Bit Masking

Overview

In this project I used bit masking to store several values in a single 8-bit integer and keep memory use down. It's a technique that suits game state like player abilities.

The player collects abilities scattered around the level, and each one is a single bit in the integer. Collecting an ability switches its bit on, and some pickups switch one off. The on-screen counter shows the byte changing as you play. Besides saving memory, this keeps the logic simple: checking or updating an ability is one fast bitwise operation, which also makes the system easy to extend.

Technical breakdown

Each ability is a power of two in a [Flags] enum (Magic, Charisma, Fly, Intelligence and Invisible), so it occupies exactly one bit:

public class Ability : MonoBehaviour
{
    public bool deActive;
    [Flags]
    public enum Spell
    {
        Magic =1,
        Charisma =2,
        Fly = 4,
        Intelligence = 8,
        Invisible =16
    }
    public Spell MySpell;
}

When the player touches an item, OR sets the item's bit. Items marked deActive clear it instead, with AND against the inverted mask:

public class Item : Ability
{
    private void OnTriggerEnter(Collider other)
    {
        Player playerItem = other.GetComponent<Player>();
        if (playerItem != null)
        {
            if (deActive)
            {
                playerItem.myItem &= ~ (int) MySpell;
            }
            else if(!deActive)
            {
                playerItem.myItem |= (int) MySpell;
            }
        }
    }
}