implement very simple demo mode

frontend/src/app/components/start/start.component.ts

@@ -3,6 +3,8 @@ import { Subscription } from 'rxjs';
 import { MarkBlockState, StateService } from '../../services/state.service';
 import { specialBlocks } from '../../app.constants';
 import { BlockExtended } from '../../interfaces/node-api.interface';
+import { Router } from '@angular/router';
+import { sleep$ } from '../../shared/common.utils';
 
 @Component({
   selector: 'app-start',
@@ -61,6 +63,7 @@ export class StartComponent implements OnInit, AfterViewChecked, OnDestroy {
   constructor(
     public stateService: StateService,
     private cd: ChangeDetectorRef,
+    private router: Router
   ) {
     this.isiOS = ['iPhone','iPod','iPad'].includes((navigator as any)?.userAgentData?.platform || navigator.platform);
     if (this.stateService.network === '') {
@@ -68,7 +71,27 @@ export class StartComponent implements OnInit, AfterViewChecked, OnDestroy {
     }
   }
 
+  async demoMode() {
+    // @ts-ignore
+    if (!window.demoMode) {
+      // @ts-ignore
+      window.demoMode = true;
+      const paths = ['', 'acceleration', 'mining', 'graphs'];
+      let i = 0;
+      while ('Bitcoin is still alive') {
+        i = (i + 1) % paths.length;
+        this.router.navigateByUrl(paths[i]);
+        await sleep$(30000);
+      }
+    }
+  }
+
   ngOnInit() {
+    // @ts-ignore
+    if (window.location.search === '?demo=1') {
+      this.demoMode();
+    }
+
     this.firstPageWidth = 40 + (this.blockWidth * this.dynamicBlocksAmount);
     this.blockCounterSubscription = this.stateService.blocks$.subscribe((blocks) => {
       this.blockCount = blocks.length;

frontend/src/app/shared/common.utils.ts

@@ -226,6 +226,14 @@ export function insecureRandomUUID(): string {
   return uuid.slice(0, -1);
 }
 
+export function sleep$(ms: number): Promise<void> {
+  return new Promise((resolve) => {
+     setTimeout(() => {
+       resolve();
+     }, ms);
+  });
+}
+
 // https://stackoverflow.com/a/60467595
 export function md5(inputString): string {
     var hc="0123456789abcdef";