About the Fortress layout

Thick walls, four corner towers and a keep in the courtyard. The towers have to be taken apart from the top down.

Free the tiles on the upper layers and in long rows first — they block the most neighbours.
When three identical tiles are open, choose the pair carefully: keep the one that doesn't block anything.
Don't rush to remove edge pairs that don't unlock anything — they will be useful later.

Mahjong Fortress