Special halvening block and fireworks.

fixes #50

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

@@ -1,5 +1,6 @@
 import { Component, OnInit } from '@angular/core';
 import { WebsocketService } from 'src/app/services/websocket.service';
+import { StateService } from 'src/app/services/state.service';
 
 @Component({
   selector: 'app-start',
@@ -9,11 +10,24 @@ import { WebsocketService } from 'src/app/services/websocket.service';
 export class StartComponent implements OnInit {
   view: 'blocks' | 'transactions' = 'blocks';
 
+  isHalveningeEvent = false;
+
   constructor(
     private websocketService: WebsocketService,
+    private stateService: StateService,
   ) { }
 
   ngOnInit() {
     this.websocketService.want(['blocks', 'stats', 'mempool-blocks']);
+
+    this.stateService.blocks$
+      .subscribe((block) => {
+        if (block.height % 210000 === 0) {
+          this.isHalveningeEvent = true;
+          setTimeout(() => {
+            this.isHalveningeEvent = false;
+          }, 60 * 60 * 1000);
+        }
+      });
   }
 }