代码片段：
this.update = function () {
var lastPoint = { x: _this.x, y: _this.y };
// Move points over time
_this.radians = _this.velocity;
// Drag effect
_this.lastMouse.x = (mouse.x - _this.lastMouse.x) * 0.05;
_this.lastMouse.y = (mouse.y - _this.lastMouse.y) * 0.05;
// Circular Motion
_this.distanceFromCenter.x = _this.prevDistanceFromCenter.x Math.sin(_this.radians) * 100;
_this.distanceFromCenter.y = _this.prevDistanceFromCenter.x Math.sin(_this.radians) * 100;
_this.x = _this.lastMouse.x Math.cos(_this.radians) * _this.distanceFromCenter.x;
_this.y = _this.lastMouse.y Math.sin(_this.radians) * _this.distanceFromCenter.y;
_this.draw(lastPoint);
};
