diff --git a/sim/visuals/microbit.ts b/sim/visuals/microbit.ts
index 6ca2f35e..99f01e2f 100644
--- a/sim/visuals/microbit.ts
+++ b/sim/visuals/microbit.ts
@@ -162,6 +162,9 @@ namespace pxsim.visuals {
         }
     `;
     const MB_HIGHCONTRAST = `
+svg.sim {
+    border: solid white 0.15em;
+}
 .sim-led {
     stroke: red;
 }