Nicely done. Drag and click works well on my iPhone with my fat fingers. Zoom also. I found the invisible boundary a little annoying. I laid out a Canfield base, but found the invisible boundary only when I moved a card up to the foundation. Grrr.

FWIW. Made me think, why have a boundary at all? Even better, why not have a snap-to grid you can toggle? A preset layout (save option?) which best lays out your gameplay.

Great job.