OK, finally made fonts generally nice.

index.html

@@ -79,14 +79,22 @@ function check_cuberoot(e) {
   start_round();
 }
 
-window.onload = function() {
+function make_text_readable() {
   if (screen.width <= 480) {
     document.body.style.fontSize = "8vw";
+    cuberoot.style = "font-size:8vw;";
   } else if (screen.width <= 1024) {
     document.body.style.fontSize = "6vw";
+    cuberoot.style = "font-size:6vw;";
+  } else {
+    document.body.style.fontSize = "48px";
+    cuberoot.style = "font-size:48px;";
   }
 }
 
+window.onload = make_text_readable;
+window.onresize = make_text_readable;
+
 start_round();
   </script>
   </body>