Apply 2-column layout to "systems" in mobile

Author: nattyo1226

src/styles/top.scss

@@ -99,7 +99,7 @@
     grid-template-columns: repeat(2, 1fr);
   }
   @media (max-width: 640px) {
-    grid-template-columns: 1fr;
+    gap: 0.5em;
   }
 
   & > li > a {
@@ -109,6 +109,10 @@
     color: color.$black-gray;
     text-align: center;
 
+    @media (max-width: 640px) {
+      font-size: 0.75rem;
+    }
+
     // ロゴ画像・Material Icons
     & > img,
     & > span.material-icon {