Magnet

Lesson 14 of 20 in Coddy's Unity Game: Sky Lanes course.

Power-ups make a run feel different from the last. The first is a magnet: for 8 seconds every coin near the runner flies to it.

The Runner keeps the time left in magnet and counts it down. Each coin looks at the runner, and while the magnet is on and the runner is near, moves towards it:

if (runner.magnet > 0f && Vector3.Distance(transform.position, runner.transform.position) < pullRange)
{
    transform.position = Vector3.MoveTowards(transform.position, runner.transform.position, pullSpeed * Time.deltaTime);
}

The coin flies into the runner and its trigger does the rest. Now and then a piece of road gets a pink magnet pickup, 6 units before its obstacles.

Challenge

Easy

In Runner add public float magnetTime = 8f; and public float magnet;. Count it down every frame while it is above 0.
In OnTriggerEnter, a Magnet tag sets magnet = magnetTime and destroys the pickup.
In Coin add pullRange = 7f, pullSpeed = 30f, find the Runner in Start and pull as above.
In Road add magnetPrefab. At the end of Fill, float roll = Random.value; and if roll < 0.06f place a magnet in a random lane at y 1, z -6.

Try it yourself

using UnityEngine;

public class Runner : MonoBehaviour
{
    public float laneWidth = 2.5f;
    public float laneSpeed = 16f;
    public float jumpHeight = 1.6f;
    public float gravity = -40f;
    public float slideTime = 0.7f;

    public int lane;

    private CharacterController controller;
    private GameManager game;
    private float fallSpeed;
    private float slide;

    void Start()
    {
        controller = GetComponent<CharacterController>();
        game = FindFirstObjectByType<GameManager>();
    }

    void Update()
    {
        if (!game.over)
        {
            if (Input.GetKeyDown(KeyCode.A) || Input.GetKeyDown(KeyCode.LeftArrow)) lane = Mathf.Max(-1, lane - 1);
            if (Input.GetKeyDown(KeyCode.D) || Input.GetKeyDown(KeyCode.RightArrow)) lane = Mathf.Min(1, lane + 1);
            bool jump = Input.GetKeyDown(KeyCode.W) || Input.GetKeyDown(KeyCode.UpArrow) || Input.GetKeyDown(KeyCode.Space);
            if (jump && controller.isGrounded)
            {
                fallSpeed = Mathf.Sqrt(jumpHeight * -2f * gravity);
                StopSlide();
            }
            if ((Input.GetKeyDown(KeyCode.S) || Input.GetKeyDown(KeyCode.DownArrow)) && controller.isGrounded)
            {
                slide = slideTime;
                Resize(0.5f);
            }
        }

        if (slide > 0f)
        {
            slide -= Time.deltaTime;
            if (slide <= 0f) StopSlide();
        }

        if (controller.isGrounded && fallSpeed < 0f) fallSpeed = -2f;
        fallSpeed += gravity * Time.deltaTime;

        float targetX = lane * laneWidth;
        float x = Mathf.MoveTowards(transform.position.x, targetX, laneSpeed * Time.deltaTime);
        Vector3 move = new Vector3(x - transform.position.x, fallSpeed * Time.deltaTime, 0f);
        controller.Move(move);
    }

    void StopSlide()
    {
        if (transform.localScale.y < 1f) Resize(1f);
        slide = 0f;
    }

    void Resize(float height)
    {
        controller.enabled = false;
        transform.position += Vector3.up * (height - transform.localScale.y);
        transform.localScale = new Vector3(1f, height, 1f);
        controller.enabled = true;
    }

    void OnTriggerEnter(Collider other)
    {
        if (game.over) return;
        if (other.CompareTag("Obstacle"))
        {
            game.GameOver();
        }
        else if (other.CompareTag("Coin"))
        {
            game.AddCoin();
            Destroy(other.gameObject);
        }
    }
}