every time you come in a higher Level , the falling speed of the Pipes already Increases ( not showen in video , i was cheating ).

You can loose of course , at the starting level its mutch easier as in later levels , in later levels you have bombs , unrotateable Pipes , Pipes falling faster and more.
And there is a time running down and if you place a pipe without an opening to the bottom , you loose 10 time points.

About the special missions , i will make bonus levels , in these levels i can use your examples . The idea with using only the closen pipes and let them disapear if closen , sounds not bad , i will think about that.

Thanks...