Thank you for your work on Brook City 
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Concerning Keys to the Kingdom rules, there is no specific rules. You can see the page giving in the box in this video (at time 4m15s)
https://www.youtube.com/watch?v=hfYt7ZxCe5g
Could it be possible to get the original image files of these two expansions: Velocity and The Sixth Cycle? I send you a private message. Thanks
.Concerning Keys to the Kingdom rules, there is no specific rules. You can see the page giving in the box in this video (at time 4m15s)
https://www.youtube.com/watch?v=hfYt7ZxCe5g
Could it be possible to get the original image files of these two expansions: Velocity and The Sixth Cycle? I send you a private message. Thanks