CodeProject, Unity3D

How to build a 2D Space shooter with efficiency calculation in Unity3D

In this blog post I’m going to show you how to build a 2D Space shooter with efficiency calculation in Unity3D.

I followed these two blog posts: post #1 and post #2, and updated it for the use with Unity 4.5 and added the counters for number of bullets fired and number of rocks generated and showed the precision efficiency.

You can try my version, or you can download the project on GitHub. Following are the steps on how to make it your self:

Start a new 2D project in Unity3D
Create folders Scripts, Scenes, Prefabs, Textures
Put all the texture assets to Textures folder
Save the (ctrl +s) scene to Scenes folder with some name
Drag background to Hierarchy
Drag ship to Hierarchy
1. set y to -4
2. add Rigidbody2D
3. check IsKinematic (the gravity doesn’t affect it)

Add script to ship:

#pragma strict
// A variable that will contain our bullet prefab
public var bullet : GameObject;
public var brzina: int;
var score : int;

function Start(){
    	score = 0;
}

function Update() {  
    // Move the spaceship horizontally  
    rigidbody2D.velocity.x = Input.GetAxis("Horizontal") * 10;
    rigidbody2D.velocity.y = Input.GetAxis("Vertical") * 10;

	//add support for mobile phone tilting
	transform.Translate(Input.acceleration.x*Time.deltaTime*20, 0, 0);
    
    if (Input.GetKeyDown("space") || Input.GetMouseButtonDown(0)) {   
    	Instantiate(bullet, transform.position, Quaternion.identity);
    }    
}

Add bullet to Hierarchy

add Physics2D -> Rigidbody 2D

add script:

public var speed : int = 6;

// Gets called once when the bullet is created
function Start () {  
    // Set the Y velocity to make the bullet move upward
    rigidbody2D.velocity.y = speed;
}

// Gets called when the object goes out of the screen
function OnBecameInvisible() {  
    // Destroy the bullet 
    Destroy(gameObject);
}

add bullet to Prefabs folder and delete it from the Hierarchy
drag the bullet from Prefabs folder to the bullet variable in Inspector when the spaceship is selected

Add an enemy (from Textures) to the Hierarchy

add Rigidbody 2D
set IsKinematic

add script:

// Public variable that contains the speed of the enemy
public var speed : int = -5;

// Function called when the enemy is created
function Start () {  
    // Add a vertical speed to the enemy
    rigidbody2D.velocity.y = speed;

    // Make the enemy rotate on itself
    rigidbody2D.angularVelocity = Random.Range(-200, 200);

    // Destroy the enemy in 3 seconds,
    // when it is no longer visible on the screen
    Destroy(gameObject, 3);
}

function OnTriggerEnter2D(obj : Collider2D) {  
    var name = obj.gameObject.name;

    // If it collided with a bullet
    if (name == "bullet(Clone)") {
        // And destroy the bullet
        Destroy(obj.gameObject);
        
        handleDestroy(gameObject);
    }

    // If it collided with the spaceship
    if (name == "spaceship") {
        handleDestroy(gameObject);
    }
}

function handleDestroy(gameObject: GameObject){
	gameObject.Find("ScoreText").SendMessage("Hit");
    Destroy(gameObject);
}

Add enemy from Hierarchy to Prefabs folder and delete it from Hierarchy

Add spawn object to Hierarchy

position it above the background
add script:

public var enemy : GameObject;

// Variable to know how fast we should create new enemies
public var spawnTime : float = 1.3;

function Start() {  
    // Call the 'addEnemy' function every 'spawnTime' seconds
    InvokeRepeating("addEnemy", spawnTime, spawnTime);
}

// New function to spawn an enemy
function addEnemy() {  
    // Variables to store the X position of the spawn object
    // See image below
    var x1 = transform.position.x - renderer.bounds.size.x/2;
    var x2 = transform.position.x + renderer.bounds.size.x/2;

    // Randomly pick a point within the spawn object
    var spawnPoint = new Vector2(Random.Range(x1, x2), transform.position.y);

    // Create an enemy at the 'spawnPoint' position
    Instantiate(enemy, spawnPoint, Quaternion.identity);
}

drag enemy prefab to spawn object

For the spaceship, the enemy prefab, and the bullet prefab do the following
1. add Component -> Physics 2D -> Box Collider 2D
2. for enemy Box Collider 2D check IsTrigger and this will give you the OnTriggerEnter2D function

Create -> UI -> Text (name it ScoreText)

Canvas -> RenederMode -> World space, no camera
Rect transform – 450×340 (WxH)

Add -> Script -> ScoreScript.js:

import UnityEngine.UI.Text;

var Counter : int;
var text : UnityEngine.UI.Text;

function Start () {
	text = GetComponent(UnityEngine.UI.Text);
	Counter = 0;
}

function Update () {    
     text.text = "Kills: "+Counter;
}   
         
function Hit () {            
    Counter++;
}

Create -> UI -> Text (name it RocksText)

Add -> Script -> RocksScript.js:

import UnityEngine.UI.Text;

var Counter : int;
private var text : UnityEngine.UI.Text;

function Start () {
	text = GetComponent(UnityEngine.UI.Text);
	Counter = 0;
}

function Update () {    
     text.text = "Rocks: "+Counter;
}   
         
function RockAdd () {            
    Counter++;
}

Create -> UI -> Text (name it EffText)

Add -> Script -> EffScript.js:

import UnityEngine.UI.Text;

private var Kills : int;
private var Rocks : int;
private var Eff : float;
private var text : UnityEngine.UI.Text;

function Start () {
	text = GetComponent(UnityEngine.UI.Text);
	Eff = 0;
	Kills = 0;
	Rocks = 0;
}

function Update () {    
     Kills = gameObject.Find("ScoreText").GetComponent(ScoreScript).Counter;
     Rocks = gameObject.Find("RocksText").GetComponent(RocksScript).Counter;
          
     if (Kills == 0 || Rocks == 0)
     	Eff = 0;
     else
     	Eff = Kills * 1.0f / Rocks * 100;
     	
     text.text = "Eff: " + Eff.ToString("F0") + "%";
}