WPF实现泡泡龙小游戏效果。

    /// -Ball to Ball Collision - Detection and Handling
    /// http://stackoverflow.com/questions/345838/ball-to-ball-collision-detection-and-handling
    /// -Introduction - The World Of Bouncing Balls:    
    /// http://www.ntu.edu.sg/home/ehchua/programming/java/J8a_GameIntro-BouncingBalls.html
    ///  -How to: Render on a Per Frame Interval Using CompositionTarget 
    /// http://msdn.microsoft.com/en-us/library/ms748838.aspx
    ///  -The Physics of an Elastic Collision (Part 2):  
    /// http://www.director-online.com/buildArticle.php?id=532
    ///  -Elastic collision:                             
    /// http://en.wikipedia.org/wiki/Elastic_collision
    ///  -Determine where two circles intersect in C#    

    /// http://blog.csharphelper.com/2010/03/29/determine-where-two-

    ///https://segmentfault.com/a/1190000012890618