try to use system sans-serif font

static/css/style.css

@@ -3,7 +3,7 @@
 
 body {
     font-size: 1.2em;
-    font-family: 'Droid Sans', sans-serif;
+    font-family: -apple-system, BlinkMacSystemFont, avenir next, avenir, segoe ui, helvetica neue, helvetica, Ubuntu, roboto, noto, arial, sans-serif;
     margin: 0px;
     padding: 0px;
 }