done

Assets/Scripts/HiddenObject.cs

@@ -0,0 +1,49 @@
+using System;
+using System.Collections;
+using System.Collections.Generic;
+using UnityEngine;
+using UnityEngine.Assertions;
+
+public class HiddenObject : MonoBehaviour
+{
+    private MeshRenderer _renderer;
+    private GameManager _gameManager;
+
+    private void Awake()
+    {
+        _renderer = GetComponent<MeshRenderer>();
+        Assert.IsNotNull(_renderer);
+        _renderer.enabled = false;
+        
+        _gameManager = GameObject.Find("GameManager").GetComponent<GameManager>();
+        Assert.IsNotNull(_gameManager);
+    }
+
+    public void ShowObjectForSeconds(int seconds)
+    {
+        if (_renderer.enabled)
+        {
+            return;
+        }
+        StartCoroutine(ShowObjectForSecondsEnumerator(seconds));
+    }
+
+
+    private IEnumerator ShowObjectForSecondsEnumerator(int seconds)
+    {
+        _renderer.enabled = true;
+        yield return new WaitForSeconds(seconds);
+        _renderer.enabled = false;
+    }
+
+    private void OnTriggerEnter(Collider other)
+    {
+        if (!other.name.Equals("Player"))
+        {
+            return;
+        }
+        
+        _gameManager.CollectKey();
+        Destroy(gameObject);
+    }
+}