first commit

assets/scripts/TopSensor.ts

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+import { _decorator, Component, BoxCollider2D, Contact2DType, IPhysics2DContact, Node, Color } from 'cc';
+import { Fruit } from './Fruit';
+import { GameManager } from './GameManager';
+const { ccclass, property } = _decorator;
+
+@ccclass('TopSensor')
+export class TopSensor extends Component {
+  @property(GameManager)
+  game!: GameManager;
+
+  @property
+  holdSeconds = 2.0; // 触顶持续秒数
+
+  private touching = new Map<Node, number>(); // node -> enterTime
+
+  onEnable() {
+    const col = this.getComponent(BoxCollider2D)!;
+    col.sensor = true;
+    col.on(Contact2DType.BEGIN_CONTACT, this.onBegin, this);
+    col.on(Contact2DType.END_CONTACT, this.onEnd, this);
+  }
+  onDisable() {
+    const col = this.getComponent(BoxCollider2D)!;
+    col.off(Contact2DType.BEGIN_CONTACT, this.onBegin, this);
+    col.off(Contact2DType.END_CONTACT, this.onEnd, this);
+  }
+
+  private onBegin(_self: BoxCollider2D, other: any, _c: IPhysics2DContact | null) {
+    const f = (other.node as Node).getComponent(Fruit);
+    if (f) this.touching.set(other.node, performance.now() / 1000);
+  }
+  private onEnd(_self: BoxCollider2D, other: any) {
+    this.touching.delete(other.node);
+  }
+
+  update() {
+    if (!this.game || this.game.isGameOver) return;
+    const now = performance.now() / 1000;
+    for (const [node, t] of this.touching) {
+      if (now - t >= this.holdSeconds) {
+        this.game.onGameOver();
+        break;
+      }
+    }
+    // 可选：把状态交给 GameManager 显示红线闪烁
+    this.game.setDanger(this.touching.size > 0);
+  }
+}