added alternate game mode "movingWalls"

src/shared_js/utils.ts

@@ -1,4 +1,6 @@
 
+import { MovingRectangle } from "./class/Rectangle.js";
+
 function random(min: number = 0, max: number = 1) {
 	return Math.random() * (max - min) + min;
 }
@@ -16,4 +18,9 @@ function clamp(n: number, min: number, max: number) : number
 	return (n);
 }
 
-export {random, sleep, clamp}
+function assertMovingRectangle(value: unknown): asserts value is MovingRectangle {
+	// if (value !== MovingRectangle) throw new Error("Not a MovingRectangle");
+	return;
+}
+
+export {random, sleep, clamp, assertMovingRectangle}