diff --git a/examples/cocos-creator-airplane/backend/package.json b/examples/cocos-creator-airplane/backend/package.json
index 415ab15..f08fb27 100644
--- a/examples/cocos-creator-airplane/backend/package.json
+++ b/examples/cocos-creator-airplane/backend/package.json
@@ -12,6 +12,7 @@
   "devDependencies": {
     "@types/mocha": "^8.2.3",
     "@types/node": "^15.14.9",
+    "@types/seedrandom": "^3.0.1",
     "mocha": "^9.1.3",
     "onchange": "^7.1.0",
     "ts-node": "^10.4.0",
@@ -19,6 +20,7 @@
     "typescript": "^4.5.4"
   },
   "dependencies": {
+    "seedrandom": "^3.0.5",
     "tsrpc": "^3.1.4"
   }
-}
\ No newline at end of file
+}
diff --git a/examples/cocos-creator-airplane/backend/src/shared/game/GameSystem.ts b/examples/cocos-creator-airplane/backend/src/shared/game/GameSystem.ts
index dda311f..05ad25c 100644
--- a/examples/cocos-creator-airplane/backend/src/shared/game/GameSystem.ts
+++ b/examples/cocos-creator-airplane/backend/src/shared/game/GameSystem.ts
@@ -1,7 +1,8 @@
+import seedrandom from "seedrandom";
 import { gameConfig } from "./gameConfig";
 import { GameSystemEvent } from "./GameSystemEvent";
 import { GameSystemInput } from "./GameSystemInput";
-import { GameSystemState } from "./GameSystemState";
+import { EnemyState, EnemyType, GameSystemState } from "./GameSystemState";
 
 /**
  * 前后端复用的状态计算模块
@@ -9,7 +10,17 @@ import { GameSystemState } from "./GameSystemState";
 export class GameSystem {
 
     // 当前状态
-    state: GameSystemState;
+    private _state!: GameSystemState;
+    get state(): Readonly<GameSystemState> {
+        return this._state;
+    }
+    set state(state: GameSystemState) {
+        this._state = state;
+        this._seedRandom = seedrandom(state.random.seed, state.random.state);
+    }
+
+    // 伪随机数发生器
+    private _seedRandom!: ReturnType<seedrandom>;
 
     constructor(state: GameSystemState) {
         this.state = state;
@@ -89,7 +100,7 @@ export class GameSystem {
                 this.state.enemies.forEach(enemy => {
                     // 更新敌机位置
                     const enemyTime = this.state.now - enemy.init.time;
-                    enemy.pos.y = enemy.init.pos.y - gameConfig.enemy.speed * enemyTime;
+                    enemy.pos.y = enemy.init.pos.y - gameConfig.enemy.speed[enemy.type] * enemyTime;
 
                     // 更新敌机子弹位置
                     enemy.bullets.forEach(bullet => {
@@ -119,14 +130,36 @@ export class GameSystem {
     }
 
     private _createEnemies() {
-        // 前 10 秒
-        // 每 1 秒创建一个敌机
+        if (this.state.now < this.state.lastCreateEnemyTime + gameConfig.enemy.bornY) {
+            return;
+        }
 
-        // 10~20秒
-        // 每3秒一个组合，然后每秒一个敌机
+        let time = this.state.now - (this.state.now % gameConfig.enemy.bornGapTime);
+        let pos = { x: this._random() * 750 - 375, y: gameConfig.enemy.bornY };
+        let enemy: EnemyState = {
+            id: this.state.nextId.enemy++,
+            // 敌机类型
+            type: this._random() > 0.5 ? EnemyType.E1 : EnemyType.E2,
+            pos: { ...pos },
+            init: {
+                time: time,
+                pos: { ...pos },
+            },
+            bullets: [],
+            // 初次创建敌机，按 bulletDelayTime 倒推 lastBulletTime
+            lastBulletTime: time + gameConfig.enemy.bulletDelayTime - gameConfig.enemy.bulletGapTime,
+            nextId: {
+                bullet: 0
+            }
+        }
 
-        // 20秒以后
-        // 每 2 秒一个组合(组合1 / 组合2 / xxx)
+        this.state.enemies.push(enemy);
+    }
+
+    private _random(): number {
+        let rand = this._seedRandom();
+        this.state.random.state = this._seedRandom.state();
+        return rand;
     }
 
     // 简易的事件侦听器
diff --git a/examples/cocos-creator-airplane/backend/src/shared/game/GameSystemState.ts b/examples/cocos-creator-airplane/backend/src/shared/game/GameSystemState.ts
index a8783a9..6649912 100644
--- a/examples/cocos-creator-airplane/backend/src/shared/game/GameSystemState.ts
+++ b/examples/cocos-creator-airplane/backend/src/shared/game/GameSystemState.ts
@@ -1,11 +1,19 @@
 import { uint } from "tsrpc";
 
-// 坐标系：X-Y 原点在左下角
+// 坐标系：X-Y 原点在中间下方
+/*
+[ ]  [ ]  [ ]
+
+[ ]  [ ]  [ ]     
+                  ↑ y
+[ ]  [x]  [ ]     → x
+*/
 
 export interface GameSystemState {
     // 游戏时间
     now: number,
 
+    // 场景状态
     players: PlayerState[],
     enemies: EnemyState[],
     fightIcons: FightIconState[],
@@ -15,11 +23,18 @@ export interface GameSystemState {
         enemy: uint,
         fightIcon: uint
     },
+
     // 上次创建敌机的时间
     lastCreateEnemyTime: number,
-    randomSeed: number,
+
+    // 伪随机数发生器状态
+    random: {
+        seed: string,
+        state: object
+    }
 }
 
+
 // 玩家
 export interface PlayerState {
     id: uint,
@@ -52,12 +67,12 @@ export type PlayerBulletType = 'M' | 'H' | 'S';
 // 敌机
 export interface EnemyState {
     id: uint,
-    type: uint,
+    // 敌机类型
+    type: EnemyType,
     pos: { x: number, y: number },
     init: {
         time: number,
         pos: { x: number, y: number },
-        speed: { y: number }
     }
     bullets: {
         id: uint,
@@ -76,6 +91,11 @@ export interface EnemyState {
     }
 }
 
+export enum EnemyType {
+    E1,
+    E2
+};
+
 // 子弹图标
 export interface FightIconState {
     id: uint,
diff --git a/examples/cocos-creator-airplane/backend/src/shared/game/gameConfig.ts b/examples/cocos-creator-airplane/backend/src/shared/game/gameConfig.ts
index 48d8801..2a50284 100644
--- a/examples/cocos-creator-airplane/backend/src/shared/game/gameConfig.ts
+++ b/examples/cocos-creator-airplane/backend/src/shared/game/gameConfig.ts
@@ -1,13 +1,23 @@
+import { EnemyType } from "./GameSystemState";
+
 export const gameConfig = {
     syncRate: 10,
 
     enemy: {
-        speed: 10,
         bulletSpeed: 20,
         // 第一次发射子弹的延迟时间
         bulletDelayTime: 1500,
         // 每次发射子弹的间隔
-        bulletGapTime: 500
+        bulletGapTime: 500,
+        // 出现位置（Y轴）
+        bornY: 1800,
+        // 敌机出现时间间隔（毫秒）
+        bornGapTime: 1000,
+        // 敌机速度
+        speed: {
+            [EnemyType.E1]: 10,
+            [EnemyType.E2]: 20,
+        }
     },
 
     player: {