<style>
  * {
    margin: 0px;
    padding: 0px;
  }
 canvas{
 border: 1px solid #000;
 display: block;
 margin: auto;
 }
</style>

<!-- 先创建一个画布 -->
<canvas id="canvas" width="480" height="640"></canvas>

<script>
 var canvas = document.getElementById("canvas");
  var context = canvas.getContext("2d");

  // 0游戏初始化
  // 0.1定义游戏开始的五个阶段
  var START = 0;
  var STARTING = 1;
  var RUNNING = 2;
  var PAUSE = 3;
  var GAMEOVER = 4;

  // 0.2 定义一个自己的状态，时刻去和上面的五个状态作比较

  // 0.3 页面加载时
  var state = START;
  // 0.4 背景图片的宽和高
  var WIDTH = 480;
  var HEIGHT = 640;
  // 0.5 定义分数
  var score = 0;
  // 0.6 定义生命条数 
  var life = 3;


  // 1 游戏开始前
  // 1.1 加载背景图片
  // 1.1.1 背景图片的对象
  var bg = new Image();// 创建一个背景图片
  bg.src = "images/background.png";
  // 1.1.2 背景图片的数据
  var BG = {
    imgs: bg,
    width: 480,
    height: 852
  }

  // 1.1.3 背景图片的构造函数
  function Bg(config) {
    this.imgs = config.imgs;
    this.width = config.width;
    this.height = config.height;

    // 绘制图片的坐标（两张背景图片进行轮流滑动）
    this.x1 = 0;
    this.y1 = 0;
    this.x2 = 0;
    this.y2 = -this.height;
    // 背景图片绘制
    this.paint = function () {
      context.drawImage(this.imgs, this.x1, this.y1);
      context.drawImage(this.imgs, this.x2, this.y2);
    }
    // 图片的运动
    this.step = function () {
      this.y1++;
      this.y2++;
      // 判断图片的临界点
      if (this.y1 == this.height) {
        this.y1 = -this.height;
      }
      if (this.y2 == this.height) {
        this.y2 = -this.height;
      }
    }
  }
  // 1.1.4创建对象
  var sky = new Bg(BG);
  // console.log(sky);

  // 1.2 创建页面加载时的飞机大战图片
  var logo = new Image();
  logo.src = "images/start.png";


  // 2.游戏开始前
  // 2.1 开始前动画的对象
  var loadings = [];
  loadings[0] = new Image();
  loadings[0].src = "images/game_loading1.png";
  loadings[1] = new Image();
  loadings[1].src = "images/game_loading2.png";
  loadings[2] = new Image();
  loadings[2].src = "images/game_loading3.png";
  loadings[3] = new Image();
  loadings[3].src = "images/game_loading4.png";
  // 2.2 开始前加载的动画图片的数据
  var LOADINGS = {
    imgs: loadings,
    length: loadings.length,
    width: 186,
    height: 38
  }
  // 2.3 开始前动画的构造函数
  function Loading(config) {
    this.imgs = config.imgs;
    this.length = config.length;
    this.width = config.width;
    this.height = config.height;
    // 定义一个索引
    this.startIndex = 0;
    // 绘制
    this.paint = function () {
      context.drawImage(this.imgs[this.startIndex], 0, HEIGHT - this.height);
    }

    // 定义一个速度
    this.time = 0;
    this.step = function () {
      this.time++;
      if (this.time % 3 == 0) { 
        // 页面加载时下面小飞机运行的速度
        this.startIndex++;
      }

      // 当动画运行完成进入下一个阶段
      if (this.startIndex == this.length) {
        state = RUNNING;
      }
    }
  }
  // 2.4创建对象
  var loading = new Loading(LOADINGS);
  // 2.5绑定时间
  canvas.onclick = function () {
    if (state == START) {
      state = STARTING;
    }
  }

  // 3.1.1游戏开始时的图片
  var heros = [];
  heros[0] = new Image();
  heros[0].src = "images/hero1.png";
  heros[1] = new Image();
  heros[1].src = "images/hero2.png";

  heros[2] = new Image();
  heros[2].src = "images/hero_blowup_n1.png";
  heros[3] = new Image();
  heros[3].src = "images/hero_blowup_n2.png";
  heros[4] = new Image();
  heros[4].src = "images/hero_blowup_n3.png";
  heros[5] = new Image();
  heros[5].src = "images/hero_blowup_n4.png";
  // 3.1.2游戏开始时加载数据
  var HEROS = {
    imgs: heros,
    length: heros.length,
    width: 99,
    height: 124,
    // 我方飞机有两种状态，增加标识
    frame: 2
  }
  // 3.1.3我方飞机的构造器
  function Hero(config) {
    this.imgs = config.imgs;
    this.length = config.length;
    this.width = config.width;
    this.height = config.height;
    this.frame = config.frame;
    // 定义索引
    this.startIndex = 0;
    // 绘制坐标
    this.x = WIDTH / 2 - this.width / 2;
    this.y = HEIGHT - 150;

    // 增加标识符
    this.down = false;  //表示一直没有撞击
    // 增加标识符
    this.candel = false; //表示撞击以后的动画是否运行完成，完成以后的恢复运行的状态

    // 定义绘制方法
    this.paint = function () {
      context.drawImage(this.imgs[this.startIndex], this.x, this.y)
    }
    // 定义运动的方法
    this.step = function () {
      // 两个状态
      // 1.正常运动状态
      // 2.碰撞以后的状态
      if (!this.down) {//正常运动状态
        // 没有发生撞击的时候 一直在0和1之间切换
        this.startIndex++;
        this.startIndex = this.startIndex % 2;
      }
      else {//撞击以后的状态
        // 脚标就要不停的加1，模拟出从碰撞到爆炸完成的动画
        this.startIndex++;
        // 判断是否完成撞击
        if (this.startIndex == this.length) {
          life--//爆炸一次生命值减1；
          if (life == 0) {
            state = GAMEOVER;
            // 如果死了，动画保存最后一张爆破的照片
            this.startIndex = this.length - 1;
          }
          else {
            hero = new Hero(HEROS);
          }
        }
      }
    }

    // 我方飞机增加射击方法
    this.time = 0;
    this.shoot = function () {
      this.time++;
      if (this.time % 2 == 0) {
        bullets.push(new Bullet(BULLET));
      }
    }
    // 撞击以后触发
    this.bang = function () {
      this.down = true;
    }
  }

  // 3.1.4我方飞机的对象 
  var hero = new Hero(HEROS);
  // 3.1.5绑定鼠标移动事件
  canvas.onmousemove = function (e) {
    if (state == RUNNING) {
      var x = e.offsetX;
      var y = e.offsetY;
      hero.x = x - hero.width / 2;
      hero.y = y - hero.height / 2;
    }
  }

  // 3.2 绘制子弹
  // 3.2.1 图片
  var bullet = new Image();
  bullet.src = "images/bullet1.png";
  // 3.2.2数据
  var BULLET = {
    imgs: bullet,
    width: 9,
    height: 21
  }
  // 3.2.3 子弹的构造函数
  function Bullet(config) {
    this.imgs = config.imgs;
    this.width = config.width;
    this.height = config.height;
    // 子弹坐标
    this.x = hero.x + hero.width / 2 - this.width / 2;
    this.y = hero.y - this.height;
    // 绘制
    this.paint = function () {
      context.drawImage(this.imgs, this.x, this.y);
    }
    // 运动 往上运动
    this.step = function () {
      this.y -= 10;
    }
    this.candel = false;//表示撞击以后的动画是否运行完成，完成以后的恢复运行的状态
    this.bang = function () {
      this.candel = true;
    }
  }
  // 3.2.4 存放所有子弹
  var bullets = [];
  // 3.2.5 绘制所有子弹
  function bulletsPaint() {
    for (var i = 0; i < bullets.length; i++) {
      bullets[i].paint();
    }
  }
  // 3.2.6 绘制所有子弹的运动
  function bulletsStep() {
    for (var i = 0; i < bullets.length; i++) {
      bullets[i].step();
    }
  }
 // 3.2.7 删除子弹
 function bulletsDel(){
 for(var i = 0; i < bullets.length;i++){
  if(bullets[i].y < -bullets[i].height || bullets[i].candel){
  bullets.splice(i,1)
  }
 }
 // console.log(bullets)
 }
  // 3.3 敌方飞机
  // 3.3.1 敌方飞机的图片（3种）
  // 小号
  var enemy1 = [];
  enemy1[0] = new Image();
  enemy1[0].src = "images/enemy1.png";

  enemy1[1] = new Image();
  enemy1[1].src = "images/enemy1_down1.png";
  enemy1[2] = new Image();
  enemy1[2].src = "images/enemy1_down2.png";
  enemy1[3] = new Image();
  enemy1[3].src = "images/enemy1_down3.png";
  enemy1[4] = new Image();
  enemy1[4].src = "images/enemy1_down4.png";
  // 中号
  var enemy2 = [];
  enemy2[0] = new Image();
  enemy2[0].src = "images/enemy2.png";

  enemy2[1] = new Image();
  enemy2[1].src = "images/enemy2_down1.png";
  enemy2[2] = new Image();
  enemy2[2].src = "images/enemy2_down2.png";
  enemy2[3] = new Image();
  enemy2[3].src = "images/enemy2_down3.png";
  enemy2[4] = new Image();
  enemy2[4].src = "images/enemy2_down4.png";
  // 大号
  var enemy3 = [];
  enemy3[0] = new Image();
  enemy3[0].src = "images/enemy3_n1.png";
  enemy3[1] = new Image();
  enemy3[1].src = "images/enemy3_n2.png";

  enemy3[2] = new Image();
  enemy3[2].src = "images/enemy3_down1.png";
  enemy3[3] = new Image();
  enemy3[3].src = "images/enemy3_down2.png";
  enemy3[4] = new Image();
  enemy3[4].src = "images/enemy3_down3.png";
  enemy3[5] = new Image();
  enemy3[5].src = "images/enemy3_down4.png";
  enemy3[6] = new Image();
  enemy3[6].src = "images/enemy3_down5.png";
  enemy3[7] = new Image();
  enemy3[7].src = "images/enemy3_down6.png";

  // 3.2.2 数据
  var ENEMY1 = {
    imgs: enemy1,
    length: enemy1.length,
    width: 57,
    height: 51,
    type: 1, //增加标识符，区分飞机的种类。小号的设置成1
    frame: 1, //增加标识符，1种状态就为1，2种状态就为2
    life: 1, //增加标识符，被子弹打击的次数
    score: 1  //打倒一只的得分
  }
  var ENEMY2 = {
    imgs: enemy2,
    length: enemy2.length,
    width: 69,
    height: 95,
    type: 2, //增加标识符，区分飞机的种类。中号的设置成2
    frame: 1, //增加标识符，1种状态就为1，2种状态就为2
    life: 3, //增加标识符，被子弹打击的次数
    score: 5 //打倒一只的得分
  }
  var ENEMY3 = {
    imgs: enemy3,
    length: enemy3.length,
    width: 169,
    height: 258,
    type: 3, //增加标识符，区分飞机的种类。大号的设置成3
    frame: 2, //增加标识符，，1种状态就为1，2种状态就为2
    life: 10, //增加标识符，被子弹打击的次数
    score: 15  //打倒一只的得分
  }
  // 3.3.3 构造函数
  function Enemy(config) {
    this.imgs = config.imgs;
    this.length = config.length;
    this.width = config.width;
    this.height = config.height;
    this.type = config.type;
    this.frame = config.frame;
    this.life = config.life;
    this.score = config.score;

    // 图片的索引
    this.startIndex = 0
    this.down = false;  //表示一直没有撞击
    this.candel = false; //表示撞击以后的动画是否运行完成，完成以后的恢复运行的状态

    // 绘制坐标
    this.x = Math.random() * (WIDTH - this.width);
    this.y = -this.height;
    // 绘制的方法
    this.paint = function () {
      context.drawImage(this.imgs[this.startIndex], this.x, this.y);
    }
    // 运动方法
 this.step = function(){
  if(!this.down){  //正常
  // 小号的，中号 角标始终是0
  // 大号的是在0和1之间切换
  this.startIndex ++;
  this.startIndex = this.startIndex % this.frame;

  this.y += 2;
  }else {  //爆炸
  this.startIndex ++;
  if(this.startIndex == this.length){
   this.candel = true;
   this.startIndex = this.length - 1;
  }
  }
 }

    // 爆炸的方法
 this.bang = function(){
  this.life -- ;
  if(this.life == 0){
  this.down = true;
  score += this.score;
  }
 }
    // 检测是否撞击
 this.checkHit = function(wo){
  // 1.撞击到子弹
  // 2.撞击到我方飞机
  return wo.y + wo.height > this.y 
  && wo.x + wo.width > this.x
  && wo.y < this.y + this.height
  && wo.x < this.x + this.width;
 }
  }

  // 3.3.4 创建数组 存储敌方飞机
  var enemies = [];
  // 3.3.5 创建飞机
  function enterEnemies() {
    var num = Math.random();
    if (num < 0.1) {
      enemies.push(new Enemy(ENEMY1))
    } else if (num < 0.15) {
      enemies.push(new Enemy(ENEMY2))
    } else if (num < 0.16) {
      enemies.push(new Enemy(ENEMY3))
    }
  }
  // 3.3.6 绘制
  function paintEnemies() {
    for (var i = 0; i < enemies.length; i++) {
      enemies[i].paint();
    }
  }
  // 3.3.7 运动
  function stepEnemies() {
    for (var i = 0; i < enemies.length; i++) {
      enemies[i].step();
    }
  }
  // 3.3.8 删除
 function delEnemies(){
 for(var i = 0;i < enemies.length;i++){
  if(enemies[i].y > HEIGHT || enemies[i].candel){
  enemies.splice(i,1)
  }
 }
 }
  // 3.4 检测撞击
  function hitEnemies() {
    for (var i = 0; i < enemies.length; i++) {
      if (enemies[i].checkHit(hero)) {
        enemies[i].bang();
        hero.bang();
      }
      for (var j = 0; j < bullets.length; j++) {
        if (enemies[i].checkHit(bullets[j])) {
          enemies[i].bang();
          bullets[j].bang();
        }
      }
    }
  }
 // 3.5 我方飞机的生命和得分
 function paintText(){
 context.font = "bold 30px 微软雅黑";
 context.fillText("SCORE:" + score,10,30);
 context.fillText("LIFE:" + life,380,30)
 }

  // 4.暂停阶段
  canvas.onmouseover=function(){
    if(state==PAUSE){
      state=RUNNING;
    }
  }
  canvas.onmouseout=function(){
    if(state==RUNNING){
      state=PAUSE;
    }
  }
  var pause=new Image();
  pause.src="/UploadFiles/2021-04-02/game_pause_nor.png">

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