Revert "Remove position: sticky polyfill"

This reverts commit 6ab127f293.

_assets/css/_archive.scss

@@ -6,8 +6,6 @@
   margin-bottom: 2em;
   @include breakpoint($medium) {
     @include span(10 of 12 last);
-  }
-  @include breakpoint($large) {
     @include suffix(3 of 12);
   }
 }

_assets/css/_page.scss

@@ -3,7 +3,6 @@
    ========================================================================== */
 
 #main {
-  position: relative;
   @include container;
   @include clearfix;
   margin-top: 2em;
@@ -14,8 +13,6 @@
 .page {
   @include breakpoint($medium) {
     @include span(10 of 12 last);
-  }
-  @include breakpoint($large) {
     padding-right: $right-sidebar-width;
   }
 }
@@ -26,6 +23,7 @@
 }
 
 .page__content {
+  position: relative;
   p, li {
     font-size: 16px;
   }

_assets/css/_toc.scss

@@ -8,12 +8,15 @@
   color: $gray;
   text-transform: uppercase;
   letter-spacing: 1px;
-  @include breakpoint($large) {
-    position: absolute;
-    top: 0;
-    right: calc(50% - 512px + 2em); // 50% - 1/2 of wrapper's max-width + wrapper padding
-    width: $right-sidebar-width;
-    padding-left: 2em;
+  background-color: #fff;
+  &.sticky {
+    @include breakpoint($large) {
+      position: fixed;
+      top: 0;
+      right: calc(50% - 512px + 2em); // 50% - 1/2 of wrapper's max-width + wrapper padding
+      width: $right-sidebar-width;
+      padding-left: 2em;
+    }
   }
 }
 
@@ -33,7 +36,6 @@
   padding: 0;
   width: 100%;
   list-style: none;
-  background-color: #fff;
   border: 1px solid $border-color;
   border-top: none;
   border-bottom-right-radius: $border-radius;

_assets/css/_utilities.scss

@@ -152,6 +152,26 @@ body:hover .visually-hidden button {
 }
 
 
+/*
+   Sticky, fixed to top content
+   ========================================================================== */
+
+.sticky {
+  > * {
+    display: none;
+  }
+  @include breakpoint($small) {
+    @include clearfix();
+    position: -webkit-sticky;
+    position: sticky;
+    top: 3em;
+    > * {
+      display: block;
+    }
+  }
+}
+
+
 /*
    Wells
    ========================================================================== */

_assets/css/_variables.scss

@@ -92,10 +92,10 @@ $susy: (
   gutter-position: after,
   container: $large,
   global-box-sizing: border-box,
-  // debug: (
-  //   image: show,
-  //   color: blue,
-  //   output: overlay,
-  //   toggle: top right,
-  // ),
+  debug: (
+    image: show,
+    color: blue,
+    output: overlay,
+    toggle: top right,
+  ),
 );