コンテナ: widthの代わりにmax-widthを使用

_includes/style.scss

@@ -26,8 +26,9 @@ $selection-font-color: #fff;
 
 // コンテナ
 $container-box-shadow: 0 0 10px 0 #ddd;
+$container-columns: 30% 70%;
 $container-padding-top-mobile: 1em;
-$container-width: 80vw;
+$container-max-width: 1024px;
 
 // ヘッダ
 $header-background: #f2f2f2;

_sass/_container.scss

@@ -8,16 +8,16 @@
     box-shadow: $container-box-shadow;
     box-sizing: border-box;
     display: grid;
-    grid-template-columns: auto 1fr;
+    grid-template-columns: $container-columns;
     grid-template-rows: auto 1fr auto;
     // IE11 ~
     display: -ms-grid;
-    -ms-grid-columns: auto 1fr;
+    -ms-grid-columns: $container-columns;
     -ms-grid-rows: auto 1fr auto;
     // ~ IE11
     margin: 0 auto;
     min-height: 100vh;
-    width: $container-width;
+    max-width: $container-max-width;
 
     header {
       border-bottom: $border-default;