space-shmup/Assets/__Scripts/Enemy.cs

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

public class Enemy : MonoBehaviour
{
    [Header("Set in Inspector: Enemy")]
    public float speed = 10f;      // The speed in m/s
    public float fireRate = 0.3f;  // Seconds/shot (Unused)
    public float health = 10;
    public int score = 100;      // Points earned for destroying this
    public float showDamageDuration = 0.1f;
    [Header("Set Dynamically: Enemy")]
    public Color[] originalColors;
    public Material[] materials;
    public bool showingDamage = false;
    public float damageDoneTime;
    public bool notifiedOfDestruction = false;
    protected BoundsCheck bndCheck;

    void Awake() {
        bndCheck = GetComponent<BoundsCheck>();
        // Get materials and colors for this GameObject and its children
        materials = Utils.GetAllMaterials(gameObject);
        originalColors = new Color[materials.Length];
        for (int i = 0; i < materials.Length; ++i) {
            originalColors[i] = materials[i].color;
        }
    }

    // This is a Property: A method that acts like a field
    public Vector3 pos {
        get {
            return( this.transform.position );
        }
        set {
            this.transform.position = value;
        }
    }

    public virtual void Move() {
        Vector3 tempPos = pos;
        tempPos.y -= speed * Time.deltaTime;
        pos = tempPos;
    }

    void OnCollisionEnter(Collision coll) {
        GameObject otherGO = coll.gameObject;
        switch (otherGO.tag) {
            case "ProjectileHero":
                Projectile p = otherGO.GetComponent<Projectile>();
                // If this Enemy is off screen, don't damage it.
                if (!bndCheck.isOnScreen) {
                    Destroy(otherGO);
                    break;
                }

                // Hurt this Enemy
                ShowDamage();
                health -= 1;
                if (health <= 0) {
                    if (!notifiedOfDestruction) {
                        Main.S.ShipDestroyed(this);
                    }
                    notifiedOfDestruction = true;
                    // Destroy this Enemy
                    Destroy(this.gameObject);
                }
                Destroy(otherGO);
                break;

            default:
                print("Enemy hit by non-ProjectileHero: " + otherGO.name );
                break;
        }
    }

    void ShowDamage() {
        foreach(Material m in materials) {
            m.color = Color.red;
        }
        showingDamage = true;
        damageDoneTime = Time.time + showDamageDuration; 
    }

    void UnShowDamage() {
        for (int i = 0; i < materials.Length; ++i) {
            materials[i].color = originalColors[i];
        }
        showingDamage = false;
    }

    void Update()
    {
        Move();
        if (showingDamage && Time.time > damageDoneTime) {
            UnShowDamage();
        }
        if (bndCheck != null && bndCheck.offDown) {
            // We're off the bottom, so destroy this GameObject
            Destroy(gameObject);
        }
    }
}