效果如下
代码目录
<!DOCTYPE html>
<html lang="zh-CN">
<head>
<meta charset="utf-8">
<title>弹球</title>
<link rel="stylesheet" href="style.css">
<script src="main.js" defer></script>
</head>
<body>
<h1>弹球</h1>
<p></p>
<canvas></canvas>
</body>
</html>
//main.js
const BALLS_COUNT = 25;
const BALL_SIZE_MIN = 10;
const BALL_SIZE_MAX = 20;
const BALL_SPEED_MAX = 7;
// 设定画布和初始数据
const para = document.querySelector('p');
const canvas = document.querySelector('canvas');
const ctx = canvas.getContext('2d');
// 将画布窗尺寸置为窗口内尺寸
const width = canvas.width = window.innerWidth;
const height = canvas.height = window.innerHeight;
// 设定形状类层次结构
class Shape {
constructor(x, y, velX, velY, exists) {
this.x = x;
this.y = y;
this.velX = velX;
this.velY = velY;
this.exists = exists;
}
}
//es6中的继承
class Ball extends Shape {
constructor(x, y, velX, velY, color, size, exists) {
super(x, y, velX, velY, exists);
this.color = color;
this.size = size;
}
//绘制
draw() {
ctx.beginPath();
ctx.fillStyle = this.color;
ctx.arc(this.x, this.y, this.size, 0, 2 * Math.PI);
ctx.fill();
}
//更新
update() {
if ((this.x + this.size) >= width) {
this.velX = -(this.velX);
}
if ((this.x - this.size) <= 0) {
this.velX = -(this.velX);
}
if ((this.y + this.size) >= height) {
this.velY = -(this.velY);
}
if ((this.y - this.size) <= 0) {
this.velY = -(this.velY);
}
this.x += this.velX;
this.y += this.velY;
}
//碰撞检测
collisionDetect() {
for (let j = 0; j < balls.length; j++) {
if ( this !== balls[j] ) {
const dx = this.x - balls[j].x;
const dy = this.y - balls[j].y;
const distance = Math.sqrt(dx * dx + dy * dy);
if (distance < this.size + balls[j].size && balls[j].exists) {
balls[j].color = this.color = randomColor();
}
}
}
}
}
//恶魔圈也继承自shape
class EvilCircle extends Shape {
constructor(x, y, exists) {
super(x, y, exists);
this.velX = BALL_SPEED_MAX;
this.velY = BALL_SPEED_MAX;
this.color = "white";
this.size = 10;
this.setControls();
}
// 绘制
draw() {
ctx.beginPath();
ctx.strokeStyle = this.color;
ctx.lineWidth = 3;
ctx.arc(this.x, this.y, this.size, 0, 2 * Math.PI);
ctx.stroke();
}
checkBounds() {
if ((this.x + this.size) >= width) {
this.x -= this.size;
}
if ((this.x - this.size) <= 0) {
this.x += this.size;
}
if ((this.y + this.size) >= height) {
this.y -= this.size;
}
if ((this.y - this.size) <= 0) {
this.y += this.size;
}
}
setControls() {
window.onkeydown = e => {
switch(e.key) {
case 'a':
case 'A':
case 'ArrowLeft':
this.x -= this.velX;
break;
case 'd':
case 'D':
case 'ArrowRight':
this.x += this.velX;
break;
case 'w':
case 'W':
case 'ArrowUp':
this.y -= this.velY;
break;
case 's':
case 'S':
case 'ArrowDown':
this.y += this.velY;
break;
}
};
}
collisionDetect() {
for (let j = 0; j < balls.length; j++) {
if (balls[j].exists) {
const dx = this.x - balls[j].x;
const dy = this.y - balls[j].y;
const distance = Math.sqrt(dx * dx + dy * dy);
if (distance < this.size + balls[j].size) {
balls[j].exists = false;
count--;
para.textContent = '还剩 ' + count + ' 个球';
}
}
}
}
}
// 球和恶魔圈
const balls = [];
const evilBall = new EvilCircle(
random(0, width),
random(0, height),
true
);
let count = 0;
// 执行动画
loop();
// 生成随机数的函数
function random(min, max) {
return Math.floor(Math.random()*(max-min)) + min;
}
// 生成随机颜色的函数
function randomColor() {
return 'rgb(' +
random(0, 255) + ', ' +
random(0, 255) + ', ' +
random(0, 255) + ')';
}
// 定义一个循环来不停地播放
function loop() {
ctx.fillStyle = 'rgba(0, 0, 0, 0.25)';
ctx.fillRect(0, 0, width, height);
while (balls.length < BALLS_COUNT) {
const size = random(BALL_SIZE_MIN, BALL_SIZE_MAX);
//绘制球
const ball = new Ball(
// 为避免绘制错误，球至少离画布边缘球本身一倍宽度的距离
random(0 + size, width - size),
random(0 + size, height - size),
random(-BALL_SPEED_MAX, BALL_SPEED_MAX),
random(-BALL_SPEED_MAX, BALL_SPEED_MAX),
randomColor(),
size,
true
);
balls.push(ball);
count++;
para.textContent = '还剩 ' + count + ' 个球';
}
for (let i = 0; i < balls.length; i++) {
//绘制球
if (balls[i].exists) {
balls[i].draw();
balls[i].update();
balls[i].collisionDetect();
}
}
evilBall.draw();
evilBall.checkBounds();
evilBall.collisionDetect();
requestAnimationFrame(loop);
}
//style.css
body {
margin: 0;
overflow: hidden;
font-family: '微软雅黑', sans-serif;
height: 100%;
}
h1 {
font-size: 2rem;
letter-spacing: -1px;
position: absolute;
margin: 0;
top: -4px;
right: 5px;
color: transparent;
text-shadow: 0 0 4px white;
}
p {
position: absolute;
margin: 0;
top: 35px;
right: 5px;
color: #aaa;
}