Removed the border of code snippets.

assets/css/_colors/dark-syntax.scss

@@ -77,7 +77,6 @@
 
   /*-----  My styles ------*/
 
-  --code-highlighter-rouge: #272822;
   --highlight-bg-color: #272822;
   --highlighter-rouge-color: #de6b18;
 
@@ -85,7 +84,6 @@
   --highlight-lineno-border-color: #3c4042;
 
   .highlight {
-    @include highlight-box-shadow(none);
     .gp { color: #818c96; }
   }
   pre { color: #818c96 } /* override Bootstrap */

assets/css/_colors/light-syntax.scss

@@ -71,7 +71,6 @@
   .highlight .il { color: #009999 } /* Literal.Number.Integer.Long */
 
   /*--- custom light colors ---*/
-  --code-highlighter-rouge: #e9ecef;
   --highlight-bg-color: #f7f7f7;
   --highlighter-rouge-color: #353a3d;
   --highlight-lineno-color: #c2c6cc;

assets/css/_colors/light-typography.scss

@@ -30,7 +30,7 @@
 
   --text-muted-color: gray;
 
-  --tb-odd-bg: #f8f9fa;
+  --tb-odd-bg: #fbfcfd;
 
   --tb-even-border-color: rgba(210, 215, 217, 0.75);
 

assets/css/syntax.scss

@@ -12,12 +12,6 @@
 @import "_colors/dark-syntax";
 
 
-@mixin highlight-box-shadow($val) {
-  -moz-box-shadow: $val;
-  -webkit-box-shadow: $val;
-  box-shadow: $val;
-}
-
 html:not([mode]), html[mode=light] {
   @include light-syntax;
 }
@@ -56,12 +50,10 @@ html[mode=dark] {
 .highlight {
   @extend %code-snippet-radius;
   background: var(--highlight-bg-color);
-
   @at-root figure#{&} {
     background: var(--highlight-bg-color);
   }
   overflow: auto;
-  @include highlight-box-shadow(inset 0 0 2px #c2c6cc);
   .lineno {
     margin: .8rem 0rem;
     padding: 0 .5rem;
@@ -105,9 +97,8 @@ code {
   hyphens: none;
   &.highlighter-rouge {
     padding: 2px 4px;
-    margin: 0 .3rem;
+    margin: 0 .15rem;
     border-radius: 4px;
-    border: 1px solid var(--code-highlighter-rouge);
   }
   @at-root a>&.highlighter-rouge {
     padding-bottom: 0; // show link's underlinke