ax: 20000};
  window.onmousemove = function(e) {
    e = e || window.event;

    warea.x = e.clientX;
    warea.y = e.clientY;
  };
  window.onmouseout = function(e) {
    warea.x = null;
    warea.y = null;
  };

  // 添加粒子
  // x，y为粒子坐标，xa, ya为粒子xy轴加速度，max为连线的最大距离
  var dots = [];
  for (var i = 0; i < 300; i++) {
    var x = Math.random() * canvas.width;
    var y = Math.random() * canvas.height;
    var xa = Math.random() * 2 - 1;
    var ya = Math.ra