Ok,

I just fixed the "I lost the coin toss but I can play cards anyway" bug and the "cancel" function will now give the card back, but not the mana (you have to pay for your errors somehow ).
Thank you for reporting the bugs.

I also changed the "Create new account" button to a less intimidating "Play Now!"

The "guest" option is still the best idea but it takes longer (I have to change the scipts or otherwise the game would send garbage to the database, trying to auto-save the game).

Thanks again, more improvements are on their way.