:root {
  --bg: #ffffff; --fg: #1f2328; --muted: #59636e; --border: #d1d9e0;
  --panel: #f6f8fa; --accent: #0969da; --err: #cf222e; --err-bg: #ffebe9;
  --hl: #fff8c5;
  --mono: 14px/1.5 ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;
  color-scheme: light dark;
  font-family: system-ui, -apple-system, "Segoe UI", sans-serif;
}
@media (prefers-color-scheme: dark) {
  :root {
    --bg: #0d1117; --fg: #e6edf3; --muted: #9198a1; --border: #3d444d;
    --panel: #151b23; --accent: #4493f8; --err: #f85149; --err-bg: #3c1618;
    --hl: #4b3b0a;
  }
}
* { box-sizing: border-box; }
[hidden] { display: none !important; }
body { margin: 0; background: var(--bg); color: var(--fg); }
a { color: var(--accent); }
header { padding: 16px 24px 0; }
h1 { font-size: 1.4rem; margin: 0 0 4px; }
header p { margin: 0; color: var(--muted); }
main {
  display: grid; grid-template-columns: minmax(0, 2fr) minmax(0, 3fr);
  gap: 16px; padding: 16px 24px 24px;
}
@media (max-width: 900px) {
  header { padding: 16px 16px 0; }
  main { grid-template-columns: minmax(0, 1fr); padding: 16px; }
}
.input label { display: block; font-size: .85rem; color: var(--muted); margin-bottom: 4px; }
select { margin-bottom: 8px; max-width: 100%; font: inherit; }

/* The textarea sits over a mirror of its text; marks in the mirror show the
   error and hover ranges through the transparent textarea. */
.editor { position: relative; }
.editor textarea, .backdrop {
  font: var(--mono); padding: 10px; margin: 0; width: 100%;
  border: 1px solid var(--border); border-radius: 6px;
  white-space: pre-wrap; overflow-wrap: anywhere;
  scrollbar-gutter: stable;
}
.editor textarea {
  position: relative; display: block; height: 10rem; resize: vertical;
  background: transparent; color: var(--fg);
}
.backdrop {
  position: absolute; inset: 0;
  /* overflow:hidden ignores scrollbar-gutter; overflow:auto reserves the same
     gutter as the textarea. The scrollbar is kept (hiding it would drop the
     gutter) but painted transparent, and the element takes no input. */
  overflow: auto; pointer-events: none; scrollbar-color: transparent transparent;
  color: transparent; background: var(--panel); border-color: transparent;
}
.backdrop mark { color: transparent; border-radius: 2px; }
.backdrop mark.hl { background: var(--hl); }
.backdrop mark.err {
  background: transparent;
  text-decoration: underline wavy var(--err); text-decoration-skip-ink: none;
}
.backdrop mark.caret { background: transparent; border-left: 2px solid var(--err); margin-left: -1px; }

.banner { margin-top: 8px; padding: 8px 10px; border-radius: 6px; font-size: .9rem; overflow-wrap: anywhere; }
.banner.error { background: var(--err-bg); color: var(--err); }
#load-error { margin: 16px 24px 0; }

nav[role=tablist] { display: flex; flex-wrap: wrap; gap: 4px; border-bottom: 1px solid var(--border); }
nav button {
  font: inherit; background: none; border: none; cursor: pointer;
  border-bottom: 2px solid transparent; padding: 6px 10px; color: var(--muted);
}
nav button[aria-selected=true] { color: var(--fg); border-bottom-color: var(--accent); }
.pane {
  margin: 0; padding: 12px; min-height: 16rem; max-height: 70vh; overflow: auto;
  background: var(--panel); border: 1px solid var(--border); border-top: none;
  border-radius: 0 0 6px 6px; font: var(--mono); font-size: 13px;
}
#panes.stale .pane { opacity: .45; }
#listing .instr:hover { background: var(--hl); }
#graph svg { max-width: 100%; height: auto; }