Add parallax

src/page/background/background.ts

@@ -0,0 +1,24 @@
+import { PageElement } from "../../framework/page-element";
+import { createElement } from "../../framework/element-factory";
+import { generate } from "./background.html";
+
+export class PageBackground extends PageElement {
+  public constructor(
+    private speed: number,
+    count: number,
+    width: number,
+    probability: number,
+    color: string
+  ) {
+    super();
+    this.setElement(createElement(generate(count, probability, width, color)));
+  }
+
+  public onAfterLoad(parent: HTMLElement) {
+    window.addEventListener("scroll", () => {
+      this.getElement().style.transform = `translateY(-${window.scrollY *
+        this.speed}px)`;
+    });
+    super.onAfterLoad(parent);
+  }
+}