diff --git a/web/light9-timeline-audio.ts b/web/light9-timeline-audio.ts
--- a/web/light9-timeline-audio.ts
+++ b/web/light9-timeline-audio.ts
@@ -36,6 +36,7 @@ export class Light9TimelineAudio extends
           /* shouldn't be seen, but black is correct for 'no
          audio'. Maybe loading stripes would be better */
           background: #202322;
+          outline: 1px solid #333;
         }
         div {
           width: 100%;