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Or make them give 2 spins unupped and 1 spin upped!
A good idea, I think. "33% upped cards". However, hard to change rewards later.
It avoids the situation with unupped and upped copies in a spin, which make AI5 win rates lower. Very intuitive. Not all players know, that Halfbloods have 30% upped cards and that you can win them. Change the description in the main menu, and players see, that something "changed", and can estimate upped win rate better.
Edit:
Could be too little room in the main menu for the text.