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

:root {
  --bg: #0f1419;
  --bg-card: #1a1f29;
  --bg-elev: #232936;
  --bg-muted: #2a3142;
  --border: #2f3744;
  --text: #e6e9ef;
  --text-muted: #8a93a6;
  --text-dim: #5e6677;
  --accent-ll: #10b981;
  --accent-stack: #f59e0b;
  --accent-queue: #a855f7;
  --amber: #f59e0b;
  --purple: #a855f7;
  --emerald: #10b981;
  --pink: #ec4899;
  --teal: #14b8a6;
  --red: #ef4444;
  --rose: #f43f5e;
  --radius: 12px;
  --radius-sm: 8px;
}

html, body {
  font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', 'Noto Sans Thai', Roboto, sans-serif;
  background: var(--bg);
  color: var(--text);
  line-height: 1.55;
  min-height: 100vh;
  font-size: 14px;
}

body { display: flex; flex-direction: column; min-height: 100vh; }

a { color: inherit; text-decoration: none; }
button { font-family: inherit; cursor: pointer; border: none; background: none; color: inherit; }
input, select { font-family: inherit; font-size: inherit; }

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

/* ============ Layout ============ */
.container { max-width: 1280px; margin: 0 auto; padding: 0 20px; width: 100%; }

header.app-header {
  border-bottom: 1px solid var(--border);
  background: rgba(15, 20, 25, 0.85);
  backdrop-filter: blur(8px);
  position: sticky;
  top: 0;
  z-index: 30;
}
header.app-header .container {
  display: flex; align-items: center; justify-content: space-between;
  padding-top: 12px; padding-bottom: 12px; gap: 12px;
}
.header-left { display: flex; align-items: center; gap: 12px; min-width: 0; }
.header-icon {
  width: 36px; height: 36px; border-radius: 10px;
  display: flex; align-items: center; justify-content: center;
  color: white; flex-shrink: 0;
}
.header-icon.ll { background: var(--accent-ll); }
.header-icon.stack { background: var(--accent-stack); }
.header-icon.queue { background: var(--accent-queue); }
.header-title { font-size: 16px; font-weight: 700; line-height: 1.2; }
.header-sub { font-size: 11px; color: var(--text-muted); }
.header-sub.hidden-mobile { display: none; }
@media (min-width: 640px) { .header-sub.hidden-mobile { display: block; } }

.btn-back {
  display: inline-flex; align-items: center; gap: 4px;
  padding: 6px 12px; border-radius: 8px;
  background: transparent; color: var(--text-muted);
  font-size: 13px; transition: all .15s;
}
.btn-back:hover { background: var(--bg-muted); color: var(--text); }

main.app-main {
  flex: 1;
  padding: 24px 0;
}
.layout-grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: 24px;
}
@media (min-width: 1024px) {
  .layout-grid { grid-template-columns: 280px 1fr; }
  .ops-panel-wrapper { position: sticky; top: 88px; align-self: start; }
}

footer.app-footer {
  border-top: 1px solid var(--border);
  padding: 16px 0;
  font-size: 12px; color: var(--text-muted);
}
footer.app-footer .container {
  display: flex; flex-wrap: wrap; align-items: center; justify-content: space-between; gap: 8px;
}

/* ============ Cards ============ */
.card {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  box-shadow: 0 1px 3px rgba(0,0,0,0.2);
}
.card-header {
  padding: 10px 16px;
  border-bottom: 1px solid var(--border);
  background: rgba(255,255,255,0.02);
  display: flex; align-items: center; justify-content: space-between;
  font-size: 13px; font-weight: 600;
}
.card-header .meta { font-size: 11px; color: var(--text-muted); font-family: 'JetBrains Mono', monospace; }
.card-body { padding: 16px; }

/* ============ Operations Panel ============ */
.ops-panel { padding: 16px; display: flex; flex-direction: column; gap: 20px; }
.ops-section { display: flex; flex-direction: column; gap: 12px; }
.ops-section-title {
  display: flex; align-items: center; gap: 8px;
  font-size: 13px; font-weight: 600;
}
.ops-section-bar { width: 4px; height: 16px; border-radius: 2px; }
.ops-section-bar.emerald { background: var(--emerald); }
.ops-section-bar.rose { background: var(--red); }
.ops-section-bar.amber { background: var(--amber); }
.ops-section-bar.violet { background: var(--purple); }

.input {
  width: 100%; padding: 8px 12px;
  background: var(--bg-elev); color: var(--text);
  border: 1px solid var(--border); border-radius: 8px;
  font-family: 'JetBrains Mono', monospace; font-size: 13px;
}
.input:focus { outline: none; border-color: var(--accent-ll); }

.select {
  width: 100%; padding: 8px 12px;
  background: var(--bg-elev); color: var(--text);
  border: 1px solid var(--border); border-radius: 8px;
  font-size: 13px; cursor: pointer;
  appearance: none;
  background-image: url("data:image/svg+xml;utf8,<svg xmlns='http://www.w3.org/2000/svg' width='12' height='12' viewBox='0 0 24 24' fill='none' stroke='%238a93a6' stroke-width='2'><polyline points='6 9 12 15 18 9'/></svg>");
  background-repeat: no-repeat;
  background-position: right 10px center;
  padding-right: 32px;
}

.btn {
  display: inline-flex; align-items: center; justify-content: center; gap: 6px;
  padding: 8px 14px; border-radius: 8px;
  font-size: 13px; font-weight: 500;
  background: var(--bg-elev); color: var(--text);
  border: 1px solid var(--border);
  transition: all .15s; cursor: pointer;
  white-space: nowrap;
}
.btn:hover:not(:disabled) { background: var(--bg-muted); }
.btn:disabled { opacity: 0.4; cursor: not-allowed; }
.btn.btn-primary { background: var(--accent-ll); color: white; border-color: var(--accent-ll); }
.btn.btn-primary:hover:not(:disabled) { background: #0e9c6f; }
.btn.btn-danger { background: var(--red); color: white; border-color: var(--red); }
.btn.btn-danger:hover:not(:disabled) { background: #dc2626; }
.btn.btn-amber { background: var(--amber); color: white; border-color: var(--amber); }
.btn.btn-amber:hover:not(:disabled) { background: #d97706; }
.btn.btn-purple { background: var(--purple); color: white; border-color: var(--purple); }
.btn.btn-purple:hover:not(:disabled) { background: #9333ea; }
.btn.btn-outline-amber { border-color: var(--amber); color: var(--amber); background: transparent; }
.btn.btn-outline-amber:hover:not(:disabled) { background: rgba(245,158,11,0.1); }
.btn.btn-outline-purple { border-color: var(--purple); color: var(--purple); background: transparent; }
.btn.btn-outline-purple:hover:not(:disabled) { background: rgba(168,85,247,0.1); }
.btn.btn-outline-pink { border-color: var(--pink); color: var(--pink); background: transparent; }
.btn.btn-outline-pink:hover:not(:disabled) { background: rgba(236,72,153,0.1); }
.btn.btn-ghost { background: transparent; border-color: transparent; color: var(--text-muted); }
.btn.btn-ghost:hover:not(:disabled) { background: var(--bg-muted); color: var(--text); }

.btn-grid-3 { display: grid; grid-template-columns: repeat(3, 1fr); gap: 8px; }
.btn-grid-2 { display: grid; grid-template-columns: repeat(2, 1fr); gap: 8px; }
.btn-grid-4 { display: grid; grid-template-columns: repeat(4, 1fr); gap: 8px; }
.btn-tall {
  flex-direction: column; gap: 2px;
  padding: 10px 6px;
  font-size: 12px;
  height: auto;
}
.btn-tall svg { width: 18px; height: 18px; }

/* ============ Slider ============ */
.slider-row { display: flex; flex-direction: column; gap: 6px; }
.slider-label-row {
  display: flex; justify-content: space-between; align-items: center;
  font-size: 11px; color: var(--text-muted);
}
.slider-label-row .mono { font-family: 'JetBrains Mono', monospace; }
input[type="range"] {
  -webkit-appearance: none; appearance: none;
  width: 100%; height: 4px; background: var(--bg-muted); border-radius: 2px;
  outline: none;
}
input[type="range"]::-webkit-slider-thumb {
  -webkit-appearance: none; appearance: none;
  width: 16px; height: 16px; border-radius: 50%;
  background: var(--purple); cursor: pointer; border: 2px solid var(--bg);
}
input[type="range"]::-moz-range-thumb {
  width: 16px; height: 16px; border-radius: 50%;
  background: var(--purple); cursor: pointer; border: 2px solid var(--bg);
}

/* ============ Visualizer Area ============ */
.viz-area {
  position: relative;
  min-height: 280px;
  overflow-x: auto;
  overflow-y: hidden;
  padding: 24px;
}
.viz-inner { display: flex; align-items: center; gap: 8px; min-width: max-content; justify-content: center; }

.progress-bar {
  height: 4px; background: var(--bg-muted);
}
.progress-bar-fill {
  height: 100%; background: var(--accent-ll);
  transition: width 200ms ease;
  width: 0%;
}
.progress-bar-fill.amber { background: var(--amber); }
.progress-bar-fill.purple { background: var(--purple); }

/* ============ Node Box ============ */
.node {
  display: inline-flex; align-items: stretch;
  border: 2px solid var(--border); border-radius: 10px;
  background: var(--bg-card);
  overflow: hidden;
  box-shadow: 0 2px 4px rgba(0,0,0,0.15);
  font-family: 'JetBrains Mono', monospace;
  transition: all .25s;
  position: relative;
}
.node-cell-data {
  padding: 12px 18px;
  font-size: 18px; font-weight: 600;
  min-width: 60px; text-align: center;
  display: flex; align-items: center; justify-content: center;
}
.node-cell-meta {
  padding: 12px 14px;
  font-size: 12px;
  color: var(--text-muted);
  background: rgba(255,255,255,0.03);
  border-left: 1px solid var(--border);
  display: flex; align-items: center; gap: 4px;
  min-width: 60px;
}
.node-idx {
  padding: 12px 10px;
  font-size: 11px;
  color: var(--text-dim);
  background: rgba(255,255,255,0.03);
  border-right: 1px solid var(--border);
  display: flex; align-items: center; justify-content: center;
  min-width: 40px;
}
.node-role-current { border-color: var(--amber); background: rgba(245,158,11,0.12); box-shadow: 0 0 0 2px rgba(245,158,11,0.3); }
.node-role-prev { border-color: var(--purple); background: rgba(168,85,247,0.12); box-shadow: 0 0 0 2px rgba(168,85,247,0.25); }
.node-role-found { border-color: var(--emerald); background: rgba(16,185,129,0.15); box-shadow: 0 0 0 2px rgba(16,185,129,0.35); }
.node-role-target { border-color: var(--pink); background: rgba(236,72,153,0.12); box-shadow: 0 0 0 2px rgba(236,72,153,0.3); }
.node-role-new { border-color: var(--teal); background: rgba(20,184,166,0.15); box-shadow: 0 0 0 2px rgba(20,184,166,0.35); }
.node-role-removing { border-color: var(--red); background: rgba(239,68,68,0.15); box-shadow: 0 0 0 2px rgba(239,68,68,0.35); }
.node-role-overflow { border-color: var(--rose); background: rgba(244,63,94,0.18); box-shadow: 0 0 0 2px rgba(244,63,94,0.4); }
.node-role-top { border-color: var(--amber); background: rgba(245,158,11,0.12); box-shadow: 0 0 0 2px rgba(245,158,11,0.3); }
.node-role-front { border-color: var(--amber); background: rgba(245,158,11,0.12); box-shadow: 0 0 0 2px rgba(245,158,11,0.3); }
.node-role-rear { border-color: var(--purple); background: rgba(168,85,247,0.12); box-shadow: 0 0 0 2px rgba(168,85,247,0.3); }
.node-role-both { border-color: var(--emerald); background: rgba(16,185,129,0.15); box-shadow: 0 0 0 2px rgba(16,185,129,0.35); }
.node-role-peeked { border-color: var(--pink); background: rgba(236,72,153,0.12); box-shadow: 0 0 0 2px rgba(236,72,153,0.3); }

/* Pointer chip above node */
.pointer-stack {
  display: flex; flex-direction: column; align-items: center; gap: 2px;
  min-height: 50px;
  justify-content: flex-end;
}
.pointer-chips-row { display: flex; flex-wrap: wrap; gap: 4px; justify-content: center; }
.pointer-chip {
  padding: 2px 8px; border-radius: 6px;
  font-size: 10px; font-weight: 700; text-transform: uppercase;
  letter-spacing: 0.05em; color: white;
  white-space: nowrap;
  box-shadow: 0 1px 2px rgba(0,0,0,0.3);
}
.pointer-chip.head { background: var(--emerald); }
.pointer-chip.current { background: var(--amber); }
.pointer-chip.prev { background: var(--purple); }
.pointer-chip.new { background: var(--teal); }
.pointer-chip.temp { background: var(--rose); }
.pointer-chip.top { background: var(--amber); }
.pointer-chip.front { background: var(--amber); }
.pointer-chip.rear { background: var(--purple); }
.pointer-chip.found { background: var(--emerald); }
.pointer-chip.target { background: var(--pink); }
.pointer-chip.removing { background: var(--red); }
.pointer-chip.peek { background: var(--pink); }
.pointer-chip.overflow { background: var(--rose); }

.pointer-stem { width: 2px; height: 8px; background: rgba(255,255,255,0.4); }
.pointer-arrow {
  width: 0; height: 0;
  border-left: 6px solid transparent;
  border-right: 6px solid transparent;
  border-top: 8px solid currentColor;
}

.node-below-label {
  font-size: 10px; color: var(--text-muted);
  font-family: 'JetBrains Mono', monospace;
  text-align: center;
  min-height: 16px;
}

/* Arrow between nodes */
.arrow-connector {
  display: flex; align-items: center;
  color: var(--text-muted);
}
.arrow-line { width: 28px; height: 2px; background: currentColor; }
.arrow-tip {
  width: 0; height: 0;
  border-left: 8px solid currentColor;
  border-top: 5px solid transparent;
  border-bottom: 5px solid transparent;
}
.arrow-null {
  margin-left: 4px; padding: 4px 8px;
  background: var(--bg-muted); color: var(--text-muted);
  border-radius: 6px; font-size: 11px; font-family: 'JetBrains Mono', monospace;
}

/* ============ Step description ============ */
.step-desc {
  display: flex; gap: 12px; padding: 16px;
  background: rgba(245,158,11,0.05);
  border: 1px solid rgba(245,158,11,0.3);
  border-radius: 10px;
  margin-bottom: 12px;
}
.step-num {
  width: 28px; height: 28px; border-radius: 50%;
  background: var(--amber); color: white;
  display: flex; align-items: center; justify-content: center;
  font-size: 12px; font-weight: 700; flex-shrink: 0;
}
.step-body { flex: 1; min-width: 0; }
.step-meta {
  display: flex; gap: 8px; align-items: center; margin-bottom: 4px;
  flex-wrap: wrap;
}
.step-phase {
  font-size: 10px; text-transform: uppercase; letter-spacing: 0.05em;
  padding: 2px 6px; border-radius: 4px;
  background: rgba(245,158,11,0.2); color: #fbbf24;
  font-family: 'JetBrains Mono', monospace;
}
.step-counter { font-size: 10px; color: var(--text-muted); font-family: 'JetBrains Mono', monospace; }
.step-text { font-size: 13px; line-height: 1.5; }

/* Console output */
.console-box {
  background: #0a0d12;
  border-radius: 8px;
  padding: 12px;
  font-family: 'JetBrains Mono', monospace;
  font-size: 12px;
  min-height: 80px;
  overflow: auto;
  flex: 1;
}
.console-label {
  font-size: 11px; color: var(--text-muted);
  padding: 8px 12px; border-bottom: 1px solid var(--border);
  font-family: 'JetBrains Mono', monospace;
  display: flex; align-items: center; gap: 6px;
}
.console-line {
  color: #4ade80; display: flex; gap: 8px; align-items: flex-start;
}
.console-line.empty { color: #5e6677; font-style: italic; }
.console-prompt { color: #5e6677; flex-shrink: 0; }

/* ============ Code Panel ============ */
.code-panel-header {
  padding: 10px 16px;
  border-bottom: 1px solid var(--border);
  background: rgba(255,255,255,0.02);
  display: flex; align-items: center; gap: 8px;
  font-size: 13px; font-weight: 600;
}
.code-panel-header .filename {
  margin-left: auto; font-size: 11px; color: var(--text-muted);
  font-family: 'JetBrains Mono', monospace;
}
.code-block {
  margin: 0; padding: 16px;
  font-family: 'JetBrains Mono', monospace;
  font-size: 12.5px; line-height: 1.55;
  overflow: auto;
  background: #0a0d12;
  counter-reset: line;
}
.code-line {
  display: block;
  padding: 0 8px 0 32px;
  position: relative;
  min-height: 19px;
  border-left: 3px solid transparent;
  margin-left: -8px;
  transition: background 200ms, border-color 200ms;
}
.code-line::before {
  counter-increment: line;
  content: counter(line);
  position: absolute;
  left: 0;
  width: 24px;
  text-align: right;
  color: #4b5468;
  font-size: 11px;
}
.code-line.active {
  background: rgba(245,158,11,0.18);
  border-left-color: var(--amber);
}
/* token colors */
.tok-kw { color: #c678dd; }
.tok-type { color: #e5c07b; }
.tok-fn { color: #61afef; }
.tok-str { color: #98c379; }
.tok-num { color: #d19a66; }
.tok-com { color: #5c6370; font-style: italic; }
.tok-op { color: #56b6c2; }
.tok-pun { color: #abb2bf; }
.tok-id { color: #e6e9ef; }

/* ============ Legend ============ */
.legend-grid {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 8px;
}
@media (min-width: 640px) { .legend-grid { grid-template-columns: repeat(3, 1fr); } }
@media (min-width: 1024px) { .legend-grid { grid-template-columns: repeat(6, 1fr); } }
.legend-item {
  display: flex; align-items: center; gap: 8px;
  padding: 8px; border-radius: 6px;
  background: var(--bg-muted);
  font-size: 12px;
}
.legend-color {
  width: 12px; height: 12px; border-radius: 3px; flex-shrink: 0;
}
.legend-label { font-weight: 600; }
.legend-desc { font-size: 10px; color: var(--text-muted); }

/* ============ Main Menu ============ */
.menu-main {
  flex: 1;
  display: flex; align-items: center; justify-content: center;
  padding: 40px 20px;
}
.menu-hero { text-align: center; margin-bottom: 40px; }
.menu-badge {
  display: inline-flex; align-items: center; gap: 6px;
  padding: 4px 12px; border-radius: 999px;
  background: rgba(16,185,129,0.1); color: var(--emerald);
  font-size: 12px; font-weight: 500; margin-bottom: 16px;
}
.menu-title {
  font-size: 32px; font-weight: 700; line-height: 1.2; margin-bottom: 12px;
}
@media (min-width: 640px) { .menu-title { font-size: 48px; } }
.menu-title-grad {
  background: linear-gradient(to right, var(--emerald), var(--amber), var(--purple));
  -webkit-background-clip: text;
  background-clip: text;
  color: transparent;
}
.menu-sub {
  font-size: 14px; color: var(--text-muted);
  max-width: 600px; margin: 0 auto;
}
@media (min-width: 640px) { .menu-sub { font-size: 16px; } }

.menu-grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: 20px;
  max-width: 1100px;
  margin: 0 auto;
  width: 100%;
}
@media (min-width: 768px) { .menu-grid { grid-template-columns: repeat(2, 1fr); } }
@media (min-width: 1100px) { .menu-grid { grid-template-columns: repeat(3, 1fr); } }

.menu-card {
  display: block; text-align: left;
  padding: 24px;
  border-radius: 16px;
  border: 2px solid var(--border);
  background: var(--bg-card);
  transition: all 200ms;
  cursor: pointer;
}
.menu-card:hover {
  transform: translateY(-4px);
  border-color: var(--card-accent);
  background: rgba(255,255,255,0.04);
}
.menu-card-head {
  display: flex; align-items: flex-start; justify-content: space-between;
  margin-bottom: 16px;
}
.menu-card-icon {
  width: 48px; height: 48px; border-radius: 12px;
  display: flex; align-items: center; justify-content: center;
  color: var(--card-accent);
  background: rgba(255,255,255,0.05);
  border: 1px solid currentColor;
}
.menu-card-arrow {
  width: 20px; height: 20px;
  color: var(--card-accent);
  opacity: 0; transform: translateX(-4px);
  transition: all 200ms;
}
.menu-card:hover .menu-card-arrow { opacity: 1; transform: translateX(0); }
.menu-card-title { font-size: 20px; font-weight: 700; }
.menu-card-sub {
  font-size: 11px; font-family: 'JetBrains Mono', monospace;
  color: var(--card-accent); margin-bottom: 8px;
}
.menu-card-desc { font-size: 13px; color: var(--text-muted); line-height: 1.5; margin-bottom: 16px; }
.menu-card-tags { display: flex; flex-wrap: wrap; gap: 6px; padding-top: 12px; border-top: 1px solid var(--border); }
.menu-card-tag {
  font-size: 10px; font-family: 'JetBrains Mono', monospace;
  padding: 2px 6px; border-radius: 4px;
  background: var(--bg-elev); color: var(--text-muted);
  border: 1px solid var(--border);
}

/* per-card accent colors */
.menu-card.ll-array { --card-accent: var(--emerald); }
.menu-card.ll-pointer { --card-accent: #34d399; }
.menu-card.stack-array { --card-accent: var(--amber); }
.menu-card.stack-pointer { --card-accent: #fbbf24; }
.menu-card.queue-array { --card-accent: var(--purple); }
.menu-card.queue-pointer { --card-accent: #c084fc; }

.menu-footer-note {
  margin-top: 40px; text-align: center;
  font-size: 12px; color: var(--text-muted);
  display: flex; align-items: center; gap: 6px; justify-content: center;
}

/* ============ Responsive ============ */
.layout-stack {
  display: grid;
  grid-template-columns: 1fr;
  gap: 16px;
}
@media (min-width: 768px) {
  .layout-stack { grid-template-columns: 1fr 1fr; }
}

/* Animations */
@keyframes node-enter {
  from { opacity: 0; transform: translateY(-20px) scale(0.7); }
  to { opacity: 1; transform: translateY(0) scale(1); }
}
@keyframes node-exit {
  from { opacity: 1; transform: translateY(0) scale(1); }
  to { opacity: 0; transform: translateY(30px) scale(0.5); }
}
.node-enter { animation: node-enter 350ms ease-out; }
.node-exit { animation: node-exit 350ms ease-in forwards; }

/* SVG icons sizing */
.icon-xs { width: 14px; height: 14px; }
.icon-sm { width: 16px; height: 16px; }
.icon-md { width: 18px; height: 18px; }
.icon-lg { width: 24px; height: 24px; }