Quick Start

Create a class that inherits from Singleton.

public class SomeManager : Singleton<SomeManager>
{
    public string HelloWorld = "Hello, World!";
}

That's it! Now, whenever SomeManager.Instance is called, Singleton will search for an existing instance of SomeManager in the scene or create a new one. Now, any script can access HelloWorld without needing to have a local reference of SomeManager:

public class SomeOtherScript : MonoBehaviour
{
    private void Start()
    {
        Debug.Log(SomeManager.Instance.HelloWorld);
    }
}