add Block.tsx

src/ui/Duel/PlayMat2/Block.tsx

+import "@/styles/mat.css";
+
+import classnames from "classnames";
+import React from "react";
+
+export const Block: React.FC<{
+  isExtra?: boolean;
+  highlight?: boolean;
+}> = ({ isExtra = false, highlight = false }) => (
+  <div
+    className={classnames("block", {
+      "block-extra": isExtra,
+    })}
+    style={
+      {
+        "--highlight-on": highlight ? 1 : 0,
+      } as any
+    }
+  />
+);

src/ui/Duel/PlayMat2/index.ts

+export * from "./Block";
 export * from "./Card";