public class GameManager : MonoBehaviour {

   // reference to other scripts
   public Controller2D controller2D;

   public float screenPositionX;
   public float screenPositionY;
   int sw = Screen.width;
   int sh = Screen.height;
   public float iconSizeX = 25;
   public float iconSizeY = 25;

   static public int bulletDamage = 1;

   static public int curHealth;
   public int maxHealth;
   public int curExp = 0;
   int maxExp = 50;
   int level = 1;
   public int curCoins = 0;

   bool pauseMenu;

   private void Awake() {
      print("AWAKE1() bulletDamage: " + bulletDamage); // 1
      curExp = PlayerPrefs.GetInt("Player Exp");
      level = PlayerPrefs.GetInt("Player Level");
      curCoins = PlayerPrefs.GetInt("Player Coins");
      bulletDamage = PlayerPrefs.GetInt("Player Damage");
      print("AWAKE2() bulletDamage: " + bulletDamage); // 0
      // ...
   }

   private void Update() {
      // ...
   }

   void OnGUI() {
      if(pauseMenu) {
         if(GUI.Button(new Rect(sw * 0.25f, sh * 0.3f, sw * 0.5f, sh * 0.1f), "Save")) {
            SaveGame();
         }
         // ...
      }
   }

   public void SaveGame() {
      PlayerPrefs.SetInt("Player Level", level);
      PlayerPrefs.SetInt("Player Exp", curExp);
      PlayerPrefs.SetInt("Player Coins", curCoins);
      print("SAVEGAME() bd: " + bulletDamage); // 0
      PlayerPrefs.SetInt("Player Damage", bulletDamage);
   }

   void PlayerDamaged(int damage) {
      if(curHealth > 0) {
         curHealth -= damage;
      }
      if(curHealth <= 0) {
         curHealth = 0;
         RestartScene();
      }
   }
}

public class Bullet : MonoBehaviour {

   private void OnTriggerEnter(Collider other) {
      if(other.gameObject.tag == "Enemy") {
         Destroy(gameObject);
         other.gameObject.SendMessage("EnemyDamaged", GameManager.bulletDamage, SendMessageOptions.DontRequireReceiver);
         other.gameObject.SendMessage("TakenDamage", SendMessageOptions.DontRequireReceiver);
      }
      if(other.gameObject.tag == "Wall") {
         Destroy(gameObject);
      }
   }

   private void FixedUpdate() {
      Destroy(gameObject, 1.25f);
   }
}

public class Controller2D : MonoBehaviour {

   // references to other scripts
   CharacterController characterController;
   public GameManager gameManager;

   Renderer rend;

   public float gravity = 10;
   public float walkSpeed = 5;
   public float jumpHeight = 5;

   float takenDamage = 0.2f;

   Vector3 moveDirection = Vector3.zero;
   float horizontal = 0;

   public Rigidbody bulletPrefab;
   float attackRate = 0.2f;
   float coolDown;

   bool lookRight = true;

   void Start() {
      characterController = GetComponent<CharacterController>();
      rend = GetComponent<Renderer>();
   }

   void Update() {
      characterController.Move(moveDirection * Time.deltaTime);
      horizontal = Input.GetAxis("Horizontal");
      moveDirection.y -= gravity * Time.deltaTime;
      if(horizontal == 0) {
         moveDirection.x = horizontal;
      }
      if(horizontal > 0.01f) {
         lookRight = true;
         moveDirection.x = horizontal * walkSpeed;
      }
      if(horizontal < -0.01f) {
         lookRight = false;
         moveDirection.x = horizontal * walkSpeed;
      }
      if(characterController.isGrounded) {
         if(Input.GetKeyDown(KeyCode.Space)) {
            moveDirection.y = jumpHeight;
         }
      }
      if(Time.time >= coolDown) {
         if(Input.GetKeyDown(KeyCode.F)) {
            BulletAttack();
         }
      }
   }

   void BulletAttack() {
      if(lookRight) {
         Rigidbody bPrefab = Instantiate(bulletPrefab, transform.position, Quaternion.identity) as Rigidbody;
         bPrefab.AddForce(Vector3.right * 500);
         coolDown = Time.time + attackRate;
      }
      else {
         Rigidbody bPrefab = Instantiate(bulletPrefab, transform.position, Quaternion.identity) as Rigidbody;
         bPrefab.AddForce(-Vector3.right * 500);
         coolDown = Time.time + attackRate;
      }
   }

   public IEnumerator TakenDamage() {
      rend.enabled = false;
      yield return new WaitForSeconds(takenDamage);
      rend.enabled = true;
      yield return new WaitForSeconds(takenDamage);
      rend.enabled = false;
      yield return new WaitForSeconds(takenDamage);
      rend.enabled = true;
      yield return new WaitForSeconds(takenDamage);
      rend.enabled = false;
      yield return new WaitForSeconds(takenDamage);
      rend.enabled = true;
      yield return new WaitForSeconds(takenDamage);
   }
}

public class Enemy2D : MonoBehaviour {

   // references to other scripts
   public GameManager gameManager;

   Renderer rend;

   Rigidbody rb;

   float startingPos;
   float endPos;

   public int unitsToMove = 5;
   public int moveSpeed = 2;
   bool moveRight = true;
   int damageValue = 1;
   int enemyHealth = 1;
   public bool basicEnemy = true;
   public bool advancedEnemy;
   float takenDamage = 0.2f;

   private void Start() {
      rb = GetComponent<Rigidbody>();
      rend = GetComponent<Renderer>();
   }

   private void Update() {
      if(moveRight) {
         rb.position += Vector3.right * moveSpeed * Time.deltaTime;
      }
      if(rb.position.x >= endPos) {
         moveRight = false;
      }
      if(!moveRight) {
         rb.position -= Vector3.right * moveSpeed * Time.deltaTime;
      }
      if(rb.position.x <= startingPos) {
         moveRight = true;
      }
   }

   private void Awake() {
      startingPos = transform.position.x;
      endPos = startingPos + unitsToMove;
      if(basicEnemy) {
         enemyHealth = 3;
      }
      if(advancedEnemy) {
         enemyHealth = 6;
      }
   }

   void OnTriggerEnter(Collider col) {
      if(col.gameObject.tag == "Player") {
         gameManager.SendMessage("PlayerDamaged", damageValue, SendMessageOptions.DontRequireReceiver);
         gameManager.controller2D.SendMessage("TakenDamage", SendMessageOptions.DontRequireReceiver);
      }
    }

   void EnemyDamaged(int damage) {
      if(enemyHealth > 0) {
         enemyHealth -= damage;
      }
      if(enemyHealth <= 0) {
         enemyHealth = 0;
         Destroy(gameObject);
         if(basicEnemy) {
            gameManager.curExp += 5;
            gameManager.curCoins += 5;
         }
         if(advancedEnemy) {
            gameManager.curExp += 10;
            gameManager.curCoins += 10;
         }
      }
   }

   public IEnumerator TakenDamage() {
      rend.enabled = false;
      yield return new WaitForSeconds(takenDamage);
      rend.enabled = true;
      yield return new WaitForSeconds(takenDamage);
      rend.enabled = false;
      yield return new WaitForSeconds(takenDamage);
      rend.enabled = true;
      yield return new WaitForSeconds(takenDamage);
      rend.enabled = false;
      yield return new WaitForSeconds(takenDamage);
      rend.enabled = true;
      yield return new WaitForSeconds(takenDamage);
   }
}