text: ///////////////////////////////////////////////////////////////////////////
  
  //定义画布宽高和生成点的个数
  var WIDTH = window.innerWidth, HEIGHT = window.innerHeight, POINT = 20;
  
  var canvas = document.getElementById('Mycanvas')
  canvas.width = WIDTH,
      canvas.height = HEIGHT;
  var context = canvas.getContext('2d');
  context.strokeStyle = 'rgba(0,0,0,0.04)',
      context.strokeWidth = 1,
      context.fillStyle = 'rgba(0,0,0,0.08)';
  var circleArr = [];
  
  //线条：开始xy坐标，结束xy坐标，线条透明度
  function Line (x, y, _x, _y, o) {
      this.beginX = x,
          this.beginY = y,
          this.closeX = _x,
          this.closeY = _y,
          this.o = o;
  }
  //点：圆心xy坐标，半径，每帧移动xy的距离
  function Circle (x, y, r, moveX, moveY) {
      this.x = x,
          this.y = y,
          this.r = r,
          this.moveX = moveX,
          this.moveY = moveY;
  }
  //生成max和min之间的随机数
  function num (max, _min) {
      var min = arguments[1] || 0;
      return Math.floor(Math.random()*(max-min+1)+min);
  }
  // 绘制原点
  function drawCricle (cxt, x, y, r, moveX, moveY) {
      var circle = new Circle(x, y, r, moveX, moveY)
      cxt.beginPath()
      cxt.arc(circle.x, circle.y, circle.r, 0, 2*Math.PI)
      cxt.closePath()
      cxt.fill();
      return circle;
  }
  //绘制线条
  function drawLine (cxt, x, y, _x, _y, o) {
      var line = new Line(x, y, _x, _y, o)
      cxt.beginPath()
      cxt.strokeStyle = 'rgba(0,0,0,'+ o +')'
      cxt.moveTo(line.beginX, line.beginY)
      cxt.lineTo(line.closeX, line.closeY)
      cxt.closePath()
      cxt.stroke();
  
  }
  //初始化生成原点
  function init () {
      circleArr = [];
      for (var i = 0; i < POINT; i++) {
          circleArr.push(drawCricle(context, num(WIDTH), num(HEIGHT), num(15, 2), num(10, -10)/40, num(10, -10)/40));
      }
      draw();
  }
  
  //每帧绘制
  function draw () {
      context.clearRect(0,0,canvas.width, canvas.height);
      for (var i = 0; i < POINT; i++) {
          drawCricle(context, circleArr[i].x, circleArr[i].y, circleArr[i].r);
      }
      for (var i = 0; i < POINT; i++) {
          for (var j = 0; j < POINT; j++) {
              if (i + j < POINT) {
                  var A = Math.abs(circleArr[i+j].x - circleArr[i].x),
                      B = Math.abs(circleArr[i+j].y - circleArr[i].y);
                  var lineLength = Math.sqrt(A*A + B*B);
                  var C = 1/lineLength*7-0.009;
                  var lineOpacity = C > 0.03 ? 0.03 : C;
                  if (lineOpacity > 0) {
                      drawLine(context, circleArr[i].x, circleArr[i].y, circleArr[i+j].x, circleArr[i+j].y, lineOpacity);
                  }
              }
          }
      }
  }
  
  //调用执行
  window.onload = function () {
      init();
      setInterval(function () {
          for (var i = 0; i < POINT; i++) {
              var cir = circleArr[i];
              cir.x += cir.moveX;
              cir.y += cir.moveY;
              if (cir.x > WIDTH) cir.x = 0;
              else if (cir.x < 0) cir.x = WIDTH;
              if (cir.y > HEIGHT) cir.y = 0;
              else if (cir.y < 0) cir.y = HEIGHT;
  
          }
          draw();
      }, 50);
  }
  