console
var contain = document.getElementById("contain");
var box = document.getElementById("box");
var board = document.getElementsByClassName("board")[0];
var ball = document.getElementsByClassName("ball")[0];
var btn = document.getElementsByTagName("button")[0];
var score = document.getElementsByClassName("score")[0];
//分别代表board左距离、右距离;ball左距离、右距离
var board_left,board_top,ball_left,ball_top ;
var interval,flag=1,sum=0;
//设置小球的速度
var speedX = -1,speedY = -1;
//监听鼠标进入box
box.onmousemove = function() {
//事件对象(兼容)
var e = event || window.event;
//更改board的left和top
board_left = event.pageX - box.offsetLeft -50;
board_top = event.pageY - box.offsetTop;
//检测board是否超出边框并更改board和ball位置
if(board_left>=0 && board_left<=400) {
board.style.left = board_left + "px";
//flag的作用是防止点击按钮后再次进入Box后球的位置再变化
if(flag) {
ball_left = board_left + 45;
ball.style.left = ball_left + "px";
}
}
if(board_top>=0 && board_top<=390){
board.style.top = board_top + "px";
if(flag) {
ball_top = board_top - 15;
ball.style.top = ball_top +"px";
}
}
}
//监听按钮点击事件
btn.onclick = function() {
//清除定时器,防止定时器重叠
clearInterval(interval);
//flag=0后ball不再随board位置变化
flag=0;
//设置定时器
interval = setInterval(function(){
ball_left += speedX;
ball_top += speedY;
if(ball_left>=0 && ball_left<=485){
ball.style.left = ball_left + "px";
}
if(ball_top>=0 && ball_top<=385){
ball.style.top = ball_top + "px";
}
//球的方向改变
//撞d到左边右边边框
if(ball_left<0|| ball_left>485 ){
speedX = -speedX;
}else if(ball_top<0){//撞到上边边框边框
speedY = -speedY;
}
//检测ball碰到board
if((ball_top+15) >= board_top && ball_left>=board_left && ball_left <= (board_left+50)){
speedX = -speedX;
speedY = -speedY;
//分数改变
sum+=5;
score.innerHTML = sum;
}
//游戏结束
if(ball_top>385 ){
alert("游戏结束,刷新后重新开始");
clearInterval(interval);
}
},5)
}
<div id="contain">
<div id="box">
<div class="board"></div>
<div class="ball"></div>
</div>
<button>开始游戏</button><br>
<span>Score:</span>
<span class="score">0</span>
</div>
*{
margin: 0;
padding: 0;
}
#contain {
width: 500px;
height: 480px;
margin: 0 auto;
margin-top: 100px;
}
#box {
width: 500px;
height: 400px;
margin: 0 auto;
/* 子绝父相 */
position:relative ;
border: 1px solid #ccc;
}
.board {
width: 100px;
height: 10px;
background-color: black;
/* 子绝父相 */
position:absolute;
/* board水平居中 */
left:200px;
top: 80%;
}
.ball {
width: 15px;
height: 15px;
border-radius: 50%;
background-color: coral;
/* 子绝父相 */
position: absolute;
left:242px;
top:76%;
}
button {
width: 100px;
background-color: dodgerblue;
border-radius: 10%;
color: white;
padding: 4px 0;
margin: 5px 0;
}