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

/* ── CSS Custom Properties ───────────────────────────────── */
:root {
  --bg-primary:   #0a0e27;
  --bg-secondary: #111638;
  --bg-card:      #161b4a;
  --bg-card-alt:  #1c2255;
  --accent:       #6c63ff;
  --accent-glow:  rgba(108, 99, 255, .35);
  --accent2:      #00d4ff;
  --orange:       #ff9f43;
  --orange-glow:  rgba(255, 159, 67, .4);
  --green:        #2ecc71;
  --red:          #ff6b6b;
  --text:         #e8eaf6;
  --text-dim:     #8d93c8;
  --border:       rgba(108, 99, 255, .18);
  --radius:       12px;
  --transition:   .25s ease;
  --font-sans:    'Inter', system-ui, sans-serif;
  --font-mono:    'JetBrains Mono', 'Fira Code', monospace;
}

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

html {
  font-size: 16px;
  scroll-behavior: smooth;
}

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

/* ── Header ──────────────────────────────────────────────── */
.app-header {
  position: sticky;
  top: 0;
  z-index: 100;
  display: flex;
  align-items: center;
  gap: 16px;
  padding: 12px 24px;
  background: linear-gradient(135deg, var(--bg-secondary), var(--bg-card));
  border-bottom: 1px solid var(--border);
  backdrop-filter: blur(12px);
}

.btn-back {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  padding: 8px 16px;
  background: rgba(108, 99, 255, .12);
  color: var(--accent2);
  font-weight: 600;
  font-size: .875rem;
  border: 1px solid var(--border);
  border-radius: 8px;
  cursor: pointer;
  transition: var(--transition);
  text-decoration: none;
}
.btn-back:hover {
  background: rgba(108, 99, 255, .28);
  transform: translateX(-3px);
}

.app-header h1 {
  font-size: 1.15rem;
  font-weight: 700;
  background: linear-gradient(135deg, var(--accent), var(--accent2));
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

/* ── Stage Tabs ──────────────────────────────────────────── */
.stage-tabs {
  display: flex;
  justify-content: center;
  gap: 6px;
  padding: 10px 16px;
  background: var(--bg-secondary);
  border-bottom: 1px solid var(--border);
  flex-wrap: wrap;
}

.stage-tab {
  padding: 8px 18px;
  font-size: .82rem;
  font-weight: 600;
  color: var(--text-dim);
  background: transparent;
  border: 1px solid transparent;
  border-radius: 24px;
  cursor: pointer;
  transition: var(--transition);
  white-space: nowrap;
}
.stage-tab:hover {
  color: var(--text);
  background: rgba(108, 99, 255, .1);
}
.stage-tab.active {
  color: #fff;
  background: linear-gradient(135deg, var(--accent), #8b5cf6);
  border-color: var(--accent);
  box-shadow: 0 0 18px var(--accent-glow);
}

/* ── App Container ───────────────────────────────────────── */
.app-container {
  max-width: 1200px;
  margin: 0 auto;
  padding: 20px;
}

/* ── Stage Sections ──────────────────────────────────────── */
.stage-section {
  display: none;
  animation: fadeIn .35s ease;
}
.stage-section.active {
  display: block;
}
@keyframes fadeIn {
  from { opacity: 0; transform: translateY(10px); }
  to   { opacity: 1; transform: translateY(0); }
}

/* ── Cards ───────────────────────────────────────────────── */
.card {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 20px;
  margin-bottom: 20px;
}
.card h2, .card h3 {
  font-size: 1rem;
  font-weight: 600;
  margin-bottom: 12px;
  color: var(--accent2);
}

/* ── Textarea ────────────────────────────────────────────── */
.input-textarea {
  width: 100%;
  min-height: 100px;
  padding: 14px;
  font-family: var(--font-mono);
  font-size: .9rem;
  color: var(--text);
  background: var(--bg-secondary);
  border: 1px solid var(--border);
  border-radius: 8px;
  resize: vertical;
  transition: border-color var(--transition);
  line-height: 1.5;
}
.input-textarea:focus {
  outline: none;
  border-color: var(--accent);
  box-shadow: 0 0 12px var(--accent-glow);
}

/* ── Buttons ─────────────────────────────────────────────── */
.btn {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 10px 22px;
  font-family: var(--font-sans);
  font-size: .85rem;
  font-weight: 600;
  color: #fff;
  border: none;
  border-radius: 8px;
  cursor: pointer;
  transition: all var(--transition);
}
.btn:active { transform: scale(.96); }

.btn-primary {
  background: linear-gradient(135deg, var(--accent), #8b5cf6);
  box-shadow: 0 4px 18px var(--accent-glow);
}
.btn-primary:hover {
  box-shadow: 0 6px 28px var(--accent-glow);
  transform: translateY(-2px);
}
.btn-primary:disabled {
  opacity: .45;
  cursor: not-allowed;
  transform: none;
}

.btn-orange {
  background: linear-gradient(135deg, var(--orange), #e67e22);
  box-shadow: 0 4px 18px var(--orange-glow);
}
.btn-orange:hover {
  box-shadow: 0 6px 28px var(--orange-glow);
  transform: translateY(-2px);
}

.btn-green {
  background: linear-gradient(135deg, var(--green), #27ae60);
}
.btn-green:hover { transform: translateY(-2px); }

.btn-group {
  display: flex;
  gap: 10px;
  flex-wrap: wrap;
  margin-top: 14px;
}

/* ── Bar Chart ───────────────────────────────────────────── */
.bar-chart-container {
  width: 100%;
  overflow-x: auto;
  -webkit-overflow-scrolling: touch;
}

#bar-chart {
  width: 100%;
  min-height: 220px;
}

#bar-chart .bar {
  fill: var(--accent);
  transition: fill .2s;
}
#bar-chart .bar:hover {
  fill: var(--accent2);
}
#bar-chart .bar-label, #bar-chart .bar-value {
  fill: var(--text);
  font-family: var(--font-mono);
  font-size: 12px;
}

/* ── SVG Tree Container ──────────────────────────────────── */
.tree-container {
  width: 100%;
  overflow: auto;
  -webkit-overflow-scrolling: touch;
  border: 1px solid var(--border);
  border-radius: var(--radius);
  background: radial-gradient(circle at 50% 30%, rgba(108,99,255,.06), transparent 70%);
  touch-action: pan-x pan-y pinch-zoom;
  min-height: 350px;
  position: relative;
}

#tree-svg {
  display: block;
  min-width: 600px;
}

/* Tree nodes */
.tree-node circle {
  fill: var(--bg-card-alt);
  stroke: var(--accent);
  stroke-width: 2.5;
  transition: fill .3s, stroke .3s;
}
.tree-node.highlight circle {
  fill: var(--orange);
  stroke: var(--orange);
  filter: drop-shadow(0 0 10px var(--orange-glow));
}
.tree-node.decoded circle {
  fill: var(--green);
  stroke: var(--green);
}
.tree-node text {
  fill: var(--text);
  font-family: var(--font-mono);
  font-size: 11px;
  text-anchor: middle;
  pointer-events: none;
}

/* Tree links */
.tree-link {
  fill: none;
  stroke: var(--text-dim);
  stroke-width: 1.8;
  transition: stroke .3s, stroke-width .3s;
}
.tree-link.active-path {
  stroke: var(--orange);
  stroke-width: 4;
  filter: drop-shadow(0 0 6px var(--orange-glow));
}
.tree-link-label {
  fill: #5b8def;
  font-family: var(--font-mono);
  font-size: 13px;
  font-weight: 700;
}

/* ── Queue Visualization ─────────────────────────────────── */
.queue-vis {
  display: flex;
  gap: 8px;
  flex-wrap: wrap;
  padding: 10px 0;
  min-height: 48px;
}
.queue-node {
  display: flex;
  align-items: center;
  justify-content: center;
  min-width: 52px;
  padding: 6px 10px;
  font-family: var(--font-mono);
  font-size: .78rem;
  font-weight: 600;
  background: var(--bg-card-alt);
  border: 1px solid var(--border);
  border-radius: 8px;
  color: var(--text);
  transition: all .3s;
}
.queue-node.highlight {
  border-color: var(--orange);
  background: rgba(255, 159, 67, .15);
  color: var(--orange);
  box-shadow: 0 0 12px var(--orange-glow);
}

/* ── Code Table ──────────────────────────────────────────── */
.code-table-wrap {
  overflow-x: auto;
  -webkit-overflow-scrolling: touch;
}
.code-table {
  width: 100%;
  border-collapse: collapse;
  font-family: var(--font-mono);
  font-size: .82rem;
}
.code-table th {
  padding: 10px 14px;
  background: var(--bg-secondary);
  color: var(--accent2);
  font-weight: 600;
  text-align: left;
  border-bottom: 2px solid var(--border);
  white-space: nowrap;
}
.code-table td {
  padding: 8px 14px;
  border-bottom: 1px solid var(--border);
  color: var(--text);
}
.code-table tbody tr:nth-child(even) {
  background: rgba(108, 99, 255, .04);
}
.code-table tbody tr:hover {
  background: rgba(108, 99, 255, .1);
}

/* ── Bitstream ───────────────────────────────────────────── */
.bitstream-display {
  font-family: var(--font-mono);
  font-size: .82rem;
  line-height: 1.8;
  word-break: break-all;
  padding: 14px;
  background: var(--bg-secondary);
  border-radius: 8px;
  border: 1px solid var(--border);
  max-height: 200px;
  overflow-y: auto;
}
.bitstream-display .bit {
  display: inline-block;
  width: 14px;
  text-align: center;
  transition: all .15s;
  border-radius: 2px;
}
.bitstream-display .bit.active {
  background: var(--orange);
  color: #000;
  font-weight: 700;
  box-shadow: 0 0 6px var(--orange-glow);
}
.bitstream-display .bit.decoded {
  color: var(--green);
  opacity: .6;
}

/* ── Recovered Text ──────────────────────────────────────── */
.recovered-text {
  font-family: var(--font-mono);
  font-size: 1rem;
  padding: 14px;
  background: var(--bg-secondary);
  border: 1px solid var(--border);
  border-radius: 8px;
  min-height: 48px;
  color: var(--green);
  word-break: break-all;
}

/* ── Stats Panel ─────────────────────────────────────────── */
.stats-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(180px, 1fr));
  gap: 14px;
}
.stat-card {
  background: var(--bg-card-alt);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 14px 16px;
  text-align: center;
}
.stat-card .stat-label {
  font-size: .72rem;
  font-weight: 500;
  color: var(--text-dim);
  text-transform: uppercase;
  letter-spacing: .06em;
  margin-bottom: 6px;
}
.stat-card .stat-value {
  font-family: var(--font-mono);
  font-size: 1.25rem;
  font-weight: 700;
  background: linear-gradient(135deg, var(--accent), var(--accent2));
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

/* ── Speed Slider ────────────────────────────────────────── */
.speed-control {
  display: flex;
  align-items: center;
  gap: 12px;
  margin-top: 12px;
}
.speed-control label {
  font-size: .82rem;
  color: var(--text-dim);
  white-space: nowrap;
}
.speed-slider {
  -webkit-appearance: none;
  appearance: none;
  flex: 1;
  height: 6px;
  background: var(--bg-secondary);
  border-radius: 3px;
  outline: none;
}
.speed-slider::-webkit-slider-thumb {
  -webkit-appearance: none;
  width: 18px;
  height: 18px;
  border-radius: 50%;
  background: var(--accent);
  cursor: pointer;
  box-shadow: 0 0 8px var(--accent-glow);
}

/* ── Status Badge ────────────────────────────────────────── */
.status-badge {
  display: inline-block;
  padding: 4px 12px;
  font-size: .75rem;
  font-weight: 600;
  border-radius: 12px;
  text-transform: uppercase;
  letter-spacing: .04em;
}
.status-badge.ready    { background: rgba(46,204,113,.15); color: var(--green); }
.status-badge.building { background: rgba(255,159,67,.15); color: var(--orange); }
.status-badge.complete { background: rgba(108,99,255,.15); color: var(--accent); }

/* ── Responsive ──────────────────────────────────────────── */
@media (max-width: 768px) {
  .app-header { padding: 10px 14px; gap: 10px; }
  .app-header h1 { font-size: .95rem; }
  .app-container { padding: 12px; }
  .stage-tab { padding: 7px 13px; font-size: .76rem; }
  .stats-grid { grid-template-columns: repeat(2, 1fr); gap: 10px; }
  .card { padding: 14px; }
  #tree-svg { min-width: 500px; }
  .btn { padding: 9px 16px; font-size: .8rem; }
}

@media (max-width: 480px) {
  .stats-grid { grid-template-columns: 1fr 1fr; }
  .stage-tab { padding: 6px 10px; font-size: .72rem; }
  #tree-svg { min-width: 400px; }
}