diff --git a/README.md b/README.md
index b600c7b..7e269a7 100644
--- a/README.md
+++ b/README.md
@@ -1,4 +1,24 @@
 # cssgrid
-Responsive CSS helper classes based on CSS Grid Layout.
+
+Responsive CSS helper classes based on [CSS3 Grid Layout module](https://www.w3.org/TR/css-grid-1/).
 
 View [demo](https://bordertech.github.io/cssgrid/demo).
+
+## Building
+
+Use [yarn](https://yarnpkg.com/) to build.
+
+1. `yarn install` (first time only)
+2. `yarn build`
+
+## IE support
+
+IE is kinda broke. We have some beginnings of support but it does not yet include any attempt to set the `-ms-grid-column` offsets or use margins instead of `grid-space`. The file `ie.scss` will be built as a separate file. There is a var which allows this same IE specific CSS to be built into the main CSS file if required.
+
+## Tests
+
+The tests are not really set up yet. The `/test/` directory contains a couple of primitive HTML pages which depend on the built CSS. This is still very much a work in progress.
+
+## Configuration
+
+Configuration is done through Sass variables. More info later!
diff --git a/sass/vars/_main.scss b/sass/vars/_main.scss
index 9f39150..867e082 100644
--- a/sass/vars/_main.scss
+++ b/sass/vars/_main.scss
@@ -20,6 +20,6 @@ $cg-gap-sm-m: ($cg-gap-m / 2) !default;
 $cg-gap-sm-l: ($cg-gap-l / 2) !default;
 
 // gaps on large viewports
-$cg-gap-sm-s: ($cg-gap-s * 2) !default;
-$cg-gap-sm-m: ($cg-gap-m * 2) !default;
-$cg-gap-sm-l: ($cg-gap-l * 2) !default;
+$cg-gap-lg-s: ($cg-gap-s * 2) !default;
+$cg-gap-lg-m: ($cg-gap-m * 2) !default;
+$cg-gap-lg-l: ($cg-gap-l * 2) !default;