diff --git a/frontend/js/labs/periodic.js b/frontend/js/labs/periodic.js
index bb60c88..535ef96 100644
--- a/frontend/js/labs/periodic.js
+++ b/frontend/js/labs/periodic.js
@@ -507,11 +507,9 @@ class PeriodicTableSim {
       const div = this._cellMap[el.Z];
       if (!div) continue;
       if (el.Z === Z) {
-        div.style.outline = '2px solid #fff';
-        div.style.outlineOffset = '1px';
+        div.style.boxShadow = 'inset 0 0 0 2px #fff';
       } else {
-        div.style.outline = '';
-        div.style.outlineOffset = '';
+        div.style.boxShadow = '';
       }
     }
     this._updateCard(ELEMENTS.find(e => e.Z === Z));
@@ -612,7 +610,7 @@ class PeriodicTableSim {
       this._updateCard(null);
       for (const e2 of ELEMENTS) {
         const div = this._cellMap[e2.Z];
-        if (div) { div.style.outline = ''; div.style.outlineOffset = ''; }
+        if (div) { div.style.boxShadow = ''; div.style.outline = ''; div.style.outlineOffset = ''; }
       }
     });