diff --git a/js/play_browser/src/App.css b/js/play_browser/src/App.css
index 3aac9a9f1..31e36bd2f 100644
--- a/js/play_browser/src/App.css
+++ b/js/play_browser/src/App.css
@@ -49,6 +49,11 @@ span.stats {
   float: right;
 }
 
+canvas {
+  aspect-ratio: 4 / 3;
+  width: 100%
+}
+
 .global-row {
   display: flex;
 }