🎉 containersを追加

scss/elements/_index.scss

@@ -1,3 +1,4 @@
 @charset "utf-8";
 
 @import "buttons.scss";
+@import "containers.scss";

scss/elements/containers.scss

@@ -0,0 +1,68 @@
+.container {
+  position: relative;
+  padding: 1.5rem 2rem;
+
+  &::before,
+  &::after {
+    position: absolute;
+    z-index: -1;
+    content: "";
+  }
+
+  &::before {
+    top: 0;
+    right: 0;
+    bottom: 0;
+    left: 0;
+  }
+
+  &::after {
+    top: 2px;
+    right: 2px;
+    bottom: 2px;
+    left: 2px;
+    border-color: $base-color;
+    border-style: solid;
+    border-width: 4px;
+    border-radius: 4px;
+  }
+
+  &.with-title {
+    display: flex;
+    flex-direction: column;
+    justify-content: flex-start;
+    padding-top: 2rem;
+
+    > .title {
+      position: absolute;
+      top: 0;
+      padding: 0 0.5rem;
+      margin: 0;
+      font-size: 1rem;
+      background-color: $background-color;
+    }
+
+    &.is-center {
+      align-items: center;
+    }
+
+    &.is-right {
+      align-items: right;
+    }
+  }
+
+  &.is-dark {
+    &::before {
+      background-color: $base-color;
+    }
+
+    &::after {
+      border-color: #fff;
+    }
+
+    > .title {
+      color: $background-color;
+      background-color: $base-color;
+    }
+  }
+}