WIP

Assets/Scripts/DoorController.cs

@@ -0,0 +1,15 @@
+using System.Collections;
+using System.Collections.Generic;
+using UnityEngine;
+
+public class DoorController : MonoBehaviour
+{
+    private void OnTriggerEnter2D(Collider2D collision)
+    {
+        if (collision.tag == "Player")
+        {
+           //if player have key, door will open
+           //else player can't pass
+        }
+    }
+}

Assets/Scripts/DoorController.cs.meta

@@ -0,0 +1,11 @@
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+guid: b3ead8e41e973dd43b93a8638ea30a36
+MonoImporter:
+  externalObjects: {}
+  serializedVersion: 2
+  defaultReferences: []
+  executionOrder: 0
+  icon: {instanceID: 0}
+  userData: 
+  assetBundleName: 
+  assetBundleVariant: 

Assets/Scripts/IDoor.cs

@@ -0,0 +1,8 @@
+namespace Assets.Scripts
+{
+    public interface IDoor
+    {
+        void OpenDoor();
+        void ToggleDoor();
+    }
+}

Assets/Scripts/IDoor.cs.meta

@@ -0,0 +1,11 @@
+fileFormatVersion: 2
+guid: 62a1e4daba023c94f9fe4c576570cbf4
+MonoImporter:
+  externalObjects: {}
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Assets/Scripts/PlayerController.cs

@@ -17,6 +17,7 @@ public class PlayerController : MonoBehaviour
     private BoxCollider2D _boxCollider;
     private bool _isFall;
     private bool _facingRight = true;
+    private bool _haveKey = false;
 
 
     void Start()
@@ -106,4 +107,13 @@ public class PlayerController : MonoBehaviour
 
         _facingRight = !_facingRight;
     }
+
+    private void OnTriggerEnter2D(Collider2D collision)
+    {
+        var door = collision.GetComponent<DoorController>();
+        if (door != null)
+        {
+            door.OpenDoor();
+        }
+    }
 }