注：如果小球与底部方块的角碰撞，积分可能有些许bug
<style>
#box {
width: 400px;
height: 400px;
border: 1px solid #000000;
margin: 50px auto;
position: relative;
}
#ball {
height: 60px;
width: 60px;
border-radius: 50%;
background-color: red;
position: absolute;
left: 0;
top: 0;
}
#block {
width: 100px;
height: 20px;
position: absolute;
left: 150px;
bottom: 0;
background-color: black;
}
#count {
color: #ff0000;
font-size: 18px;
position: absolute;
width: 20px;
height: 20px;
left: -20px;
top: 0;
}
</style>
<body>
<div id="box">
<div id="count">0</div>
<div id="ball"></div>
<div id="block"></div>
</div>
</body>
<script>
var oBox = document.querySelector('#box');
var oBall = document.querySelector('#ball');
var oBlock = document.querySelector('#block');
var oCount = document.querySelector('#count');
var speedBlock = 5;
var speedX = 5;
var speedY = 4;
var maxLeft = oBox.clientWidth - oBall.offsetWidth;
var maxTop = oBox.clientHeight - oBall.offsetHeight;
var max = oBox.clientWidth - oBlock.offsetWidth;
setInterval(function () {
var left = oBall.offsetLeft;
var top = oBall.offsetTop;
left += speedX;
top += speedY;
if (left < 0 || left > maxLeft) {
speedX = -speedX;
}
if (top < 0) {
speedY *= -1;
}
var r = oBall.offsetWidth / 2;
if (left >= oBlock.offsetLeft - r && // 左边线碰撞条件
left <= oBlock.offsetLeft - r + oBlock.offsetWidth && // 右边线碰撞条件
top >= maxTop - oBlock.offsetHeight // 下边线碰撞条件
) {
// console.log('撞上了');
speedY = -Math.abs(speedY);
// speedY *= -1;
oCount.innerHTML = oCount.innerHTML * 1 + 1;
}
if (top > maxTop) {
left = 0;
top = 0;
}
oBall.style.left = left + 'px';
oBall.style.top = top + 'px';
}, 50);
document.onkeydown = function (e) {
var ev = event || e;
var keyCode = ev.keyCode || ev.which;
var left = oBlock.offsetLeft;
if (keyCode === 37) {
left -= speedBlock;
}
if (keyCode === 39) {
left += speedBlock;
}
if (left <= 0) {
left = 0
}
if (left >= max) {
left = max;
}
oBlock.style.left = left + 'px';
}
</script>
