This may have been pointed out once before, but since I'm not going to go back and read 100+ comments to find out...
When starting a single player game and you're prompted to select your deck: If you click the dropdown menu to select a different deck and then decide you want to leave that window for some reason, the dropdown list won't disappear to reveal the cancel button. Instead you have to sort of guess where the button is and click there.
This could be easily fixed by adding a mouseover action or time delay to the dropdown that allows it to roll-up when the user isn't using it.
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