Negative frozen should probably not be spendable. The problem was that the adventurer difficulty bonus allowed the frozen status to be applied at 0, which seems to mean it just stays frozen forever. Rather than removing frozen if it decrements to 0 from 1, it may make sense to remove it if it is ever 0 or less. Also the text isn't grayed out but nothing happens when the card is played (not even 'single use')
I have fixed the main problem, now negative frozen will not disable the card.
Regarding the secondary bug of quest applying Frozen 0: do you think this quest will be too hard for non-Adventurer if I change the frozen formula to (difficulty + 2)? The other solution would be to just 'cap' formula: max(difficulty + 1, 1), but I try to make sure that at least difficulty of +-1 affects as many quests as possible.
Wouldn't frozen 2 make it free for non-Adventurers and very hard for adventurers? Because even frozen cancels the upgrade effect *and* single use, but odd only cancels upgrade? Maybe I am misunderstanding how that works. In any case, the quest is only particularly difficult if playing the upgrade card an integer number of times doesn't result in winning-- in that case you need some sort of special effect to change the amount of frozen it is. I don't think having to play it another time would be particularly hard
Every time Frozen is played, it is reduced by 1 and the rest of the card is skipped. So 'Frozen 2' card will have to cycle through the deck 2 times before it works. When reaching zero, Frozen disappears. I will improve effect description to make it more clear.
The previous bug was due to the fact that I compared "frozen === 0" rather than "frozen <= 0".
>I don't think having to play it another time would be particularly hard
Ok, changed it to (difficulty + 2)