Two very basic needs for the Select Kingdom Cards screen:
1. Clear Selection button needs a confirmation dialog. It's very close to the Done button and a magnet for stray clicks, and takes effect immediately and mercilessly.
2. Basic undo for the last card selected or de-selected. A stray click on a selected card (say attempting to read it's contents) immediately removes it back to the larger pack, with no trace of which card it was. Macbooks are especially easy to confuse right(double-finger) clicks with left(single) clicks, so please provide a way to gracefully undo or at least know which card was last moved.
Thanks for the suggestions, Baaka!
Those are reasonable requests, especially considering some input methods are more error prone than others, as you describe.