Added a bunch of features

Assets/Scripts/Flash.cs

@@ -0,0 +1,41 @@
+using System.Collections;
+using System.Collections.Generic;
+using UnityEngine;
+
+public class Flash : MonoBehaviour {
+	SpriteRenderer spriteRenderer;
+
+	float alpha = 1.0f;
+	const float gradient = 0.1f;
+	const float period = 0.1f;
+
+	float lastClick; //prevent double exposure
+
+	void Awake() {
+		spriteRenderer = GetComponent<SpriteRenderer> ();
+
+		spriteRenderer.color = new Color (1f, 1f, 1f, 0f);
+	}
+
+	public void StartFlash() {
+		StartCoroutine (FlashCoroutine ());
+	}
+
+	IEnumerator FlashCoroutine() {
+		lastClick = Time.time;
+		float thisClick = lastClick;
+
+		alpha = 1.0f;
+
+		while (alpha > 0) {
+			yield return new WaitForSeconds (period);
+
+			if (thisClick != lastClick) {
+				break;
+			}
+
+			alpha -= gradient;
+			spriteRenderer.color = new Color (1f, 1f, 1f, alpha);
+		}
+	}
+}

Assets/Scripts/Flash.cs.meta

@@ -0,0 +1,13 @@
+fileFormatVersion: 2
+guid: 5f42feb702d6b2b49a80e802d2811da4
+timeCreated: 1523426005
+licenseType: Free
+MonoImporter:
+  externalObjects: {}
+  serializedVersion: 2
+  defaultReferences: []
+  executionOrder: 0
+  icon: {instanceID: 0}
+  userData: 
+  assetBundleName: 
+  assetBundleVariant: 

Assets/Scripts/Monster.cs

@@ -5,19 +5,31 @@ using UnityEngine;
 public class Monster : MonoBehaviour {
 	public int value;
 
+	Rigidbody2D rigidBody;
+
 	void Awake() {
-		StartCoroutine (DestroySelfAfter (30f));
+		rigidBody = GetComponent<Rigidbody2D> ();
+
+		StartCoroutine (ReverseDirectionAfter (2f));
+		StartCoroutine (DestroySelfAfter (4f));
 	}
 
 	void OnMouseOver() {
 		if (Input.GetMouseButtonDown(0)) {
-			//TODO: play death sound
+			GameObject.Find ("SoundController").GetComponent<SoundController> ().PlaySnapShot ();
+			GameObject.Find ("Flash").GetComponent<Flash> ().StartFlash ();
 			PersistentData.score += value;
 			Destroy (gameObject);
 		}
 	}
 
+	IEnumerator ReverseDirectionAfter(float seconds) {
+		yield return new WaitForSeconds (seconds);
+		rigidBody.velocity = new Vector2 (-rigidBody.velocity.x, -rigidBody.velocity.y);
+	}
+
 	IEnumerator DestroySelfAfter(float seconds) {
+		//clean up lost objects
 		yield return new WaitForSeconds (seconds);
 		Destroy (gameObject);
 	}

Assets/Scripts/SoundController.cs

@@ -0,0 +1,16 @@
+using System.Collections;
+using System.Collections.Generic;
+using UnityEngine;
+
+public class SoundController : MonoBehaviour {
+	AudioSource audioSource;
+	public AudioClip snapShot;
+
+	void Awake() {
+		audioSource = GetComponent<AudioSource> ();
+	}
+
+	public void PlaySnapShot() {
+		audioSource.PlayOneShot (snapShot, 1.0f);
+	}
+}

Assets/Scripts/SoundController.cs.meta

@@ -0,0 +1,13 @@
+fileFormatVersion: 2
+guid: c721dd74b396cd74c8a87e1944178d3e
+timeCreated: 1523425291
+licenseType: Free
+MonoImporter:
+  externalObjects: {}
+  serializedVersion: 2
+  defaultReferences: []
+  executionOrder: 0
+  icon: {instanceID: 0}
+  userData: 
+  assetBundleName: 
+  assetBundleVariant: