2D Games Core Programming: Quickly Collect Pickups

Objective: When the ‘C’ key is pressed by the Player, Pickups quickly move to the player.

Before adding code to the Player.cs script, I added code to the Powerup.cs script to handle changing their movement when the C key is pressed.

In the Powerup.cs script, I added a boolean variable for keeping track of the movement state and a reference to the player.

private bool _moveTowardsPlayer = false;
private Player _player;

In the Start() method, I initialized _player to reference the user’s ship. I don’t need to null check for it because the player could be dead.

_player = GameObject.Find("Player").GetComponent<Player>();

In the Powerup.cs script’s Update() method, I added conditionals around the movement code to check _moveTowardsPlayer. If it’s false, movement is normal, but if it’s true, I used the function MoveTowards() to make the powerup move towards the player.

void Update()
{

    if (!_moveTowardsPlayer) // NEW
    {
        // move down at a speed
        transform.Translate(Vector3.down * _speed * Time.deltaTime);
    }
    else if ((_moveTowardsPlayer) & (_player != null)) // NEW
    {
        // NEW
        transform.position = Vector2.MoveTowards(transform.position, _player.transform.position, _speed * 2.0f * Time.deltaTime);
    }

    // when leave screen, destroy object
    if (transform.position.y <= -_verticalLimit)
    {
        Destroy(this.gameObject);
    }
}

For the _moveTowardsPlayer boolean variable, I added two public methods for changing it.

public void MoveTowardsPlayerEnable()
{
    _moveTowardsPlayer = true;
}

public void MoveTowardsPlayerDisable()
{
    _moveTowardsPlayer = false;
}

Back in the Player.cs script, in the Update() method, I added conditionals for the C key input press and release. After the C key is pressed, I followed these instructions:

• Do a null check for the powerupContainer in the _spawnManager.
• Put all the powerups in the powerupContainer into an array for counting and direct access.
• If there are powerups in the level, enable moving towards the player.

void Update()
{
    // Check charge level. Restrict to min, max values
    _thrusterChargeLevel = Mathf.Clamp(_thrusterChargeLevel, 0, _thrusterChargeLevelMax);

    // Set _canUseThrusters depending on _thrusterChargeLevel
    if (_thrusterChargeLevel <= 0.0f)
    {
        _canUseThrusters = false;
    }
    else if (_thrusterChargeLevel >= 0.0f)
    {
        _canUseThrusters = true;
    }

    if (Input.GetKeyDown(KeyCode.LeftShift) && _canUseThrusters)
    {
        SpeedBoostActiveShift();
    }  
    
    if (Input.GetKeyUp(KeyCode.LeftShift))
    {
        SpeedReset();
    }
    
    // NEW
    // If "c" key is pressed, call method to make powerups move towards player
    if (Input.GetKeyDown(KeyCode.C))
    {
        if (_spawnManager.powerupContainer != null)
        {
            Powerup[] _allPowerups = _spawnManager.powerupContainer.GetComponentsInChildren<Powerup>();
            if (_allPowerups.Length > 0)
            {
                for (int i = 0; i < _allPowerups.Length; i++)
                {
                    _allPowerups[i].MoveTowardsPlayerEnable();
                }
            }
        }
    }

    // NEW
    if (Input.GetKeyUp(KeyCode.C))
    {
        if (_spawnManager.powerupContainer != null)
        {
            Powerup[] _allPowerups = _spawnManager.powerupContainer.GetComponentsInChildren<Powerup>();
            if (_allPowerups.Length > 0)
            {
                for (int i = 0; i < _allPowerups.Length; i++)
                {
                    _allPowerups[i].MoveTowardsPlayerDisable();
                }

            }
        }

    }


    CalculateMovement();

    if (Input.GetKeyDown(KeyCode.Space) && Time.time > _canFire )
    {
        Firelaser();
    }

}

When the game is tested, pressing the C key will make the powerups move quickly towards the player.