/* PDA Simulator — merged spec: palette #0f1117 / #4f8ef7 / #22c97a + premium polish */

:root {
  --bg-base: #0f1117;
  --bg-surface: #1a1d27;
  --bg-elevated: #222636;
  --bg-hover: #2a2e42;
  --border: #2e3148;
  --border-bright: #3d4560;
  --accent: #4f8ef7;
  --accent-glow: rgba(79, 142, 247, 0.22);
  --accent-soft: rgba(79, 142, 247, 0.12);
  --green: #22c97a;
  --green-glow: rgba(34, 201, 122, 0.18);
  --red: #f25f5c;
  --red-glow: rgba(242, 95, 92, 0.16);
  --amber: #f5a623;
  --purple: #a78bfa;
  --purple-glow: rgba(167, 139, 250, 0.2);
  --text-primary: #e8eaf0;
  --text-secondary: #8892a4;
  --text-muted: #5c6578;
  --radius-sm: 6px;
  --radius-md: 10px;
  --radius-lg: 16px;
  --edge-flow-duration: 400ms;
  --diagram-label-px: 13px;
}

body[data-theme="light"] {
  --bg-base: #f8f9fb;
  --bg-surface: #ffffff;
  --bg-elevated: #f3f5fa;
  --bg-hover: #edf1f9;
  --border: #e2e5ec;
  --border-bright: #b4bfd8;
  --text-primary: #1a1e2c;
  --text-secondary: #4d5a72;
  --text-muted: #7a869f;
  --accent-soft: rgba(79, 142, 247, 0.1);
  background-image: radial-gradient(circle at 1px 1px, rgba(0,0,0,0.045) 1px, transparent 0);
}

* { box-sizing: border-box; }

/* Reserve scrollbar width; limit scroll-anchoring jumps when content reflows. */
html {
  scrollbar-gutter: stable;
  overflow-anchor: none;
}

body {
  margin: 0;
  font-family: Inter, system-ui, "Segoe UI", sans-serif;
  font-size: 14px;
  color: var(--text-primary);
  background-color: var(--bg-base);
  background-image:
    radial-gradient(circle at 1px 1px, rgba(255,255,255,0.04) 1px, transparent 0);
  background-size: 22px 22px;
}

body.preset-shimmer .app-grid {
  animation: panelShimmer 0.42s ease-out;
}

@keyframes panelShimmer {
  0% { opacity: 0.72; filter: brightness(1.08); }
  100% { opacity: 1; filter: none; }
}

button, input, select {
  color: inherit;
  font: inherit;
}

button:focus-visible, input:focus-visible, select:focus-visible {
  outline: 2px solid var(--accent);
  outline-offset: 2px;
}

/* ——— Top bar ——— */
.topbar {
  height: 56px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 12px;
  padding: 0 16px;
  border-bottom: 1px solid var(--border);
  background: color-mix(in srgb, var(--bg-surface), transparent 8%);
  backdrop-filter: blur(12px);
  position: sticky;
  top: 0;
  z-index: 40;
}

.brand { display: flex; align-items: center; gap: 10px; min-width: 0; }
.brand-title { font-size: 17px; font-weight: 600; letter-spacing: -0.02em; }
.badge, .count-pill {
  border-radius: 999px;
  border: 1px solid var(--border);
  padding: 2px 8px;
  color: var(--text-secondary);
  font-size: 11px;
  font-weight: 500;
}

.preset-pill {
  display: flex;
  align-items: center;
  gap: 8px;
  flex: 1;
  justify-content: center;
  max-width: 280px;
  background: rgba(255, 255, 255, 0.04);
  border: 1px solid var(--border);
  border-radius: 999px;
  padding: 0 12px;
  height: 36px;
  transition: border-color 0.15s, box-shadow 0.15s;
}
.preset-pill:hover { border-color: var(--border-bright); }
.preset-pill-icon { opacity: 0.85; font-size: 14px; }
.preset-pill select {
  background: transparent;
  border: 0;
  width: 100%;
  outline: none;
  cursor: pointer;
  font-weight: 500;
}

.top-actions { display: flex; align-items: center; gap: 8px; flex-shrink: 0; }
.btn-icon-label { display: inline-flex; align-items: center; gap: 6px; }
.btn-ic { font-size: 12px; opacity: 0.8; }
.theme-toggle { min-width: 40px; font-size: 16px; }

.btn {
  border: 1px solid var(--border);
  background: var(--bg-elevated);
  border-radius: var(--radius-sm);
  padding: 8px 12px;
  cursor: pointer;
  transition: background 0.15s, transform 0.1s, border-color 0.15s, filter 0.15s;
}
.btn:active { transform: scale(0.97); }
.btn:hover { background: var(--bg-hover); }
.btn.primary {
  border: 0;
  color: #fff;
  min-height: 40px;
  background: linear-gradient(135deg, #4f8ef7, #7c6ef5);
  box-shadow: 0 4px 16px rgba(79, 142, 247, 0.38);
}
.btn.primary:hover { filter: brightness(1.08); }
.btn.outline { background: transparent; }
.btn.ghost, .btn.text { background: transparent; }
.btn.dashed { border-style: dashed; }
.btn.full { width: 100%; }

/* ——— Mobile tabs ——— */
.mobile-tabs {
  display: none;
  gap: 4px;
  padding: 8px 12px;
  background: var(--bg-surface);
  border-bottom: 1px solid var(--border);
  overflow-x: auto;
  scroll-behavior: smooth;
  -webkit-overflow-scrolling: touch;
}
.mobile-tab {
  flex: 1 0 auto;
  padding: 8px 14px;
  border-radius: 999px;
  border: 1px solid var(--border);
  background: transparent;
  color: var(--text-secondary);
  font-size: 13px;
  font-weight: 500;
  cursor: pointer;
  transition: background 0.15s, color 0.15s, border-color 0.15s;
}
.mobile-tab.is-active {
  background: var(--accent-soft);
  border-color: var(--accent);
  color: var(--accent);
}

/* ——— Grid ——— */
.app-grid {
  display: grid;
  grid-template-columns: minmax(260px, 300px) minmax(0, 1fr) minmax(190px, 220px);
  grid-template-rows: auto auto;
  gap: 16px;
  padding: 16px;
  min-height: calc(100vh - 56px);
  min-height: calc(100svh - 56px);
  align-items: start;
}
.left-panel {
  grid-column: 1;
  grid-row: 1;
}
.center-panel {
  grid-column: 2;
  grid-row: 1;
}
.right-panel {
  grid-column: 3;
  grid-row: 1;
}
.diagram-panel {
  grid-column: 1 / -1;
  grid-row: 2;
  min-width: 0;
}

.card {
  background: var(--bg-surface);
  border: 1px solid var(--border);
  border-radius: var(--radius-md);
  box-shadow: 0 2px 12px rgba(0, 0, 0, 0.12), 0 4px 24px rgba(0, 0, 0, 0.28);
  padding: 16px;
  min-height: 0;
}

.left-panel, .right-panel {
  overflow: auto;
  display: flex;
  flex-direction: column;
  max-height: calc(100vh - 88px);
  max-height: calc(100svh - 88px);
  min-width: 0;
}
.center-panel {
  overflow: auto;
  display: flex;
  flex-direction: column;
  gap: 10px;
  max-height: calc(100vh - 88px);
  max-height: calc(100svh - 88px);
  min-height: 0;
  min-width: 0;
}
/* Full-width diagram below the three columns — large viewport for the SVG */
.diagram-panel {
  display: flex;
  flex-direction: column;
  min-height: 0;
  overflow: visible;
}

.section-title {
  display: flex;
  align-items: center;
  gap: 8px;
  color: var(--text-muted);
  font-size: 11px;
  font-weight: 600;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  margin-bottom: 10px;
}
.accent { width: 2px; height: 14px; border-radius: 2px; flex-shrink: 0; }
.accent.blue { background: var(--accent); }
.accent.green { background: var(--green); }

.panel-divider {
  border: 0;
  border-top: 1px solid var(--border);
  margin: 14px 0;
}

.add-row-btn { min-height: 34px; margin-bottom: 8px; }

/* ——— States ——— */
.states-list, .transitions-list { overflow: auto; padding-right: 2px; flex: 1; min-height: 0; }
.states-list { max-height: 22vh; }

.state-row-premium {
  display: grid;
  grid-template-columns: 12px 1fr auto auto;
  align-items: center;
  gap: 8px;
  padding: 10px 8px;
  border-radius: var(--radius-sm);
  margin-bottom: 6px;
  border-left: 2px solid transparent;
  background: color-mix(in srgb, var(--bg-elevated), transparent 35%);
  animation: rowIn 0.35s ease backwards;
  animation-delay: var(--stagger, 0ms);
}
@keyframes rowIn {
  from { opacity: 0; transform: translateY(4px); }
  to { opacity: 1; transform: none; }
}
.state-row-premium.active {
  background: var(--accent-soft);
  border-left-color: var(--accent);
}
.state-dot {
  width: 10px;
  height: 10px;
  border-radius: 50%;
  background: #5f677d;
  justify-self: center;
}
.state-dot.is-live {
  background: var(--accent);
  box-shadow: 0 0 0 3px var(--accent-glow);
  animation: dotPulse 2s ease-in-out infinite;
}
@keyframes dotPulse {
  50% { box-shadow: 0 0 0 5px var(--accent-glow); }
}
.state-name {
  border: 0;
  outline: none;
  background: transparent;
  max-width: 72px;
  font-weight: 600;
  border-bottom: 1px dashed transparent;
}
.state-name:focus { border-bottom-color: var(--accent); }
.state-badge-row { display: flex; gap: 4px; }
.state-badge {
  width: 26px;
  height: 26px;
  padding: 0;
  border-radius: 8px;
  border: 1px solid var(--border);
  background: transparent;
  font-size: 11px;
  font-weight: 700;
  color: var(--text-muted);
  cursor: pointer;
  transition: background 0.15s, border-color 0.15s, color 0.15s;
}
.state-badge-start.on {
  border-color: var(--accent);
  color: var(--accent);
  background: rgba(79, 142, 247, 0.15);
}
.state-badge-accept.on {
  border-color: var(--green);
  color: var(--green);
  background: rgba(34, 201, 122, 0.12);
}
.state-menu { position: relative; justify-self: end; }
.state-menu-trigger {
  width: 28px;
  height: 28px;
  border-radius: 8px;
  border: 1px solid transparent;
  background: transparent;
  color: var(--text-muted);
  cursor: pointer;
  opacity: 0;
  transition: opacity 0.15s, background 0.15s;
}
.state-row-premium:hover .state-menu-trigger { opacity: 1; }
.state-menu-trigger:hover { background: var(--bg-hover); color: var(--text-primary); }
.state-menu-dropdown {
  position: absolute;
  right: 0;
  top: 100%;
  margin-top: 4px;
  min-width: 140px;
  padding: 4px;
  background: var(--bg-surface);
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  box-shadow: 0 8px 28px rgba(0,0,0,0.35);
  z-index: 20;
}
.state-menu-delete {
  width: 100%;
  text-align: left;
  padding: 8px 10px;
  border: 0;
  border-radius: 6px;
  background: transparent;
  color: var(--red);
  cursor: pointer;
  font-size: 13px;
}
.state-menu-delete:hover { background: var(--red-glow); }

/* ——— Transitions ——— */
.transition-card {
  background: var(--bg-elevated);
  border: 1px solid var(--border);
  border-radius: var(--radius-md);
  padding: 12px;
  margin-bottom: 8px;
  animation: rowIn 0.35s ease backwards;
  animation-delay: var(--stagger, 0ms);
  transition: border-color 0.15s, box-shadow 0.15s;
}
.transition-card.active {
  border-color: var(--green);
  box-shadow: 0 0 0 1px rgba(34, 201, 122, 0.45);
}
.transition-card.invalid { border-left: 3px solid var(--red); }
.transition-head {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 10px;
}
.transition-arrow { font-size: 13px; color: var(--text-secondary); }
.transition-arrow .t-arr { color: var(--accent); margin: 0 4px; }
.transition-del { padding: 4px 8px; opacity: 0.75; }
.transition-grid {
  display: grid;
  grid-template-columns: 1fr 1fr 2fr;
  gap: 8px;
}
.transition-grid-row2 { margin-top: 8px; }
.tbox { display: grid; gap: 4px; }
.tbox input, .tbox select {
  background: var(--bg-base);
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  padding: 8px 9px;
  outline: none;
  font-family: Consolas, "Courier New", monospace;
  font-size: 13px;
}
.tbox input.is-eps { color: var(--amber); font-style: italic; }
.tbox small { color: var(--text-muted); font-size: 10px; text-transform: lowercase; }

/* ——— Center: input ——— */
.input-card {
  border: 1px solid var(--border);
  border-radius: var(--radius-md);
  padding: 16px;
  background: var(--bg-elevated);
}
.input-card-label {
  font-size: 11px;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.06em;
  color: var(--text-muted);
  margin-bottom: 8px;
}
.token-row {
  display: flex;
  gap: 6px;
  min-height: 40px;
  flex-wrap: wrap;
  align-items: center;
}
.token {
  min-width: 32px;
  height: 32px;
  border-radius: 8px;
  display: grid;
  place-items: center;
  background: var(--bg-surface);
  border: 1px solid var(--border);
  font-family: Consolas, monospace;
  font-weight: 700;
  font-size: 16px;
  transition: transform 0.15s, box-shadow 0.15s, border-color 0.15s;
}
.token.consumed { opacity: 0.35; text-decoration: line-through; }
.token.current {
  background: var(--accent-soft);
  border-color: var(--accent);
  color: var(--accent);
  transform: scale(1.1);
  box-shadow: 0 0 14px var(--accent-glow);
  animation: tokenGlow 2s ease-in-out infinite;
}
@keyframes tokenGlow {
  50% { box-shadow: 0 0 20px var(--accent-glow); }
}
.current-char-hint {
  font-size: 12px;
  color: var(--text-muted);
  margin-top: 4px;
  min-height: 18px;
  opacity: 0;
}
.current-char-hint.is-visible { opacity: 1; }
.position-label { color: var(--text-muted); margin: 10px 0 6px; font-size: 12px; }
.input-main {
  width: 100%;
  letter-spacing: 4px;
  font-size: 18px;
  font-family: Consolas, monospace;
  background: var(--bg-base);
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  padding: 10px 12px;
}

.controls-row {
  display: flex;
  align-items: center;
  flex-wrap: wrap;
  gap: 8px;
}
kbd {
  background: var(--bg-base);
  border: 1px solid var(--border);
  border-radius: 4px;
  padding: 1px 5px;
  font-size: 11px;
}
.speed-wrap, .toggle-wrap {
  display: flex;
  align-items: center;
  gap: 8px;
  color: var(--text-secondary);
  font-size: 13px;
}
.speed-wrap input[type="range"] {
  width: 130px;
  height: 3px;
  accent-color: var(--accent);
}
.speed-presets { display: flex; gap: 4px; }
.speed-btn { padding: 6px 8px; font-size: 12px; }

/* ——— Result banner ——— */
.result-banner {
  display: flex;
  align-items: center;
  gap: 12px;
  min-height: 44px;
  padding: 10px 14px;
  border-radius: var(--radius-sm);
  border-left: 3px solid var(--green);
  background: linear-gradient(90deg, rgba(34, 201, 122, 0.14), transparent);
  animation: bannerIn 0.22s ease-out;
}
.result-banner.reject {
  border-left-color: var(--red);
  background: linear-gradient(90deg, rgba(242, 95, 92, 0.16), transparent);
}
@keyframes bannerIn {
  from { opacity: 0; transform: translateY(-10px); }
  to { opacity: 1; transform: none; }
}
.result-banner-icon {
  font-size: 18px;
  font-weight: 700;
  color: var(--green);
  flex-shrink: 0;
}
.result-banner.reject .result-banner-icon { color: var(--red); }
.result-banner-text { flex: 1; font-weight: 500; font-size: 14px; color: var(--text-primary); }
.result-banner.reject .result-banner-text { color: var(--red); }
.result-dismiss {
  border: 0;
  background: transparent;
  color: var(--text-muted);
  font-size: 22px;
  line-height: 1;
  cursor: pointer;
  padding: 4px 8px;
  border-radius: 6px;
}
.result-dismiss:hover { background: var(--bg-hover); color: var(--text-primary); }

.hidden { display: none !important; }

/* ——— Log table ——— */
.log-head { display: flex; justify-content: space-between; align-items: center; margin: 4px 0 6px; }
.log-table-wrap {
  overflow: auto;
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  min-height: 120px;
  max-height: 26vh;
}
.log-table { width: 100%; border-collapse: collapse; font-size: 13px; }
.log-table thead th {
  text-align: left;
  padding: 8px 10px;
  font-size: 11px;
  letter-spacing: 0.06em;
  text-transform: uppercase;
  color: var(--text-muted);
  background: var(--bg-base);
}
.log-table td {
  padding: 6px 10px;
  border-top: 1px solid var(--border);
  height: 36px;
  vertical-align: middle;
}
.log-table tbody tr:nth-child(odd) { background: color-mix(in srgb, var(--bg-elevated), transparent 55%); }
.log-table tr.current {
  border-left: 3px solid var(--accent);
  background: rgba(79, 142, 247, 0.08);
}
.mono { font-family: Consolas, monospace; font-weight: 600; }
.stack-cells-td { white-space: normal; }
.stack-chip {
  display: inline-flex;
  align-items: center;
  padding: 2px 8px;
  margin: 2px 4px 2px 0;
  border-radius: 6px;
  font-size: 12px;
  font-family: Consolas, monospace;
  font-weight: 600;
  border: 1px solid var(--accent);
  color: var(--accent);
  background: var(--accent-soft);
}
.stack-chip.is-z0 {
  border-color: var(--purple);
  color: var(--purple);
  background: var(--purple-glow);
}
.action-td { line-height: 1.5; }

.tag {
  border-radius: 999px;
  font-size: 11px;
  padding: 3px 8px;
  border: 1px solid var(--border);
  margin: 2px 4px 2px 0;
  display: inline-block;
  font-weight: 600;
}
.tag.push { color: var(--green); border-color: var(--green); background: rgba(34, 201, 122, 0.12); }
.tag.pop { color: var(--red); border-color: var(--red); background: rgba(242, 95, 92, 0.12); }
.tag.eps { color: var(--amber); border-color: var(--amber); background: rgba(245, 166, 35, 0.14); font-style: italic; }
.tag.consume { color: var(--accent); border-color: var(--accent); background: var(--accent-soft); }
.tag.tstart { color: var(--text-secondary); border-color: var(--border-bright); background: var(--bg-hover); }

.branching-tree { margin-top: 8px; }
.branching-tree-inner {
  display: flex;
  flex-direction: column;
  gap: 4px;
  padding: 8px 10px;
  border-radius: var(--radius-sm);
  border: 1px dashed var(--border);
  background: color-mix(in srgb, var(--bg-elevated), transparent 40%);
}
.branch-ghost {
  display: flex;
  align-items: center;
  gap: 8px;
  font-size: 12px;
  color: var(--text-muted);
  opacity: 0.72;
  padding: 4px 6px;
  border-radius: 6px;
}
.branch-ghost.chosen {
  opacity: 1;
  color: var(--text-secondary);
  background: var(--accent-soft);
  border: 1px solid color-mix(in srgb, var(--accent), transparent 60%);
}
.branch-ic { font-size: 14px; }
.branch-sep { opacity: 0.5; }
.branching-hint { margin-top: 6px; color: var(--text-secondary); font-size: 12px; min-height: 18px; }

/* ——— Stack panel ——— */
.stack-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-bottom: 8px;
}
.stack-title { margin-bottom: 0; }
.stack-icon {
  display: flex;
  flex-direction: column;
  gap: 3px;
  width: 22px;
}
.stack-icon span {
  display: block;
  height: 3px;
  border-radius: 2px;
  background: linear-gradient(90deg, var(--accent), var(--purple));
  opacity: 0.85;
}
.stack-icon.shuffle span {
  animation: stackBarShuffle 0.48s ease-in-out;
}
.stack-icon.shuffle span:nth-child(2) { animation-delay: 0.05s; }
.stack-icon.shuffle span:nth-child(3) { animation-delay: 0.1s; }
@keyframes stackBarShuffle {
  0%, 100% { transform: translateX(0); opacity: 0.85; }
  50% { transform: translateX(4px); opacity: 1; }
}

.stack-overflow-banner {
  font-size: 12px;
  padding: 8px 10px;
  border-radius: var(--radius-sm);
  background: rgba(242, 95, 92, 0.12);
  border: 1px solid rgba(242, 95, 92, 0.35);
  color: var(--red);
  margin-bottom: 8px;
}

.stack-view {
  position: relative;
  border: 1px dashed var(--border);
  border-radius: var(--radius-md);
  padding: 14px 12px 14px 28px;
  min-height: 200px;
  flex: 1;
  max-height: 56vh;
  overflow: auto;
}
.stack-view::before {
  content: "top ▾";
  position: absolute;
  left: 8px;
  top: 18px;
  font-size: 11px;
  color: var(--text-muted);
  writing-mode: vertical-rl;
  transform: rotate(180deg);
  letter-spacing: 0.04em;
}
.stack-view::after {
  content: "";
  position: absolute;
  left: 22px;
  top: 44px;
  bottom: 14px;
  border-left: 1px dashed var(--border);
}
.stack-empty {
  min-height: 120px;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  gap: 8px;
  color: var(--text-muted);
  font-style: italic;
  font-size: 14px;
  border: 1px dashed var(--border);
  border-radius: var(--radius-md);
  margin-left: 8px;
}
.stack-empty-icon { font-size: 28px; opacity: 0.25; }
.stack-cell {
  height: 52px;
  max-width: 180px;
  margin-left: 8px;
  margin-bottom: 6px;
  border-radius: 10px;
  display: grid;
  place-items: center;
  font: 700 20px Consolas, monospace;
  border: 1.5px solid var(--accent);
  color: var(--accent);
  background: var(--bg-elevated);
  box-shadow: 0 0 12px var(--accent-glow);
  transition: box-shadow 0.6s ease;
}
.stack-cell.bottom {
  border-color: var(--purple);
  color: var(--purple);
  background: var(--purple-glow);
  box-shadow: none;
}
.stack-cell.push-glow {
  box-shadow: 0 0 20px var(--green-glow), 0 0 6px rgba(34, 201, 122, 0.45);
}
.stack-cell-enter {
  animation: stackEnter 0.35s cubic-bezier(0.34, 1.56, 0.64, 1) forwards;
}
@keyframes stackEnter {
  from { opacity: 0; transform: translateY(-48px) scale(0.88); }
  to { opacity: 1; transform: none; }
}
.depth-label { margin-top: 10px; color: var(--text-secondary); font-size: 12px; }
.stack-warning { margin-top: 6px; font-size: 12px; color: var(--red); }

/* ——— Diagram ——— */
.diagram-panel .diagram-inline {
  display: grid;
  grid-template-rows: auto 1fr;
  gap: 10px;
  width: 100%;
  min-width: 0;
  min-height: 0;
}
.diagram-head {
  display: flex;
  justify-content: space-between;
  align-items: center;
}
.btn-auto-layout { font-size: 12px; }
.diagram-wrap {
  position: relative;
  border: 1px solid var(--border);
  border-radius: var(--radius-md);
  overflow: auto;
  -webkit-overflow-scrolling: touch;
  padding: 8px 10px 12px;
  /* Tall pane: scroll page or this box; SVG scales to fill width/height */
  min-height: 600px;
  height: clamp(600px, min(80vh, 1100px), 1100px);
  max-height: min(1100px, 96vh);
  background: radial-gradient(circle at 1px 1px, rgba(255,255,255,0.05) 1px, transparent 0);
  background-size: 18px 18px;
  background-color: var(--bg-surface);
}
.diagram-empty {
  position: absolute;
  inset: 0;
  display: flex;
  align-items: center;
  justify-content: center;
  text-align: center;
  padding: 24px;
  font-size: 14px;
  color: var(--text-muted);
  z-index: 2;
  pointer-events: none;
  background: color-mix(in srgb, var(--bg-surface), transparent 15%);
}
#diagram {
  width: 100%;
  min-width: 0;
  height: 100%;
  min-height: 560px;
  display: block;
  position: relative;
  z-index: 1;
  overflow: visible;
}

.node { cursor: grab; transition: transform 0.15s ease; }
.node:active { cursor: grabbing; }
.node:hover { transform: scale(1.08); }
.node circle { fill: var(--bg-elevated); stroke: var(--border-bright); stroke-width: 2; }
.node.is-start circle { stroke: var(--accent); }
.node text {
  fill: var(--text-primary);
  font-size: calc(var(--diagram-label-px, 13px) + 0.5px);
  font-weight: 600;
  text-anchor: middle;
  dominant-baseline: middle;
  pointer-events: none;
}
.node.accept .inner { fill: none; stroke: var(--accent); stroke-width: 2; }
.node.active circle {
  fill: var(--accent);
  filter: drop-shadow(0 0 10px rgba(79, 142, 247, 0.55));
  animation: nodePulse 2s ease-in-out infinite;
}
.node.active text { fill: #fff; }
.node.visited circle {
  fill: rgba(79, 142, 247, 0.14);
  stroke: var(--accent);
}
.edge { stroke: #5f6986; stroke-width: 2; fill: none; opacity: 0.88; }
.edge.used { stroke: #6f89c4; opacity: 0.95; }
.edge.hover {
  stroke: var(--accent);
  stroke-width: 2.2;
  opacity: 1;
  filter: drop-shadow(0 0 4px var(--accent-glow));
}
.edge.active {
  stroke: var(--accent);
  stroke-width: 2.6;
  opacity: 1;
  stroke-dasharray: 8 6;
  animation: edgeFlow var(--edge-flow-duration) linear infinite;
}
.edge-label-pill {
  fill: color-mix(in srgb, var(--bg-surface), transparent 4%);
  stroke: var(--border);
  stroke-width: 1;
}
.edge-label-text {
  fill: var(--text-secondary);
  font-size: var(--diagram-label-px, 12px);
  font-family: Consolas, monospace;
  font-weight: 600;
}
.edge-label-text .eps { fill: var(--amber); font-style: italic; }

@keyframes edgeFlow { to { stroke-dashoffset: -28; } }
@keyframes nodePulse {
  0%, 100% { filter: drop-shadow(0 0 8px rgba(79, 142, 247, 0.45)); }
  50% { filter: drop-shadow(0 0 16px rgba(79, 142, 247, 0.85)); }
}

.toast-container {
  position: fixed;
  right: 16px;
  bottom: 16px;
  display: grid;
  gap: 8px;
  z-index: 99;
}
.toast {
  background: var(--bg-surface);
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  padding: 10px 14px;
  box-shadow: 0 8px 30px rgba(0,0,0,0.35);
  animation: toastIn 0.25s ease-out;
}
@keyframes toastIn {
  from { opacity: 0; transform: translateX(12px); }
  to { opacity: 1; transform: none; }
}

::-webkit-scrollbar { width: 4px; height: 4px; }
::-webkit-scrollbar-track { background: var(--border); }
::-webkit-scrollbar-thumb { background: var(--accent); border-radius: 99px; }

@media (max-width: 1279px) {
  .app-grid {
    grid-template-columns: minmax(240px, 280px) 1fr;
    grid-template-rows: auto auto auto;
  }
  .left-panel { grid-column: 1; grid-row: 1 / span 3; }
  .center-panel { grid-column: 2; grid-row: 1; }
  .right-panel { grid-column: 2; grid-row: 2; }
  .diagram-panel { grid-column: 2; grid-row: 3; }
  .left-panel, .center-panel, .right-panel, .diagram-panel { max-height: none; }
}

@media (max-width: 980px) {
  .mobile-tabs { display: flex; }
  .topbar { flex-wrap: wrap; height: auto; min-height: 56px; padding: 8px 12px; }
  .preset-pill { order: 3; max-width: none; width: 100%; }
  .app-grid {
    display: flex;
    flex-direction: column;
    gap: 12px;
    padding: 12px;
  }
  .left-panel,
  .center-panel,
  .right-panel,
  .diagram-panel {
    display: none;
    max-height: none;
    overflow: visible;
  }
  body[data-mobile-panel="define"] .left-panel { display: flex; }
  body[data-mobile-panel="simulate"] .center-panel,
  body[data-mobile-panel="simulate"] .diagram-panel { display: flex; }
  body[data-mobile-panel="stack"] .right-panel { display: flex; }
  .states-list { max-height: 200px; }
  .log-table-wrap { max-height: 200px; }
  .diagram-wrap {
    min-height: 520px;
    height: clamp(520px, 65vh, 820px);
    max-height: 90vh;
  }
  #diagram { min-height: 480px; }
}