In programming my Temporum client; I had to include some really weird edge cases. Like visiting Age of Cats when you can't afford to score a card. So... why would you visit Age of Cats if you can't afford to score a card? (Age of Cats says "you may pay $10. If you do, score a card twice, paying twice"). Aside from the fact that the rule allow it, and thus I had to program for it; I believe I found a reason why it could be the right move. When?