Derivatives sound like a highpass filter.

tsconfig.json

@@ -0,0 +1,16 @@
+{
+    // Change this to match your project
+    "include": ["src/game.js"],
+
+    "compilerOptions": {
+        // Tells TypeScript to read JS files, as normally they are ignored as source files
+        "allowJs": true,
+        // Generate d.ts files
+        "declaration": true,
+        // This compiler run should only output d.ts files
+        "emitDeclarationOnly": true,
+        // Types should go into this directory.
+        // Removing this would place the definition files next to the .js files
+        "outDir": "dist",
+    }
+}