[Unity] ゲームの進行を管理するGameManagerの簡単な例

こういうことができる

GameManager.cs

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

public enum GameState{
	Start,
	Prepare,
	Playing,
	End
}

public class GameManager : MonoBehaviour {

	public static GameManager Instance;

	// 現在の状態
	private GameState currentGameState;


	// 例

	public Text label;
	public Button button;

	void Awake(){
		Instance = this;
		SetCurrentState (GameState.Start);
	}


	// 外からこのメソッドを使って状態を変更
	public void SetCurrentState(GameState state){
		currentGameState = state;
		OnGameStateChanged (currentGameState);
	}

	// 状態が変わったら何をするか
	void OnGameStateChanged(GameState state){
		switch (state) {
		case GameState.Start:
			StartAction ();
			break;
		case GameState.Prepare:
			StartCoroutine (PrepareCoroutine ());
			break;
		case GameState.Playing:
			PlayingAction ();
			break;
		case GameState.End:
			EndAction ();
			break;
		default:
			break;
		}
	}

	// Startになったときの処理
	void StartAction(){
	}

	// Prepareになったときの処理
	IEnumerator PrepareCoroutine(){
		label.text = "3";
		yield return new WaitForSeconds(1);
		label.text = "2";
		yield return new WaitForSeconds(1);
		label.text = "1";
		yield return new WaitForSeconds(1);
		label.text = "";
		SetCurrentState (GameState.Playing);
	}
	// Playingになったときの処理
	void PlayingAction(){
		label.text = "ゲーム中";
	}
	// Endになったときの処理
	void EndAction(){
	}
}

外部スクリプトからの状態の変更の仕方

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

public class ButtonEvent : MonoBehaviour {

	public void OnStartButton(){
		GameManager.Instance.SetCurrentState (GameState.Prepare);
	}
}