:root {
  --bg: #f6f7f9;
  --panel: #ffffff;
  --border: #d9dde3;
  --text: #1f2430;
  --muted: #6b7280;
  --accent: #2563eb;
  --accent-soft: #dbeafe;
  --error-bg: #fdecec;
  --error-fg: #9f1d1d;
  --error-border: #f3b4b4;
  --warn-bg: #fff7e6;
  --warn-fg: #8a5a00;
  --warn-border: #f5d58a;

  --node-fill: #ffffff;
  --node-stroke: #475569;
  --compound-fill: #f8fafc;
  --edge: #334155;
  --edge-internal: #9ca3af;
  --label-bg: #ffffff;
  --region-fill: rgba(255, 255, 255, 0.55);
  --grid: #d4d8de;
  --legend-bg: rgba(255, 255, 255, 0.85);
  color-scheme: light;

  font-family: "Inter", system-ui, -apple-system, "Segoe UI", Roboto, sans-serif;
  font-size: 14px;
  color: var(--text);
}

@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) {
  --bg: #0f1115;
  --panel: #171a21;
  --border: #2b313d;
  --text: #e6e8ee;
  --muted: #98a2b3;
  --accent: #60a5fa;
  --accent-soft: #1e3a8a;
  --error-bg: #3a1618;
  --error-fg: #fca5a5;
  --error-border: #7f1d1d;
  --warn-bg: #362a0b;
  --warn-fg: #fcd34d;
  --warn-border: #78500a;

  --node-fill: #1e232e;
  --node-stroke: #aab4c3;
  --compound-fill: #181c25;
  --region-fill: rgba(255, 255, 255, 0.04);
  --edge: #c3cbd8;
  --edge-internal: #6b7280;
  --label-bg: #171a21;
  --grid: #2b313d;
  --legend-bg: rgba(23, 26, 33, 0.88);
  color-scheme: dark;
  }
}

:root[data-theme="dark"] {
  --bg: #0f1115;
  --panel: #171a21;
  --border: #2b313d;
  --text: #e6e8ee;
  --muted: #98a2b3;
  --accent: #60a5fa;
  --accent-soft: #1e3a8a;
  --error-bg: #3a1618;
  --error-fg: #fca5a5;
  --error-border: #7f1d1d;
  --warn-bg: #362a0b;
  --warn-fg: #fcd34d;
  --warn-border: #78500a;

  --node-fill: #1e232e;
  --node-stroke: #aab4c3;
  --compound-fill: #181c25;
  --region-fill: rgba(255, 255, 255, 0.04);
  --edge: #c3cbd8;
  --edge-internal: #6b7280;
  --label-bg: #171a21;
  --grid: #2b313d;
  --legend-bg: rgba(23, 26, 33, 0.88);
  color-scheme: dark;
}

* { box-sizing: border-box; }

html, body {
  margin: 0;
  height: 100%;
  background: var(--bg);
}

body {
  display: flex;
  flex-direction: column;
}

.topbar {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 16px;
  padding: 10px 16px;
  background: var(--panel);
  border-bottom: 1px solid var(--border);
  flex-wrap: wrap;
}

.brand {
  display: flex;
  align-items: baseline;
  gap: 10px;
}

.brand-mark {
  display: inline-block;
  width: 12px;
  height: 12px;
  border-radius: 3px;
  background: var(--accent);
  transform: translateY(1px);
}

.brand h1 {
  font-size: 16px;
  font-weight: 600;
  margin: 0;
}

.brand-note {
  color: var(--muted);
  font-size: 12px;
}

.toolbar {
  display: flex;
  align-items: center;
  gap: 10px;
  flex-wrap: wrap;
}

.control {
  display: flex;
  align-items: center;
  gap: 6px;
  font-size: 13px;
  color: var(--muted);
}

select, button {
  font: inherit;
  font-size: 13px;
  color: var(--text);
  background: var(--panel);
  border: 1px solid var(--border);
  border-radius: 6px;
  padding: 5px 10px;
}

button {
  cursor: pointer;
}

button:hover {
  border-color: var(--accent);
  color: var(--accent);
}

.workspace {
  flex: 1;
  display: flex;
  min-height: 0;
}

.editor-pane {
  display: flex;
  flex-direction: column;
  width: 38%;
  min-width: 260px;
  max-width: 70%;
  background: var(--panel);
  border-right: 1px solid var(--border);
}

.pane-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 6px 12px;
  font-size: 12px;
  text-transform: uppercase;
  letter-spacing: 0.04em;
  color: var(--muted);
  border-bottom: 1px solid var(--border);
}

.stats {
  text-transform: none;
  letter-spacing: 0;
}

#source {
  flex: 1;
  width: 100%;
  resize: none;
  border: 0;
  outline: none;
  padding: 12px;
  font-family: "JetBrains Mono", ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;
  font-size: 12.5px;
  line-height: 1.5;
  color: var(--text);
  background: var(--panel);
  tab-size: 2;
}

.splitter {
  width: 6px;
  cursor: col-resize;
  background: transparent;
  margin-left: -3px;
  margin-right: -3px;
  z-index: 2;
}

.splitter:hover,
.splitter.active {
  background: var(--accent-soft);
}

.diagram-pane {
  flex: 1;
  position: relative;
  display: flex;
  flex-direction: column;
  min-width: 0;
}

.messages {
  position: absolute;
  top: 12px;
  left: 12px;
  right: 12px;
  z-index: 3;
  display: flex;
  flex-direction: column;
  gap: 6px;
  pointer-events: none;
}

.message {
  pointer-events: auto;
  padding: 8px 12px;
  border-radius: 6px;
  font-size: 13px;
  border: 1px solid;
  box-shadow: 0 1px 3px rgba(0, 0, 0, 0.06);
}

.message-error {
  background: var(--error-bg);
  color: var(--error-fg);
  border-color: var(--error-border);
}

.message-warning {
  background: var(--warn-bg);
  color: var(--warn-fg);
  border-color: var(--warn-border);
}

.message code {
  font-family: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;
  font-size: 12px;
}

.diagram {
  flex: 1;
  width: 100%;
  height: 100%;
  cursor: grab;
  background:
    radial-gradient(circle, var(--grid) 1px, transparent 1px) 0 0 / 22px 22px,
    var(--bg);
  touch-action: none;
  user-select: none;
}

.diagram.dragging {
  cursor: grabbing;
}

.diagram.stale {
  opacity: 0.45;
}

.empty {
  position: absolute;
  inset: 0;
  display: flex;
  align-items: center;
  justify-content: center;
  color: var(--muted);
  pointer-events: none;
  font-size: 15px;
}

.empty.hidden {
  display: none;
}

.legend {
  position: absolute;
  right: 12px;
  bottom: 10px;
  display: flex;
  gap: 14px;
  font-size: 12px;
  color: var(--muted);
  background: var(--legend-bg);
  padding: 6px 10px;
  border-radius: 6px;
  border: 1px solid var(--border);
  pointer-events: none;
}

.legend span {
  display: inline-flex;
  align-items: center;
  gap: 5px;
}

.legend i {
  display: inline-block;
  font-style: normal;
}

.lg-initial {
  width: 10px;
  height: 10px;
  border-radius: 50%;
  background: var(--edge);
}

.lg-final {
  width: 16px;
  height: 12px;
  border-radius: 3px;
  border: 1px solid var(--edge);
  box-shadow: inset 0 0 0 1.5px var(--panel), inset 0 0 0 2.5px var(--edge);
}

.lg-history {
  width: 14px;
  height: 14px;
  border-radius: 50%;
  border: 1.5px solid var(--edge);
  font-size: 9px;
  line-height: 11px;
  text-align: center;
  color: var(--edge);
}

.lg-region {
  width: 16px;
  height: 11px;
  border: 1.5px solid var(--edge);
  border-radius: 2px;
  background: linear-gradient(to bottom, var(--edge) 0 1px, transparent 1px) 50% 0 / 1.5px 3px repeat-y;
}

/* ---- SVG diagram styles ---- */

.node text {
  font-family: "Inter", system-ui, -apple-system, "Segoe UI", Roboto, sans-serif;
  pointer-events: none;
}

.state-box {
  fill: var(--node-fill);
  stroke: var(--node-stroke);
  stroke-width: 1.4;
}

.state-title,
.compound-title {
  font-size: 13px;
  font-weight: 600;
  fill: var(--text);
}

.detail-sep {
  stroke: var(--node-stroke);
  stroke-width: 0.8;
  opacity: 0.6;
}

.detail-head {
  font-size: 11px;
  fill: var(--muted);
  font-style: italic;
}

.detail-item {
  font-family: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;
  font-size: 11px;
  fill: var(--text);
}

.compound-box {
  fill: var(--compound-fill);
  stroke: var(--node-stroke);
  stroke-width: 1.4;
}

.parallel-box {
  fill: var(--compound-fill);
  stroke: var(--node-stroke);
  stroke-width: 1.4;
}

.region-box {
  fill: var(--region-fill);
  stroke: var(--node-stroke);
  stroke-width: 1.2;
  stroke-dasharray: 5 4;
}

.parallel-tag {
  font-size: 10px;
  text-transform: uppercase;
  letter-spacing: 0.06em;
  fill: var(--muted);
}

.initial-dot {
  fill: var(--edge);
}

.final-box {
  fill: var(--node-fill);
  stroke: var(--node-stroke);
  stroke-width: 1.4;
}

.final-box.inner {
  fill: none;
  stroke-width: 1.2;
}

.partition {
  stroke: var(--node-stroke);
  stroke-width: 1.2;
  stroke-dasharray: 5 4;
}

.history-circle {
  fill: var(--node-fill);
  stroke: var(--node-stroke);
  stroke-width: 1.4;
}

.history-label {
  font-size: 11px;
  font-weight: 600;
  fill: var(--text);
}

.edge-path {
  fill: none;
  stroke: var(--edge);
  stroke-width: 1.4;
}

.edge-internal .edge-path {
  stroke-dasharray: 4 3;
}

.arrow-head {
  fill: var(--edge);
}

.edge-label-bg {
  fill: var(--label-bg);
  stroke: var(--border);
  stroke-width: 0.8;
}

.edge-label {
  font-family: "Inter", system-ui, -apple-system, "Segoe UI", Roboto, sans-serif;
  font-size: 11px;
  fill: var(--text);
  pointer-events: none;
}

.node.highlight .state-box,
.node.highlight .compound-box,
.node.highlight .parallel-box {
  stroke: var(--accent);
  stroke-width: 2.2;
}

@media (max-width: 720px) {
  .workspace {
    flex-direction: column;
  }
  .editor-pane {
    width: 100% !important;
    max-width: none;
    height: 40%;
    border-right: 0;
    border-bottom: 1px solid var(--border);
  }
  .splitter {
    display: none;
  }
  .brand-note {
    display: none;
  }
}