Mostly done

src/styles.scss

@@ -20,17 +20,20 @@
 }
 
 html {
-  background-color: white;
+  background-color: $background;
   height: 100%;
 }
 
 body {
   @include main-font();
-  margin: auto;
   height: 100%;
-  width: 100%;
 
   & > main {
+    noscript {
+      @include square(100%);
+      @include center-children();
+    }
+
     height: 100%;
     overflow-y: auto;
     overflow-x: hidden;
@@ -48,11 +51,6 @@ body {
         border-radius: $border-radius;
       }
     }
-
-    & > * {
-      width: $body-width;
-      margin: auto;
-    }
   }
 }
 
@@ -62,3 +60,9 @@ video {
   height: auto;
   object-fit: contain;
 }
+
+@media (max-width: $breakpoint-width) {
+  html {
+    font-size: 0.8em;
+  }
+}