Let´s make this short. I just canceled a 100k g project because I forgot I already had it running. My bad, wasnt paying attention. However, that carelesness is propably due to the fact that games usually ask for your confirmation whenever you are about to do something potentially stupid. Since there are no refunds for cancelled projects, a simple missclick can cost you a bunch of gold and resources. Might aswell add a "are you sure" thingy in this case.

-rgds