Corutinas.cs

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

public class Corutinas : MonoBehaviour {
    public string state = "normal";
    public float duration = 1.5f;

    public float acceleration = 2;
    public float speedBoost = 0;
    public float _timeInPowerup = 0;
    public bool _boosting = false;
    Coroutine c = null;

    void Update () {
        if (Input.GetKeyDown(KeyCode.Space) && !_boosting) {
            this.StartCoroutine(PowerUpBehaviour());
        }

        _timeInPowerup += Time.deltaTime;
    }

    IEnumerator Pausa () {
        yield return new WaitForSeconds(Random.Range(0, 3f));
    }

    IEnumerator PowerUpBehaviour () {
        float timeWhileBoosted = 0;

        _timeInPowerup = 0;
        _boosting = true;
        state = "fast";

        yield return StartCoroutine(Pausa());

        while (timeWhileBoosted < duration) {
            speedBoost += acceleration * Time.deltaTime;
            timeWhileBoosted += Time.deltaTime;
            yield return null;
        }

        speedBoost = 0;
        _boosting = false;
        state = "normal";
    }
}