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<!DOCTYPE html><html lang="en"><head><meta charset="UTF-8"><title>Title</title><style>p {text-align: center;}.container {position: relative;width: 500px;height: 500px;border: 1px solid #ccc;background-color: #fbfbfb;margin: auto;}.container > .ball {position: absolute;border-radius: 50%;box-shadow: 0 0 10px #888888 inset;}</style></head><body><p><button id="pup-ball">弹球</button></p><div class="container"></div><script>document.getElementById('pup-ball').onclick = function () {var box = document.getElementsByClassName('container')[0],ball = document.createElement('div'),size = 20 + Math.floor(Math.random() * 5) * 10,color = ['yellow', 'green', 'blue', 'purple', 'red'][Math.floor(Math.random() * 5)],stepx = (5 + Math.floor(Math.random() * 10)) * ([-1, 1].sort((a, b) => Math.random() - 0.5).shift()),stepy = (5 + Math.floor(Math.random() * 10)) * ([-1, 1].sort((a, b) => Math.random() - 0.5).shift()),top = box.clientWidth / 2 - size / 2,left = box.clientHeight / 2 - size / 2;ball.setAttribute('class', 'ball');box.appendChild(ball);var timer = setInterval(function () {ball.style.cssText = `width:${size}px;height:${size}px;background:${color};top:${top}px;left:${left}px`;top += stepyif (top < 0 || top > box.clientHeight - size) stepy = -stepy;left += stepx;if (left < 0 || left > box.clientWidth - size) stepx = -stepx;}, 30)}</script></body></html>
