diff --git a/index.html b/index.html
index 13e4b6a..f4dd5ef 100644
--- a/index.html
+++ b/index.html
@@ -407,13 +407,15 @@ Promise.all([
 });
 
 let resizeTimer, lastWidth = 0;
-new ResizeObserver(entries => {
-  const w = Math.round(entries[0].contentRect.width);
+function onResize() {
+  const w = document.querySelector('main').clientWidth;
   if (w === lastWidth) return;
   lastWidth = w;
   clearTimeout(resizeTimer);
   resizeTimer = setTimeout(drawCharts, 120);
-}).observe(document.querySelector('main'));
+}
+new ResizeObserver(onResize).observe(document.querySelector('main'));
+addEventListener('resize', onResize);
 </script>
 </body>
 </html>