Rewrite post’s style as sass.

assets/css/post.scss

@@ -1,13 +1,16 @@
 ---
 ---
 /*!
-  Individual styles for Post
+  Post-specific style
   v2.0
   https://github.com/cotes2020/jekyll-theme-chirpy
   © 2019 Cotes Chung
   MIT License
 */
 
+$prompt-older: "{{ site.data.label.post.button.previous }}";
+$prompt-newer: "{{ site.data.label.post.button.next }}";
+
 .post img {
   margin-top: .5rem;
   margin-bottom: 1.5rem;
@@ -27,20 +30,21 @@
   font-size: 0.85rem;
 }
 
-$prompt-older: "{{ site.data.label.post.button.previous }}";
-$prompt-newer: "{{ site.data.label.post.button.next }}";
-
 .post-navigation {
   padding-top: 3rem;
   padding-bottom: 2rem;
 
-  .btn, .btn.disabled {
+  @mixin post-nav-btn {
     width: 50%;
     position: relative;
-    color: var(--link-color, #2a408e);
     border-color: var(--main-border, #e9ecef);
   }
 
+  .btn {
+    @include post-nav-btn;
+    color: var(--link-color, #2a408e);
+  }
+
   .btn:hover {
     background: #2a408e;
     color: #fff;
@@ -48,11 +52,15 @@ $prompt-newer: "{{ site.data.label.post.button.next }}";
   }
 
   .btn.disabled {
+    @include post-nav-btn;
     pointer-events: auto;
     cursor: not-allowed;
     background: none;
     color: gray;
-    // border-color: var(--main-border, #e9ecef);
+  }
+
+  .btn.disabled:hover {
+    border-color: none;
   }
 
   .btn.btn-outline-primary.disabled:focus {
@@ -146,30 +154,30 @@ $prompt-newer: "{{ site.data.label.post.button.next }}";
   font-family: 'Oswald', sans-serif;
 }
 
-#related-posts .card {
+#related-posts {
+  .card {
     border: 1px solid var(--main-wrapper-bg, #f1f1f1);
     background-color: var(--card-bg);
     box-shadow: 0 0 5px 0 var(--main-wrapper-bg, rgba(234, 234, 234, 0.7686274509803922));
-  -webkit-transition: all .3s ease-in-out;;
-  -moz-transition: all .3s ease-in-out;;
+    -webkit-transition: all .3s ease-in-out;
+    -moz-transition: all .3s ease-in-out;
     transition: all .3s ease-in-out;
+    h3 {
+      color: var(--relate-post-title, #353a3d);
+    }
   }
 
-#related-posts .card:hover {
+  .card:hover {
     -webkit-transform: translate3d(0, -3px, 0);
     transform: translate3d(0, -3px, 0);
     filter: drop-shadow(2px 4px 6px rgba(0, 0, 0, 0.08));
   }
 
-#related-posts .card h3 {
-  color: var(--relate-post-title, #353a3d);
-}
-
-#related-posts .timeago {
+  .timeago {
     color: var(--text-muted-color, rgba(30, 55, 70, .4));
   }
 
-#related-posts p {
+  p {
     font-size: .9rem;
     margin-bottom: .5rem;
     overflow: hidden;
@@ -179,16 +187,16 @@ $prompt-newer: "{{ site.data.label.post.button.next }}";
     -webkit-box-orient: vertical;
   }
 
-#related-posts a:hover {
+  a:hover {
     text-decoration: none;
   }
 
-#related-posts ul {
+  ul {
     list-style-type: none;
     padding-inline-start: 1.5rem;
   }
 
-#related-posts ul > li::before {
+  ul>li::before {
     background: #c2c9d4;
     width: 5px;
     height: 5px;
@@ -199,6 +207,7 @@ $prompt-newer: "{{ site.data.label.post.button.next }}";
     top: 1rem;
     right: 1rem;
   }
+}
 
 #post-extend-wrapper {
   min-height: 2rem;
@@ -208,17 +217,43 @@ $prompt-newer: "{{ site.data.label.post.button.next }}";
   color: inherit;
 }
 
-.share-wrapper a:hover,
-.share-wrapper i:hover {
+.share-wrapper {
+  vertical-align: middle;
+  user-select: none;
+
+  a:hover,
+  i:hover {
     text-decoration: none;
     color: var(--link-color, #2a408e)!important;
   }
 
-.share-wrapper {
-  vertical-align: middle;
-  user-select: none;
+  .share-icon {
+    font-size: 1.2rem;
+
+    .fab.fa-twitter {
+      color: var(--btn-sharing, rgba(29, 161, 242, 1.00));
     }
 
+    .fab.fa-facebook-square {
+      color: var(--btn-sharing, rgb(66, 95, 156));
+    }
+    .fab.fa-telegram {
+      color: var(--btn-sharing, rgb(39, 159, 217));
+    }
+
+    .fab.fa-weibo {
+      color: var(--btn-sharing, rgb(229, 20, 43));
+    }
+
+  } // .share-icon
+
+  .fas.fa-link {
+    color: var(--btn-sharing, rgb(171, 171, 171));
+  }
+
+} // .share-wrapper
+
+
 .share-label {
   font-family: 'Oswald', sans-serif;
 }
@@ -227,45 +262,22 @@ $prompt-newer: "{{ site.data.label.post.button.next }}";
   content: ":";
 }
 
-.share-wrapper .share-icon {
-  font-size: 1.2rem;
-}
+.license-wrapper {
+  line-height: 1.2rem;
 
-.share-wrapper .share-icon .fab.fa-twitter {
-  color: var(--btn-sharing, rgba(29,161,242,1.00));
-}
-
-.share-wrapper .share-icon .fab.fa-facebook-square {
-  color: var(--btn-sharing, rgb(66, 95, 156));
-}
-
-.share-wrapper .share-icon .fab.fa-telegram {
-  color: var(--btn-sharing, rgb(39, 159, 217));
-}
-
-.share-wrapper .share-icon .fab.fa-weibo {
-  color: var(--btn-sharing, rgb(229, 20, 43));
-}
-
-.share-wrapper .fas.fa-link {
-  color: var(--btn-sharing, rgb(171, 171, 171));
-}
-
-.license-wrapper .license-text>a {
+  .license-text>a {
     font-weight: 600;
   }
 
-.license-wrapper {
-  line-height: 1.2rem;
-}
-
-.license-wrapper i {
+  i {
     font-weight: 400;
   }
 
-.license-wrapper span:last-child {
+  span:last-child {
     font-size: .85rem;
   }
+} // .license-wrapper
+
 
 @media all and (max-width: 576px) {
   .post-tail-bottom {
@@ -327,7 +339,8 @@ $prompt-newer: "{{ site.data.label.post.button.next }}";
 }
 
 /*
-  The following resposive design aim to make #post-extend-wrapper margin-right same as pannel's width
+  The following resposive design aim to
+  make #post-extend-wrapper margin-right same as pannel's width
 */
 @media all and (min-width: 1200px) {
   #post-extend-wrapper {