:root {
  --bg: #fbfaf8;
  --panel: #ffffff;
  --border: #e3e0da;
  --text: #24221f;
  --muted: #77736b;
  --keyword: #8a3ffc;
  --string: #1f7a4d;
  --number: #b45309;
  --comment: #8f8a80;
  --parameter: #0e7490;
  --label: #be185d;
  --error: #d92d20;
  --mono: ui-monospace, "SF Mono", "JetBrains Mono", Menlo, Consolas, monospace;
  color-scheme: light dark;
}

@media (prefers-color-scheme: dark) {
  :root {
    --bg: #181715;
    --panel: #201f1c;
    --border: #36342f;
    --text: #e9e6df;
    --muted: #a19c92;
    --keyword: #c4a3ff;
    --string: #7fd4a4;
    --number: #f5b26b;
    --comment: #847f75;
    --parameter: #67d4e8;
    --label: #f79bc8;
    --error: #ff7a6e;
  }
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  background: var(--bg);
  color: var(--text);
  font: 15px/1.5 system-ui, sans-serif;
}

header {
  display: flex;
  align-items: baseline;
  gap: 0.75rem;
  padding: 1rem 1.5rem;
  border-bottom: 1px solid var(--border);
}

h1 {
  margin: 0;
  font-size: 1.1rem;
}

#version {
  color: var(--muted);
  font-family: var(--mono);
  font-size: 0.85rem;
}

main {
  display: grid;
  grid-template-columns: minmax(0, 1fr) minmax(0, 1fr);
  gap: 1rem;
  padding: 1rem 1.5rem;
  height: calc(100vh - 3.6rem);
}

@media (max-width: 800px) {
  main {
    grid-template-columns: minmax(0, 1fr);
    height: auto;
    padding: 1rem;
  }
}

section {
  display: flex;
  flex-direction: column;
  min-height: 0;
  gap: 0.75rem;
}

/* A transparent textarea stacked on a highlighted <pre> with identical metrics. */
.editor {
  position: relative;
  flex: 1;
  min-height: 16rem;
  border: 1px solid var(--border);
  border-radius: 8px;
  background: var(--panel);
}

.editor > * {
  position: absolute;
  inset: 0;
  margin: 0;
  padding: 0.9rem 1rem;
  border: 0;
  overflow: auto;
  font: 14px/1.6 var(--mono);
  white-space: pre;
  tab-size: 2;
}

textarea {
  resize: none;
  background: transparent;
  color: transparent;
  caret-color: var(--text);
  outline: none;
}

textarea::selection {
  background: color-mix(in srgb, var(--keyword) 25%, transparent);
}

#highlight .keyword { color: var(--keyword); font-weight: 600; }
#highlight .string { color: var(--string); }
#highlight .number { color: var(--number); }
#highlight .comment { color: var(--comment); font-style: italic; }
#highlight .parameter { color: var(--parameter); }
#highlight .label { color: var(--label); }
#highlight .error {
  text-decoration: wavy underline var(--error);
  text-decoration-skip-ink: none;
  text-underline-offset: 3px;
}

#diagnostics {
  margin: 0;
  padding: 0;
  list-style: none;
  max-height: 10rem;
  overflow: auto;
}

#diagnostics li {
  padding: 0.4rem 0.6rem;
  border-left: 3px solid var(--error);
  background: color-mix(in srgb, var(--error) 8%, var(--panel));
  border-radius: 4px;
  margin-bottom: 0.4rem;
  font-size: 0.9rem;
}

#diagnostics button {
  font: inherit;
  font-family: var(--mono);
  color: var(--error);
  background: none;
  border: 0;
  padding: 0;
  cursor: pointer;
}

#diagnostics .note {
  color: var(--muted);
  padding-left: 1rem;
}

nav {
  display: flex;
  gap: 0.25rem;
}

nav button {
  font: inherit;
  color: var(--muted);
  background: none;
  border: 1px solid transparent;
  border-radius: 6px;
  padding: 0.25rem 0.75rem;
  cursor: pointer;
}

nav button[aria-selected="true"] {
  color: var(--text);
  border-color: var(--border);
  background: var(--panel);
}

#output {
  flex: 1;
  min-height: 16rem;
  margin: 0;
  padding: 0.9rem 1rem;
  overflow: auto;
  border: 1px solid var(--border);
  border-radius: 8px;
  background: var(--panel);
  font: 12.5px/1.5 var(--mono);
}