FNAF 07 - Power Manager

In this video, we build the Power Manager system — the lifeblood of every FNAF-style game. Your power now drains over time, with a working usage meter that shows how much energy each action costs. As the night goes on, every choice you make — opening the map, using the doors, switching lights — brings you closer to one terrifying outcome: the blackout.

When power hits 0%, the screen fades, the lights die, and something starts moving in the dark. This episode combines the Power Manager and the full Blackout sequence, turning the resource system into a real horror mechanic that keeps players watching that meter until the very end.

You can copy and paste the complete code directly from the tutorial below, or…

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PowerManager.cs

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

public class PowerManager : MonoBehaviour
{
    public float startingValue = 100.0f;
    public float baseDrainRate = 0.15f;

    private Dictionary activeRates = new Dictionary();
    private bool isRunning = true;
    private bool powerOutageRaised = false;

    public event Action OnPowerOut;
    public event Action OnPowerChanged;
    public event Action OnUsageChanged;

    [SerializeField] private float currentPower;
    [SerializeField] private int currentPowerInteger;

    private void Awake()
    {
        currentPower = Mathf.Clamp(startingValue, 0, 100);
        currentPowerInteger = Mathf.RoundToInt(currentPower);
        CheckPowerIntChange();
    }

    private void Start()
    {
        OnPowerChanged?.Invoke(currentPowerInteger);
        OnUsageChanged?.Invoke(GetUsage());
    }

    // Update is called once per frame
    void Update()
    {
        if(isRunning || !powerOutageRaised)
        {
            //Remove base rate 
            float powerDrawRate = baseDrainRate;

            //Remove drains
            foreach(string name in activeRates.Keys )
            {
                powerDrawRate += activeRates[name];
            }

            currentPower = Mathf.Max(0.0f, currentPower - (powerDrawRate * Time.deltaTime));

            CheckPowerIntChange();

            if (!powerOutageRaised && currentPower <= 0.0f)
            {
                powerOutageRaised = true;
                OnPowerOut?.Invoke();
            }
        }
    }

    public void AddDraw(string id, float drainPerSec)
    {
        if (string.IsNullOrEmpty(id)) return;
        activeRates[id] = drainPerSec;
        OnUsageChanged?.Invoke(GetUsage());
    }

    public int GetUsage()
    {
        int currentUsage = 0;
        //if the system is running, usage is always 1
        if (isRunning)
            currentUsage += 1;

        if (activeRates.Count > 0)
        {
            currentUsage = Mathf.Clamp(currentUsage, currentUsage, 5);
        }

        //Get the number of objects drawing power, max is 5
        return currentUsage;
    }

    public void RemoveDraw(string id)
    {
        if(string.IsNullOrEmpty(id)) return;
        activeRates.Remove(id);
        OnUsageChanged?.Invoke(GetUsage());
    }

    private void CheckPowerIntChange()
    {
        int rounded = Mathf.RoundToInt(currentPower);
        if(rounded != currentPowerInteger)
        {
            currentPowerInteger = rounded;
            OnPowerChanged?.Invoke(currentPowerInteger);
        }
    }

    public void Reset()
    {
        activeRates.Clear();
        powerOutageRaised = false;
        currentPower = Mathf.Clamp(startingValue, 0.0f, 100.0f);
        isRunning = true;
        currentPowerInteger = Mathf.RoundToInt(currentPower);
        OnPowerChanged?.Invoke(currentPowerInteger);
        OnPowerOut?.Invoke();
    }
}

PowerUI.cs

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

public class PowerUI : MonoBehaviour
{
    [Header("References")]
    public UnityEngine.UI.Image powerUIPanel;
    public PowerManager powerManager;
    public TMPro.TMP_Text powerRemainingText;
    public UnityEngine.UI.Image[] batteryUsageBars;

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

    private void OnEnable()
    {
        if (powerManager != null)
        {
            powerManager.OnPowerChanged += OnPowerChanged;
            powerManager.OnUsageChanged += OnUsageChanged;
            powerManager.OnPowerOut += OnPowerOut;
        }
    }

    private void OnDisable()
    {
        if(powerManager != null)
        {
            powerManager.OnPowerChanged -= OnPowerChanged;
            powerManager.OnUsageChanged -= OnUsageChanged;
        }
    }

    void UpdateUsageUI(int usage)
    {
        for(int i = 0; i < batteryUsageBars.Length; i++)
        {
            if (i < usage)
                batteryUsageBars[i].enabled = true;
            else
                batteryUsageBars[i].enabled = false;
        }
    }

    void UpdatePowerUI(int power)
    {
        powerRemainingText.text = $"{power}%";
    }

    void OnPowerChanged(int power)
    {
        //Debug.Log("Power changed.");
        UpdatePowerUI(power);
    }

    void OnUsageChanged(int usage)
    {
        //Debug.Log("Usage changed.");
        UpdateUsageUI(usage);
    }

    void OnPowerOut()
    {
        powerUIPanel.gameObject.SetActive(false);
    }
}

BlackOutController.cs

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

public class BlackOutController : MonoBehaviour
{
    [Header("Managers & Controllers")]
    public CameraManager cameraManager;
    public JumpScareSequence jumpScareSequence;
    public PowerManager powerManager;

    [Header("BG Texture References")]
    public Texture2D tex_securityRoom_normal;
    public Texture2D tex_securityRoom_noPower;
    public Texture2D tex_securityRoom_anim_01;
    public Texture2D tex_securityRoom_anim_02;
    public Texture2D tex_securityRoom_backOut;

    [Header("Audio References")]
    public AudioSource as_breaker_switch;
    public AudioSource as_animatronic_long_walk;
    public AudioSource as_generator_slow_die;
    public AudioSource as_power_outage_music;
    public AudioSource as_animatronic_3_last_steps;

    // Start is called before the first frame update
    void Start()
    {
        powerManager.OnPowerOut += OnPowerOut;
    }

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

    public void OnPowerOut()
    {
        StartCoroutine(C_BlackOutSequence());
    }

    IEnumerator C_BlackOutSequence()
    {
        //Wait to allow other things to react to the blackout sequence.
        //This is actually a very poor way to do this, it would be better
        //If we implemented a manager over the room and have its state controlled by a 
        //class that hides all this messiness I'm doing with timing... maybe next time...
        yield return null;

        //Swap room texture to dark blue
        cameraManager.SetRoomBackground(tex_securityRoom_noPower);
        as_breaker_switch.Play();
        //Open doors (Not implemented yet)

        //Play low-pitched generator whine
        as_generator_slow_die.Play();
        float time_To_footsteps = as_generator_slow_die.clip.length - as_animatronic_long_walk.clip.length;
        yield return new WaitForSeconds(time_To_footsteps);
        //Play footsteps getting closer
        as_animatronic_long_walk.Play();
        yield return new WaitForSeconds(as_animatronic_long_walk.clip.length);
        //Play carnival music
        as_power_outage_music.Play();
        //Flicker face ?In time with music?
        yield return StartCoroutine(RandomFaceFlicker(as_power_outage_music.clip.length - 7.5f));
        yield return new WaitForSeconds(1.5f);
        //Change room texture to dark black
        as_breaker_switch.Play();
        cameraManager.SetRoomBackground(tex_securityRoom_backOut);
        //Play footsteps
        yield return new WaitForSeconds(1.5f);
        as_animatronic_3_last_steps.Play();
        yield return new WaitForSeconds(as_animatronic_3_last_steps.clip.length);
        //Jumpscare
        jumpScareSequence.Play();
    }

    IEnumerator RandomFaceFlicker(float length)
    {
        float acc_time = 0.0f;

        Texture2D[] swapArray = { tex_securityRoom_noPower, tex_securityRoom_anim_01, tex_securityRoom_anim_02 };
        int currentIndex = swapArray.Length - 1;

        while (acc_time < length)
        {
            //Should we swap the face?
            if(currentIndex == 0)
            {
                //50 / 50 chance to hold on dark room
                if(Random.Range(0,2) == 0)
                {
                    acc_time += Time.deltaTime;
                    yield return null;
                }
            }
            //How long to swap?
            float waitTime = Random.Range(0.01f, 0.2f);
            yield return new WaitForSeconds(waitTime);
            //What should we swap to? Equal chance to swap among all options. 
            //Probabilities are : {0.833, 0.16665, 0.16665}
            currentIndex = Random.Range(0, swapArray.Length);
            cameraManager.SetRoomBackground(swapArray[currentIndex]);
            acc_time += waitTime;
            yield return null;
        }
        //Swap back to off screen.
        cameraManager.SetRoomBackground(swapArray[0]);
    }
}