First off, let me give a big Thank You for the excellent game!

When playing Canfield, if I move the starter card off of the top-left foundation I find that I cannot move it (nor any other card) back onto that foundation.  This makes the game unwinnable.  The undo button will move the card back into place, however.

Many times I will accidentally tap the top-left card (fat fingers don't play nice with touchscreens) and if there is a space open for it on one of the tableaus, the auto-play feature will move it down.  This has happened more than once without me noticing for long enough to make it impractical to "unwind" my game (using the undo button) far enough to fix it.  I would recommend either making the starter card immovable, giving it a special flag that allows it to be moved back onto the top-left foundation, or treating the top-left foundation as any other foundation and allowing any card of the matching value to be placed on it.