js代码雨

<!DOCTYPE html>
<html>
<head>
    <title>黑客帝国代码雨</title>
</head>

<body>
<canvas id="canvas"></canvas>
<style type="text/css">
    body{margin: 0; padding: 0; overflow: hidden;}
</style>
<script type="text/javascript">
    var canvas = document.getElementById('canvas');
    var ctx = canvas.getContext('2d');


    canvas.height = window.innerHeight;
    canvas.width = window.innerWidth;

    var texts = '0123456789'.split('');

    var fontSize = 16;
    var columns = canvas.width/fontSize;
    // 用于计算输出文字时坐标，所以长度即为列数
    var drops = [];
    //初始值
    for(var x = 0; x < columns; x++){
        drops[x] = 1;
    }

    function draw(){
        //让背景逐渐由透明到不透明
        ctx.fillStyle = 'rgba(0, 0, 0, 0.05)';
        ctx.fillRect(0, 0, canvas.width, canvas.height);
        //文字颜色
        ctx.fillStyle = '#0F0';
        ctx.font = fontSize + 'px arial';
        //逐行输出文字
        for(var i = 0; i < drops.length; i++){
            var text = texts[Math.floor(Math.random()*texts.length)];
            ctx.fillText(text, i*fontSize, drops[i]*fontSize);

            if(drops[i]*fontSize > canvas.height || Math.random() > 0.95){
                drops[i] = 0;
            }

            drops[i]++;
        }
    }

    setInterval(draw, 33);
</script>
</body>
</html>
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