:root {
  --bg: #f4f5f7;
  --surface: #ffffff;
  --surface-2: #f8f9fb;
  --border: #dde1e7;
  --text: #1b2230;
  --text-muted: #5f6b7a;
  --accent: #2f6fd6;
  --accent-contrast: #ffffff;
  --error: #c0392b;
  --warning: #a56a00;

  --canvas: #fbfcfd;
  --grid: #eceff3;
  --edge: #3d4550;
  --action-fill: #eef3fb;
  --action-stroke: #3d5a80;
  --diamond-fill: #fdf6e3;
  --diamond-stroke: #9a6b12;
  --loop-fill: #e3f3ef;
  --loop-stroke: #1d7a6b;
  --terminal: #1b2230;
  --guard: #5b4a8a;
  --frame: #8a93a0;
  --highlight: #2f6fd6;

  --mono: ui-monospace, "Cascadia Code", "Consolas", "SF Mono", Menlo, monospace;
  --sans: system-ui, -apple-system, "Segoe UI", Roboto, sans-serif;
  color-scheme: light;
}

@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) {
    --bg: #111418;
    --surface: #181c21;
    --surface-2: #1e232a;
    --border: #2c333c;
    --text: #e3e7ec;
    --text-muted: #97a2b0;
    --accent: #6a9ef0;
    --accent-contrast: #0d1117;
    --error: #ff7b6b;
    --warning: #e0a940;

    --canvas: #14181d;
    --grid: #1c2127;
    --edge: #b5bec9;
    --action-fill: #1f2b3d;
    --action-stroke: #7ea3d8;
    --diamond-fill: #2e2716;
    --diamond-stroke: #d5a54a;
    --loop-fill: #12302b;
    --loop-stroke: #4cc2ac;
    --terminal: #e3e7ec;
    --guard: #b9a8ea;
    --frame: #5d6773;
    --highlight: #6a9ef0;
    color-scheme: dark;
  }
}

:root[data-theme="dark"] {
  --bg: #111418;
  --surface: #181c21;
  --surface-2: #1e232a;
  --border: #2c333c;
  --text: #e3e7ec;
  --text-muted: #97a2b0;
  --accent: #6a9ef0;
  --accent-contrast: #0d1117;
  --error: #ff7b6b;
  --warning: #e0a940;

  --canvas: #14181d;
  --grid: #1c2127;
  --edge: #b5bec9;
  --action-fill: #1f2b3d;
  --action-stroke: #7ea3d8;
  --diamond-fill: #2e2716;
  --diamond-stroke: #d5a54a;
  --loop-fill: #12302b;
  --loop-stroke: #4cc2ac;
  --terminal: #e3e7ec;
  --guard: #b9a8ea;
  --frame: #5d6773;
  --highlight: #6a9ef0;
  color-scheme: dark;
}

* { box-sizing: border-box; }

html, body { height: 100%; }

body {
  margin: 0;
  display: flex;
  flex-direction: column;
  background: var(--bg);
  color: var(--text);
  font: 14px/1.45 var(--sans);
}

.visually-hidden {
  position: absolute; width: 1px; height: 1px; overflow: hidden;
  clip: rect(0 0 0 0); white-space: nowrap;
}

button, select {
  font: inherit;
  color: var(--text);
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 6px;
  padding: 5px 11px;
  cursor: pointer;
}
button:hover, select:hover { border-color: var(--text-muted); }
button:focus-visible, select:focus-visible, textarea:focus-visible, .viewport:focus-visible {
  outline: 2px solid var(--accent);
  outline-offset: 1px;
}
button.link {
  border: 0; background: none; padding: 0;
  color: var(--accent); font-size: 12px;
}

/* ------------------------------------------------------------ top bar */

.topbar {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: space-between;
  gap: 8px 16px;
  padding: 10px 16px;
  background: var(--surface);
  border-bottom: 1px solid var(--border);
}
.toolbar { display: flex; flex-wrap: wrap; align-items: center; gap: 6px; }
.version {
  margin-right: 6px;
  color: var(--text-muted);
  font-size: 12px;
  font-variant-numeric: tabular-nums;
}

.icon-button {
  display: inline-flex; align-items: center; justify-content: center;
  width: 34px; padding: 5px 0;
}
.icon-button svg {
  display: block;
  fill: none; stroke: currentColor; stroke-width: 1.8;
  stroke-linecap: round; stroke-linejoin: round;
}
/* The toggle shows the theme it switches *to*: a moon in light mode, a sun in dark. */
.icon-button .icon-sun { display: none; }
:root[data-theme="dark"] .icon-button .icon-sun { display: block; }
:root[data-theme="dark"] .icon-button .icon-moon { display: none; }
@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) .icon-button .icon-sun { display: block; }
  :root:not([data-theme="light"]) .icon-button .icon-moon { display: none; }
}

/* ---------------------------------------------------------- workspace */

.workspace {
  flex: 1;
  min-height: 0;
  display: grid;
  /* --editor-w is set by dragging the divider (js/app.js). */
  grid-template-columns: var(--editor-w, minmax(300px, 38%)) 7px minmax(0, 1fr);
}

.pane { min-width: 0; min-height: 0; display: flex; flex-direction: column; }

.editor-pane { background: var(--surface); }

/* Drag handle between the editor and the diagram: a 1px rule in a 7px grab area. */
.divider {
  position: relative;
  cursor: col-resize;
  touch-action: none;
  background: var(--canvas);
}
.divider::before {
  content: "";
  position: absolute; top: 0; bottom: 0; left: 0;
  width: 1px;
  background: var(--border);
  transition: background 0.15s, width 0.15s;
}
.divider:hover::before,
.divider:focus-visible::before,
.divider.dragging::before { width: 3px; background: var(--accent); }
.divider:focus-visible { outline: none; }
body.resizing { cursor: col-resize; user-select: none; }

.pane-head {
  display: flex; justify-content: space-between; align-items: center;
  padding: 8px 14px;
  font-size: 12px; font-weight: 600; text-transform: uppercase; letter-spacing: 0.06em;
  color: var(--text-muted);
  border-bottom: 1px solid var(--border);
}
.pane-head .link { text-transform: none; letter-spacing: 0; font-weight: 500; }

.syntax {
  padding: 10px 14px;
  font-size: 12.5px;
  background: var(--surface-2);
  border-bottom: 1px solid var(--border);
  max-height: 40%;
  overflow: auto;
}
.syntax table { border-collapse: collapse; width: 100%; }
.syntax td { padding: 3px 8px 3px 0; vertical-align: top; }
.syntax td:first-child { white-space: nowrap; }
.syntax p { margin: 8px 0 0; color: var(--text-muted); }
code { font-family: var(--mono); font-size: 0.95em; }

.editor {
  flex: 1;
  min-height: 0;
  display: flex;
  font: 13px/20px var(--mono);
}
.editor, .editor textarea {
  font-variant-ligatures: none; /* show `>=` and `<-` exactly as typed */
}
.gutter {
  margin: 0;
  padding: 10px 8px 10px 12px;
  min-width: 44px;
  text-align: right;
  color: var(--text-muted);
  opacity: 0.7;
  user-select: none;
  overflow: hidden;
  background: var(--surface-2);
  border-right: 1px solid var(--border);
  font: inherit;
}
.gutter .err { color: var(--error); opacity: 1; font-weight: 700; }
.gutter .warn { color: var(--warning); opacity: 1; font-weight: 700; }
textarea {
  flex: 1;
  min-width: 0;
  margin: 0;
  padding: 10px 12px;
  border: 0;
  resize: none;
  font: inherit;
  color: var(--text);
  background: var(--surface);
  tab-size: 4;
  white-space: pre;
  overflow: auto;
}
textarea:focus-visible { outline-offset: -2px; }

.problems {
  max-height: 30%;
  overflow: auto;
  border-top: 1px solid var(--border);
  font-size: 12.5px;
}
.problems:empty { display: none; }
.problems button {
  display: flex; gap: 8px; width: 100%;
  text-align: left; border: 0; border-radius: 0;
  padding: 5px 14px; background: none;
}
.problems button:hover { background: var(--surface-2); }
.problems .sev { font-weight: 600; min-width: 56px; }
.problems .error .sev { color: var(--error); }
.problems .warning .sev { color: var(--warning); }
.problems .loc { color: var(--text-muted); min-width: 48px; }

/* ------------------------------------------------------------ diagram */

.diagram-pane { position: relative; }

.viewport {
  flex: 1;
  min-height: 0;
  overflow: hidden;
  cursor: grab;
  touch-action: none;
  background-color: var(--canvas);
  background-image: radial-gradient(var(--grid) 1.2px, transparent 1.2px);
  background-size: 18px 18px;
}
.viewport.panning { cursor: grabbing; }
.stage { transform-origin: 0 0; width: max-content; }

.zoom {
  position: absolute; right: 16px; bottom: 16px;
  display: flex; gap: 4px;
  padding: 4px;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 8px;
  box-shadow: 0 2px 8px rgb(0 0 0 / 0.08);
}
.zoom button { padding: 3px 10px; min-width: 32px; }
.zoom-level { min-width: 58px !important; font-variant-numeric: tabular-nums; }

.toast {
  position: absolute; left: 50%; bottom: 16px; transform: translateX(-50%);
  padding: 6px 12px; border-radius: 6px;
  background: var(--text); color: var(--bg);
  font-size: 13px;
  opacity: 0; pointer-events: none; transition: opacity 0.2s;
}
.toast.show { opacity: 1; }

/* SVG diagram (classes emitted by js/render.js) */
.p2u-diagram { display: block; font-family: var(--sans); font-size: 13px; overflow: visible; }
.p2u-edge { fill: none; stroke: var(--edge); stroke-width: 1.4; }
.p2u-arrowhead { fill: none; stroke: var(--edge); stroke-width: 1.4; stroke-linejoin: round; }
.p2u-action rect { fill: var(--action-fill); stroke: var(--action-stroke); stroke-width: 1.4; }
.p2u-action text, .p2u-decision text { fill: var(--text); }
.p2u-decision polygon, .p2u-merge polygon { fill: var(--diamond-fill); stroke: var(--diamond-stroke); stroke-width: 1.4; }
.p2u-loop polygon { fill: var(--loop-fill); stroke: var(--loop-stroke); }
.p2u-loop .p2u-inner { fill: none; stroke-width: 1; }
.p2u-loop-edge, .p2u-arrowhead-loop { stroke: var(--loop-stroke); }
.p2u-initial circle, .p2u-final-dot { fill: var(--terminal); }
.p2u-final-ring { fill: var(--canvas); stroke: var(--terminal); stroke-width: 1.5; }
.p2u-guard { fill: var(--guard); font-size: 12px; }
.p2u-value { fill: var(--text); font-weight: 600; }
.p2u-frame rect, .p2u-frame-tab { fill: none; stroke: var(--frame); stroke-width: 1.2; }
.p2u-frame-title { fill: var(--text); font-size: 14px; font-weight: 600; }

.p2u-rake { fill: none; stroke: var(--action-stroke); stroke-width: 1.4; stroke-linecap: round; }
.p2u-call-edge, .p2u-arrowhead-call { stroke: var(--guard); }
.p2u-call-edge { stroke-dasharray: 5 4; }

/* Hovering a loop or a call dims everything outside it (see js/app.js). */
.p2u-node, .p2u-edge, .p2u-guard, .p2u-frame { transition: opacity 0.15s ease; }
.focus .p2u-node:not(.in-focus),
.focus .p2u-edge:not(.in-focus),
.focus .p2u-guard:not(.in-focus),
.focus .p2u-frame:not(.in-focus) { opacity: 0.18; }

.p2u-node[data-line], .p2u-frame-title { cursor: pointer; }
.p2u-node[data-line]:hover rect,
.p2u-node[data-line]:hover polygon,
.p2u-node.active rect,
.p2u-node.active polygon,
.p2u-node.active .p2u-final-ring { stroke: var(--highlight); stroke-width: 2.4; }
.p2u-frame:hover rect,
.p2u-frame:hover .p2u-frame-tab,
.p2u-frame.active rect,
.p2u-frame.active .p2u-frame-tab { stroke: var(--highlight); stroke-width: 2; }

/* ------------------------------------------------------------- mobile */

@media (max-width: 760px) {
  body { height: auto; min-height: 100%; }
  .workspace { grid-template-columns: 1fr; grid-template-rows: minmax(320px, 45vh) minmax(420px, 60vh); }
  .editor-pane { border-bottom: 1px solid var(--border); }
  .divider { display: none; }
  .topbar { padding: 10px 16px; }
}