Continue.cs

using UnityEngine;
using UnityEngine.UI;
using System.Collections;
using UnityEngine.SceneManagement;

public class Continue : MonoBehaviour {

	public Image blackImage;
	private Color blackImageColor;

	private float pushedTime = 0f;
	private Vector3 origPos;

	// Use this for initialization
	void Start () {
		origPos = transform.position;
		blackImageColor = blackImage.color;
	}
	
	// Update is called once per frame
	void Update () {
	
		if (pushedTime > 0f) {
			float t = Time.time - pushedTime;
			if (t < 0.5f) {
				blackImageColor.a = 0f;
			}
			else if (t >= 0.5f && t <= 1.5f) {
				blackImageColor.a = t - 0.5f;
			} else if (t > 1.5f) {
				blackImageColor.a = 1f;
				pushedTime = 0f;
				SceneManager.LoadScene("gameScene");
			}
			blackImage.color = blackImageColor;
		}
	}

	public void Push() {
		if (pushedTime == 0f) {
			pushedTime = Time.time;
			Vector3 newPos = new Vector3 (origPos.x, origPos.y-0.1f, origPos.z);
			iTween.MoveTo(gameObject, iTween.Hash("position", newPos, "oncomplete", "PushAnimCompleted", "time", 0.5f));
		}
	}

	public void PushAnimCompleted() {
		iTween.MoveTo(gameObject, iTween.Hash("position", origPos, "time", 0.5f));
	}
}

Gate.cs

using UnityEngine;
using System.Collections;
using System.Collections.Generic;

public class Gate : MonoBehaviour {

	public int max = 3;
	public float duration = 30f;
	public float initial = 0f;
	public float durationDelta = 3f;
	public float durationMin = 10f;

	public Player player;
	public GameObject enemyPrefab;
	public ParticleSystem particeSystem;

	private float lastCreated;
	private List<GameObject> enemies = new List<GameObject>();

	// Use this for initialization
	void Start () {
		lastCreated = initial - duration + Time.time;
	}

	// Update is called once per frame
	void Update () {
// --- 4/9 add start ---
		if (player.isGameover) {
			return;
		}
// --- 4/9 add end ---

		if ((Time.time - lastCreated > duration) && enemies.Count < max) {

			lastCreated = Time.time;
			duration -= durationDelta;
			if (duration < durationMin)
				duration = durationMin;

			GameObject obj = GameObject.Instantiate (enemyPrefab);
			obj.transform.parent = transform;
			obj.transform.position = transform.position;
			Skeleton skeleton = obj.GetComponent<Skeleton> ();
			skeleton.gate = this;
			skeleton.player = player;

			particeSystem.Play ();
		}
	}

	public void Remove(GameObject obj) {
		enemies.Remove (obj);
		GameObject.Destroy (obj);
	}
}

Player.cs

using UnityEngine;
using System.Collections;
using UnityEngine.UI;

public class Player : MonoBehaviour {

	public  Image damageImage; 
	private Color damageImageColor;
	private float damagedTime = 0f;

// --- 4/9 add start ---
	public Image gameOverImage;
	public TextMesh gameOverText;
	private Color gameOverColor;
	private Color gameOverTextColor;
	private float gameoverTime = 0f;
	public bool isGameover = false;

	public GameObject cont;
// --- 4/9 add end ---

	// Use this for initialization
	void Start () {
		damageImageColor = damageImage.color;
		ShowHP ();

// --- 4/9 add start ---
		gameOverColor = gameOverImage.color;
		gameOverTextColor = gameOverText.color;

		cont.SetActive (false);
// --- 4/9 add end ---
	}
	
	// Update is called once per frame
	void Update () {
	
		if (damagedTime > 0f) {
			float t = Time.time - damagedTime;
			if (t <= 1f) {
				damageImageColor.a = 1f - t;
			}
			else {
				damagedTime = 0f;
				damageImageColor.a = 0f;
			}
			damageImage.color = damageImageColor;
		}

// --- 4/9 add start ---
		if (gameoverTime > 0f) {
			float t = Time.time - gameoverTime;
			if (t <= 2f) {
				gameOverColor.a = t / 2f;
			} else if (t > 2f && t <= 3) {
				isGameover = true;
				cont.SetActive (true);
				gameOverColor.a = 3f - t;
				gameOverTextColor.a = (t - 2f); 
			} else {
				gameOverColor.a = 0f;
				gameOverTextColor.a = 1f;
			}
			gameOverImage.color = gameOverColor;
			gameOverText.color = gameOverTextColor;
		}
// --- 4/9 add end ---
	}

	public void Damage() {
		if (damagedTime == 0f) {
			damagedTime = Time.time;
// --- 4/9 add start ---
			HP-=0.5f;
			if (HP <= 0 && gameoverTime == 0f) {
				gameoverTime = Time.time;
			}
// --- 4/9 add end ---
			ShowHP ();
		}
	}

// --- 4/9 add start ---
	public GameObject lifePartsPrefab;
	public GameObject life;
	public float HP = 3;
	private void ShowHP() {

		if (life.transform.childCount == 0) {
			for (int i = 0; i < HP; i++) {
				GameObject lifeParts = Instantiate (lifePartsPrefab);
				lifeParts.transform.parent = life.transform;
				lifeParts.transform.localPosition = new Vector3 (i * 0.25f, 0, 0);
				lifeParts.transform.name = (i+1).ToString ();
			}
		}

		for (int i = 0; i < life.transform.childCount; i++) {
			GameObject obj = life.transform.GetChild (i).gameObject;
			float l = float.Parse (obj.name);
			SpriteRenderer sprite = obj.GetComponent<SpriteRenderer> ();
			if (l <= HP) {
				sprite.color = Color.red;
			} else {
				float col = HP - (l - 1);
				if (col < 0)
					col = 0;
				sprite.color = new Color (col, 0, 0);
			}
		}
	}
// --- 4/9 add end ---
}

Skeleton.cs

using UnityEngine;
using System.Collections;

public class Skeleton : MonoBehaviour {

// --- 3/27 modify start ---
	//public GameObject player;
	public Player player;
// --- 3/27 modify end ---

	private Vector3 nextDirection = Vector3.zero;
	private float nextDistance;
	private Vector3 startPoint;
	private float speed = 0.5f;

// --- 3/27 add start ---
	private int HP = 3;
	private bool damagingInvalid = false;
	private bool damagedPlayer = false;

	public ParticleSystem particle;
// --- 3/27 add end ---

// --- 4/2 add start ---
	public Gate gate;
// --- 4/2 add end ---

	private Animator anim;

	// Use this for initialization
	void Start () {

		anim = GetComponent<Animator>();
// --- 4/2 add start ---
		ChangeState ("Appear");
// --- 4/2 add end ---
	}

	// Update is called once per frame
	void Update () {
// --- 4/9 add start ---
		if (player.isGameover) {
			gate.Remove (gameObject);
		}
// --- 4/9 add end ---

		if (IsStateChanging ())
			return;

		AnimatorStateInfo info = anim.GetCurrentAnimatorStateInfo (0);

// --- 4/2 add start ---
		if (info.IsName ("Appear")) {
			float t = info.normalizedTime;

			if (t >= 1f) {
				ChangeState ("Idle");
			} else {
				transform.position = new Vector3 (transform.position.x, -1.4f + t * 1.6f, transform.position.z);
			}
		}
		else if (info.IsName ("Idle")) {
// --- 4/2 add end ---
		// if (info.IsName ("Idle")) { // remove 4/2
// --- 3/27 add start ---
			damagingInvalid = false;
			damagedPlayer = false;
// --- 3/27 add end ---
			if (player != null) {
				if (nextDirection == Vector3.zero) {
					float dist = Vector3.Distance (player.transform.position, transform.position);
					float randAngle = dist < 3.0f ? 0f : (Random.value - 0.5f) * dist * 8;
					nextDirection = Quaternion.LookRotation (player.transform.position - transform.position).eulerAngles;
					nextDirection.y += randAngle;
					if (nextDirection.y < 0)
						nextDirection.y += 360;
					nextDirection.x = 0;
					nextDirection.z = 0;

					nextDistance = dist < 3.0f ? dist : dist / 4 + Random.value * (dist / 4);
					startPoint = transform.position;

				} else {
					transform.rotation = Quaternion.Slerp (transform.rotation, Quaternion.Euler (nextDirection), Time.deltaTime);
					if (Mathf.Abs (Mathf.DeltaAngle (transform.rotation.eulerAngles.y, nextDirection.y)) <= 1.0f) {
						ChangeState ("Walk");
					}
				}
			}
		} else if (info.IsName ("Walk")) {
			
			float playerDist = Vector3.Distance (player.transform.position, transform.position);
			if (playerDist <= 2) {
				ChangeState ("Attack");
			} else {
				transform.position += transform.TransformDirection (Vector3.forward) * Time.deltaTime * speed;
				float dist = Vector3.Distance (startPoint, transform.position);
				if (dist >= nextDistance) {
					nextDirection = Vector3.zero;
					ChangeState ("Idle");
				}
			}
// 3/27 add start
		} else if (info.IsName ("Attack")) {
			float t = info.normalizedTime;
			if (t > 0.35f && !damagedPlayer) {
				damagedPlayer = true;
				player.Damage ();
			}
		} else if (info.IsName ("Damage")) {
			float t = info.normalizedTime;
			if (HP <= 0f && t > 0.5f) {
				ChangeState ("Dead");
			} else {
				transform.position += transform.TransformDirection (Vector3.back) * Time.deltaTime;
			}			
		} else if (info.IsName ("Dead")) {
			float t = info.normalizedTime;
			if (t >= 2f) {
// --- 4/2 add start ---
				if (gate != null) {
					gate.Remove (gameObject);
				}
// --- 4/2 add end ---
				GameObject.Destroy (gameObject);
			}
		}
// 3/27 add end
	}

	private string changingStateName = null;
	private void ChangeState(string name) {
		changingStateName = name;
		anim.SetTrigger (name);
	}

	private bool IsStateChanging() {
		AnimatorStateInfo next = anim.GetNextAnimatorStateInfo (0);
		bool ret = changingStateName != null && next.IsName (changingStateName);
		if (changingStateName != null && !ret) {
			changingStateName = null;
		}
		return ret;
	}
		
// --- 3/27 add start ---
	public void Damage() {
		if (!damagingInvalid) {
			HP -= 1;
			damagingInvalid = true;
			ChangeState ("Damage");
			particle.Play ();
		}
	}
// --- 3/27 add end ---
}