Talk:Bridge/@comment-3991817-20130913232113/@comment-3991817-20130930091403

I'm not sure how the special blueprints (like for the Bridge) are triggered to appear, but normal blueprints all have their respective probabilities. First every class of scroll and every set of blueprints has a probability for being picked to appear in an empty slot. Then from that class or set one of the members is selected, also based on respective probabilities (large scrolls < medium scrolls < small scrolls, but mostly all blueprints within a set have the same prob.). If this works the same for the special blueprints sets it could theoretically take ages for a certain blueprint piece to appear. It's all based on (bad) luck, but could still bring your game to a halt for almost a year as in my case.