Halloween Event (#2285)

## Description:

Changed theme colors for an "autumn" ambiance:

<img width="395" height="254" alt="image"
src="https://github.com/user-attachments/assets/67bd07d3-e74b-49e2-ba0b-c87958767d45"
/>

Changed structures pixel art:

<img width="756" height="605" alt="image"
src="https://github.com/user-attachments/assets/5158ae81-0641-413c-8862-367259496a9a"
/>


Change existing FX with new halloween-themed ones:


https://github.com/user-attachments/assets/fb99be49-43cd-4d85-ad77-8c153070edaf

Added new FX playing randomly on the map:


https://github.com/user-attachments/assets/16631113-77e6-4b8c-b1b6-c147f5f1d275

Added a couple of new emojis, which are used by the bots when attacked:
👻🎃

## Please complete the following:

- [x] I have added screenshots for all UI updates
- [x] I process any text displayed to the user through translateText()
and I've added it to the en.json file
- [x] I have added relevant tests to the test directory
- [x] I confirm I have thoroughly tested these changes and take full
responsibility for any bugs introduced

## Please put your Discord username so you can be contacted if a bug or
regression is found:

IngloriousTom

src/client/graphics/layers/FxLayer.ts

@@ -13,7 +13,7 @@ import { AnimatedSpriteLoader } from "../AnimatedSpriteLoader";
 import { conquestFxFactory } from "../fx/ConquestFx";
 import { Fx, FxType } from "../fx/Fx";
 import { nukeFxFactory, ShockwaveFx } from "../fx/NukeFx";
-import { SpriteFx } from "../fx/SpriteFx";
+import { FadeFx, MoveSpriteFx, SpriteFx } from "../fx/SpriteFx";
 import { TargetFx } from "../fx/TargetFx";
 import { TextFx } from "../fx/TextFx";
 import { UnitExplosionFx } from "../fx/UnitExplosionFx";
@@ -21,6 +21,8 @@ import { Layer } from "./Layer";
 export class FxLayer implements Layer {
   private canvas: HTMLCanvasElement;
   private context: CanvasRenderingContext2D;
+  private lastRandomEvent: number = 0;
+  private randomEventRate: number = 8;
 
   private lastRefresh: number = 0;
   private refreshRate: number = 10;
@@ -40,6 +42,14 @@ export class FxLayer implements Layer {
   }
 
   tick() {
+    if (!this.game.config().userSettings()?.fxLayer()) {
+      return;
+    }
+    this.lastRandomEvent += 1;
+    if (this.lastRandomEvent > this.randomEventRate) {
+      this.lastRandomEvent = 0;
+      this.randomEvent();
+    }
     this.manageBoatTargetFx();
     this.game
       .updatesSinceLastTick()
@@ -116,6 +126,72 @@ export class FxLayer implements Layer {
     this.allFx.push(textFx);
   }
 
+  randomEvent() {
+    const randX = Math.floor(Math.random() * this.game.width());
+    const randY = Math.floor(Math.random() * this.game.height());
+    const ref = this.game.ref(randX, randY);
+    if (this.game.isOcean(ref) && !this.game.isShoreline(ref)) {
+      const animation = Math.floor(Math.random() * 4);
+      if (animation === 0) {
+        const fx = new SpriteFx(
+          this.animatedSpriteLoader,
+          randX,
+          randY,
+          FxType.Shark,
+        );
+        this.allFx.push(fx);
+      } else if (animation === 1) {
+        const fx = new SpriteFx(
+          this.animatedSpriteLoader,
+          randX,
+          randY,
+          FxType.Bubble,
+        );
+        this.allFx.push(fx);
+      } else if (animation === 2) {
+        const fx = new MoveSpriteFx(
+          new SpriteFx(
+            this.animatedSpriteLoader,
+            randX,
+            randY,
+            FxType.Tornado,
+            6000,
+          ),
+          randX - 40,
+          randY,
+          0.1,
+          0.8,
+        );
+        this.allFx.push(fx);
+      } else if (animation === 3) {
+        const fx = new FadeFx(
+          new SpriteFx(
+            this.animatedSpriteLoader,
+            randX,
+            randY,
+            FxType.Tentacle,
+          ),
+          0.1,
+          0.8,
+        );
+        this.allFx.push(fx);
+      }
+    } else {
+      const ghost = new FadeFx(
+        new SpriteFx(
+          this.animatedSpriteLoader,
+          randX,
+          randY,
+          FxType.MiniSmoke,
+          4000,
+        ),
+        0.1,
+        0.8,
+      );
+      this.allFx.push(ghost);
+    }
+  }
+
   onUnitEvent(unit: UnitView) {
     switch (unit.type()) {
       case UnitType.TransportShip: {