Max line width only in main section and add zen-gutters-reverse variable.

assets/sass/_variables.scss

@@ -128,6 +128,7 @@ $max-line-width: 70ch;
 
 // The default left/right gutter/padding.
 $zen-gutters: calc(5px + 1.5625vw);
+$zen-gutters-reverse: calc(0px - (5px + 1.5625vw));
 
 // Border radius.
 $s-radius: 3px;

assets/sass/reset/sections/_sections.scss

@@ -70,11 +70,13 @@ h6,
 
 // Set max text line width for redability.
 
-h2,
-h3,
-h4,
-h5,
-h6,
-p {
-  max-width: $max-line-width;
+.main {
+  h2,
+  h3,
+  h4,
+  h5,
+  h6,
+  p {
+    max-width: $max-line-width;
+  }
 }