  background: var(--surface-2);
  border-color: var(--primary);
  color: var(--primary);
}
.anim-btn:disabled { opacity: 0.35; cursor: not-allowed; }
.anim-btn.active   { background: var(--primary-dim); border-color: var(--primary); color: var(--primary); }

.step-counter {
  font-family: 'JetBrains Mono', monospace;
  font-size: 0.8rem;
  color: var(--text-dim);
  margin-left: auto;
}

.speed-label {
  font-size: 0.75rem;
  color: var(--text-dim);
}

.speed-select {
  background: var(--surface-3);
  border: 1px solid var(--border-2);
  border-radius: var(--radius-sm);
  color: var(--text);
  font-size: 0.8rem;
  padding: 4px 8px;
  cursor: pointer;
  font-family: 'Inter', sans-serif;
}

/* ─────────────────────────────────────────
   DFA GRAPH CONTAINER
───────────────────────────────────────── */
.dfa-container {
  background: var(--code-bg);
  border: 1px solid var(--border-2);
  border-radius: var(--radius-lg);
  overflow: hidden;
  position: relative;
}

.dfa-canvas {
  width: 100%;
  height: 480px;
  display: block;
}

.dfa-controls {
  position: absolute;
  bottom: 16px;
  right: 16px;
  display: flex;
  gap: 6px;
}

.dfa-ctrl-btn {
  width: 34px; height: 34px;
  display: flex; align-items: center; justify-content: center;
  background: var(--surface-2);
  border: 1px solid var(--border-2);
  border-radius: var(--radius-sm);
  cursor: pointer;
  color: var(--text-muted);
  font-size: 0.85rem;
  transition: all var(--dur) var(--ease);
}
.dfa-ctrl-btn:hover { background: var(--surface-3); color: var(--text); }

/* DFA Node / Edge tooltip */
.dfa-tooltip {
  position: absolute;
  background: var(--surface-2);
  border: 1px solid var(--border-2);
  border-radius: var(--radius-sm);
  padding: 10px 14px;
  font-family: 'JetBrains Mono', monospace;
  font-size: 0.78rem;
  color: var(--text);
  pointer-events: none;
  opacity: 0;
  transition: opacity var(--dur) var(--ease);
  max-width: 300px;
  z-index: 100;
  line-height: 1.6;
}
.dfa-tooltip.visible { opacity: 1; }

/* ─────────────────────────────────────────
   PARSE TREE
───────────────────────────────────────── */
.tree-container {
  background: var(--code-bg);
  border: 1px solid var(--border-2);
  border-radius: var(--radius-lg);
  min-height: 360px;
  display: flex;
  align-items: center;
  justify-content: center;
  overflow: auto;
  padding: 24px;
}

.tree-svg { overflow: visible; }

/* ─────────────────────────────────────────
   PIPELINE / FLOW DIAGRAMS
───────────────────────────────────────── */
.pipeline {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 0;
}

.pipeline-step {
  position: relative;
  background: var(--surface-2);
  border: 1px solid var(--border-2);
  border-radius: var(--radius);
  padding: 16px 32px;
  min-width: 240px;
  text-align: center;
  transition: all var(--dur) var(--ease);
  cursor: default;
}
.pipeline-step:hover {
  border-color: var(--primary);
  background: var(--primary-dim);
}
.pipeline-step.active {
  border-color: var(--primary);
  background: var(--primary-dim);
  box-shadow: 0 0 0 4px var(--primary-glow);
}

.pipeline-step h4 { color: var(--text); font-size: 0.95rem; margin-bottom: 4px; }
.pipeline-step p  { font-size: 0.8rem; color: var(--text-dim); margin: 0; }

.pipeline-arrow {
  width: 2px; height: 28px;
  background: linear-gradient(180deg, var(--border-2), var(--primary));
  position: relative;
}
.pipeline-arrow::after {
  content: '';
  position: absolute;
  bottom: 0; left: 50%; transform: translateX(-50%);
  border-left: 6px solid transparent;
  border-right: 6px solid transparent;
  border-top: 8px solid var(--primary);
}

/* ─────────────────────────────────────────
   INFO BOXES
───────────────────────────────────────── */
.info-box {
  border-radius: var(--radius);
  padding: 16px 20px;
  display: flex;
  gap: 12px;
  align-items: flex-start;
  margin-bottom: 16px;
}

.info-box-icon { font-size: 1.1rem; flex-shrink: 0; margin-top: 2px; }
.info-box-body h4 { font-size: 0.9rem; margin-bottom: 4px; }
.info-box-body p  { font-size: 0.85rem; margin: 0; }

.info-box.info    { background: var(--goto-bg);     border: 1px solid var(--goto-border);     }
.info-box.info    .info-box-icon, .info-box.info h4 { color: var(--goto); }
.info-box.tip     { background: var(--shift-bg);    border: 1px solid var(--shift-border);    }
.info-box.tip     .info-box-icon, .info-box.tip h4  { color: var(--shift); }
.info-box.warn    { background: var(--reduce-bg);   border: 1px solid var(--reduce-border);   }
.info-box.warn    .info-box-icon, .info-box.warn h4 { color: var(--reduce); }
.info-box.danger  { background: var(--conflict-bg); border: 1px solid var(--conflict-border); }
.info-box.danger  .info-box-icon, .info-box.danger h4 { color: var(--conflict); }

/* ─────────────────────────────────────────
   PARSER MOTIVATION BANNER ("Why This Parser Exists")
───────────────────────────────────────── */
.why-banner {
  border-radius: var(--radius-lg);
  padding: 24px 28px;
  border: 1px solid;
  margin-bottom: 40px;
  position: relative;
  overflow: hidden;
}

.why-banner::before {
  content: '';
  position: absolute;
  top: 0; left: 0; right: 0; bottom: 0;
  background: linear-gradient(135deg, rgba(255,255,255,0.03) 0%, transparent 60%);
  pointer-events: none;
}

.why-banner.lr0    { border-color: var(--conflict-border); background: var(--conflict-bg); }
.why-banner.slr    { border-color: var(--shift-border);    background: var(--shift-bg); }
.why-banner.clr    { border-color: var(--lookahead-border); background: var(--lookahead-bg); }
.why-banner.lalr   { border-color: var(--goto-border);     background: var(--goto-bg); }

.why-banner h3 { font-size: 1.1rem; margin-bottom: 8px; }
.why-banner.lr0  h3 { color: var(--conflict); }
.why-banner.slr  h3 { color: var(--shift); }
.why-banner.clr  h3 { color: var(--lookahead); }
.why-banner.lalr h3 { color: var(--goto); }

.why-chain {
  display: flex;
  flex-direction: column;
  gap: 6px;
  margin-top: 16px;
}

.why-chain-item {
  display: flex;
  align-items: center;
  gap: 10px;
  font-size: 0.88rem;
  font-family: 'JetBrains Mono', monospace;
}

.why-chain-item .wc-tag {
  min-width: 56px;
  text-align: center;
  padding: 3px 10px;
  border-radius: 6px;
  font-size: 0.78rem;
  font-weight: 700;
}

/* ─────────────────────────────────────────
   COMPARISON TABLE
───────────────────────────────────────── */
.cmp-table-wrap { overflow-x: auto; border-radius: var(--radius-lg); border: 1px solid var(--border-2); }

.cmp-table {
  width: 100%;
  border-collapse: collapse;
  font-size: 0.9rem;
}

.cmp-table th {
  background: var(--surface-2);
  color: var(--text-muted);
  font-size: 0.75rem;
  font-weight: 700;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  padding: 14px 18px;
  border-bottom: 1px solid var(--border-2);
  text-align: left;
}

.cmp-table td {
  padding: 14px 18px;
  border-bottom: 1px solid var(--border);
  vertical-align: middle;
  color: var(--text);
}
.cmp-table tr:last-child td { border-bottom: none; }
.cmp-table tr:hover td { background: rgba(255,255,255,0.02); }

.cmp-table td:first-child { font-weight: 700; font-family: 'JetBrains Mono', monospace; color: var(--primary); }

.badge-yes { color: var(--shift); }
.badge-no  { color: var(--conflict); }
.badge-few { color: var(--shift); }
.badge-many { color: var(--reduce); }

/* ─────────────────────────────────────────
   DERIVATION DISPLAY
───────────────────────────────────────── */
.derivation-chain {
  display: flex;
  flex-direction: column;
  align-items: flex-start;
  gap: 0;
  font-family: 'JetBrains Mono', monospace;
  font-size: 0.95rem;
}

.deriv-step {
  display: flex;
  align-items: center;
  gap: 12px;
  padding: 8px 0;
  opacity: 0.3;
  transition: opacity 0.4s var(--ease);
}
.deriv-step.shown { opacity: 1; }
.deriv-step.active { }

.deriv-str { color: var(--text); }
.deriv-rule {
  font-size: 0.78rem;
  color: var(--text-dim);
  background: var(--surface-2);
  border-radius: 5px;
  padding: 2px 8px;
  border: 1px solid var(--border);
}
.deriv-rule .nt { color: #93c5fd; }
.deriv-rule .arrow { color: var(--text-dim); }
.deriv-rule .prod { color: var(--text-muted); }

.deriv-arrow {
  width: 1px;
  height: 20px;
  background: var(--border-2);
  margin-left: 8px;
}
.deriv-arrow-label {
  font-size: 0.72rem;
  color: var(--reduce);
  margin-left: 32px;
  font-style: italic;
}

/* ─────────────────────────────────────────
   SETS DISPLAY (FIRST/FOLLOW)
───────────────────────────────────────── */
.sets-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(220px, 1fr));
  gap: 12px;
}

.set-card {
  background: var(--code-bg);
  border: 1px solid var(--border-2);
  border-radius: var(--radius);
  padding: 14px 16px;
  font-family: 'JetBrains Mono', monospace;
  font-size: 0.85rem;
  transition: border-color var(--dur) var(--ease);
}
.set-card.highlight { border-color: var(--primary); background: var(--primary-dim); }

.set-card .set-name { color: #93c5fd; font-weight: 700; margin-bottom: 6px; }
.set-card .set-val  { color: var(--shift); }
.set-card .set-eps  { color: var(--text-dim); font-style: italic; }
.set-card .set-dollar { color: var(--reduce); }

/* ─────────────────────────────────────────
   STEP LOG
───────────────────────────────────────── */
.step-log {
  background: var(--code-bg);
  border: 1px solid var(--border-2);
  border-radius: var(--radius);
  padding: 16px;
  max-height: 220px;
  overflow-y: auto;
  font-family: 'JetBrains Mono', monospace;
  font-size: 0.82rem;
  line-height: 1.8;
  scrollbar-width: thin;
  scrollbar-color: var(--surface-3) transparent;
}

.log-entry { color: var(--text-muted); }
.log-entry .log-step { color: var(--primary); margin-right: 8px; }
.log-entry.log-new   { color: var(--text); }
.log-entry.log-shift  .log-op { color: var(--shift); }
.log-entry.log-reduce .log-op { color: var(--reduce); }
.log-entry.log-goto   .log-op { color: var(--goto); }
.log-entry.log-accept .log-op { color: var(--accept); font-weight: 700; }

/* ─────────────────────────────────────────
   CALL STACK (Recursive Descent)
───────────────────────────────────────── */
.call-stack {
  display: flex;
  flex-direction: column;
  gap: 4px;
  font-family: 'JetBrains Mono', monospace;
}

.stack-frame {
  background: var(--surface-2);
  border: 1px solid var(--border-2);
  border-radius: var(--radius-sm);
  padding: 10px 16px;
  font-size: 0.88rem;
  color: var(--text);
  display: flex;
  align-items: center;
  gap: 10px;
  transition: all var(--dur) var(--ease);
  transform: translateX(0);
}
.stack-frame.entering { animation: frame-enter 0.3s var(--ease); }
.stack-frame.active   { border-color: var(--primary); background: var(--primary-dim); }
.stack-frame.returning { opacity: 0.4; text-decoration: line-through; }

@keyframes frame-enter {
  from { transform: translateX(-20px); opacity: 0; }
  to   { transform: translateX(0);     opacity: 1; }
}

.frame-depth { color: var(--text-dim); font-size: 0.75rem; min-width: 24px; }
.frame-fn    { color: var(--primary); font-weight: 700; }
.frame-input { color: var(--text-muted); font-size: 0.8rem; margin-left: auto; }

/* ─────────────────────────────────────────
   PAGE NAVIGATION (Prev / Next)
───────────────────────────────────────── */
.page-nav {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 48px 0 64px;
  gap: 16px;
}

.page-nav-btn {
  display: flex;
  align-items: center;
  gap: 12px;
  padding: 16px 24px;
  background: var(--surface);
  border: 1px solid var(--border-2);
  border-radius: var(--radius-lg);
  cursor: pointer;
  text-decoration: none;
  transition: all var(--dur) var(--ease);
  max-width: 280px;
}
.page-nav-btn:hover {
  border-color: var(--primary);
  background: var(--primary-dim);
  text-decoration: none;
}
.page-nav-btn .pnb-dir { font-size: 0.72rem; font-weight: 700; letter-spacing: 0.1em; text-transform: uppercase; color: var(--text-dim); margin-bottom: 4px; }
.page-nav-btn .pnb-title { font-size: 0.9rem; font-weight: 600; color: var(--text); }
.page-nav-btn .pnb-icon { font-size: 1.2rem; flex-shrink: 0; }

/* ─────────────────────────────────────────
   UTILITY CLASSES
───────────────────────────────────────── */
.flex       { display: flex; }
.flex-col   { display: flex; flex-direction: column; }
.items-center { align-items: center; }
.justify-between { justify-content: space-between; }
.gap-2 { gap: 8px; }
.gap-3 { gap: 12px; }
.gap-4 { gap: 16px; }
.gap-6 { gap: 24px; }
.gap-8 { gap: 32px; }
.mb-1 { margin-bottom: 4px; }
.mb-2 { margin-bottom: 8px; }
.mb-3 { margin-bottom: 12px; }
.mb-4 { margin-bottom: 16px; }
.mb-6 { margin-bottom: 24px; }
.mb-8 { margin-bottom: 32px; }
.mt-4 { margin-top: 16px; }
.mt-6 { margin-top: 24px; }
.text-sm { font-size: 0.85rem; }
.text-xs { font-size: 0.75rem; }
.text-muted { color: var(--text-muted); }
.text-dim { color: var(--text-dim); }
.font-mono { font-family: 'JetBrains Mono', monospace; }
.font-bold { font-weight: 700; }
.text-center { text-align: center; }

.divider {
  height: 1px;
  background: var(--border);
  margin: 40px 0;
}

.tag {
  display: inline-flex;
  align-items: center;
  padding: 3px 10px;
  border-radius: 6px;
  font-size: 0.75rem;
  font-weight: 600;
}
.tag-shift    { background: var(--shift-bg);    color: var(--shift);    border: 1px solid var(--shift-border); }
.tag-reduce   { background: var(--reduce-bg);   color: var(--reduce);   border: 1px solid var(--reduce-border); }
.tag-goto     { background: var(--goto-bg);     color: var(--goto);     border: 1px solid var(--goto-border); }
.tag-lookahead{ background: var(--lookahead-bg); color: var(--lookahead); border: 1px solid var(--lookahead-border); }
.tag-conflict { background: var(--conflict-bg); color: var(--conflict); border: 1px solid var(--conflict-border); }
.tag-primary  { background: var(--primary-dim); color: var(--primary);  border: 1px solid rgba(108,99,255,0.3); }

/* ─────────────────────────────────────────
   HIGHLIGHT ANIMATIONS
───────────────────────────────────────── */
@keyframes fade-in-up {
  from { opacity: 0; transform: translateY(12px); }
  to   { opacity: 1; transform: translateY(0); }
}

@keyframes glow-pulse {
  0%, 100% { box-shadow: 0 0 0 0 var(--primary-glow); }
  50%       { box-shadow: 0 0 0 8px transparent; }
}

.animate-in { animation: fade-in-up 0.4s var(--ease) both; }

/* ─────────────────────────────────────────
   RESPONSIVE
───────────────────────────────────────── */
@media (max-width: 768px) {
  :root { --gap: 16px; }
  .page-hero { padding: 48px 16px 32px; }
  .container, .container-wide { padding: 0 16px; }
  .card { padding: 18px; }
  .grammar-box { font-size: 0.82rem; }
  .parse-table { font-size: 0.75rem; }
  .sim-table { font-size: 0.78rem; }
  .card-grid { grid-template-columns: 1fr; }
  .page-nav { flex-direction: column; }
  .page-nav-btn { max-width: 100%; width: 100%; }
}

@media (max-width: 480px) {
  h1 { font-size: 1.8rem; }
  h2 { font-size: 1.4rem; }
}