@font-face {
  font-family: "Maple Mono";
  src: url("fonts/maple-mono-800.woff2") format("woff2");
  font-weight: 800;
  font-display: optional;
}

:root {
  color-scheme: dark;
  --font-label: "Maple Mono", ui-monospace, Menlo, Consolas, monospace;
  --bg: #0a0a0b;
  --card: #0e0e10;
  --ink: #e6e7e8;
  --muted: #8c8f93;
  --faint: #797b80;
  --line: #212325;
  --good: #6fbf8a;
  --bad: #d1706a;
}

* { box-sizing: border-box; }

html, body {
  height: 100%;
}

body {
  margin: 0;
  background: var(--bg);
  color: var(--ink);
  font-family: "Inter", -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
  font-size: 14.5px;
  display: flex;
  flex-direction: column;
}

code, pre, textarea, .mono {
  font-family: "JetBrains Mono", ui-monospace, Menlo, Consolas, monospace;
}

header {
  padding: 24px 28px;
  border-bottom: 1px solid var(--line);
  flex: 0 0 auto;
}

.brand h1 {
  margin: 0 0 6px;
  font-size: 19px;
  font-weight: 700;
  letter-spacing: -0.02em;
}

.brand p {
  margin: 0;
  color: var(--muted);
  max-width: 72ch;
  line-height: 1.6;
  font-size: 13.5px;
}

main {
  flex: 1 1 auto;
  min-height: 0;
  display: grid;
  grid-template-columns: minmax(380px, 1fr) minmax(500px, 1.4fr);
}

main > .editor-pane {
  border-right: 1px solid var(--line);
}

@media (max-width: 900px) {
  main { grid-template-columns: 1fr; height: auto; }
  main > .editor-pane { border-right: none; border-bottom: 1px solid var(--line); }
  body { height: auto; }
}

.editor-pane, .viz-pane {
  padding: 24px 28px;
  display: flex;
  flex-direction: column;
  gap: 14px;
  min-height: 0;
  overflow: auto;
}

.pane-header {
  display: flex;
  justify-content: space-between;
  align-items: baseline;
  color: var(--ink);
  font-family: var(--font-label);
  font-size: 12px;
  font-weight: 800;
  flex: 0 0 auto;
}

.pane-header::before {
  content: "# ";
  color: var(--faint);
  font-weight: 400;
}

.example-picker {
  display: flex;
  align-items: center;
  gap: 8px;
  font-family: "Inter", sans-serif;
  font-size: 13px;
  font-weight: 400;
  color: var(--muted);
}

textarea#source {
  width: 100%;
  flex: 1 1 auto;
  min-height: 220px;
  background: var(--card);
  border: 1px solid var(--line);
  border-radius: 10px;
  color: var(--ink);
  font-family: "JetBrains Mono", ui-monospace, Menlo, Consolas, monospace;
  font-weight: 400;
  font-size: 13.5px;
  line-height: 1.6;
  padding: 16px 18px;
  resize: none;
  tab-size: 2;
}

textarea#source:focus, select:focus, button:focus-visible {
  outline: 2px solid var(--ink);
  outline-offset: 2px;
}

.controls {
  display: flex;
  gap: 8px;
  flex-wrap: wrap;
  align-items: center;
  flex: 0 0 auto;
}

button, select {
  background: var(--card);
  color: var(--ink);
  border: 1px solid var(--line);
  border-radius: 7px;
  padding: 7px 13px;
  font-family: "Inter", sans-serif;
  font-size: 13px;
  font-weight: 500;
  cursor: pointer;
  transition: border-color 0.15s ease, color 0.15s ease;
}

button:hover { border-color: var(--muted); }
button:disabled { color: var(--faint); cursor: default; opacity: 0.5; }
button:disabled:hover { border-color: var(--line); }

.hint {
  color: var(--faint);
  font-size: 11px;
  margin-top: -6px;
}

button#btn-step, button#btn-run {
  color: var(--ink);
  border-color: var(--ink);
}

.speed {
  margin-left: auto;
  color: var(--muted);
  display: flex;
  gap: 7px;
  align-items: center;
  font-size: 13px;
}

.speed input[type="checkbox"] {
  accent-color: var(--ink);
  cursor: pointer;
}

pre#output {
  background: var(--card);
  border: 1px solid var(--line);
  border-radius: 10px;
  padding: 14px 18px;
  height: 110px;
  overflow: auto;
  margin: 0;
  white-space: pre-wrap;
  flex: 0 0 auto;
  line-height: 1.6;
  font-size: 13px;
}

#error {
  color: var(--bad);
  min-height: 1.2em;
  flex: 0 0 auto;
  font-size: 13px;
}

.viz-row {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 16px;
  flex: 0 0 auto;
}

.viz-box {
  display: flex;
  flex-direction: column;
  gap: 10px;
}

.viz-pane > .viz-box:last-child {
  flex: 1 1 auto;
  min-height: 360px;
}

pre#instr {
  margin: 0;
  color: var(--ink);
  font-size: 13px;
  min-height: 1.4em;
  white-space: pre-wrap;
  word-break: break-word;
}

#frames {
  display: flex;
  flex-direction: column;
  gap: 14px;
  overflow: auto;
  min-height: 90px;
  max-height: 260px;
}

.stack-group-label {
  font-family: var(--font-label);
  font-weight: 800;
  font-size: 10px;
  color: var(--faint);
  margin-bottom: 6px;
}

.stack-group.active .stack-group-label {
  color: var(--good);
}

.stack-group:not(.active) {
  opacity: 0.6;
}

.stack-frames {
  display: flex;
  flex-direction: column-reverse;
  gap: 7px;
}

.frame {
  border: 1px solid var(--line);
  border-radius: 8px;
  padding: 9px 11px;
  background: var(--card);
}

.stack-group.active .frame:first-child {
  border-color: var(--muted);
}

.frame .frame-title {
  color: var(--faint);
  font-size: 11px;
  margin-bottom: 7px;
  font-family: var(--font-label);
  font-weight: 800;
}

.frame .frame-stack {
  display: flex;
  gap: 6px;
  flex-wrap: wrap;
  min-height: 20px;
}

.frame .frame-stack:empty::after {
  content: "empty";
  color: var(--faint);
  font-size: 12px;
}

.slot {
  border: 1px solid var(--line);
  border-radius: 5px;
  padding: 2px 8px;
  font-size: 11px;
  font-family: var(--font-label);
  font-weight: 800;
  background: var(--bg);
}

svg#heap-graph {
  width: 100%;
  flex: 1 1 auto;
  min-height: 300px;
  background: var(--card);
  border: 1px solid var(--line);
  border-radius: 10px;
}

.heap-empty {
  fill: var(--faint);
  font-size: 12px;
  font-family: "Inter", sans-serif;
}

.heap-node circle {
  fill: var(--bg);
  stroke: var(--muted);
  stroke-width: 1.5;
}

.heap-node.marked circle {
  stroke: var(--good);
}

.heap-node.gone circle {
  stroke: var(--bad);
  stroke-dasharray: 3 2;
  opacity: 0.6;
}

.heap-node text {
  fill: var(--ink);
  font-size: 10px;
  font-family: var(--font-label);
  font-weight: 800;
  text-anchor: middle;
}

.heap-node .heap-kind {
  fill: var(--faint);
  font-size: 9px;
  font-weight: 800;
}

.heap-edge {
  stroke: var(--faint);
  stroke-width: 1;
  fill: none;
  opacity: 0.7;
}

.legend {
  display: flex;
  gap: 16px;
  color: var(--muted);
  font-size: 12px;
  flex: 0 0 auto;
}

.legend span {
  display: inline-flex;
  align-items: center;
  gap: 6px;
}

.legend .dot {
  width: 8px;
  height: 8px;
  border-radius: 50%;
  border: 1.5px solid var(--muted);
  display: inline-block;
}

.legend .dot.marked { border-color: var(--good); }
.legend .dot.gone { border-color: var(--bad); border-style: dashed; }