Same as AttackSequenceDemo but with coroutines

AttackSequencingDemo2.cs

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

// @kurtdekker
//
// from Unity forums: https://forum.unity.com/threads/logic-to-create-turns-of-attacks.1137946/
//
// Rewriting AttackSequencingDemo as coroutines, as per GroZZler's suggestion.
//
// Observation: process can be shorter in terms of LoC, but is the
// logic more-evident to a new user? Indeterminate...
//
// goal: a random attack starts in 2-5 seconds, you have 1 second to defend against it
//
// implementation: coroutines and timers
//
// To use:
//	- make an empty scene
//	- add a single GameObject
//	- put this script on it
//	- press PLAY
//	- pay attention to the console
//

public class AttackSequencingDemo2 : MonoBehaviour
{
	// goes up if you defend
	int score;
	// needed to win
	const int ScoreRequired = 5;

	// goes down if you fail to defend, game over at 0 hp
	int lifeHitpoints = 3;

	// it will choose one of these keys to defend
	KeyCode[] possibleDefenseKeys = new KeyCode[]
	{
		KeyCode.A, KeyCode.S, KeyCode.D,
	};

	string GameStateDetails()
	{
		return "Score: " + score + ", HP: " + lifeHitpoints;
	}

	// Start is our master coroutine
	IEnumerator Start()
	{
		while(true)
		{
			Debug.Log( "Get ready for a random attack... incoming...");

			float randomCooldownTimer = Random.Range( 2.0f, 5.0f);

			// wait for it to begin...
			while( randomCooldownTimer > 0)
			{
				randomCooldownTimer -= Time.deltaTime;

				CheckForSpammedKeys();

				yield return null;
			}

			// choose how to defend
			KeyCode chosenDefenseKey = possibleDefenseKeys[ Random.Range( 0, possibleDefenseKeys.Length)];

			Debug.Log( "ATTACK BEGINS! Attack pending in 1 second! Press " + chosenDefenseKey + " to defend!!");

			float attackIsUnderwayCountdown = 1.0f;

			// wait for attack to land
			while( true)
			{
				// check for keys, both legit and otherwise
				if (Input.GetKeyDown( chosenDefenseKey))
				{
					score++;

					Debug.Log( "DEFENDED! " + GameStateDetails());

					break;
				}
				else
				{
					CheckForSpammedKeys();
				}

				attackIsUnderwayCountdown -= Time.deltaTime;

				if (attackIsUnderwayCountdown < 0)
				{
					lifeHitpoints--;

					Debug.Log( "YOU GOT HIT!! " + GameStateDetails());

					break;
				}

				yield return null;
			}

			// necessary otherwise your last keystroke will be counted as spam at the top...
			yield return null;
		}
	}

	void CheckForSpammedKeys()
	{
		foreach( var key in possibleDefenseKeys)
		{
			if (Input.GetKeyDown( key))
			{
				score--;

				if (score < 0)
				{
					score = 0;
				}

				Debug.Log( "PENALTY FOR SPAMMING! " + GameStateDetails());

				// NOTE: even if you spam, the attack continues!
			}
		}
	}

	void UpdateHandleWinLose()
	{
		if (lifeHitpoints <= 0)
		{
			Debug.Log( "YOU DIED!");
			Destroy(this);
			return;
		}

		if (score >= ScoreRequired)
		{
			Debug.Log( "YOU WIN!");
			Destroy(this);
			return;
		}
	}

	void Update()
	{
		UpdateHandleWinLose();
	}
}