diff --git a/assets/css/_board.scss b/assets/css/_board.scss
index bd4f1c8..807ab12 100644
--- a/assets/css/_board.scss
+++ b/assets/css/_board.scss
@@ -1,19 +1,15 @@
 .board {
-  border: 0.3vmin solid black;
+  border: 0.3vmin solid $board-border-color;
+  height: 80vmin;
   margin: 0 auto;
   width: 80vmin;
-  height: 80vmin;
-}
-
-.board-rank {
 }
 
 .board-square {
-  border: 0.2vmin solid $square-outline-color;
-
-  background-size: 100%;
-  background-repeat: no-repeat;
   background-position: center;
+  background-repeat: no-repeat;
+  background-size: 100%;
+  border: 0.2vmin solid $square-outline-color;
 
   @each $colour in $colours {
     @each $piece in $pieces {
@@ -24,7 +20,7 @@
   }
 }
 
-%black-square {
+@mixin black-square {
   background-color: $black-square-color;
 
   &.selected {
@@ -33,7 +29,7 @@
   }
 }
 
-%white-square {
+@mixin white-square {
   background-color: $white-square-color;
 
   &.selected {
@@ -44,18 +40,20 @@
 
 .board-rank:nth-child(odd) {
   .board-square:nth-child(even) {
-    @extend %black-square;
+    @include black-square;
   }
+
   .board-square:nth-child(odd) {
-    @extend %white-square;
+    @include white-square;
   }
 }
 
 .board-rank:nth-child(even) {
   .board-square:nth-child(even) {
-    @extend %white-square;
+    @include white-square;
   }
+
   .board-square:nth-child(odd) {
-    @extend %black-square;
+    @include black-square;
   }
 }
diff --git a/assets/css/_layout.scss b/assets/css/_layout.scss
index 1506e7f..92e93f9 100644
--- a/assets/css/_layout.scss
+++ b/assets/css/_layout.scss
@@ -7,7 +7,10 @@ a {
   color: mix($background-color, $link-color, 30%);
 }
 
-h1, h2, h3, h4 {
+h1,
+h2,
+h3,
+h4 {
   font-variant: small-caps;
   font-weight: 300;
 }
@@ -17,8 +20,8 @@ h1 {
 }
 
 .container {
-  width: 80%;
   margin: 0 auto;
+  width: 80%;
 }
 
 .form-group {
diff --git a/assets/css/_variables.scss b/assets/css/_variables.scss
index fb66213..e96f4a0 100644
--- a/assets/css/_variables.scss
+++ b/assets/css/_variables.scss
@@ -3,13 +3,15 @@ $foreground-color: white;
 
 $link-color: #ffdd00;
 
+$board-border-color: #000;
+
 $board-square-size: 9vmin;
 $base-font-size: 16px;
 
 $black-square-color: #777;
 $white-square-color: #bbb;
 
-$selected-square-color: #66ff00;
+$selected-square-color: #6f0;
 
 $square-outline-color: darken($black-square-color, 20%);
 $selected-outline-color: lighten($selected-square-color, 20%);