It is a strategic castle in Solitaire.
It is so famous, there is fun like free cell.
Besides competing for speed, it is good to think carefully and enjoy.
I think that winning percentage is about 10% in normal castle castle but in this application remarkably disadvantage plays the arrangement, so if you do your best you can keep about 50% or so.
Although it is good to maximize the speed, it may be good to aim for a winning percentage of 50% keep.
It also supports net ranking.