Bouncy Box

Setup the project

Switch to 2D

Bouncy Box will be a 2D game. Unity provides this capability.

Create a bounce

We want the player to be able to press space to apply an upward to the box. This bounce effect will provide a unique player controller and lead to the core game mechanics of the game.

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

public class BoxBehavior : MonoBehaviour
{
    public float flapForce = 80;
    public float health = 100;
    public int numCoins = 0;

    // Update is called once per frame
    void Update()
    {

    }
}
          

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

public class BoxBehavior : MonoBehaviour
{
    public float flapForce = 80;
    public float health = 100;
    public int numCoins = 0;

    // Update is called once per frame
    void Update()
    {
        if(Input.GetKeyDown(KeyCode.Space))
        {
            GetComponent<Rigidbody>().AddForce(0, flapForce, 0);
        }
    }
}
          

if(Input.GetKeyDown(KeyCode.Space))
{
    GetComponent<Rigidbody>().AddForce(0, flapForce, 0);
}

this.gameObject.GetComponent<Rigidbody>().AddForce(0, flapForce, 0);

if(Input.GetKeyDown(KeyCode.Space) || Input.GetMouseButtonDown(0))
{
    GetComponent<Rigidbody>().AddForce(0, flapForce, 0);
}

Add constraints

Currently, the box can bounce upward or fall downward right out of the camera view. It is time to constrain the box so it remains in the player's view.

Add color

Add a fireball

In the game, fireballs will move across the screen. While the Box relied on the physics engine for its movement (forces being applied to a Rigidbody), the fireballs will move through code that directly modifies their position values. First, we need to create a single fireball.

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

public class FlyLeft : MonoBehaviour
{

    public float minSpeed;
    public float maxSpeed;
    float speed;

    // Start is called before the first frame update
    void Start()
    {
        
    }

    // Update is called once per frame
    void Update()
    {

    }
}
          

public class FlyLeft : MonoBehaviour
{

    public float minSpeed;
    public float maxSpeed;
    float speed;

    // Start is called before the first frame update
    void Start()
    {
        speed = Random.Range(minSpeed, maxSpeed);
    }

    // Update is called once per frame
    void Update()
    {

    }
}
          

public class FlyLeft : MonoBehaviour
{

    public float minSpeed;
    public float maxSpeed;
    float speed;

    // Start is called before the first frame update
    void Start()
    {
        speed = Random.Range(minSpeed, maxSpeed);
    }

    // Update is called once per frame
    void Update()
    {
        transform.Translate(Vector3.left * speed * Time.deltaTime);
    }
}
          

Spawn fireballs

To spawn fireballs, you will set up a GameController that drops new fireballs into the game on a timed interval. The first step is to turn the Fireball into a Prefab that can be used to generate many fireballs.

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

public class GameController : MonoBehaviour
{
    public float fireballSpawnTime = 3;
    float fireballTimeElapsed = 0;

    // Update is called once per frame
    void Update()
    {
        
    }
}
          

public class GameController : MonoBehaviour
{
    public float fireballSpawnTime = 3;
    float fireballTimeElapsed = 0;

    // Update is called once per frame
    void Update()
    {
        fireballTimeElapsed += Time.deltaTime;
    }
}
          

public class GameController : MonoBehaviour
{
    public float fireballSpawnTime = 3;
    float fireballTimeElapsed = 0;

    // Update is called once per frame
    void Update()
    {
        fireballTimeElapsed += Time.deltaTime;

        if(fireballTimeElapsed > fireballSpawnTime)
        {
          fireballTimeElapsed = 0;
          print("spawn fireball");
        }
    }
}
          

public class GameController : MonoBehaviour
{
    public GameObject fireballPrefab;

    public float fireballSpawnTime = 3;
    float fireballTimeElapsed = 0;

    // Update is called once per frame
    void Update()
    {
        fireballTimeElapsed += Time.deltaTime;

        if(fireballTimeElapsed > fireballSpawnTime)
        {
          fireballTimeElapsed = 0;
          print("spawn fireball");
        }
    }
}
          

public class GameController : MonoBehaviour
{
    public GameObject fireballPrefab;

    public float fireballSpawnTime = 3;
    float fireballTimeElapsed = 0;

    // Update is called once per frame
    void Update()
    {
        fireballTimeElapsed += Time.deltaTime;

        if(fireballTimeElapsed > fireballSpawnTime)
        {
          fireballTimeElapsed = 0;
          
          GameObject fireball = Instantiate(fireballPrefab);
        }
    }
}
          

public class GameController : MonoBehaviour
{
    public GameObject fireballPrefab;

    public float fireballSpawnTime = 3;
    float fireballTimeElapsed = 0;

    // Update is called once per frame
    void Update()
    {
        fireballTimeElapsed += Time.deltaTime;

        if(fireballTimeElapsed > fireballSpawnTime)
        {
            fireballTimeElapsed = 0;
          
            GameObject fireball = Instantiate(fireballPrefab);
            float x = fireball.transform.position.x;
            float z = fireball.transform.position.z;
            float y = Random.Range(-3f, 5f);
            fireball.transform.position = new Vector3(x, y, z);
        }
    }
}
          

Destroy fireballs

To maintain performance and a desired frame rate for your game, you should always destroy objects that are no longer needed in the game. As fireballs continually spawn during the entire game, it is important that they are also destroyed.

public class FlyLeft : MonoBehaviour
{

    public float minSpeed;
    public float maxSpeed;
    float speed;

    // Start is called before the first frame update
    void Start()
    {
        speed = Random.Range(minSpeed, maxSpeed);
    }

    // Update is called once per frame
    void Update()
    {
        transform.Translate(Vector3.left * speed * Time.deltaTime);

        if(transform.position.x < -12)
        {
            Destroy(gameObject);
        }
    }
}
          

Collision damage

Fireballs should also be destroyed, as well as deal damage, when they collide with the box.

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

public class DamageOnCollision : MonoBehaviour
{
    private void OnTriggerEnter(Collider other)
    {
        if(other.tag == "Player")
        {
            Destroy(gameObject);
        }
    }
}
          

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

public class DamageOnCollision : MonoBehaviour
{
    public float damage = 10;

    private void OnTriggerEnter(Collider other)
    {
        if(other.tag == "Player")
        {
            other.GetComponent<BoxBehavior>().health -= damage;

            if(other.GetComponent<BoxBehavior>().health <= 0)
            {
                Destroy(other.gameObject);
            }

            Destroy(gameObject);
        }
    }
}
          

Ending the game

When the player dies, there is no need to continue spawning new GameObjects. One solution is to disable the GameController when there is no longer a player in the scene.

public class GameController : MonoBehaviour
{
    public GameObject fireballPrefab;

    public float fireballSpawnTime = 3;
    float fireballTimeElapsed = 0;

    // Update is called once per frame
    void Update()
    {
        if(GameObject.FindWithTag("Player") == null)
        {
            print("Player has been destroyed. Game Over.");
            this.enabled = false;
        }

        fireballTimeElapsed += Time.deltaTime;

        if(fireballTimeElapsed > fireballSpawnTime)
        {
            fireballTimeElapsed = 0;
          
            GameObject fireball = Instantiate(fireballPrefab);
            float x = fireball.transform.position.x;
            float z = fireball.transform.position.z;
            float y = Random.Range(-3f, 5f);
            fireball.transform.position = new Vector3(x, y, z);
        }
    }
}
          

GoodStuff challenge

Challenge yourself by adding some good stuff to the game!

1. Use a sphere with a yellow material to create a GoodStuff GameObject.
2. Scale the GoodStuff GameObject down or scale up the Fireball prefab so the GoodStuff is smaller than the fireballs.
3. Add the FlyLeft script to the GoodStuff and increase the properties for the min and max speed so that GoodStuff moves faster on average than the fireballs.
4. Create a Prefab from the GoodStuff and update the GameController to spawn GoodStuff in the same manner that the Fireballs are spawned. Here is a portion of the updated code:
   
   

   public class GameController : MonoBehaviour
   {
       public GameObject fireballPrefab;
       public GameObject goodStuffPrefab;
   
       public float fireballSpawnTime = 3;
       float fireballTimeElapsed = 0;
   
       public float goodStuffSpawnTime = 1.2f;
       float goodStuffTimeElapsed = 0;
             

5. Create a CoinOnCollision script to provide additional behavior to the GoodStuff. When the GoodStuff collides with the player, it should be destroyed and the value of numCoins (a property previously defined for the BoxBehaviour class) should increase by one.
6. Add print statements to provide output to the player, including displaying the player's number of coins each time a coin is collected and the player’s health each time damage is dealt.

Wrap-up Activity

Bouncy Box Playthrough