Use percentages for main view flex-basis.

src/App.scss

@@ -243,13 +243,13 @@ nav {
 }
 
 .main {
-    flex: 2;
-    flex-basis: 500px;
+    flex: 1;
+    flex-basis: 65%;
 }
 
 .sidebar {
     flex: 1;
-    flex-basis: 300px;
+    flex-basis: 35%;
 }
 
 .mobile-shown {